A number of environmental cues factor into signaling plants along the various stages of their life cycles. Seasonal changes such as temperature and day length help plants determine the right times to enter each stage. Cold hardiness plants are able to regulate their needs based on these environmental factors, including when spring arrives later or earlier than average.
Let’s examine a few examples.
What do plants do to survive cold winter temperatures?
Some plants with woodsy stems can prepare for cold winter months by “shunting” the water from their exteriors (twigs, leaves, branches and trunks) to their interior core and root system. This process is triggered by shorter amounts of sunlight per day and cold weather mornings and evenings.
The plant cells recognize these signals and releases chemical compounds internally to begin the shunting process. This conserves as much of the sugars, salts, and organic compounds in the interior of the plant as the leaves are left barren and fall away. With all of its energy resources bundled tightly within, it has lowered its own freezing temperatures point of interior cells and tissues, which allows it to survive the winter season of lower temperatures.
What happens when spring comes early and temperatures spike prematurely compared to the average last frost date?
Plants are getting input from their environments all winter long, and they sense as the days begin getting longer and temperatures gradually rise. They sense their need to to leaf out as early as they can, since they want to take advantage of as much of the prime growing season as possible. For many plants this means before the strong heat of the summer’s sun arrives.
During this time, plants begin moving water and nutrients out of their core, from roots to the developing leaves and flowers. Thus, the concentration of sugars, salts, and organic compounds in their roots and core decrease, which leaves the plant’s core tissues vulnerable to surprise cold temperature snaps.
For all species, it is risky to leaf out too early since late frosts can deeply damage the core of the plant and/or its leaves and flowers.
What can I do if my plants have suffered from a late frost after budding leaves and flowers?
Do nothing! Removing the dead and/or damaged leaves and buds may stimulate the plant in the same way pruning does. The plant may then spend all of its energy producing more right away. Or, this could expose additional vulnerable parts of the plant at a time when it needs to focus on recovery.
Instead, if you do nothing, the plant can compartmentalize the damaged areas, withdrawing nutrients temporarily from those areas to recover and prevent additional damage.
Once the threat of late frosts are past and new growth has started beneath the old, then you can prune.
Data According to the National Centers for Environmental Information: