Mother nature can be very harsh, and sometimes it seems that winter is over. However, late frosts suddenly return, and for some plants, it may not end well. So you need to be prepared for this situation and know what to do.
Frost can hurt hostas if they start to grow. This often happens with late spring frosts. The leaves may be partially damaged or wither completely.
If the hosta has not yet formed the leaves and only young shoots have emerged from the ground, the damage will be minimal. Hostas that are dormant are not afraid of frost at all. They can withstand up to -40 ° F if there is a thick layer of snow above them.
However, if the foliage has already unfolded, it will definitely freeze. The amount of damage depends on many factors, such as variety, next we’ll talk about it in more detail. I will also tell you what can be done to avoid frostbite and what to do to reduce the consequences.
Does frost kill hostas?
In general, frost will not destroy hostas. This is a very hardy plant and can withstand severe frosts in hibernation. Even in spring, late frosts will not be fatal, the plant will lose some foliage (or all), but the rhizome will remain alive. After a while, the hostas will recover.
However, there is a risk of crown rot. If the frost was severe and the plant was seriously damaged, it may begin to rot the crown. This is quite serious and can lead to plant loss. Therefore, if late frost occurs and there is high humidity, be vigilant and watch the hostas to detect the disease in time and cure them with fungicide.
What temperature can hostas tolerate?
Temperatures of 32 ° F (0 ° C) and below can damage the hosta leaves. If there was a strong wind, the plants would definitely be damaged.
Some varieties can tolerate slightly lower temperatures (28 ° F), such as hostas with hard leaves. It also matters how long the frost lasted. If it was a few hours, then the plants may not get serious damage. If the frost was all night and repeated the next night, the damage would be significant.
Usually, the young leaves are very tender, and even a slight frost will leave its mark on them.
You need to cover hostas from frost
The first thing you can do to protect hostas from frost is to cover them. There are several other ways; however, shelter is a simpler and more effective solution.
Covering the plants, you form an air cushion over them that will protect them from frost. Under fabric, the air will heat up from the ground and move upwards, so there will always be a suitable temperature around the leaves.
It often happens that frosts occur before the leaves have unfolded, but young shoots have already appeared. In this case, you should bury them with compost so that they are not visible. Under such a cover, they will survive. Here it is important to use good clean compost so as not to harm the plants. Also, after frost, remove all compost from the shoots to avoid rotting.
In case the foliage has already unfolded, then you should act differently. If you have compact varieties of hostas or you have planted only a few bushes, then you can use plastic buckets or boxes of appropriate size. Just cover the plants with a bucket upside down. In such conditions, they will survive short periods of frost.
It is important that there are no holes or cracks in the buckets or boxes. Otherwise, the heat from the ground will not be retained, and the hostas will freeze.
With a large number of bushes, it will be most optimal to cover them all. The frost blanket is best for this. This is a special fabric that is used in the cultivation of plants and protects them from adverse weather conditions. You can buy it in any garden center.
Before covering, you should create a frame over the plants. As I wrote above, between the leaves and the fabric should be a layer of air. If the leaves touch the fabric, frost can damage them.
Often the frame is sold together with a frost blanket. If you did not manage to get the frame, then you can just insert a stick higher than the plant into the ground near each bush. Next, put the protective material on top. Put stones (or something heavy) on the edge of the cover to press it to the ground, the stones will not let the wind break it. You can also fix the frost blanket with pegs.
When should I cover my hostas?
Hosta is a very hardy plant, so it does not need to be covered for the winter. The only time this may be needed is spring. Depending on which hardiness zone you are in, late frosts can occur at different times.
Below you can see a table showing the date until which late frosts can occur in each climate zone where hostas can grow. A map of the winter hardiness zones can be found here.
|USDA Zone||Spring frost|
|Zone 3||May 15|
|Zone 4||May 15-20|
|Zone 5||April 15|
|Zone 6||April 10-15|
|Zone 7||April 15|
|Zone 8||Marth 30|
As can be seen from the table, the farther north, the later frosts can occur. In rare cases, frosts occurred in early summer.
Every year everything happens differently, so you should check the weather forecast, especially in the spring. If weather forecasters report a drop in temperature to 32 ° F (0 ° C), then you should not risk and cover your hostas. Even if the forecast was wrong and there was no frost, you will not lose anything.
When should you uncover hostas?
Hostas should not be uncovered immediately, as frosts may recur. Remove the cover during the day when it is warm, cover again at night. Then watch the weather for a few days. If the temperature does not fall below the critical level, then you can remove the cover completely.
Other ways to avoid frostbite
There are other ways you can avoid damaging your hostas with frost. The first is if the hostas grow in pots, you should move them indoors. It does not have to be a heated room, a garage or a basement is perfect for this.
If your hostas grow in the ground, but they are very valuable (rare varieties), and you do not have the opportunity to cover them. In this case, dig them up with the roots and put them in a plastic box. Fill all the free space in the box with earth and transfer it to the room, as in the first case. Do not let the ground dry out.
This is quite a time-consuming method and should be used if the plants are worth it. It is usually justified for miniature varieties.
Some gardeners use water sprayers to avoid frostbite. They turn on the watering at night, and the water slightly heats the space around the plants. As a result, they suffer less.
However, this is not the best way to solve the problem, as excess water can lead to hosta rot. Instead, I suggest using another method.
You need plastic buckets with lids or small plastic barrels with lids. If frost is expected, fill the buckets with warm water and cover them with lids. The water should not be hot but slightly warm. Place one bucket next to each bush so that the leaves do not touch the bucket. When you place the buckets, cover it all with a frost blanket.
If frost is also expected the next night, you should replace the cold water in the buckets with warm water.
Under such protection, hostas are not afraid of any frost. Of course, this is a lot of work and not cheap, but if you value your hostas, it is worth it.
I want to tell you about another method used in industrial fruit horticulture. It often happens that apple trees begin to bloom and suddenly late frosts approach. To preserve the harvest, the owners smoke their gardens.
This is a rather complex process whose essence is to create a cloud of smoke over the plants. This cloud will not allow the cold mass of air to touch the young shoots and leaves on plants.
Of course, this method is not suitable for many gardeners. However, if you live far from the city and you have a large garden, then it can be useful for you.
Will hostas come back after a freeze?
This is another common issue that worries many new gardeners.
In most cases, the hosta will recover from damage caused by frost, although there may be exceptions.
It often happens that frost damages only the leaves, sometimes even a single leaf is not completely damaged. Therefore, the plants, after a while, will be fine.
For vigorous varieties and for hostas that have already grown a large rhizome, the recovery process will be fast. A few weeks, maybe a month, and new leaves will appear. Of course, the plant will not look the same as if there were no frostbite, but in general, everything will be ok.
For medium varieties and hostas that do not yet have a large size, the recovery may be delayed for the entire season. The plant will look good only in late summer. It may also be that new leaves will not appear. New growth will begin only next spring. You should not worry about this; hostas are living organisms that need time to recover.
The most threatening late frosts are for dwarf varieties. They usually have a tiny crown, and frost damage can be fatal. They can freeze not only the leaves but also the stems and even the rhizome. Therefore, you should take care of them first. Due to their compact size, they can be easily hidden from low temperatures, such as under a plastic container or box.
What to do with damaged tissue?
If your plants have been damaged by frost, do not rush to prune them because you can remove the undamaged part of the plant. The leaves can first wither and then recover without signs of damage. If you prune all the leaves at once, then next year, the hosta will lag behind in growth, and the leaves will be small.
Wait a week or two and watch the plant. In case of partial damage to the leaves, it will begin to dry at the edges. Cut or tear off the dry parts of the leaf, try not to damage the living tissue.
If the leaves have withered and become transparent (watery), most likely, they will not survive. The best solution is to cut it completely. Prune it where it joins the stem. Leave the stems to grow, they will produce chlorophyll, and the plant will accumulate strength to recover next year.
In the worst case, if the stems are also frozen, try to cut them not too close to the roots. Otherwise, you can damage the dormant buds hiding in the axils of the stems, and next year the hostas will be small and not dense. Prune the stems at the height of at least 2 inches above ground level.
As I mentioned earlier, hostas can start to rot after frostbite. So you should keep an eye on them. If you notice the first signs of crown rot, then remove the affected tissue and spray the plant and the affected area with a fungicide designed for this purpose.
If the disease has developed too much, then you should dig up the plant and clean it from the soil. Then wash it with water and remove all the damaged parts of the plant. Soak the hosta in an aqueous solution of fungicide for a few minutes. Next, let the plant dry a little in the shade, then sprinkle the wounds with crushed ash.
Plant the hosta in a pot with clean, sterile soil and place it in the shade undercover. Water it moderately. The recovery process can take a long time.
Additional measures to reduce consequences and speed up recovery
- Create a complete shade for the hosta. After significant damage, the plant needs the most favorable conditions. Therefore, if it grew in partial sun, provide it with maximum shade. A healthy plant can withstand partial sun; the weakened need more gentle conditions.
- Give the plant enough moisture. The soil should be slightly moist, do not let it dry completely. The plant needs a lot of moisture to recover. However, you should not overwater it because it can lead to rot of the crown.
- Fertilize the hosta. The plant needs a lot of energy to recover quickly, so you need to fertilize it. In addition to organic compost and slow-release fertilizers, water the hosta once or twice a season with liquid fertilizer. You can also spray it with foliar fertilizer no more than twice a year.
- Pour a layer of mulch around. Pine bark or shredded hardwood bark is best suited as mulch. These types of mulch will cope well with moisture retention in the soil and protect the plant during the winter. The thickness of the layer should be 1-2 inches. Do not pour too much mulch, and do not pour mulch on the stems.
- Be sure to spray the hosta from diseases and pests. You need to act ahead and not wait for something bad to happen. In fact, pests and diseases primarily attack weakened plants, so a frost-damaged hosta is an ideal target for them. Two or three times a season, spray the plant with various fungicides and pesticides from reliable manufacturers.
- Protect hostas from snails. As in the previous case, you should use all methods of protection against snails. Iron sulfate and beer traps are best for this. I recommend using both of these methods together to get a good result.
- In no case, do not transplant or divide the hostas. This can lead to even greater weakening, and as a result, the plants will recover for a very long time.
Early frost damage.
Fall is another time of year when hostas can freeze. Early frosts can damage leaves that have not yet turned yellow. However, this is a normal process and will not harm the plant.
To avoid this, you can cut the leaves in late summer or early autumn. Remains of stems can be removed later in late autumn.
If you don’t do this, nothing will happen. The leaves turn yellow or freeze, and you just need to tear it off along with the stems from the crown at the end of the season.