What happened to our trees this year? 2020 has already truly been the year of the unexpected, the plant world included. You may have noticed this past spring that there were few if any blooms and many trees were very slow to leaf out. Many evergreen trees and shrubs looked completely torched and “rusted” out. Well, you can blame the weather. In October, we had a dramatic temperature change from warm 80 degree days to 18 degrees in the beginning of the month and another swing at the end of the month. The fall is a crucial time for trees to prepare themselves or “harden off” for winter. A key element for this process is time. In October, they didn’t have enough time to prepare for the below freezing temperatures and were not adequately hardened off for the winter like weather. This was followed by a dry spell mid-winter and topped off with the storm in April, freezing many new buds and blossoms. We’re now left with some stressed looking trees and shrubs this year which may be more prone to pest infestation and die back as a result.
What can I do? Trees require regular care and maintenance year round, especially in a place like Colorado. There are 3 rules of thumb to maintaining a healthy tree to help it resist damage from frost, drought and pests. Consider species selection when planting new trees and shrubs, as many popular choices are actually not suited to our climate (I’m looking at you, arborvitae).
1. Prune
As branches and twigs naturally die off from age or extreme weather events like those seen this season, they need to be safely and skillfully removed to allow the remainder of the canopy to thrive. Most trees require pruning every 2-3 years.
2. Water
We live in a semi-arid climate and many trees planted here are not naturally suited to the periods of dry heat. Give your trees extra water during dry spells and throughout the winter. Your evergreens especially will thank you for the extra water in the winter, as they hold on to their needles year round and are prone to drying during the winter months. Deep root watering ensures little run off and delivery straight to the roots.
3. Fertilize
Our rocky mountain soil tends to be high in clay content and alkaline. This doesn’t allow for the required nutrients to be accessible to the trees root system. A slow release, deep root fertilizer will help to amend the soil and reduce the chance of runoff. Mychorriza treatments will also allow for the development of fine root hairs that are the most efficient at grabbing essential nutrients.
Will they recover?
Some may, some may not. Evergreens that still have mostly brown foliage will likely lose those needles. They take a few years to produce new growth so the hope is that they will come in later. Deciduous trees may have set new buds this summer in anticipation of a come back next year. Keep in mind, trees concept of time is a bit different than ours. One brutal season that makes them look terrible isn’t necessarily indicative of “the end”. Stressed trees have plenty of tricks up their sleeves for recovering from dramatic environmental conditions and if we give them enough time and TLC, they may make a full recovery in the next season or two. If you’ve consistently done all three and still find persistent pests or signs of stress, turn to the experts for a treatment plan. Check out this article for more on Denver’s weather events: https://www.washingtonpost.com/weather/2019/11/01/denver-endured-month-record-breaking-temperature-swings-summer-winter-back-again/
