This January brought severe weather, including snow and freezing temperatures, to many areas across the US. Some of the winter storms were not kind to our plants and may have caused dieback or worse. As we survey the damage, it's easy to feel discouraged and give up hope on the plants with the most damage. However, plants can make miraculous comebacks and surprise us if we care for them properly and give them time to recoup. Here are some tips for assessing the damage and helping your plants recover from winter damage.
1. Deciduous shrubs - some deciduous shrubs like hibiscus, burning bush, and butterfly bush are late to leaf out in the spring. Those plants may come back from the ground, or their branches may start producing new growth, depending on the plant and the winter damage to it. If you still don't see any growth in early June, the plant is more than likely dead, but don't throw in the towel too early.
2. Tender and tropical plants - extended hard freezes are most damaging to tropical plants and tender herbaceous perennials, including lantana, elephant ear, annual geraniums, tropical ferns, begonias, impatiens, fuchsias, salvias, and purple fountain grass. If you notice these plants have mushy black or brown stems, the plant may not be able to recover. You can remove the mushy parts to help prevent future fungal and bacterial infections.
3. Succulents and cacti - many may still be alive, depending on the variety. An easy way to tell is by the "firmness test". Feel the center of collapsed leaves or center of the plant for rigidity. You can also feel the trunk on larger succulents like yuccas and agaves. If it's still firm, then the plant should be okay. If it's mushy, that means the crown has rotted and the plant is probably dead.
4. Evergreen shrubs - some foliage may turn brown due to winter burn. As long as some of the foliage stays green, the shrub will likely recover. The shrub may also lose some of its leaves in spring. Evergreens naturally shed their oldest leaves in the interior of the shrub and replace them with new growth at the ends of branches. If the newer growth is affected or new growth does not replace the old, the shrub may be in trouble.
Dead stems don't always mean the shrubs are dead, but it will take a long time for the shrub to recover and look nice again. Some broadleaf evergreens, like nandina and mahonia, may die back to the ground and start new growth from the ground up, rather than on the existing wood. Some may lose most of the upper branches and leaves, but retain lower growth. Here is how to assess the damage on an evergreen:
Twigs - these should still be flexible and springy.
Leaves - dead leaves should shed naturally and easily. If all the leaves turn brown, the shrub may not recover, especially if it is a conifer like pine, spruce or fir.
Scratch test - a simple scratch test on one of the lower branches can reveal the damage. Simply make a scratch or small cut on a lower part of the plant. If you see green, that's a good sign. If you see nothing but brown, that part of the plant is dead.
5. Potted plants - many borderline hardy plants growing in containers may die after a harsh winter. The pots provide less insulation than the ground soil and expose the roots to greater fluctuations in temperature. You can try to salvage these plants by moving them to a protected space like a garage, shed, greenhouse, or even covered porch for the remainder of the season.
Tips to help recovery
1. Once the damage has been done, few interventions will help your plants recover faster. To provide extra insulation for the rest of the winter, apply a thick layer of mulch over the root zone.
2. Water evergreens before a hard freeze if conditions have been dry.
3. Avoid fertilizing the plant until new growth appears in the spring.
4. Cover the plant with burlap or plastic to provide insulation during future cold snaps. Tie up branches that may be susceptible to breakage during future snow storms.
5. For deciduous shrubs, you can prune out obvious dead or damaged growth. The plant is dormant and will not mind a trim. Avoid pruning shrubs that flower in the spring or bloom on old wood because you'll likely remove flower buds.
6. Avoid pruning borderline hardy perennials and shrubs until growth is well underway in the spring. Some exotic evergreen shrubs like grevilleas, fatsia, rosemary, cistus, loropetalum, hebes, and gardenias are sensitive to prolonged hard freezes and will "sulk" until temperatures pick up in late spring. Some tender perennials like phormium, certain salvias and euphorbias, and cordyline are also susceptible to cold damage and may need extra time to recover. Avoid cutting back these plants until late spring, and only remove dieback to avoid further stress to the plant.
7. Plants may come back from the ground up, which means the old growth is all dead, but not the plant's roots. It may take a while, but watching a plant come back from the dead is a satisfying process and worth your patience.
8. If you don't want to take the wait and see approach, feel free to start replacing plants after the last frost date.