Colder weather can decrease plant enzyme activity. This then disrupts plant nutrient intake because plants secrete enzymes to digest surrounding materials for soil. Consequently, this can stunt growth or more severely cause them to die.
I did some research and found out that houseplants need to be taken indoors before overnight temperatures dip below 45 degrees. Most tropical plants suffer harm from temperatures below 40 degrees.
While some plants are well adapted to the cold, a bad season can cause damage to even the hardier trees, shrubs, and perennials. Plants are vulnerable to a range of different damage throughout the winter season. Simply freezing, for those plants that are not cold tolerant, usually means death for the plant.
First, as the days shorten and the cold sets in, many plants become “hardened”. Water is pumped out of plant cells into the roots and any remaining sap, which is a sugary solution, often acts as antifreeze. Broadleaf trees, like maples and oaks, shed their thin, flat leaves each fall to reduce water loss.
Plants grow low and close together to protect themselves from the wind by trapping pockets of air. They usually have hairy stems and tiny hairs on their leaves to trap heat, and their leaves are thin and waxy to reduce water loss through transpiration.
There are any number of adaptions plants have developed to survive sub-freezing temperatures, and probably the first that comes to mind is dormancy. Dormancy is an adaptation used by many plants to conserve resources and survive winter weather extremes by entering in to a period of rest or metabolic inactivity.
Plants can cool themselves by pumping water out through the leaves for a kind of swamp cooler effect. They can also make “heat-shock” proteins which reduce problems from overheating. All these strategies do take resources away from a plant's other needs like growth, flowering and fruiting.
Leaves Wilt or Droop — As the cell damage occurs, the leaves will lose their rigidity and start to droop or even curl in on themselves. If you have been watering as usual, it is time to consider other causes for your plants' wilting and drooping appearance including cold shock.
The amount of damage depends on the severity and duration of the freezing temperatures. If you have light freezes for short periods of time, plants can usually recover. After hard, long freezes, there's no guarantee. After the freeze, you should be patient.
When Should You Cover Plants? Cover your plants at night and remove them during the day when the temperatures rise above 32 degrees F, so that the soil can warm up again. Some outdoor plants won't survive the harsh conditions of winter, bring them inside and use these tips for caring for them through winter.
Cold Temperature's Effects On Plants and Vegetation
MODERATE FREEZE: 25 degrees F to 28 degrees F / -4 degrees C to -2 degrees C. Wide destruction on most vegetation with heavy damage to fruit blossoms and tender semi-hardy plants. SEVERE FREEZE: 24 degrees F / -4 degrees C and colder. Heavy damage to most plants.
A fabric covering is best because it will allow moisture to escape while still protecting your plants from frost. Fabric coverings will prevent the freezing air from coming into direct contact with the moisture on the plant while also capturing the heat that is radiating from the ground.
Skip Watering if: The ground is frozen. There's a hard freeze (at least 4 hours of 25 degrees F) The temperature outside is under 40 degrees.
Avoid watering when temperatures are below 40°F or when sustained freezing temperatures are expected within 24 hours as this water will freeze and not be available to the plants. Evergreen foliage can also be protected from excess water loss using anti-desiccant sprays. These sprays are sold at most garden centers.
Choose days when no snow is on the ground and the soil isn't frozen. In cold weather, water should be trickled slowly into the soil. Water only when air temperatures are above 40 degrees F.
The general rule of thumb is that most plants freeze when temperatures remain at 28°F for five hours. Of course, there are exceptions to this rule. Seedlings, with their tender new leaves, often give up the ghost when temperatures dip to 32-33°F. Tropical plants have differing low-temperature thresholds.
Second, know that a light frost—32°F and colder—kills all tender plants such as tomatoes. Hardier plants such as spinach and kale will survive until there's a hard freeze—28°F and colder.
To know when to cover your plants, you need to know when the plants you have are susceptible to frost damage. Some frost-tender plants need to be covered as soon as the temperature hits 32°F, while others can handle lower temperatures and/or longer freezing periods.
As the wind grows cooler, leaves drop and snow begins to fall, it's easy to look at a shriveled, brown plant in the yard and think it's dead. But that's just what's above the surface. Below ground, the plant is still alive, just settled in for a long winter's nap.
Plants respond to cold temperatures by activating metabolic pathways that protect their cells from cold and freezing conditions. One protection strategy is to accumulate sugars, which decreases the temperature at which ice forms, similar to the effect of putting salt on roads.
Exposure of plants to extreme temperatures will limit the ability of the plant to produce fruit due to disruption of the pollination process. The magnitude of this impact varies among species; however, there is a consistent negative impact on plants.
Deciduous: trees and plants that lose their leaves in the fall. These species will go dormant during the winter to conserve energy. Because they slow down so much in the winter, these plants store up nutrients during the spring and summer months to prepare for the winter.
A covered porch usually provides protection from light frost, but the garage or sun room is better for freezing temperatures. A couple days in darkness won't hurt the plant. Or move them out during the day and back in at night, if cold temperatures persist.
40 to 50 degrees can cause death in one to three hours. 32 to 40 degrees can cause death in 30 to 90 minutes. 32 degrees or less can cause death in as little as 15 to 45 minutes.