Roots and Shoots: Gardening in Weird Weather

It’s been an eventful growing season already and summer is still a month away. I’m hearing a lot of questions from gardeners about how to manage different weather conditions. “Is it dead?” has come up repeatedly, too. The impacts of last year’s drought are still being felt as landscape plants and trees are not growing or leafing out.

When I talked with growers with decades of experience last fall about what to expect for native plants’ survival during the drought, there was hope but also a collective sense of being in uncharted territory. The combination of record-breaking heat and lack of rain was more extreme than in past droughts. Our warming planet is creating stressors that we haven’t seen before and the answer to questions about plant health has become, “That depends…”

It depends on the microclimate and whether the plant has other stressors from being planted in the wrong type of soil or sun. It can also depend on when the plant was put in the ground.

fall foliage

The colors of fall foliage were affected by drought and heat last fall. (Photo by P. Doan)

Newer plantings with less root structure might suffer more than mature plants. It depends on the plant and its tolerance for extreme conditions like high heat; or extended drought; or heavy rainfall; or a mild winter; or a few days of unusually cold temperatures; or a late, late frost; or cooler than usual evenings that will affect soil temperature for vegetables that we usually plant in mid-May. It’s a confusing time to be a gardener.

It depends on how well the plant can handle an April heat wave like the one we had last month, and where it was in its growth cycle at that time. If it’s trying to bloom, that takes a lot of energy. If the plant is still mostly dormant, it won’t mind as much. When gardeners asked if they should be watering plants in April — not typically a time when established perennials would need it — I could only say, “Maybe.”

My advice was to observe the plant. Is it wilting? Has growth stopped? Are leaves discolored or faded? Should it be blooming? Is the soil dry a couple of inches down? If the answers were yes, then it would benefit from a good soak.

Trees and woody plants could be showing signs of drought damage more than they did last year. While trees dropped leaves and went dormant earlier than usual, it wasn’t easy to diagnose what was happening. Water is essential to plant life, as much as it is to human life. Trees experience metabolic, hormonal and physiological changes during drought that make them weaker and more susceptible to disease, pests and winter damage.

To help landscape trees and woody plants recover, follow some best practices that can also help them handle the weird weather we’re experiencing:

■Remove weeds and lawn from the base. Grass takes up water quickly and more efficiently than a tree and will compete with the tree. Create a circle of bare soil, then cover it with coarse mulch, meaning wood chips that are not a uniform shape. Fine mulches can actually prevent water from soaking in, so avoid those.

■ Make sure mulch doesn’t touch the trunk. This can lead to rot, cultivate pathogens and make a cover for voles and other animals to damage the tree unobserved.

■ Landscape trees and plants need an inch of water per week during the growing season. If running a sprinkler or irrigation system, put a tuna can in the ground near plants that are being watered and stop when that can is full. Substitute at your convenience with any 1-inch-deep container.

■ I read a good tip for measuring water in a Washington state guide. It advises 10 gallons of water per inch of tree caliper. For example, a 2-inch trunk needs 20 gallons during a watering session when there isn’t precipitation. Newly planted trees may need supplemental water for up to 2 seasons to recover from being transplanted and to establish a deep root system.

■Generally, smaller, less-mature trees and woody plants will need supplemental water during a drought more frequently than an established tree. Check the soil to determine dryness, but a guideline could be to water smaller woody plants every two weeks, medium-sized every three weeks and large trees once a month, according to the Washington state guide. That makes sense, since larger trees will have the deepest roots and can access ground water sources that smaller shrubs cannot.

Hang in there, gardeners. We can do this.

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