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Autumn is the golden time of leaf fall. Observant gardeners have long noticed that different species and even varieties begin to shed their leaves at different times. Winter varieties of apple trees stay green longer than summer ones. But it also happens that seedlings or fruit-bearing trees meet winter with leaves. Why did the apple tree not shed its leaves for the winter, and what measures should be taken? Does it fit into the norm and what does it signal?
Briefly about the physiology of November
Before thinking about the causes and consequences of the apple tree’s reluctance to part with foliage in the fall, let’s recall from the school botany course why this happens at all. First, the leaf loses its green color, which is associated with the destruction of chlorophyll. Why is it collapsing? Due to lack of water and with a reduction in the length of daylight hours in autumn. Important processes take place in the color-changing leaves: the outflow of nutrients into the parenchyma and the formation of a cork layer at the base of the petiole. When these processes are completed, the leaf falls off.
In the course of evolution, deciduous plants have adapted to severe prolonged cold. By changing the length of the day and temperature, the trees “determine” when it is necessary to start preparing for winter. Under natural conditions, healthy trees shed their old leaves in a timely manner, which signals the end of the growing season and going into deep sleep.
If the apple tree shed its yellowed leaves in a timely manner, then be sure that all growth processes have stopped in it, the bark has matured on a young growth and its frost resistance is at a high level. If the leaves have not fallen off, then peeling and cutting will not solve the problem. You need to help the apple tree in a different way.
What can cause failed leaf fall
Understanding the physiology of leaf fall, the gardener should not consider its absence to be the norm, even if this situation has been repeated for more than a year and the tree safely endures the winter.
In addition to external manifestations (freezing of young growth), characteristic in regions with severe winters, there may be hidden deviations, expressed in low productivity and short life of the apple tree itself.
Why does the leaf remain green and firmly attached to the petiole even in late autumn? Growth processes in the tree are still active and leaf nutrition continues, as there is a need for photosynthesis products. The reasons for this phenomenon may be the following:
- violation of the fertilizer application scheme: overfeeding with nitrogen in the second half of summer or introducing humus into tree trunks in autumn provokes an active growth of green mass; seedlings planted in well-filled pits lengthen their growing season and do not have time to go to rest before the cold weather;
- incorrect watering scheme or heavy rains in the fall after a dry summer: excess moisture in the soil prevents the apple tree from slowing down its growth; in a warm autumn, a second wave of shoot growth is possible;
- inconsistency of the apple variety with the growing region: southern varieties with a long growing season, planted in the Middle lane or the Volga region, simply do not have time to complete it by winter;
- a natural anomaly when winter comes early with a sharp drop in temperature.
In addition to the listed reasons for the violation of leaf fall, foliage can remain on the apple tree due to disease damage. For example, seedlings and individual branches of fruit-bearing apple trees affected by a bacterial burn turn black along with the leaves and become waxy. At the same time, the leaves hold tightly and do not fly around.
Partially, the leaves can remain on apple trees until late autumn, especially in winter varieties, but with the first winter winds they fly around. This phenomenon is normal and should not be alarming.
Common gardening mistakes
Unfortunately, summer residents notice too late the unpreparedness of apple tree seedlings for winter. In the fall, they begin to go to the dacha less often (due to bad weather), and after harvesting the root crops, they stop altogether. As a result: we arrived at the dacha after the first snow to cover the flowers, and there – a green garden. And what to do?
If the snow has already fallen and the leaves are frozen, then it is better to do nothing and hope for a mild winter. It would be a mistake to take a pruner and cut off frozen leaves or, even worse, cut them off by hand. By doing this, you will not help the apple tree in any way, you will exhaust yourself and leave damage to the young bark at the place where the petiole is attached. It is not worth picking off the leaves in the fall before frost, as they are only a sign, and not the cause of low winter hardiness. If there is still an opportunity to build a shelter for apple tree seedlings, then this will be more useful.
For an adult apple tree, wintering with leaves and unripened growth is only fraught with freezing. Young trees and seedlings may die from frost or dry out in early spring. Therefore, they require special attention.
Some gardeners recommend treating the leaves of the apple tree with a high concentration of pesticides in the fall in order to provoke a drop. Such a measure is unacceptable, since the tree gets a severe burn, and the leaves fall off as a result of severe stress. Such “help” will negatively affect the winter hardiness of the apple tree. It is possible to treat with chemicals, but they must have a specific purpose. We will consider them below.
What action to take
There are several recommendations that will help avoid problems with leaf fall on an apple tree:
- do not plant capricious southern varieties of apple trees on your site, purchase seedlings from local gardeners;
- do not delay planting seedlings, give them time to prepare for winter;
- when planting in the autumn, add only phosphorus and potassium to the planting pit under the apple tree, and leave organic matter and nitrogen fertilizers in the spring;
- follow the rules for fertilizing and do not overfeed, an adult apple tree grows well on soils with an average level of fertility and without fertilizers;
- under adverse conditions, fertilize the apple tree with phosphorus-potassium fertilizers.
If in the fall you see that your trees or seedlings are not going to shed their foliage, then you need to take measures to additionally protect the apple tree from low temperatures and winter winds. Prepare the frame for attaching the covering material.
Close the trunk circles of apple tree seedlings with a 10-centimeter layer of mulch from needles, peat, mowed grass or dry leaves without infection. Aesthetic and protective function will be performed by decorative chips from the bark.
It is advisable to wrap the trunk of an apple tree seedling with covering material up to the crown. If the seedlings are annual and compact, they wrap the entire crown with leaves. You can use burlap or agrofibre.
How to properly cover a young apple tree, see the video:
This procedure will help the apple tree to endure frost. If there is a lot of snow, then sprinkle them with trees. Since a leaf remains on the branches, it is necessary to remove the shelter immediately after positive temperatures are established so that the buds do not rot.
Features of the use of preparations for dropping leaves
If at the beginning of autumn apple trees do not show signs of slowing down growth processes (yellowing of leaves, lignification of young shoots, differentiation of buds), then special preparations based on growth regulators can be used.
Ethylene is synthesized in plants to activate leaf shedding. Powerful natural growth inhibitors are coumarin and abscisic acid.
Synthetic inhibitors designed to remove leaves are called defoliants. Ethylene-based defoliants have previously been used in horticulture.
Do not use outdated toxic drugs for processing apple trees in the fall: whopper, etafon, etrel, magnesium chlorate, decitrel and others. Such treatments will do more harm than good. Side effects include damage to growth points, marginal burns, and reduced viability.
In industrial nurseries, to prepare apple seedlings for digging, copper chelate and sitrel (based on silicon) are used. Spraying is carried out only after the treatment of trees with sulfur-containing preparations. The effectiveness of the defoliant will depend on the condition of the tree, weather conditions during the growing season and during the dormant period.
Penetrating into plant tissues through the leaf, defoliants accelerate the aging process, destroy chlorophyll in the leaves and cause artificial leaf fall. Treatment with preparations should be carried out at the beginning of the natural aging process of the leaf in order to accelerate it. Earlier use leads to reduced efficiency.
Defoliation is also carried out with a forced transplant of an adult tree. In any case, it is not recommended to exceed the dosages indicated by the manufacturer. Failure to follow the instructions will lead to the death of the kidneys and growth arrest. With a mild degree of damage in the spring, there is a delay in bud break and, as a result, a shift in vegetation and again leaving in winter with leaves.
In recent years, with the vagaries of nature, foliage often remains on the apple tree in winter, regardless of the region of cultivation. But not only the natural factor is the cause. Often, the reluctance to study zoned varieties or the deliberate acquisition of large-fruited and sweet apple trees of southern varieties leads to the death of the orchard.
The remaining green foliage indicates a low winter hardiness of the apple tree, so the main task of the gardener is to increase winter hardiness and preserve shoots and buds. Once again, we note that partial leaves with lignified shoots should not be alarming. For some varieties of apple trees, this phenomenon is especially characteristic, for example, for the common Antonovka.