Why do plants die in winter? There can be many causes. Let’s first explore how plants ordinarily react to low temperatures.
Before a sudden cold spell in Arizona, this hibiscus was doing great.
Photo Credit: Jenny Hooks
Unexpected freezing temperatures are taking a toll on the little bloomer.
Photo Credit: Jenny Hooks
Evergreens and deciduous plants adapt to cold differently. If you have evergreens that have dropped all their leaves, that’s a serious problem. For deciduous plants, it’s completely normal. Some evergreens survive pretty cold temperatures, such as conifers or cone-bearing plants, but many plants that thrive in subzero-degree climates are deciduous species.
Some plants fail to survive because they don’t “harden-off,” or adjust to cold temperatures. Tropical hibiscus would not be expected to survive below-freezing temperatures; on the other hand, hardy hibiscus – found as shrubs and small trees – generally lose their leaves as the days shorten and go dormant before winter arrives.
Plants sometimes never harden-off due to cultural practices; if they were pruned late in summer or were overfertilized in fall, the cold can catch them unprepared for winter. This often happens with roses. Underfertilized plants can suffer as well. If they don’t have enough carbohydrates stored in their stems and roots, they can fail to form buds in the spring.
If plants are small and recently planted, they might not have had time to establish good root systems by winter. Has it been cold enough for the ground to freeze? Freezing and thawing can dislodge your plants (since there’s no root system to hold them down), sometimes causing them to pop out of the ground – a condition called heaving.
And were the plants watered immediately after they were planted? Watering-in is a crucial element to good plant establishment. In dry winters, evergreens should be given adequate water; root systems don’t go dormant and need moisture to survive.
Finally, there’s what is called provenance, or the origin of the seed source of the plant. For example, a plant native to the Upper Midwest – let’s say bur oak – would not do well in the Deep South because it would not receive adequate cold in the winter (chilling); a bur oak native to south Louisiana likely would freeze in Fargo.
There’s a condition common to the southern US called “periodicity,” or the suddenness of change. In Texas, it can be 80 degrees F one day and freezing the next. We lose a lot of plants this way.
If you are expecting a severe cold spell in your area, consider placing some old blankets or quilts around tender plants’ roots overnight. Remove them in the morning if the sun comes out, so you don’t “cook” the root systems. Old-timers used kerosene lanterns and smudge pots in their orchards, so if you have one of these around you might try it out – but be careful – they can burn you severely if you’re not careful! (Plus, those old burners will stink up your landscape for a few days with that kerosene odor!)
If your plants have winter damage, it might not be visible until spring. Some signs include failure to form buds and develop leaves and flowers, cracked bark (particularly at ground level), leaf loss on evergreens, browning appearance of leaves, brittle limbs, failure of the plant to take up water and a general failure to grow.
The bad news: If you’re trying to grow plants that aren’t hardy to your area, you’re fighting a losing battle. If this is a particularly bad year, you may have to accept that you were unlucky and just start again in spring.
The good news: A bunch of dead leaves does not necessarily mean that your plants are dead. Think positively and take steps to protect your plants. Make sure they have adequate water, and don’t fertilize. Use something breathable to cover them (think burlap, not plastic). If branches break, prune them cleanly, but don’t prune randomly.