Gardening

How to save your trees in a drought

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irrigated plastic bags around the trees save water and regularly
Normally a large tree requires watering only once a month, while a year-old tree needs it twice a week. Adobe Stock

What to do this week: This is Tree Check Month, and the best time to spot the Asian longhorned beetle, an invasive wood-boring beetle that attacks 12 types of hardwood trees in North America.. Call the ALB hotline at 866-702-9938 for more information. Take a photo or capture and freeze it. It has an inch-long, shiny, black body with white spots and striped antennae longer than its body.

An Asian longhorn beetle at Cornell University in Ithaca, N.Y., with a sample of the extensive damage it can do to wood.
An Asian longhorn beetle at Cornell University in Ithaca, N.Y., with a sample of the extensive damage it can do to wood. (AP Photo/Cornell University, Charles Harrington)

Q. I just returned from a two-week vacation and found so many plants brown and dried up. My hydrangeas are scorched, and the viburnums have dropped leaves. Should I cut some of the hydrangeas back? I have never seen them like this.

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S.B., Needham

Q. All my hydrangeas have died. It looks like a catastrophe in the hydrangea patch. Do you have any suggestions for regrowth?

B.G., Lexington

A. Water them if your municipality allows it! (Hand-watering is sometimes permitted even when there are other restrictions, so check with local officials.)

Many plants are dying from one of the worst droughts in the entire nation. Even some recent showers have not made up the water deficit. Hydrangeas are particularly sensitive to lack of moisture. Mine put out new leaves on seemingly dead stems when I watered. But though I love them, I am considering replacing mine with tougher species that will better survive the cycles of droughts and floods that climate change is bringing.

Meanwhile, I am saving money by not watering my lawn, as it goes naturally dormant in drought and will green up again when fall brings rain. And I don’t let carbon dioxide-producing lawn care services mow when the grass hasn’t grown in months. Instead, I concentrate on watering trees, which are our best allies in fighting global warming because they draw carbon dioxide from the atmosphere.

Please water municipal street trees within reach of your hose as well, as there’s little chance your local department of public works will get to it. Fill 20-gallon watering bags zipped around new trees twice a week. Watch a video from Milton officials on how to use them.

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Trees show distress when their leaves first droop, curl and brown, and finally drop. Unlike lawns, they are not going dormant; they are dying. Throw them a lifeline in the form of your garden hose, and they may throw the earth a lifeline.

Q. You mentioned watering trees with a dribbling hose. I have a large, old maple tree whose roots spread out far. If I just water near the trunk, will the roots get it, or do I need to water farther out also? How frequently and long should I be watering the trees?

S.N., Newton

A. Your goal is to water deeply, which means slowly. Place the hose with or without a sprinkler next to the tree trunk, and turn it on low enough that the trickle does not run off. Every half-hour, pick up the hose and move it to another spot a little farther from the trunk. Keep doing this spiral until you have moved out from under the leaf canopy or run into an obstacle such as paving. How long you water depends on the size of the leaf canopy. Most of the roots are about a foot underground, and this helps the water penetrate deeper than a sprinkler but doesn’t waste this valuable resource. Size matters. Normally a large tree requires watering only once a month, while a year-old tree needs it twice a week.

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A soaker hose spiraled around the trunk also works. If you can’t reach the tree with a hose, drill a few holes in a 5-gallon bucket with a -inch bit, cover them with duct tape, fill the bucket with water, carry it out to your tree, and remove the tape for slow watering. Move the bucket out and around the trunk with each refill. You can do the same for shrubs. Do not fertilize plants, as this increases the need for water.

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