Last updated on October 23rd, 2023 at 08:15 pm
While caring for hardy herbs in the cold season is really a breeze, there’s a little more to consider for the less hardy plants. In this article, you’ll learn how to properly protect your herbs – whether in a container or outdoors – from frost and ensure that they survive the cold unscathed.
Contents
Who can stay outside, who can’t?
Let’s start with the hardy guys and gals that you can safely leave outside despite the cold. Mint “Mojo”, chives “Siggi”, sage “Salvador”, lemon balm “Melissa” and lavender “Larissa” can easily tolerate temperatures in the double-digit minus range (winter hardiness zone 5: up to -28 degrees are possible!) and need little protection; in milder regions they will even forgive you if you forget to do so. Our oregano as well as thyme and parsley (curly and smooth) may also spend their winter vacation in the open air, but they definitely need protection from the cold. If your herbs grow in tubs or pots, no matter how hardy they are, you must always remember to protect them from the cold.
And then we have the candidates that can’t spend the winter in the open air. In addition to lemongrass “Zorro,” these include the herbs rosemary and tarragon, which are designated as hardy. Both do not cope with temperatures well below freezing and have their tolerance limit already at just below 0 degrees. Therefore, we advise cultivating both herbs in tubs rather than outdoors from the start; this way you can get them through the cold season in a warmer place. Rosemary and tarragon can also be kept warm in a sheltered corner outside, if you can’t find a suitable place for them. Last but not least, we have a little surprise for you: Marjoram, basil and Thai basil, all of which are not hardy and are traded as annual herbs, can, with proper care and a little luck, spend the winter on your windowsill at home and thus bring you another year of joy.
Before you start the preparations, it is absolutely important to know that the old foliage of the plants should not be removed and the herbs should not be pruned again in any case. On the one hand, the remains of the plants serve as protection from the cold and winter quarters for many small animals. Secondly, pruning at this time causes the plant to lose too much water, causing unnecessary stress.
Winter hardy herbs in the pot
As we know, with potted plants we have the disadvantage that frost can strike from all sides. As a result, in extreme cases, the entire soil and roots may freeze. And whether even the most robust plants survive this is written in the stars. So if you want to avoid potentially unpleasant surprises and enjoy freshly sprouting herbs again next year, you should give the pots and balcony boxes a winter suit.
What you need:
Insulating material (cold protection fleece or bubble wrap).
Wooden/styrofoam board or similar.
Mulch material (leaves, straw, fir branches, sheep wool or brushwood are great)
String for fastening
Optional
Robust and weatherproof box
Heating cable
The protection is installed in no time and is much less complex than that of our Mediterranean and heat-loving plants. We have explained how you can best overwinter the exotics using the example of Olive “Olivia” and here using the example of Lemon “Zeus”. Depending on how much effort you want to put in and how large or numerous your containers and boxes are, you have two options.
Option 1: Start by mulching the soil with a decent layer. Sheep’s wool, brushwood, fir branches or straw are excellent materials and will primarily ensure that the water balance is correct and that the root systems are spared from the cold. Next, wrap the tubs generously in the insulating material of your choice. Make sure that there are enough small gaps at the bottom of the pot so that rain and melt water can drain off easily (drainage, e.g. in the form of clay shards, is obligatory for potted plants anyway). The surface can remain open, the mulch layer is effective enough together with the old foliage. Then find a sheltered spot on the wall of the house and move the boxes and tubs there. Place them on the wooden or styrofoam board; this will prevent frost from sneaking into the pot ball from below, and water will be able to drain better through the elevation.
Option 2: If you have several small pots, you can make it even easier! Grab a sturdy and weatherproof box, place the styrofoam/wood sheet inside, and then place all the pots on top of it. You don’t need to wrap the individual containers. Cover the soil again with the mulch material and at the end also fill all the spaces with it generously. Place against the protected wall of the house – done! If it gets extremely cold and uncomfortable, you can temporarily place a protective fleece over the plants or spread a heating cable between them (the latter is usually rarely necessary in our latitudes!). Also, especially if the containers are covered or it is dry for a long time, you should regularly give a sip of water on frost-free days (about every 10 to 14 days is enough). That way, your charges will feel comfortable throughout the winter.
Winter-hardy herbs outdoors
Outdoors in a bed, preparing and caring for herbs is far easier. While we have some very hardy plants with us, they’re all grateful for a little protection and you’ll be on the safe side in case of a surprise cold snap.
What you’ll need:
Mulching material (leaves, straw, fir branches, sheep’s wool or brushwood).
Optionally a protective fleece
The most important step here is mulching: layer the selected material generously again, it can be quiet several centimeters. Also, in the open ground, you should not cut the plants in any case and leave the old foliage. If it gets so cold for several days or weeks that temperatures drop into the double digits, you can also spread a protective fleece over the more sensitive plants and fix it at the edges with stones. If the temperatures rise again, you can remove it. This way the plants will get enough light again. Watering is only necessary if it stays dry for weeks and choose a day when it does not freeze.
Non-hardy herbs: Get inside in the warm.
The herbs that are not hardy need a little more attention and can not stay outside during the winter. As mentioned earlier, in addition to lemongrass, tarragon “Esmeralda” and rosemary “Rosemarie” need to go into the warm. These herbs must move to their winter quarters as soon as it gets cooler and darker outside (around the end of October). You should also wait until spring to prune them.
If you already have one of the latter two (or maybe even both) herbs at home in the bed, you should run a heating cable around the plants and have a protective fleece in ambush in case it gets very cold. That way, rosemary and tarragon might have a chance to survive after all. Alternatively, you can transplant them into a pot in late September or early October and leave them in for the winter, as described below – in the spring, when there is no longer a threat of frost, they can then be planted out again in the bed. They can be overwintered in a bright and cool place at temperatures between 5 and 10 degrees. This will give the plants their necessary winter rest, but will not risk cold death. It is important that there is sufficient daylight. An unheated conservatory, greenhouse, light-colored shed, bright garage or cool stairwell with windows are great options. A home windowsill, on the other hand, is much too warm for rosemary and tarragon.
It’s best to place your herbs so that there is no heating nearby, as too dry air doesn’t do them any good. If this is not possible, you can place a few small bowls of water between the plants and on the heater to create a comfortable climate. You also need to water regularly, although less than in summer. A small amount of water every 10 to 14 days is a good guideline. The same applies here as elsewhere: if in doubt, water too little rather than too much to avoid waterlogging! If you have absolutely no possibility to overwinter your heat-loving herbs indoors, you can dare to try and leave them properly packed outside and cover them with a protective fleece from above; in addition, it makes sense to get a heating cable and help a little with very low temperatures.
Lemon grass, on the other hand, has very special requirements, because it must definitely be brought indoors and wintered warm. In the summer it also likes to grow in the bed, but now it’s time to transplant the fragrant grass into a container. It wants to move to winter quarters where the temperature is at least 10 degrees, but it is also happy with warmer rooms. Lemon grass even likes dry heating air. The most important thing is a place as bright and sunny as possible. Water only when the soil feels dry. If the lemongrass grows well, you can harvest some of it even in winter.