The winter cold was very late in arriving this year. As a northern transplant, I love the cold weather because it always puts me in the holiday spirit. I had to find other ways of doing that this year. It makes my work a lot easier as well and this is always a welcome break for people in the landscaping business after a long, hot grueling summer of backbreaking work.
Most landscapers take an extended vacation this time of year since the growth rate decreases significantly. The lawns I maintain are the most lush and green lawns in their neighborhoods after my two week vacation. Actually this is a great thing going into the cold and then the dry season. Well the cold has arrived but will be followed by temperatures back in the 70s and 80s.
Our landscapes have gone into a slight dormancy as the recent lower temperatures have been low enough to cause a slight slowing of growth for tropical and subtropical plants. Tropical plants and annuals do not normally adapt to withstand temperatures below freezing and can be injured when temperatures reach below 50 degrees F. Fortunately, freezing temperatures are rare for South Florida and even more rare on coastal islands like Marco.
However, subtropical plants can, under the right conditions, acclimate to withstand freezing temperatures. The ability of plants to withstand freezing temperatures is affected by temperature fluctuations and day lengths before a freeze. A gradual decrease in temperatures helps plants to harden and withstand cold temperatures. These recent periods of lower temperatures can help to hardened our plants. However these were followed by periods of warmer temperatures which can de-acclimate plants resulting in budding or flowering making these plants more prone to freeze injury.
Cold injury can occur to the entire plant or just some parts of the plant such as fruit, flowers, buds, leaves, trunks, stems or roots. The fruit and roots are most vulnerable to cold damage. Especially roots of container plants. This damage won’t usually become evident until the plant is stressed by higher temperatures in the spring.
Another type of cold injury is plant desiccation or drying out. This causes leaf-tips to burn in mild cases and totally brown leaves in severe cases. Desiccation occurs when dry winds and solar radiation cause the loss of more water from the leaves than can be absorbed and transported by a cold or frozen root system. Leaves on a lot of shrubs and trees will begin turning yellow and dropping in the next few weeks after a cold spell. Hibiscus, gardenias, gumbo limbo trees, and most tropical and subtropical plants in our landscapes.
Steps, from selection of proper planting sites to good cultural practices, can help acclimate plants to cold temperatures and protect them from temperature extremes.
Site selection. Temperatures can fluctuate from one location to another in most yards. Thus, micro climates should be considered when choosing the planting site for cold sensitive plants. Tender plants should be planted in areas with good air flow never in low areas where cold air settles. Arranging plants, fences and other barriers to help protect plants from the cold winds of advective freezes can help. Avoid poorly drained soils which will result in shallow, weak root systems making plants more susceptible to cold damage.
Plant nutrition. Properly fertilized plants will tolerate cold temperatures better and recover from injury faster than weak, underfed plants.
Shading. Tree canopy covers can reduce cold injury caused by radiation freezes. Canopies can raise night temperatures under them by reducing heat loss into the atmosphere. Early morning sun after a freeze can cause bark splitting on plants and the shade can help prevent this problem. However, be sure shrubs planted in the shade are shade tolerant or you will end up with sickly plants which will also be more vulnerable to cold injury.
Watering your landscape before a freeze can help because a wet soil will absorb more solar radiation than dry soil and will re-radiate this heat during the night. However, it is not good to saturate soil for prolonged periods as this could cause root damage.
Avoid late fall pruning which can result in budding and a new flush of growth. This tender, new growth is more susceptible to cold injury.
Keep your plants healthy. Plants weakened by insects or diseases are not as resistant to the cold. Inspect your plants regularly and treat them as necessary to avoid serious problems.
Potted plants that can be moved indoors for a freeze should be. Larger containers that must be left out should be pushed together and mulched to reduce heat loss from the tops and sides of the containers. This will help protect the roots. The soil should be moist not dry. Be careful not to leave canopies of plants together for extended periods as this could cause leaf and stem damage.
Radiant heat from the soil will protect low growing plants on cold, calm nights. Taller plants do not enjoy this benefit as much because of their distance from the soil. Mulches help to reduce heat loss from the soil helping to protect root systems.
Covering your plants should be done carefully. Covers that extend to the ground and are not in contact with the foliage can trap radiant heat from the soil and plant. Foliage in contact with the cover can be injured because the heat transfers from the foliage to the colder cover and is lost. You can purchase special “frost blankets” from the local garden center or use old sheets or blankets. Plastic is not recommended but if it is all you have, be sure to remove it promptly the next day to avoid burning your plants with trapped solar radiation.
Marco Island is usually spared the severe damage of the inland communities due to our close proximity to the water. Just remember to be prepared as it does happen and when it does we lose a lot of our more tropical plants.
It could be worse. We could be in sub-zero weather and snow.
Eileen Ward and her husband Peter have owned and operated Greensward, a lawn maintenance and landscaping company, since 1981.