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Column


Refilling the Juliana Vanlet

Question:

This year I have installed a self-irrigating system from Juliana in my greenhouse. I have a buried tank of 1800L, to which all rainwater from the gutters is led. I have set an on/off clock on the power supply to the pump, so the irrigation is at fixed times for 1 hour. The water connection to the Juliana Vanlet irrigation system is with a hose from the pump. The water pressure is normal. The water level in the measuring glass is at the top of the scale when the water is turned on.

However, I am astonished that the tank takes more than 30 minutes to fill up before the water runs out of the drip sticks. Can that be right? If I turn up the regulating tap so that the tub fills up faster, it drips a lot from the hole by the measuring glass and sprays all over the floor. Could I have assembled it incorrectly? When the clock switches off the water, the tub and measuring glass are emptied of water, and the whole thing must be refilled the next day when the clock switches on the water. Is that normal?

I look forward to reading your answers so I can feel confident that the system is running properly in the future.

Best wishes
Isabelle from Denmark

Answer:

Hi Isabelle, Thanks for your question regarding the Vanlet.

The amount of water that can be regulated is from about 10L to 150L per 24 hours via the red control tap. As you say that the water level is at the top of the red measuring glass and it takes approximately 30 minutes to fill up the tub, it sounds like the right amount of water is supplied to the drip sticks. If it is assumed that it takes 30 minutes to fill, this is done approx. 48 times in one day. From here we have to subtract the 10 minutes that it takes to be emptied. If we do this, You use approximately 130L a day. There are a number of factors that can make the inflow vary from customer to customer, such as surface tension in the water, pressure in the water and shore (the hardness) in the neoprene gasket in the measuring glass.

When you say you turn it up further and water flows from here, I would think it is because it is already at the maximum inflow to the tub. The red measuring glass itself will be emptied when the water pressure is switched off. Why the tub itself is emptied I cannot say, as it is usually only emptied when it has reached the level for emptying.

I hope the answer can eliminate your challenges/wondering.

Best wishes
Klaus Bisgaard Lillesøe
Quality manager, Juliana Greenhouses

How do you remove disease on a vine?

Question:

Hi,
For the second year in a row, our lovely vine has been infected by a disease. So far, white spots appear on the leaves. Last year, the grapes were also attacked. Do you know if it is mildew or mould? We cut off everything away last year and washed the greenhouse down. Unfortunately, it came back this year. We ventilate and irrigate. Can we do anything now to try to stop the attack - other than removing all infected leaves? And can it infect cucumbers, tomatoes, chilli, peppers?

Best wishes
Ditte from Denmark

Answer:

Hi Ditte, Thanks for your question.
I really had no doubt that it is mildew, but since it typically occurs in the summer, I just had to investigate it further, and it is now clear to me that it is mildew. It would be great to know the age of your vine and the sort. Some sorts tend to get mildew often, while others are almost resistant. If your vine is older, I would wait and see, but everything you do is correct. Ventilate well, make sure that the plant does not lack water, remove the diseased leaves immediately, and yes, other plants can be infected in dry weather and mildew thrive in the humid air.

Once the plants are infected with mildew, you cannot do anything else but remove the sick. There is no remedy for mildew once it has infected the plants. There are various fungicides on the market that need to be sprayed on before the mildew attacks, but that can be a little difficult to know. Maybe it can have an effect on what is not infected. If your vine is a younger one, replace it. Schuyler, Himrod and Vanessa are probably the most resistant sorts to the disease.

Best wishes
Lars Lund

Can a fig tree in a pot survive frost?

Question:

Hi,
We have a fig in a pot. It is five years old. More than 3 feet in diameter. It has thrived the past years. It is placed outside. It grew 4-6 inches new shoots earlier in the spring but is completely bare now. Do not think the new shoots could tolerate the long period of night frost after it had started shooting ... Can we do something? Or is it dead? We have a large fig in the ground, which abounds in small figs and leaves.

Best wishes
Joan from Denmark

Answer:

Hi Joan,
Potted plants are always much more exposed to frost. The soil can easily freeze in the bottom and then the plants usually die, but if the pot has been insulated or not exposed to a long period with frost, branches can also freeze back. Large branches too.

This year, there had been frost in longer periods, that is several days straight and my fig is frozen quite a lot here and there. My shoots are bare too. However, it is completely normal after a long cold period and there has not really been any heat to start it all again. However, I think there is definitely life in it, so just have a little patience and cut off what does not shoot, when something else shoots but not before. You can check with a nail gently scratching in the bark of the main stem. If it is green, like mine, then there is life and hope. I believe it will catch up quickly.

Best wishes
Lars Lund

Can you thin out a wine to make the grapes grow bigger?

Question:

Hi,
This year, my beautiful vine has so many clusters of grapes. Should I prune the vine, for example, to get bigger grapes? Best wishes

Elsa from Denmark

Answer:

Hi Elsa,
You can do that if you want large uniform grapes. You can prune in two ways. If you have a lot of grapes, cut along the stem (midribs) so that half of the grapes are cut off. The grapes that are left will then develop and spread out in the direction where there is most space. The more common method for us hobbyists is to use a pair of scissors that are long and pointed and thin out the entire vine so that up to half of the grapes are cut away. Some grape varieties need thinning more than others. Avoid putting too many fingerprints on the grapes during thinning, as they will lose the fine misty surface.

Best wishes
Lars Lund

How can I make a withered citrus tree come alive?

Question: 

Hi,
I have three citrus trees that have been in the greenhouse during the winter, and they look dead. All leaves are withered, and the branches all look withered as well. However, the stem is green under the bark on the trees. How can I make them come alive again? Should I cut off all the withered branches? Fertilize? Transplant?

Best wishes
Bente from Denmark 

Answer: 

Hi Bente, 
Most citrus plants that have edible fruits do not tolerate frost. If the stem is green under the bark, you may be lucky that they have survived anyway. You must then have great patience and wait until June to see what happens. I would recommend waiting to cut back what you think is dead, but feel free to remove all dead leaves.

Best wishes 
Lars Lund 

Can leaves be used as a ground cover for tomatoes?

Question:

Hi GreenhouseForum.
I have a lot of leaves from last year that I have raked up. Can I use them as a ground cover in the greenhouse when I have transplanted tomatoes?

Best wishes
Finn from Denmark

Answer:

Hi Finn,
Thank you for the creative question. Yes, you can use the leaves as a ground cover. You can also use cut grass which will both hold moisture and fertilize, although the process is slow.

Best wishes
Lars Lund

Insulating the base of a greenhouse

Questions:

Hi,
I have soil along the entire outer edges of the greenhouse. Are there any of you who have experience using polystyrene insulation buried along the outer walls of the greenhouse to keep the greenhouse frost-free during the winter, and does the polystyrene release any harmful substances in the cultivation soil?

Best wishes
Benita from Denmark  

Answer:

Dear Benita,
If the greenhouse is not heated, as you do in homes that are insulated, it does not make sense to insulate the floor, as you also get heat from the ground. Almost all the cold in a greenhouse comes from the glass, or we can say from the outer environment, and it, therefore, makes sense to use bubble wrap in the winter. You are also asking about the base, and the answer is yes. Although, there are many discussions about whether it pays off and whether it should be on the inside or outside of the base. I recommend insulating from the outside. There is no risk of polystyrene emitting anything to the ground.

Best wishes
Lars Lund

Moving a vine

Question:

Hi,
We have bought a new and larger greenhouse. In the old one is a wonderfully tasty vine, which we will of course keep. We want to build the new greenhouse around the vine. Can it be temporarily moved, or should it be heavily pruned to make it easier to build around? It is approximately 15 years old.
I am excited to read your answer!

Best wishes
Elsa from Denmark

Answer:

Hi Elsa,
I have a good old vine myself, that is now in a larger greenhouse, but I did not move it. It just got another location, because the greenhouse was bigger. I pruned it a bit just to get more space working around it. I did it in the winter when I knew I would have a new house up the following spring and knew the location. There are several opinions on whether you can move a vine or not, and there are also different experiences. Some people think that you cannot move plants that are more than 5 years old, and others have such good experiences with moving even 15-year-old plants. Some say plants must be moved in the winter or at the latest before spring (December-April), but first, they must be pruned so it is almost just the stem that is left. You dig up the plant and make sure to get as many roots as possible, in practice only a very small part of the root can be dug up. They must be transplanted immediately so the roots do not dry out. The dormant buds will shoot the next summer, but the shoots do not become very large the first year. You must let the plant take care of itself the first year. In the 2nd year, you can begin to shape the plant with new horizontal shoots, and after 3-4 years, you can yield grapes again. Typically, I think it seems that those who have tried it have not had problems, while those who have not, do not think it is possible.

Best wishes
Lars Lund

Fertilizer and sunlight

Question:

Hi GreenhouseForum,
I'm new to this universe but I would like to grow tomatoes and cucumbers and maybe peppers.
1. If you use growbags, then should you also use fertilizer and if so, which kind is the best?
2. How do you see if plants get too much sun? And is there a difference in how much light tomatoes and cucumbers should get?

Thanks in advance.

Best wishes
Mogens from Denmark

Answer:

Hi Mogens. Thank you for your very good question.

Growbags are often associated with growing in capillary boxes, ie polystyrene boxes, where you only need to irrigate once a week, but of course, you can also just lay the bag on the ground and then irrigate with a watering can every day. Most growbags have a fertilizer that lasts the first 14 days. You must read on the back of the bag, where it says whether fertilizer has been added or not. The cheapest ones are often without any fertilizer, which is the reason for the price. Growbags with animal manure are more expensive than the ones with NPK fertilizer, also called artificial fertilizer. After 14 days, you should fertilize with a fertilizer of your choice. However, if you use capillary boxes, it must be a liquid fertilizer. Fertilizer can be composed in different ways, you just need to read on the back of the packaging what is recommended. You can also choose between organic and ordinary fertilizers. If it is not organic, it is a common fertilizer.

Tomatoes can get too much sun. If they do, they get sunscald. That is, the cells are destroyed so that they do not mature in the "stem", ie where they get sun. Bigger is the problem of too much heat, so here you have to remember all summer to ventilate well. Just leave the door open around the clock when the tomatoes are ripening.
Cucumbers are the most heat demanding compared to tomatoes. Therefore, you place them the furthest away from the doorway.
Peppers also do not require much heat and can, therefore, like many tomato sorts, be grown outdoors, but chilli, (which is also a pepper) should get as much heat as possible. Tomatoes need light, but preferably not direct sun, so leave the leaves on the plant unless they are sick or withered. Cucumbers want lots of light, so find the right location.

We all started somewhere, and it is somehow very satisfying to get wiser even if one fails a few times. There are so many factors that can come into play that you are not in control of anyway. But a really good tip: You mustn’t transplant your plants too soon. Tomatoes and cucumbers as well as peppers are already being sold in nurseries and people are being lured to transplant them far too soon. When they fail, you think it's your fault, but the mistake is that they are sold too early. Tomatoes should be transplanted no earlier than mid-May and cucumbers on June 1st.

Best wishes
Lars Lund

Gas fireplace in the greenhouse

Question: 

Hello,
I have a greenhouse of 25 square meters where I would like a gas fireplace. Does the GreenhouseForum have experience with how many KW it should be able to deliver?

Best wishes
Michael from Denmark

Answer:

Dear Michael,
I have previously had my good friend Steen Rasmussen from the Danish architect greenhouse company Drivadan, calculate it.

I most common greenhouses, without any kind of insulation (polycarbonate, curtains, aluminium profiles etc.), you need 200-250 Kcal / m2 at -12 / +18 degrees (we set the u-value of the glass to 5.8).
The number will then be smaller in terms of insulation and "only" frost-free, and you can also calculate that purely theoretically, if you have the black belt in that kind of stuff, as Steen has.
In Steen's experience, you need 100-150 kcal / m2 if it is to be kept frost-free, even on the (maybe few) cold days.
If you have a greenhouse of 25 m2 and would like it to be frost-free even on cold days, a guess is 100 kcal x 25 = 2500/860 = about 3kW, but that is without technical documentation.

As soon as you turn off the fireplace the heat will quickly disappear though. On Instagram, you can follow @glimtbybloch, who besides having a small portable wood stove that I have installed, has an electric oven and a gas fireplace. Gas has the disadvantage that it emits a lot of water, so you need to air out. I know that she mainly uses the gas fireplace in front of the greenhouse and only occasionally inside the house.

Best wishes 
Lars Lund

Curly chilli leaves

Question:

Dear GreenhouseForum,
Why do the leaves on my chilli (jalapeño) curl upwards? There are no aphids or mites on the leaves.

Best wishes
Sten from Denmark  

Answer:

Dear Sten,
There are actually many different reasons, ranging from being natural on the Chinese sorts to that it could be viruses, lack of nutrients (especially manganese) or too small pots. There is a really good website that tells you all about chillies, including how to grow them. It is made by a passionate chilli grower.
The website will teach you more about chillies.

Best wishes
Lars Lund

50 degrees warm greenhouse

Question: 

Dear GreenhouseForum,
I'm going to start my 3rd season in my Oasis from Juliana. I was planning on having some tomatoes in the greenhouse along with some other plants. My olive trees and peppers are doing fine, but the tomatoes do not thrive at all, it gets too hot. Last summer it was often not possible to get the temperature in the greenhouse below 50 degrees. I have had the Juliana shadow net, but it has affects. The tomatoes get blossom-end rot and sick leaves. There is not much natural shade. The windows do not provide enough ventilation. What can I possibly do, other than lean back with some citrus plants?

Best wishes
Ulla from Denmark

Answer:

Dear Ulla, 
Well, look at that. I have a wood stove in my Oasis, which I also use in the summer. Let me start with your citrus and heat. Citrus definitely benefit from being outside in the summer. The term orangery stems from heated greenhouses that are used in the winter, but in the summer the citrus plants will always get put outside. About the shade: Juliana makes roller shading blinds with suction cups you can place almost wherever you want. You need those and shade nets. In addition, you can with advantage leave the door completely open. Another solution is to put up a wire in the ceiling, at the height where the glass meets the roof. Here vine can crawl and provide shadow. I've done that in part of my Oasis. You can also use other creeper plants. The wires are almost invisible, and you can also hang white curtains on them.

Maybe you can find inspiration in some of these links from the GreenhouseForum:
Air out with the right window opener
How to prune your vine easily

Best wishes
Lars Lund 

Fig and apricot tree in the greenhouse

Question:

Dear GreenhouseForum,
Can you recommend the best fig and apricot tree for a greenhouse?

Best wishes
Erling from Denmark

Answer:

Dear Erling,

Figs tend to get huge in the greenhouse so most end up taking them out and putting them up against a south wall.

Figs grown in the northern countries have been in demand at Gourmet restaurants. They taste better than fresh, bought figs from abroad. The explanation is that exported figs are picked and sold long before they are actually ripe, which affects the taste. If the figs can otherwise mature, they are in other words a delicacy if grown in northern countries. And they can ripe. You just have to choose the correct sort. You cannot just take a plant home from the south and get figs out of it.
If you grow them outdoors, figs must also be in the poorest soil of the garden.

Although, the greenhouse offers the opportunity to grow sorts that you normally would not succeed with outside. Those are Petrovaca Gigante, Hardy Chicago and White Marseille, Hirta, Vallecalda and Ronde de Bordeaux.

Apricot can also be difficult to grow, even in a greenhouse, as they are very heat demanding, but nothing is impossible. Harcot and Hargrand are both healthy sorts. In Norway Kuresia prunos Amenica is a very popular sort.

Best wishes
Lars Lund

Cucumber downy mildew

Question:

Hi,
Last year I destroyed both my cucumber and melon plants due to cucumber downy mildew. It probably came with a melon plant and spread down the row. I usually wash with greenhouse cleanser and hose down cracks in the spring, but do you have a better idea to avoid mildew? It seemed like the melon plants were less attacked than the cucumber plants, so I plan to only grow cucumbers this year and maybe put the plants in the other side of the greenhouse.
Tomatoes and other plants were not affected by the attack.

Best wishes
Elsebeth from Denmark

Answer:

Dear Elsebeth,

You are writing cucumber downy mildew, pseudoperonospora cubensis, so I assume that is the case. Melons can get up to 11 different viruses and fungal infections, and some of them may well resemble each other. In the case of cucumber downy mildew, the leaves get pale yellow spots, which can also look like spider mites. The spots quickly become clearer and more angular, and resemble mosaic delimited by the leaf nerves. The leaves wither and new spores infect the other plants. In humid weather, it may be filled with grey-black spores on the back of the leaf. The mosaic pattern on melon leaves can also be caused by a virus. For us at home, there is not much else to do but check the plant regularly and remove the disease when it comes. You cannot do anything to kill viruses like that, but fungal diseases can be alleviated by ventilating well throughout the summer. You can easily leave windows and doors open once the plants are in growth. Washing and cleaning the greenhouse as you do is always good against all sorts of diseases.

Best wishes
Lars Lund

Horse manure mixed with sawdust in a hotbed

Question: 

I would like to make a hotbed and have found a place, where I can get horse manure. But it is not mixed with straw, as usual, it is mixed with sawdust. Does that affect the usability in a hotbed?

Best wishes
Ellinor from Denmark

Answer: 

Dear Ellinor,
What a good question for the column, thank you for that.

Horse manure is worth its weight in gold for us garden owners, as it is useful in many ways, both as a soil improvement, nutrient enrichment and for hotbeds. Horse manure mixed with sawdust can be used for heating beds, but as you yourself suggest, there are a few disadvantages of sawdust rather than straw. The sawdust takes a lot longer to compost, so the decomposition process will not go quite as fast as for straw. This will therefore result in a smaller heat exchange from the composting. In order for the heat release from the composting to really have a noticeable effect, you must make a good thick layer of approximately 20 inches.
I should also mention that the decomposition of fresh sawdust and wood chips will cost the soil nourishment before it is released again. Of course, it is also worth investigating whether the sawdust originates from pressure-impregnated wood or glulam, as this treatment protects the wood from decomposing.
If it was me, I would look around for a barn with straw instead, but if you make a thick enough layer, you can get away with the sawdust, that is if it comes from untreated wood.

I hope I have answered your question. Best spring wishes
Frederik
Danish garden enthusiast

Greenhouse on a west-facing balcony

Question:

Dear GreenhouseForum,
I love your urban greenhouses, but I find it difficult to judge if it makes sense to get a greenhouse for our wast-facing balcony. As our apartment is on the 1st floor and in the shade from other buildings, we only have about 2 hours of sun late in the day. Would that be enough sun to grow tomatoes, strawberries etc., in pots in the greenhouse?

Best wishes
Line from Denmark

Answer:  

Dear Line,
I agree that they are beautiful greenhouses. Tomatoes and strawberries need a lot of sunlight, so those are not optimal to grow. You can try with cherry tomatoes or heirloom tomatoes that tolerate less light. On the other hand, there are many other crops you can grow in the shade and pots. That is lettuce, spring onion, radish, parsley, rocket, potatoes, sage, chives, mint, lemon balm, kale, spinach and rhubarb.

Best wishes
Lars Lund  

Winter protection for plants

Question:

Hello GreenhouseForum,
I have seen a picture and read a description of a tent you can make, of poles and bubble-pack sheets, inside your greenhouse during the winter. I simply cannot find a tent as shown. Is it homemade or can I buy one? I hope you can help me, as I am afraid I have lost my agave to the hard frost.

Best wishes
Malene from Denmark

Answer:

Thank you for your question. I have written an article about the topic here.
It takes some time to put up and take down, so I got tired of using it, as I am way too impatient. I gave it to my brother, and he sent it back to me, so now I have given it to DanChurchSocial. But it's a matter of preference. If you have the courage and are able to use it in the garden in the summer without disassembling it or have a storage space, it is definitely a really good option.

If you want a quick solution, put your pots on a thick polystyrene plate, bought in a hardware store. Wrap the pot well in a rug or whatever you have, possibly bubble-pack sheets. Cover the plant with bubble-pack sheets, a crop-cover cloth. If you have nothing else and it is urgent then use plastic, newspapers, etc., when there is frost, and take it off when the frost is gone. It is important that there is always air for the plant and therefore the cover should not be on for too long.

Best wishes
Lars Lund

Lemon fertilizer

Question:

Dear Lars,
Should lemon trees not be fertilized from February to September?

Best wishes
Helle from Denmark

Answer:

Hello Helle,
Lemon should be fertilized like many other plants when they start to grow and they need to be fertilized throughout the growing season, so you should definitely not neglect fertilizer while they are growing, and they are growing from April to August/September. Also remember that lemon is far better off being outside in the summer than under glass. That is why orangeries were built. In the winter, the orangery was heated with central heating and in the summer, the lemons was put outside. An orangery is therefore a heated greenhouse.

Best wishes
Lars Lund

Dwarf peachtree in the greenhouse

Question:

Hi, I would like a dwarf peach tree in a pot for my greenhouse. Can you recommend a healthy sort that is also reasonably frost tolerant?

Best wishes
Karin from Denmark

Answer:

Hi Karin,
How exciting and not least delicious with a dwarf peach tree in the garden. There are many different sorts that all are interesting to grow and several of them are certainly suitable for pot cultivation. You write the sort must be tolerant to frost, to this I can say that the vast majority of peach trees in the trade are hardy and frost tolerant. With that said, they should still be protected during the winter and the pot should be insulated with a straw mat or similar.

The first sort I would recommend is the Crimson Bonfire, which gets beautiful reddish foliage, has slow growth and rarely gets taller than 4 to 6 feet. The sort bears many tasty fruits, is self-pollinating and should be tolerant to peach leaf curl. Bonanza could be another excellent option. The maximum height is 6 feet, it is also slow-growing and perfect for pot cultivation. Both Crimson Bonfire and Bonanza are created to bear fruit already in their early years of life.

Peaches bloom before leafing around April, with beautiful intense pink flowers. If you want to ensure delicious peaches in late summer, the flowers must not be damaged by the frost in spring.

Almost all sorts of peaches these days are self-pollinating, but there are rarely many insects in the air in early spring. To ensure pollination, you must act as a bee by using a fine brush or cotton swab and move pollen gently from flower to flower. When the fruit development begins, I can recommend fertilizing with tomato fertilizer, which has a high potassium content, a few times a month.

Peach trees can be attacked by the fungal disease called peach leaf curl, to prevent the fungal disease, you must avoid water and drops of water on the leaves until the beginning of May. The disease is seen by curly, discoloured leaves which must be removed immediately as the leaves quickly infect each other.

Good luck!

Best wishes Frederik
Danish garden enthusiast

Chicken wire/reinforcement mesh in a home-built greenhouse

Question:

Is it very detrimental to use chicken net/reinforcement mesh instead of glass/plexiglass in your home-built greenhouse for greens, not for tomatoes just greens?

Best wishes
Ann Marie from Denmark

Answer:

Hi Ann Marie,
I understand your question in the way that you want to make a greenhouse out of chicken wire or reinforcement mesh. You can easily do that, but it must be because you think it is beautiful and it can definitely be. There are greenhouses that are built from a lot of lists and are called shadehouses. In Sweden, I have seen houses where the framework is built of round iron, which reinforcement mesh is also made of.

If you want to do it to get a decorative element, then it is a great idea. If you pull a net over, you are free of almost all pests. However, it steals some light, but it only needs to be netted during, for example, the time the garden whites lay their eggs. Otherwise, vegetables thrive, as you know, in the open air and actually not very well in the greenhouse. You can also easily grow tomatoes in the open air. I do not grow mine in my greenhouse, but in the kitchen garden, and they yield delicious tomatoes. It just depends on the sort.

Raised beds with windows of plastic or old windows laid on top are also a solution if you want early vegetables. Here too there are many models, if you e.g., google the word garden frame. Pipes put in arches with a plastic sheet over also work fine, or with an insect net.

Caterpillars: usually it is early enough to cover around Midsummer Day, as it is usually only around the 1st of July that caterpillars really appear. You can find a few larvae of large garden whites, in May and June and a few more in July, but the number does not culminate until August, and usually the last half of August.

Previously, one could buy a pesticide that killed the caterpillars, but it is not in the trade anymore. Otherwise, you have to inspect your plants and squeeze the eggs to death. If you have more questions, you are very welcome to ask.

Get well into the spring.

Best wishes
Lars Lund

Sprouts that bend

Sprouts that bend

 

Question:

Dear experts,
I often find that many of my vegetable seeds bend after germination, even though they are regularly irrigated and stand in a window ledge. At approx. 22 degrees room temperature. 

What am I doing wrong? They often bend just a few inches from the ground.
Hope you can give me answers to this mystery that I experience every year.

Best wishes
Jan from Denmark 

Answer:

Dear Jan,
When I see the long stems, I immediately think: they lack light to a degree. In addition, they could very easily be exposed to something called root rot. Root rot is caused by several different species of soil-dwelling fungi. They attack the root collar and roots of herbaceous plants, which grow under adverse conditions, that is, too high humidity, compact and cold soil, which is not good. On the other hand, vegetable seeds should not be too hot. 10-15 degrees is best.

The attack of root rot is typically seen by a dark staining where the stem has contact with the ground, slightly below and slightly above. Eventually they dry out and become thread thin. The transportation of water becomes cumbersome, so the plant withers and dies. You can remedy this by partly using potting soil that has the right mix of gravel, that drains, and soil. Irrigate from below so the water is absorbed into the soil and use vermiculite in the top thin layer, it keeps the root collar dry. So, in your case, I think it's a mixture of lack of light and proper drainage in the ground.

Best wishes  
Lars Lund

A mistletoe in an apple tree

Question:

Dear Experts,
I have a large, very old apple tree in my garden. About 10 years ago I spotted a small cluster of mistletoe among the branches, and I now have about 20 large bunches of mistletoe in the one tree. Is this a problem for the tree, as I’ve read that mistletoe is a parasite?

Best wishes
Torben from Denmark

Answer:

Hi Torben,
Thank you for your question. Mistletoe is a semi-parasite, which means it makes its own food from its own leaves, just like other plants, but because it can’t grow in the ground it needs to live on a host tree where it taps into the tree’s water and minerals. In general, mistletoe won’t kill a healthy tree but it can weaken it, and if the tree is old or sick mistletoe can cause problems.

The berries are spread from tree to tree by birds – the sticky flesh means the mistletoe seeds end up stuck to the branches where they germinate. Mistletoe particularly likes apple trees and it’s mainly found in the south and west of the UK, with high numbers of orchards.

Mistletoe can become a problem for trees if the bunches become too big and heavy, causing branches to snap, which can in turn make the tree vulnerable to diseases. Mistletoe can be pruned, in fact in the apple orchards of Worcestershire and Herefordshire they harvest the mistletoe and sell it at mistletoe markets in the run-up to Christmas.

A few groups of mistletoe on a healthy, large tree shouldn’t be a problem, but any more and they will have an impact on the growth and health of the tree. It’s therefore best to cut back the mistletoe growth in winter, it will however regrow, so you will need to remove the branches of the tree to reduce the number of mistletoe growths. Once you have a manageable number of bunches, cut back the growth every couple of years and check branches for new seedlings that have sprouted, removing these when you spot them. If the tree is tall you may need to get a tree surgeon to do the work.

Best wishes
Lars Lund

How to use a Plant Spiral

Question:

How do you use the Juliana plant spiral?

Best wishes
Leif from Denmark

Answer:

Hi Anna,
The plant spirals hang from the roof of your greenhouse and are great for growing vegetables, such as tomatoes and cucumbers, offering support for their stems as they grow. Each spiral is made from an inner aluminium tube that’s covered in green plastic so that they’re strong and durable. The spirals look like springs but they’re not as flexible, and once you’ve pulled them you can’t shorten them, so slowly extend them to the required length – you may need an extra pair of hands.

Best wishes
Greenhouse Forum

Moving a greenhouse

Question:

I’m moving house and I wondered if you have any tips on how best to move/transport my greenhouse?

Best wishes
Susan from Denmark 

Answer:

Hi Susan,
Thank you very much for your question. All the glass will need to be removed. If the glass is held in place with mounting strips remove these – you can save them or buy new ones. If the glass is fitted with clips, carefully remove these, popping them in a plastic bag or storage box. If the glass is fixed with silicone then use a knife to remove the glass. Remember to buy new silicone for when you come to rebuild the greenhouse. Pack the glass in a sturdy box, making sure that it can stand upright and that the glass is securely packed so that it can’t move about inside the box.

The greenhouse should then be removed from the foundation. It can be transported in one piece, just without the glass, on a flatbed truck or divided into sections and put in a van. It’s important to make sure the frame doesn’t move too much during transportation as the frame can twist out of shape. Make sure you keep hold of all the fittings and store safely for the rebuild.

The other option is to completely dismantle the frame. Make sure you mark up each piece so that you know where everything needs to go when it comes to reassembling it.

It will be easiest to have a new foundation made for the greenhouse so that it is securely anchored to the ground.

Of course, you could save yourself the time and expense of moving an old greenhouse and treat yourself to a new model for your new garden. Perhaps this is the opportunity to upgrade to something bigger or to buy a model that suits your new home and garden.

Best wishes
Greenhouse Forum

Washing Vine and Peach stems

Question:

Why is important to wash the stems of grape vines and peaches?

Best wishes
Inger From Denmark

Answer:

Hi Inger, 
Thank you for your question. Scale insects can attach themselves to the stems of plants like vines and peaches. These pests suck the sap from the plants weakening their growth, so it’s a good idea to keep an eye out for these insects – they look like small, brown shells. Check the stems from late winter onwards and use a cloth dipped in rubbing alcohol, also known as surgical spirit, to wipe away any scales. With grape vines it’s a good idea to peel away any loose outer bark to expose any scale insects and other pests which might be hiding underneath.

Best wishes
Lars Lund

Greenhouse Stability

Question:

I’ve moved into a house with a greenhouse in the garden. The floor of the greenhouse consists of slabs with some gravel underneath. I’d like to remove the slabs and put fresh soil there so that I can grow directly into the ground, but my husband is concerned about the stability of the greenhouse. Is it OK to remove the slabs?

Best wishes
Natalie from Denmark 

Answer:

Hi Natalie,
If the greenhouse is sitting on a cast base it should be safe to remove the slabs. However, you should be aware that the foundation may need to be supported, so it’s a good idea to remove a few slabs at a time and provide support where the slabs have been removed. Repeat until you’ve removed all the slabs and supported the whole structure.

Best wishes
Klaus Bisgaard Lillesø
Quality manager, Juliana Greenhouses

Identifying an Unknown plant

Identifying an Unknown plant

 

Question:

Our daughter has this plant growing in her front garden. It’s about 75cm tall and produces flowers with lots of yellow pollen, which the wasps and bees love. What is its name?

Best wishes
Palle from Denmark

Answer:

Thanks for your question, Paula.
It’s a slightly blurry image, but it looks like common ivy (Hedera helix). It’s a clinging climber which can also be grown for groundcover. It flowers in autumn often when other flowers have gone over, so it’s great for providing bees and wasps with a late source of pollen and nectar so that they can build up their reserves for winter. Be aware that the plant is poisonous and can cause allergic skin reactions.

Best wishes
Lars Lund

Propagation of Artichokes

Propagation of Artichokes

 

Question:

I planted a couple of artichokes in the spring and they have grown quite tall and provided a good crop. The largest plant looks like it has divided into three separate plants at the base. Is it possible to propagate it and how should I go about this?

Best wishes
Tove from Denmark

Answer:

Hi Lisa,
Yes, these are suckers from the root base. Artichokes can be propagated from these suckers when the suckers are about 20cm tall in November or April, using a sharp knife or spade to separate the shoot from the parent plant. Pot them up into individual pots filled with a loam-based compost. Artichoke plants will be productive for several years but after this it’s a good idea to plant new plants.

It’s also a good idea to mulch the base of artichoke plants in autumn, using a thick layer of straw to protect them from the cold.

Best wishes
Lars Lund

Plants and light

Question: 

Can plants get too much sunlight in a greenhouse?

Best wishes
Christine from Denmark 

Answer: 

Hi Christine, Thank you for your question. Yes, it is possible for plants to get too much light when grown under glass. Plants have evolved to cope with the light levels in their native habitat, so plants from the desert tend to have thick, fleshy leaves which can cope with high levels of intense light and heat. Whereas plants from cooler, more northerly locations will have adapted to make the most of the available sunlight. From May to mid-August it’s easy for plants in a greenhouse to overheat and for their leaves to be scorched by strong sunshine that’s intensified by the glass. Providing sufficient ventilation on hot days by opening vents and doors can help. You can also attach blinds or shade netting to the outside of the greenhouse or apply shade paint to the glass to reduce the intensity of the light.

Best wishes
Lars Lund

Lemon tree loses its fruit

Question: 

The fruit on my lemon and orange trees have fallen off. Why has this happened?

Best wishes
Kate from Denmark 

Answer: 

Thanks for your question, Kate.
Citrus fruit can take almost a year to develop to full size, and most cultivars form too many fruit for the size of the plant. These will often be naturally shed by the plant, but it’s a good idea on young plants to thin the number of fruit in each cluster to one.  

Don’t over water in winter and keep the plant in a pot that is not much larger than the root ball of the tree. Use a specially formulated citrus feed – high nitrogen from spring to midsummer and a balanced fertiliser between midsummer and autumn.

Best wishes
Lars Lund

Fungi in the Greenhouse

Question: 

How do you avoid fungi in your greenhouse?

Answer:

There are, generally, always moulds and fungi present in humid environments. Good ventilation is key, opening vents and doors to provide air flow. It’s a good idea to do this on mild winter’s days too, just for 10–15 minutes and make sure you remember to close the windows and doors.

Good plant hygiene is important throughout the year, making sure any yellowing or dead leaves are removed promptly, and dispose of any dropped fruit.

Overcrowding is a factor, so make sure there’s plenty of space in between plants for good air flow.

Take care when watering to water the compost in the pots and avoid splashing the foliage as this can encourage mould to grow.

Best wishes
Lars Lund

 

Toad in the greenhouse

Question: 

I have a toad in my greenhouse, what should I do with it?

Answer: 

Toads in greenhouses are not uncommon. They like the humid environment and to eat the slugs and snails that inhabit the nooks and crannies of the greenhouse. They aren’t doing any harm, in fact they’re a natural pest control, so leave it alone. It’s worth bearing in mind that there are toxins in the skin of toads that are poisonous to pets, and it’s a good idea to wash your hands if you come into contact with one.

Best wishes
Lars Lund

Larvas in my Strawberry plants

Question: 

I have small, green grubs in my strawberry plants that have eaten the leaves. What should I do?

Answer: 

These sound like the strawberry sawfly. They pupate and overwinter in the soil, so in April and May check the undersides of leaves for eggs and larvae and remove them by hand. After the plants have finished fruiting cut back all the foliage, leaving just the crown of the plant, and clear away plant debris.

Best wishes
Lars Lund

Column

In the column, you can, as a reader, ask our experts questions that can't be found on the blog. A couple of times a month, we choose questions to be published, and the lucky one will receive a small gratuity as a thank you. Your question will always be answered, even though it is not published. 

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