April's Ag Advice by April Borders Our winter weather is often responsible for the damage that we see in our landscape plants in the spring. The winter, sun, wind and cold temperatures can bleach and desiccate or dry up evergreen foliage, damage bark, and injure or kill branches, flowerbuds and roots.
Injury can happen in the winter if conditions are abnormally severe or if, like this year, plants have been stressed by the environment. Injury is more prevalent and more severe when low temperatures occur in early winter or late spring, when there is little or no snow cover during the winter, or when low temperatures are of prolonged duration. Large fluctuations in temperatures can be extremely detrimental to plants too.
This year, we have experienced low soil moistures and fluctuating temperatures. These dry winter conditions can contribute to mortality of roots and desiccation of twigs and buds. Trees experiencing such injury may produce only scattered clusters of leaves in the spring, or leaf out as normal but wilt and decline by early May.
Some species of trees are more sensitive to desiccation injury than others. According to Dr. John Ball, SDSU specialist, the trees that appear to be most affected by winter dryness include birch, hawthorn, lindens (basswood and littleleaf), and maples (Norway and silver). Spruce are more sensitive than pines and Colorado blue species are probably the most sensitive of the typical evergreen trees planted in the state.
Dr. Ball says that winter watering can be very helpful but there are a couple of considerations. First, water only when the air temperatures are above freezing and the soil is not frozen. Water early in the day so the water soaks in rather than freezes at night as a puddle around the tree (the expanding ice can injure the stem). If the soil is not frozen, water can be helpful in keeping the plants roots alive. If the stem is not frozen, water can be absorbed and translocated to the twigs and on evergreens into the needles.
According to Dr. Ball, as long as we have an open winter and days with air temperatures above freezing, watering periodically can be a big help in getting our trees and shrubs through this stressful time.
Another issue that we need to start looking at is pruning our trees. Now I know that you think that this is way too early to be thinking about this subject but it really is not too early. According to Dr. Ball, we can start pruning some of our hardier trees. These would be trees like ash, cottonwood, hackberries, maples and oaks. Despite the temperature extremes we have been having, these trees are sufficiently hardy enough that they will not be injured by the wounding created by pruning.
Marginally hardy plants, particularly fruit trees, apples, pears, plum, cherry, etc., should not be pruned now. These plants may experience some winter-kill near the pruning site and these same trees may yet suffer winter injury in February and March. At that time prune away any branches that died during the winter and then if more pruning is required you can extend the pruning into live branches.
For more information about tree care please contact the Extension Office at 677-7111.
Feb. 10 � CY Irrigators annual meeting.
Feb. 11 � Pesticide applicators training � Parker.
Feb. 12 � Range and pasture management meeting � Parker.
Feb. 18 � Pesticide applicators training � Elk Point.