Gardeners advise against sealing greenhouses at night too early
A gardening specialist recommends keeping tomato greenhouse doors open at night throughout summer, since sudden temperature swings stress the plants. Greenhouses should only be closed once cold night fogs set in.
As autumn approaches, gardeners often wonder when the right time is to start closing tomato greenhouse doors at night. Saiva Bražūne, a representative of the gardening business "Neslinko", explains there's no need to rush this decision, advising that greenhouse doors stay open at night throughout the summer season to prevent condensation from building up inside.
Why sudden changes harm the plants
According to the specialist, cool night temperatures themselves aren't the biggest danger to tomatoes, since in nature plants gradually adapt to changing temperatures. Problems arise when a person disrupts this natural process by abruptly closing greenhouse doors and vents, causing sharp shifts in temperature and humidity that stress the plants.
It's also worth remembering that plants breathe, and in small home-garden greenhouses, where tomatoes often grow all the way to the ceiling, a sealed space quickly becomes overly humid from this respiration. Such conditions encourage the rapid spread of various types of rot.
When to start thinking about retaining heat
It becomes worth considering closing the greenhouse at night once evening air temperatures drop to 8–10 degrees. Even so, an open greenhouse is usually still warmer than the outdoors, since heat radiates from sun-warmed tomatoes, the soil, and barrels of water kept for watering.
Greenhouses should be fully closed only once cold night fogs appear, which can occur at different times across various parts of Latvia. Even then, plants shouldn't be kept in a completely sealed space — a vent window should always be left open, or, if there isn't one, the doors should not be closed all the way, or only their lower section should be shut.
