Lars Lund

03 May 2024 11:15

Replace Peat Moss and Cultivate in Something Other than Soil.

Peat moss is on its way out, but how do you replace peat moss, and can you cultivate in something other than soil?

Get inspired to cultivate without peat moss, for example in straw or just in pure water.


By Lars Lund


Almost all the soil you buy in plastic bags is based more or less on decomposed peat moss. That is to say, some coarse or some fine peat moss. The finer it is, the more decomposed it is, and the more pulverized it is. The fine and dark peat moss is suitable for pots because it absorbs a lot of water, while the coarse and light one is ideal for beds because besides absorbing water, it also has a coarse structure that provides oxygen to the roots. In plant bags for tomatoes, it is usually the poorer and cheaper quality that is used, that is, the dark peat moss in the bags. This is because the bags are based on water systems such as drip irrigation or capillary boxes, which constantly supply water to the soil. The soil therefore does not need a structure that retains water for a long time.


Peat Moss Is Out.

Peat moss is on its way out. It is already prohibited to buy for private use in England, while the EU hesitates. Sooner or later, however, it will disappear simply because it needs to be transported from longer and longer distances, often from Eastern Europe. Peat moss is found in the high bogs that remain after heavy cutting, where it binds a lot of CO2, which is released when it is dug up at the same time as destroying the high bogs, which have taken thousands of years to form. As a replacement for peat moss, various compost products have now emerged, such as composted bark, coconut fibers, sawdust, and composted green waste.


Make Your Own Acidic Soil for Your Acid Beds.

Acid-loving plants like rhododendrons will require acidic soil. Acidic soil can be made by mixing equal parts of garden soil with filter gravel (2-6 mm), and beech leaves, or spruce and/or pine needles. The gravel drains, and the leaves and needles make it acidic. Spruce needles are number one in terms of nutrition because they contain the most nutrients, but spruce also makes the soil just as acidic. If you have plenty of soil under a fir or spruce tree, then the soil is already acidic, and perhaps you can get some here. Also, the soil in the forest is acidic. Acidic soil can also be made from leaf compost, mixed with equal parts filter gravel and spruce and pine needles. Oak leaves are particularly useful. If you haven't limed your lawn, the moss in the lawn will be excellent to mix into the soil. A small drawback of the alternatives is that they cannot retain water as well as peat moss can. If you can get hold of sheep wool and mix it into the soil, wool stores water, and otherwise, you just need to be aware of having to water in very dry periods.


Potting Soil

In pots, you can use garden soil mixed with 1/3 coarse compost. Feel free to add biochar, which is charcoal. When wood is converted into charcoal, large amounts of microscopic pores are formed, which bind both water and nutrients.


The Greenhouse

If you grow in plant bags, you can make your own bags. It's quite easy. Mix garden soil with 1/3 compost and put it in a bag, shaping it to fit your capillary boxes. Here, as with potting soil, you can add charcoal.

If you have fixed beds, you can grow directly in the beds. You should remember that tomatoes should not be grown in soil that has previously grown tomatoes. The soil is often infected with nematodes, similar to how potato soil is infected with tiny thin potato eelworms. Previously, people changed the soil to a depth of one to two spades, but many greenhouse owners have simply changed the top ten centimeters, and it seems to be sufficient. Tomatoes prefer soil with a pH value of around 6-7. For example, this is not found in peat moss, and therefore you will see that peat moss bags for growing tomatoes have added lime. However, the soil in your garden will usually have a pH value of around 6.


Cultivate Without Soil

If your soil is so compact that you need a post hole digger to plant potatoes, and you have tried everything to get it into a looser soil, an alternative for both your greenhouse and your garden may be to grow in straw bales. Of course, it can itself be an alternative with many other advantages. In professional greenhouses, straw bales were previously a common growing medium for cucumbers and tomatoes. Today, it is often in rock wool or coconut soil. Gardeners learned from the professionals, and the method of growing in straw was in the 1960s and 1970s a not entirely uncommon method in hobby greenhouses. A bale of straw was dug into a huge hole in the greenhouse, and then it received 150 liters of water and some fertilizer. Then things happened. Billions of microorganisms took hold, and the straw almost reached boiling point. Three weeks later, the temperature dropped to just under 30 degrees, and then it was time to plant cucumbers and tomatoes in the straw bales. Since tomatoes and especially cucumbers love heat from head to toe, the plants thrived. Plant bags later replaced the bales, and the method has almost been forgotten.

However, the greenhouse plants particularly benefit from the straw bales. This is due not least to the warm straw. Instead of burying the bales, you can also make some molded bins for the bales to stand in. Successful experiments have also been made with simply placing the bales on the ground and when the system is up and running, letting a soaker hose provide water now and then. The advantage of burying them is that you get greater clearance for the plants in the greenhouse, and the bales are below ground level, reducing evaporation. However, it is quite a job to bury a straw bale.


What You Need

Straw bales

Fertilizer with high nitrogen content


Covering: Newspapers, peat moss, or straw mats

Soil thermometer or meat thermometer

Possibly agricultural lime

Possibly compost or seedling soil (only necessary if you sow seeds)


How To Do It

There are two very different methods. One is American from the book "Straw Bale Gardens" by Joel Karsten, published by Turbine.

The other Danish and is described in the books "Det økologiske drivhus" (the organic greenhouse) and  "Kom videre med dit drivhus’’ (move on with your greenhouse), both by Lars Lund, and is a very simple method. However, it is based on the bales being in a buried bin. Recently, experiments have been made with also using the same method with the bales standing directly on the ground and with successful results. You just need to make sure the bales don't dry out.

Common to the two methods is:

Choose fertilizer with the highest possible concentration of nitrogen.

Start two to three weeks before sowing or planting.

In the American method, you give the bales water and fertilizer over 12 days. In the Danish method, you start by basically soaking the bales. The cut side with holes in the straws should face upward. In both methods, you will need a total of 150 liters of water. Whether you choose an inorganic fertilizer (chemical fertilizer) or an organic fertilizer, choose a fertilizer with as high a nitrogen content as possible, for example, NPK 21-3-10 or an organic fertilizer with approximate numbers of 9-2-5 per bale. In total, you will use between 600 grams and 800 grams of NPK. If you choose organic fertilizer, you need to multiply by 6.

Organic fertilizers work slower than inorganic fertilizers, so maybe you need to start the process here a little earlier. Among organic fertilizers, pigeon manure and chicken manure contain the most nitrogen, but never use fresh manure. Organic fertilizer can be mixed in a bucket with a little water to make it a thin gruel, which you pour over.

When the temperature is below 30 degrees, you can sow or plant. It is allowed to dig small plant holes and possibly fill them with a little compost when it comes to planting plants. Otherwise, you can use seedling soil when sowing, but the trick is to avoid soil bacteria. Both lead to a good result.

The American Model

On the first day, sprinkle 100 grams of NPK per bale or 600 grams of organic fertilizer. Repeat the process on the 2nd and 3rd day with water and fertilizer. On the 4th day, only water. On the 5th and 6th days, give water and fertilizer as on the other days and water down with ten liters of water per bale. On the 7th and 10th day, give half the dose of fertilizer and water down with ten liters of water. On the 12th day, you are ready to plant or sow. The ideal planting temperature in the bale is just under 30 degrees. Water the new plants and wait five days before fertilizing further if necessary.

Remember to turn the cut side of the straw bales upwards so the water can run down into the tubes.


The Danish Model

Distribute all fertilizer on the bales, possibly distributed over a few days if you are using readily soluble fertilizer. Gently water 150 liters over a couple of days to soak the fertilizer into the straw.

Cover with 10-15 layers of newspapers, winter mats. Take the temperature, and when it reaches around 70 degrees, remove the insulation, and sprinkle some agricultural lime on the bales. When the temperature drops to 25-30 degrees, you are ready to plant.


If The Plants Lack Fertilizer

You can always add extra fertilizer if needed – for example, if the green plants become pale.


Advantages and Disadvantages of Straw Cultivation in The Greenhouse


Always new growing medium.

The temperature gets so high that many disease spores are destroyed, and weed seeds die.

Early harvest because the straw bed quickly warms up.

Especially if the bales are not buried, you have a high bed where you don't have to bend down.

Sustainable production and good material for compost.

Soil is not necessary when just planting out, and you avoid soil-borne diseases.



More preparation work compared to plant bags.

Greater water consumption from start to finish.

If the bales are not buried, the clearance for the plants in the house is reduced.


Cultivate in Water Alone.

Have you tried putting some sticks in an avocado and placing it in a glass of water, or perhaps tried the same with a potato or a hyacinth bulb, well then you have actually cultivated in water, or what is called hydroponics.

"Hydro" means water, and although you can grow in pure water, some growing medium is often included, which is anything but soil, whose sole purpose is to hold together roots and plants as such.

Hydroponic systems vary. They range from very small systems you can have on your windowsill to larger systems that fit into your greenhouse. The growth medium is the material in which the plant roots grow. The medium covers a wide range such as rock wool, perlite, coconut fiber, clay balls, or LECA, of the type that absorbs water. Unlike soil, which can contain minerals and nutrients, the medium is an inactive substance that does not provide any nutrients to the plants. All the nutrients they need come from a nutrient solution mixed in the water. The trick is that you can precisely control what the plants need. In ordinary soil cultivation, the risk is that the plants do not get exactly what they need, and the plants thus become sick. In the water system, there are none of the harmful soil bacteria or, for example, soil fleas that can harm the plants.

The simplest is a system with a wick that goes down into a water reservoir and draws water up into the growth medium. In the basin lies a pump that oxygenates the water. Read more here: 


Water culture is another system. The plants stand on a foam board (polystyrene). The board floats on a water basin (imagine a capillary box with water) In the basin, pour the amount of fertilizer you have calculated the plants need. In the water, there is also an air pump.

A third system works in such a way that you have a box of water, and on that stands a box with a growth medium, where the plants are planted. From the bottom box, water is pumped up, which branches off with drip hoses from the pump. In the tub, there is also a pump that oxygenates the water. The pump pumps the water up and via a pipe in the medium box, excess water goes back into the water box.

Om Lars Lund

Lars Lund
Danish horticulturist and journalist
Lars Lund has for many years engaged in the garden and greenhouse. Lars has published many books about greenhouses, and he has participated in many Danish horticultural TV shows. He is a walking garden encyclopaedia, and he has answers for most basic cultivation questions – also the more ambitious ones.  

Get to know Lars Lund