Table of contents:
Plant dormancy is a state in which no visible plant growth occurs. During the rest period, most of the physiological processes in the plant are suspended, and some stop altogether. It is obvious that the transition to a state of dormancy is a consequence of the adaptation of plants to climatic changes in the regions where they grow in nature. The plant organism practically stops functioning, does not waste energy resources and is not damaged by exposure to low temperatures for a long time.
In plants, organic and forced dormancy are distinguished.
Organic plant dormancy
It is caused by the hereditary properties of plants that have developed in the process of evolution. These are the so-called endogenous (deep) plant processes programmed for each species, genus or family under the influence of climatic conditions. A number of such processes are unshakable and never broken.
There is such a science, Phenology, which studies and summarizes the totality of information about seasonal natural phenomena, the timing of their occurrence and the reasons for their occurrence. The famous scientist, founder of the Moscow school of geobotany Vasily Vasilyevich Alekhin classified plants according to the type of alternation of generative and vegetative phases into three groups: proant plants, mesant plants, and metant plants.
Proantas are plants in which flowering occurs before the growing season or at the very beginning, for example, cherry. Remember, in the spring, there is not a single leaf on the cherries yet, but they are all snow-white from flowers. Among indoor flowers, this is amorphophallus, and among greenhouse flowers, the classic proant is amaryllis (not to be confused with hypeatrum). It blooms in a leafless state before growing. In addition to amaryllis, there are representatives of this group among orchids: the genus Pleione Pleione, or, for example, Calanthe dressed Calanthe vestita.
Mesants are plants that bloom in the middle of the growing season. Most plants belong to this. They build up their leaf mass and bloom at the same time. These are, for example, hibiscus, adenium, clerodendrum, jasmine, gardenia, azalea, anthurium and others.
Metants are plants that bloom at the end of the growing season. There are few such plants, among them, for example, poinsettia, cyclamens, many orchids (phalaenopsis, cymbidium and others). After flowering, they have a dormant period.
To change endogenous processes, the plant needs a certain time, a certain temperature, moisture and lighting. When studying the life of plants in nature, scientists noticed that the transition from one state to another (from vegetation to dormancy and vice versa) manifests itself in advance, some time before a sharp change in climate. So, plants of temperate latitudes begin to enter the resting phase long before the onset of real cold weather. If you grew such trees as bonsai, for example, the palmate, you might notice: even if you move containers with plants to a warm room in the fall, the trees will not resume vegetation and begin to grow leaves, they will continue to go into a dormant phase.
Short-term warming during the period of organic dormancy does not cause a transition to the growing season. In rare cases, prolonged climatic anomalies can cause premature budding. And even in this case, the plants "swing" slowly, the speed of awakening is not the same as usual in spring. But the primary role in changing the phases of vegetation and dormancy is played by the genetic program inherent in a particular species and genus of plants.
In general, there are few plants in indoor floriculture, from areas with a temperate climate, for the reason that most of them are deciduous. And even conifers, which can be grown as bonsai, require very cold wintering and necessarily go into a phase of organic dormancy. But even in summer, such plants in apartments suffer - the air is too dry and warm for them, and therefore they live for a long time only in greenhouse conditions.
Forced dormancy of plants
Forced dormancy occurs in plants with a lack of favorable conditions for growth. This is, first of all, a decrease in illumination in winter and a decrease in temperature. If there is enough light and heat, then the forced rest does not come.
Many tropical indoor plants can do without a dormant period. They are evergreen and in conditions of less light in winter and cooler content (16-18 degrees) simply slow down growth. If the temperature drops below, up to + 10-12 degrees, then the plants completely stop growing, but the processes of photosynthesis in most tropical plants stop when the temperature drops below 7 degrees.
I want to note that recently, modern materials and technologies in the construction and arrangement of houses have significantly changed the winter quarters of our flowers on the windowsill. Remember the old wooden frames that you had to plug and glue? Despite their best efforts, they significantly reduced the temperature on the windowsill. The room was 24-25 degrees, the window was 18-22. This was enough for the plants to survive the forced winter dormancy under conditions of short daylight hours and low light.
But now almost every apartment has plastic windows. And they hermetically close the window opening, reliably protected from blowing. The temperature on the windowsill is only 2 degrees lower than in the room. And only at the moments of airing, it briefly decreases by 5-10 degrees. As long as the street is just above or slightly below zero, many people leave the micro-ventilation. But as soon as the subzero temperature is stable, the windows are tightly closed for most of the day. But the illumination compared to the summer is significantly reduced.
All this leads to the fact that indoor flowers continue to grow, but due to a lack of light, they greatly lose in decorativeness: the shoots are stretched, the leaves become smaller, grow frail and pale. In some cases, especially unpretentious pets can be radically cut in the spring, divide the bush into children, selecting the strongest and most elongated ones … But some plants do not tolerate such discord between light (more precisely, darkness) and dry warm air of rooms, and die.
Houseplants can be divided into three groups
To protect the plants on the windowsill from the hot air of the batteries, you can make such a showcase (made of glass, plexiglass or polycarbonate). The width (depth) of the showcase is equal to the width of the window sill, and the height of the outer wall is at least 50 cm. Such a showcase allows you to reduce the temperature around the plants by 5-10 ° C compared to room temperature.
- Plants, under favorable growth conditions, without a dormant period (tradescantia, cyperus, palms, croton, ivy, etc.). These plants can be kept in winter under normal conditions, but it should be taken into account that some loss of leaves and growth retardation are natural with a decrease in light in winter.
- Plants that have a mandatory dormant period throughout the year (orchids, gloxinia, caladium, cypress, amarylis, myrtle, most cacti, etc.), which consists in a slight decrease in temperature and a reduction in watering. At the same time, the temperature of the content varies greatly in different families and species. For example, there are cacti that need to be kept at + 5 ° C in winter, while others need + 12 ° C. Plants of this group painfully tolerate the absence of a dormant period. For them, it is needed to lay flower buds and bloom safely next season. In the absence of a dormant period, some plants may not bloom at all, while others may simply die.
- Plants for which dormancy is optional, i.e. they may or may not have it. These plants can grow throughout the year (some dracaena, ficus, syngonium, ferns, crinums, etc.)
The duration of the rest period
The duration of dormancy is influenced by various external factors: temperature, soil moisture, light intensity, etc. The duration of organic dormancy and the need of a particular plant for cold wintering are influenced by hereditary factors.
For tropical plants under conditions of a forced dormant period, the following dependencies are true:
A low ambient temperature lengthens the rest period, a high one shortens it. Forcing plants is based on this.
Dryness of the soil lengthens the dormant period, moisture reduces it.
Intense lighting (increased illumination) also shortens the rest period.
In central Russia, climatic conditions are such that in winter daylight hours are shortened, it is not enough for good growth of natives of the tropics and subtropics. Therefore, most plants slow down the growing season and are ready for a dormant period. In this case, you should reduce the frequency of watering, lower the temperature in the room. The general conditions for keeping in winter for specific plants differ - all the recommended indicators are given in the encyclopedia section for each plant. If it is not possible to lower the temperature, then you need to increase the illumination. For this, you can use fluorescent lamps or LED lamps. But to supplement the illumination of the plants not when it is convenient for you, but during the day, so that the total daylight hours are 10-12 hours, this is approximately from 7 am to 7 pm or from 8 am to 6 pm.
Plants that have a mandatory dormant period (gloxinia, cyclamen, pomegranate) are best placed in a cool, dark basement, protected from drafts, but at the same time with enough fresh air. In city apartments, the best place for these plants to overwinter is the bathroom (under the bathtub) or the staircase.
The beginning of plant growth is a sign of the end of the dormant period. If you removed the pot with gloxinia cut for the winter under the bath, then, looking there in the spring, you will find how shoots appeared from the ground - it's time to get the flower and place it in its usual place on the window. Organic (programmed) rest is over. The usual regime of watering and feeding is gradually resumed, if necessary, the plant is transplanted. If you do not get the plant and place it in the light, the genetic program will still not allow it to "sleep" until better times. Growth will begin, but several stunted leaves will grow, and then, in the absence of light, the plant will die.
Those plants that do not need a dormant period (violets, balsam, cyperus, etc.) and are forced to winter on the windowsills need to be watered and fed less during the month, when the day is shortest. Winter-flowering potted plants that do not need a dormant period should be watered regularly and fed during flowering.
Problems of wintering indoor flowers
In fact, quite a lot of problems, diseases and plant death occur in the winter months, when there should be a forced or mandatory period of dormancy. Mainly from violations of conditions of detention: with a lack of light, not enough cool temperature, the proximity of the heating system, too dry air, plants grow poorly, often stretch, the stems are bare in the lower part, flowering does not occur in spring.
If you do not want or cannot arrange a dormant period, balance the conditions so that the plant grows correctly in winter - so that there are no twisted and small leaves and elongated shoots. To do this, first of all, you need to stop fertilizing and increase the lighting with one or more fluorescent lamps.
It's so simple - in any hardware store you can buy fluorescent lamps - within 300 rubles. A couple of screws in the wall and your plant will not only not lose its leaves over the winter, but it can bloom for a long time and please the eye. However, this applies only to plants that do not need a mandatory dormancy period.