Spring is in full swing, the most exciting concerns about the baby seedlings growing on the windowsill are behind us (they are no longer babies at all), gardeners and florists are entering the "finishing stretch". The main task of this stage is to properly prepare the seedlings for relocation to flower beds and vegetable gardens.
The speed of adaptation of plants in a permanent place, and therefore the rate of growth of roots and green mass, the time of entry into the next vegetative phase, and ultimately the volume of the harvest for garden crops and the quality of flowering for ornamental plants, will depend on how well the pre-planting preparation goes.
The most reliable and only true way to reduce transplant stress for plants is to gradually bring their maintenance conditions closer to those in which the seedlings will find themselves in the near future. That is why it is so important to start hardening off seedlings at least two weeks before planting.
Preparing seedlings for transplanting into open ground
After "moving" into the ground, seedlings of tomatoes, peppers, cucumbers, cabbage, pumpkins or flowers will experience multifactorial stress: from the usual favorable conditions of the apartment, where they were "blown away from dust", they will find themselves in the harsh circumstances of life outside. That is, they will experience all the climatic features of the region: temperature changes during the day and night, prolonged precipitation, drying gusty wind, an abundance of microorganisms (including pathogenic ones) in the soil, "creeping" harmful insects.
To prevent seedlings from stopping their development, getting sick and withering after transplantation, you need to "acquaint" the seedlings with at least some of the future tests in advance: accustom them to outdoor temperatures, direct sun and wind. This will help strengthen the plants' immunity, increase their adaptive abilities and teach them to rebuild physiological processes depending on external conditions.
When to start hardening seedlings
You can plant seedlings in open ground only after the soil at a depth of 10 cm warms up to at least 15 ° C. In each specific region, this happens at different times, which means the timing will differ. For example, in the middle zone, tomatoes and cucumbers are usually planted in open ground at the end of May, and closer to the north, the planting date will have to be shifted to mid-June.
Hardening should begin 10-15 days before the expected planting date, that is, in the middle zone this will be approximately mid-May, and in Siberia or the Urals - early June, not earlier.
If you plan to plant plants under temporary film cover, then the dates of all procedures can be shifted back one or two weeks according to the calendar. In any case, when planting in open beds, it is critically important to take into account the weather forecast and have covering material ready in case of a sharp cold snap at night.
How to care for seedlings during the hardening period
Hardening of plants begins by gradually lowering the temperature in the room. To do this, you need to regularly open the windows and ventilate the room both during the day and at night. After the seedlings get used to it, you can take them out onto a glazed, unheated balcony – there, the differences between day and night temperatures will be felt more strongly, while the plants will be protected from drafts and scorching sun rays.
If you live in a suburban area permanently, then the stage of moving to the balcony can be replaced by "walks" in the open air. About 7 days before transplanting, start taking the boxes with seedlings outside, placing them in a shaded place, and keep them there for two to three hours. Gradually increase the time to 6-8 hours, while accustoming the plants to sunlight.
The air temperature during "walks" should remain within acceptable limits: not lower than 7-10 ° C for cold-resistant plants (cabbage, salad crops, celery) and at least 12-15 ° C for all the rest.
Seedlings of some cold-resistant crops (for example, cabbage) are initially grown in a cool room, trying to protect them from overheating. In this case, hardening should begin immediately with being outdoors or in an unheated greenhouse.
During the hardening process, all other care procedures (preventive treatments, fertilizing) should be continued, but it is advisable to limit watering of plants, accustoming them to possible errors in the water regime. It is also important to protect seedlings from gusts of wind and remove phytolamps if you have been illuminating the plants until now.
A week before planting, it is recommended to fertilize with complex fertilizers (for example, Agricola) to increase resistance to stress.
The final stage of hardening occurs 2-3 days before transplanting. At this time, the plants can be left in direct sunlight for 6-8 hours. Crops that will be grown without shelter can be left outdoors overnight the day before planting. Water the seedlings generously 6-10 hours before transplanting - thanks to a well-moistened earthen lump, the roots will be less damaged.
Preparing seedlings for planting in a greenhouse
Why is hardening necessary even when planting in a greenhouse? Because the growing conditions in protected soil will also differ from indoor conditions. Plants in a greenhouse will not have to suffer from strong gusts of wind or prolonged rains, but they will receive a full range of "sensations" from overheating, changes in humidity, lack of light and fresh air.
In addition, heat-loving crops (eggplants, peppers, cucumbers, tomatoes, watermelons) are usually grown in a greenhouse, and for them, proper preparation for changing conditions is of particular importance.
Adjusting the watering regime
It is critically important to "accustom" greenhouse crops in advance to the watering regime that will be organized for them in a permanent place.
If a drip irrigation system is installed in the greenhouse, then you will have more opportunities to choose a comfortable regime for plants depending on the type of soil and the weather "overboard" - just set the timer to turn on once every 3-5 days, based on the needs of the crop.
If there is no automatic watering system, and you are at the dacha only on weekends, then you should start adjusting the frequency of moistening and the volume of water in advance so that the seedlings "learn" to withstand week-long pauses between waterings.
For example, watering tomatoes once a week is considered useful - in search of moisture in the dried soil, their roots grow better, going into the ground to a greater depth. With frequent watering, the opposite happens - the root system is located only in the upper layer of the soil, which has a negative effect on the yield.
Preventive treatment
Another important point in preparing greenhouse crops for transplantation is disease prevention. Since pathogens spread extremely quickly in a closed space and with dense planting, as is often the case in greenhouses, it is important to prevent even minimal symptoms of ill health and carry out preventive treatments in a timely manner.
To protect seedlings from diseases, biofungicides are usually used, which are sprayed on the crown of plants once every one or two weeks (Fitosporin-M) or embedded in the soil during planting. Insecticides (Fitoverm) will help prevent the appearance of pests or get rid of "settlers".
If you find affected bushes among seedling stocks, be sure to carry out preventive treatment of all plants. And it is better to get rid of severely damaged specimens (if there are not many of them) and not plant them in a greenhouse with the rest, putting the entire harvest at risk.