Tips & Tricks
Protecting Your Evergreens Against Winter Needle Sunscald
Figure 1: Sunscald needles on Pine above snowline.
A common problem that occurs this time of year in prairie landscapes is needle browning, especially above the snowline on evergreens (spruce, pine etc.). The sun at this time of year is beginning to ‘warm-up’ and with recent warm days and cool nights, the snow accumulation around the evergreens has formed a hard icy crust. This crust acts like a ‘mirror’ that reflects the sun’s rays back onto the trees and shrubs, causing the needles to warm more than normal and may begin to break dormancy. At this point, the needles need water to survive, but the rest of the shrub or tree is still dormant so the needles have no way of getting water. This in turn causes the needles to desiccate and die giving the needles a rusty red/brown appearance. When this occurs to many needles, the plant begins to look like it is ‘sun burned’ or even dying. If the sunscald is harsh enough, dormant buds that would provide the next seasons growth can desiccate and die. Evidence of sunscald is most noticeable on the south and southwest exposed sides where the sun is the hottest. Plantings next to foundations tend to be the most susceptible as the sun not only reflects off the snow, but off the house as well.
Figure 2: Example of a burlap screen for winter protection.
Here are a few helpful suggestions to alleviate this problem; 1) if this is a yearly occurrence, a plant with a screen on the sun-exposed sides is the best answer. Burlap makes the best screening material, as it tends not to heat up in the sun. Fall is the best time to protect your evergreens because the ground is soft enough to drive stakes to hold the screen securely. Ideally, there should be a 4-6 inch air gap between the branches and the screen and tall enough to provide shade necessary to protect from the sun’s rays. The air gap is necessary to reduce air temperature inside the screen, reducing chances of desiccation. 2) Later in winter, installation of a temporary screen to protect exposed branches above the snowline can be effective, be mindful that the screen does not blow away or fall over from snow melting.
3) Another means to help reduce or eliminate winter sunscald is to move the snow from around the evergreen or break up the icy crust on the snow. This reduces the amount of sun reflection onto the tree or shrub. Repeatedly breaking the ice is necessary as the snowmelts creating additional icy layers. The formation of the ice layer is most prevalent during the day when warm winter Chinook winds and subsequent cool nights.
Figure 3: Winter burn.
Normally death only occurs on the needles leaving the buds and branches alive, the plants will grow through the needle desiccation. The plant sheds the dead needles in spring and then pushes out new growth. The plant may look a bit ‘rough around the edges’ but with some care and patience the evergreen will recover fully. In the case where majority of the evergreen is desiccated or the plant was weak going into the winter, the tree or shrub may not completely recover.
Figure 4: Example of an evergreen fertilizer.
Once the ground begins to thaw and warm, watering the plant is essential. Watering aids in the replacement of lost needles. Early spring watering with water-soluble evergreen fertilizer at half the recommended label rate will give the evergreen needed nutrients to expedite recovery. Once the evergreen is actively growing follow recommendations on the label. Refrain from pruning until there are no visible signs of bud elongation and growth later in the spring. If pruning is required, remove any dead material back to visible live wood or new growth using proper pruning techniques.
Good growing and if you need any further information please do not hesitate to contact your local horticulturist…
Helpful Container Gardening Tips
It has been a very cool May; so many gardeners have not planted their annuals yet. Before planting, it is very important to prepare your containers so your plants flourish until fall.
Drainage is necessary to ensure plant roots are not oversaturated. Oversaturation can lead to root rot after rains or heavy watering. A hole in the bottom of the container is a must but by adding a thin layer rocks, bark mulch, pinecones, or other lightweight products drainage can be improved drastically.
Soil Mix or Medium – Only use bagged, soilless mixes in your pots; garden soil is too heavy and may contain weed seeds. If you are using last years soil, be sure to clean out all the roots and top up at least 25% with new-bagged product. Many retailers have specific planter mixes available.
Planting – Water plants before planting. Take them out of their pots and gently pull at the white roots to loosen them and help them grow outwards. Be sure plants are planted at same depth they were grown. When planting all new plants, we recommend using a root booster product to lessen transplant shock and encourage fine root hairs to develop.
Choosing plants to include unique focal plants and robust fillers will ensure your containers are the best you ever created.
Some plants that work great in containers include:
Petunias – all types
Snapdragons – upright and trailing types
Phormiums (New Zealand Flax)
Maintenance – Container gardens should be fertilized at least every 7-10 days to keep them looking great. Plant Prod 20-20-20 or 15-30-15 are good choices. Always ensure soil is moist before fertilizing. For extra busy gardeners, 14-14-14 slow release granules will slowly feed all summer long.
Other tips- Depending on weather, your containers may need watering every day. Always water when soil is starting to dry to touch, do not over saturate. In addition, annuals often require removal of the spent flower heads. This dead heading will ensure healthy growth all summer long.
Article By Ben Fulkerth, Assistant Superintendent Olds Golf Club