This is how you store everything delicate from the garden and greenhouse
Winter is coming
We are heading towards the first winter month, and it is reasonably certain that the frost will be more persistent and that we will not only get a single- or two-degree frost, but sometimes more, so everything is at stake. Everything that does not tolerate frost must be protected.
In general, we can divide plants that do not tolerate frost into two categories. One category is plants that do not tolerate frost but tolerate being in the dark, and the other is plants that must be kept frost-free and need a certain amount of light.
However, some of the plants that do not tolerate frost, tolerate it in short periods and down to a certain frost limit. This applies to olives and some citrus sorts, but to be sure, I categorize them as plants that do not tolerate frost.
The storage options for plants that do not tolerate frost and need light are, for example, a greenhouse covered with bubble wrap. A greenhouse glass has a U-value of 6, but with bubble wrap intended for a greenhouse, the U-value is reduced to 2.4. It provides a heat-saving of 45% and that is not so bad.
If you do not have a greenhouse, then you can buy a simple one that you can put up in a warm place. It is comparable to a tent where the fabric is made of plastic bubbles. However, I would cover it with another layer of 8 mm bubble wrap, as the bubbles that are on the purchased tents are smaller than the greenhouse plastic you buy in a hardware store.
The alternative to the greenhouse is to build your own plant hotel. It's just an insulated shed with a good, double-glazed window in it.
Plants that do not tolerate frost, but like the dark, are often a little easier to store. They can be put in flamingo boxes, in a shed and be further wrapped in something insulating when frost is forecasted. If you have a greenhouse, you can make a cellar in the greenhouse. A cellar is also easy to make by the base of the house wall. Dig a hole and lay in a drain. Put insulating sheets along all sides, and finally a lid of some insulating on top.
Whatever solution you choose, always make sure there is air for what is hidden away. For example, remove the insulation that covers the plants when there is no frost. If you store root vegetables and cabbage from the kitchen garden, make sure that they are not too dry and not too wet. Adequate humidity keeps them crisp. Remove diseased leaves from the cabbage.
Remember the exotic
Mediterranean plants such as citrus, olives, agave, Nerium, herbs such as rosemary and more, should generally be kept cool, i.e. between 5 and 10 degrees. At the same time, they should be in a place as bright as possible without direct sunlight. Olives can withstand minus 15 degrees a single night and citrus, like kumquat, can withstand minus 12 degrees. Other citrus, like dwarf lemon, can tolerate all the way down to minus 20 degrees, while regular lemons do not like a temperature lower than 5 degrees. Unless you know the exact name of the sort of your citrus plants, you should basically think of your plants as sorts that need protection during the winter. Citrus and olives prefer that the temperature at the roots is not colder or warmer than the surroundings. Therefore, it is a good idea to put them on something insulating. The more light, the more heat they require, and the more heat the more water, as it is important that they never dry out. They are not growing during the winter, therefore they should not be irrigated as often, but the soil should be a bit moist also in the winter.
If your only option is a cool bedroom, then your citrus will be able to survive here. I have one of my own kumquats standing there and it thrives quite nicely. Remember, however, that citrus should be put outside as soon as possible. They thrive much better and rarely get spider mites. Put them outside in May and take them inside again around September or later.
Some of the first things you need to look at are your potted plants. One is whether the plants tolerate frost, another is whether the pots can. Soil contains a lot of water, and when it freezes, it expands and then the pots crack. The safest way is therefore to empty the pots and transplant the plants in a bed. Place the pot upside down so that no water enters them. If the plants in the pot do not tolerate frost, then you must wrap them in bubble wrap and place them as bright as you can. In many cases that will be in a conservatory and in others, it will be in a greenhouse.
Tubers such as dahlia, begonia, gladiolus, African lilies, and some sorts of common lilies do not tolerate frost. Dig them up and leave them to dry in the sun, so mould and mildew dries out. Then place them in a polystyrene box with a little sphagnum or sand.
The kitchen garden
Head cabbage, beets, potatoes, and carrots must be stored dark and cool. Peel the large leaves off the cabbage and pull the cabbages up by the root. If you cut the root, there is access to fungi.
The delicate tall stems
Tall-stemmed roses or ornamental plants grafted onto a tall stem, in contrast to plants where the graft spot is underground, are very exposed. The graf spot does not tolerate very much frost, so it must be protected.
The graft spot is where you see a small thickening of the stem. Here you can tie a cloth bag or a similar breathable bag filled with leaves around the place. You can also wrap the plant in the spruce branches, then it will be protected. Put those kinds of plants inside the greenhouse.
Om 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.
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