Spring Freeze

Then a day before a scheduled trip to Florida, the temperature plummeted into the mid 30s. So he moved his houseplants back inside and did what he could to protect the tender tomatoes and herbs.

While in Florida, his housesitter told him that the temperatures dropped into the 20s, which meant potential disaster for many of his garden plants. The recorded low was 26 degrees F, yet when he got home, he discovered that most of his plants actually managed to survive the unexpected late-season freeze. However, several of them didn't get by unscathed.

Assessing the damage in the vegetable garden

The tomatoes seem to have survived fairly well beneath the fiberglass pots he had placed over them, but still he can't be sure. Tomatoes can survive temperatures in the low 40s without suffering any tissue damage, but cold temperatures can stunt their growth and shock them to the point where they'll never fully recover. Paul could go ahead and replant but decides to wait another week and see how they grow.

His potatoes also seemed to be fine after being left uncovered, but there is definitely some tissue damage. They should rebound and produce a bountiful harvest, because even though the top growth took a hit, the underground tubers were well insulated and will continue to produce new growth as well as more tubers.

Paul's lettuce survived just fine. In fact, the cold temperatures actually enhanced its crispness and sweetness.

All in all, Paul's ornamental plants did just fine, but a few of his Japanese maples did suffer because they had already started to produce tender, new growth. Although the new growth has been damaged beyond the point of recovery (figure A), secondary buds should produce new leaves to the point that within a few weeks and the trees should recover and look perfectly normal.

The situation is considerably worse for his crape myrtles because the freeze actually killed some of their top growth. Though hardy to USDA Zone 6 and marginally hardy to USDA Zone 5 with protection, crape myrtles will sometimes suffer dieback. In some cases, only a few branches are affected, but occasionally an entire trunk or even all the trunks will die. However, in most cases new shoots will appear in time and develop into new trunks. So, in the meantime, Paul removes the dead wood and cuts the dead trunks all the way back to the base of the plant. The same treatment can be done to other hardwood plants that show signs of damage.

The tips of the daffodil leaves were damaged (figure B), but they had already finished flowering the week before the freeze. So Paul leaves them alone to let the foliage die back naturally. By next year, they'll be good as new.

Assessing the winter damage

The top growth of Paul's akebia vine was hit hard, not by the latest freeze but instead by last winter's combination of extreme drought and cold temperatures. However, it's growing back at the base (figure C) and in no time at all should cover the area where it is growing. Because last year's dead growth is unsightly, he cuts it back to the ground to let it flush back out.

Some arborvitaes and cryptomerias (figure D) show signs of winter damage through the browning of their foliage. However, it's not unusual for these evergreens to discolor like this during the winter, so Paul decides to wait and see if the plants recover first before he does any pruning.

The fingernail test

Periodically severe weather damages plants. That's a fact of life for gardeners practically everywhere, even in subtropical climates. If you're not sure whether a plant is alive or dead following a severe winter or sudden spring freeze, you can always use the old fingernail test. To do this, scrape the outer bark of the plant with your fingernail, and if you see green tissue, chances are the plant will be fine (figure F). If you see brown tissue and the wood is brittle, most likely the stem is dead (figure G). If you're not sure, your best bet is to simply wait and see. Remember that not all plants bloom or leaf out at the same time. Wait until after the surprise spring freezes are out of the way to see if your plants will grow back out.