Amateur gardeners should take some steps now to protect their plants from frost. Frost in April can affect many plants and is especially damaging to tender new growth and flowers in the spring. You can reduce the risk by taking some simple steps that will protect plants from frost.
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How to protect plants from frost in April
There are a number of ways to protect your plants from frost in the spring:
- Less sensitive plants should be planted in a warm and sunny location, such as a south-facing wall, which will provide additional warmth and protection during the winter.
- Cover plants with a double layer of garden wool or other suitable protection when frosts are expected.
- Mulch the root zone of evergreens, conifers, tender shrubs and tender perennials with a thick layer of organic material to prevent ground frost.
- In cold weather, place container plants in a sheltered spot in the garden and wrap the pot in bubble wrap for extra protection.
- Leave the growth of more tender plants, such as wood anemone, until spring, as it provides valuable frost protection during the winter.
- Delicate plants can be lifted or moved to a more protected location or greenhouse. If this is not possible, you can protect them by wrapping them with bananas and tree ferns, for example.
- Remove tender perennials such as dahlias, cannas, geraniums and fuchsias before the first frosts.
- Protect fruit and strawberries from frost by wrapping them with willow rods or straw.
- Avoid applying nitrogen-rich fertilizers at the end of the season. They promote soft, succulent growth that is especially susceptible to frost damage.
- Plants exposed to early morning sun may thaw too quickly after frost. This can result in damage to flowers and young growth. Camellia and magnolia flowers, in particular, can be destroyed by a single frost.
- Plant tender bedding plants after the danger of frost has passed. Always harden off plants before placing them outdoors.
- Make sure tender plants are safely overwintered in the greenhouse by providing adequate heating or insulation.
How can plants protect themselves from frost?
Plants can survive frosts through several mechanisms:
- Sometimes the bark can insulate living water-conducting tissue (just as water pipes are insulated) to prevent water from freezing in the cells.
- Some plants accumulate substances, such as certain sugars and amino acids, that act as antifreeze agents and lower the freezing temperature of the cell contents.
- A more effective mechanism is the ability of some plants to “refreeze” their cell contents when the cell contents remain liquid despite falling below freezing. To accomplish this, plants must experience several days of cold weather before freezing, and this explains why even hardy plants can be damaged by a sudden fall frost.
Symptoms that plants are frostbitten
Sometimes frost damage occurs almost immediately after the frost. However, this is not always the case, and for some plants, especially woody plants, it may take several months for the damage to occur. Watch for the following signs:
- Spring frosts can damage tender young growth and cause burning and pale brown spots between leaf veins. This usually occurs on the exposed and upper edges of the plant.
- Severe frosts in winter can cause burning and browning of the leaves of hardy evergreens, which can eventually lead to the death of the plant.
- The leaves of tender perennials such as dahlias and cannas may turn black with the first fall frost. The stems usually fall off.
- Spring frosts can damage flowers and young fruit. This can result in a corky layer forming on the fruit, such as apples, and damage to the flower can result in little or no fruit forming.
- As a result of late spring frosts, summer bedding plants and tender vegetables such as potatoes and tomatoes can suffer leaf burn, browning, and even complete plant death.
- Prolonged frosts can cause leaf spots on some shrubs, such as photinia and gharial.
- The leaves of some plants that show early signs of frost damage appear waterlogged and dark green, turning black over time.
Treating plants for frost damage
Most gardeners will agree that it’s easy to be surprised by frost. And sometimes frost damage is simply unavoidable. What to do when damage has occurred?
- If no more frosts are expected, prune back the damaged growth by cutting it back to the undamaged side branch or bud.
- After pruning, apply an all-purpose fertilizer in the amount recommended by the manufacturer to encourage vigorous regrowth.
- If the fence or hedge forms “frost pockets,” create a gap or remove some of the lower growth to improve cold air drainage.
- Frost can pull newly planted shrubs out of the ground, so check and reinforce the soil around them.
- In gardens exposed to cold winds, create more protection by planting a shelterbelt.
- Gerbera and cinnamon leaves are blackened by the cold, but their roots are still alive and can be protected or pulled out and stored.
Important: Leave a plant that has suffered frost damage for now. Many plants are amazingly resilient and will rejuvenate from dormant buds at or below ground level. This takes time, so recovery may not occur until early summer. If it’s a high-value plant or you don’t absolutely need to fill the void, leave the damaged plant in the ground until mid-summer. If new growth has not formed by then, replace the plant.