Summer Tree Watering & Drought Care

Massachusetts summers have gotten hotter and drier over the past decade. July and August regularly bring stretches of 90-degree days with little rain, and municipal water bans across Middlesex County make watering everything on your property impractical. Your lawn can go dormant and come back. Your trees cannot afford the same neglect. A mature tree that gets drought-stressed in summer can take three to five years to fully recover, and a young tree can die in a single dry summer.

I am Keith McDonald. My family has been caring for trees in Billerica and the surrounding towns since 1995. Here is what we tell every homeowner about keeping their trees alive through the hottest months.

How Much Water Does a Tree Actually Need?

The general rule is 10 gallons of water per inch of trunk diameter per week during dry periods. So a tree with a 6-inch diameter trunk needs about 60 gallons per week. That sounds like a lot, but spread over a slow watering session of 30 to 45 minutes with a garden hose at half pressure, it is very manageable.

Quick reference:

• Young trees (planted in last 2 years): Water deeply twice per week, 15 to 20 gallons each session
• Established trees under 10 inches diameter: Deep water once per week during dry spells, 10 gallons per inch of trunk diameter
• Large mature trees (over 10 inches diameter): Deep water every 10 to 14 days during extended drought. Their root systems are extensive enough to access deeper moisture, but even they have limits.

The key word is deep. Shallow, frequent watering encourages shallow roots. Deep, less frequent watering encourages roots to grow down where moisture is more stable. Put the hose at the base of the tree, turn it to a slow trickle, and let it run for 30 to 45 minutes. Or set up a soaker hose in a ring around the drip line.

Signs Your Tree Is Drought-Stressed

Trees do not show drought stress immediately. By the time you see symptoms, the tree has been struggling for weeks. Here is what to watch for:

Early signs (act now):

• Wilting or drooping leaves, especially in the afternoon heat
• Leaves curling inward or rolling along the midrib
• Dull, grayish-green leaf color instead of vibrant green
• Premature yellowing of interior leaves

Advanced signs (serious stress):

• Leaf scorch: brown, crispy edges on leaves, especially on maples, birches, and dogwoods
• Early leaf drop in July or August (the tree is shedding leaves to conserve water)
• Undersized leaves or sparse canopy
• Bark cracking or splitting on thin-barked species
• Dieback in the upper canopy

We see the worst drought stress in towns with sandy, fast-draining soils. Tewksbury, Wilmington, and parts of Chelmsford have glacial outwash soils that dry out fast. Trees in these towns need supplemental water sooner than trees in the heavier clay soils of Lexington or Winchester.

Which Trees Are Most Vulnerable?

Not all trees handle drought the same way. Native species that evolved with our climate are generally more resilient, but even they have limits.

Highly drought-sensitive (water first):

• Birch trees: Paper birch and river birch are notoriously drought-sensitive. A dry August can kill a birch that has been healthy for decades.
• Hemlocks: Already stressed by hemlock woolly adelgid in most of Middlesex County, drought pushes them over the edge.
• Dogwoods: Shallow root systems and thin bark make them vulnerable.
• Japanese maples: Popular ornamentals that wilt quickly without consistent moisture.
• Any tree planted in the last 2 years that has not established its root system.

Moderately drought-tolerant:

• Red oaks and white oaks: Deep root systems help, but extended drought still causes stress. Read our oak tree care guide for more.
• Sugar maples and red maples: Better than birch but still show leaf scorch in bad years. See our guide on common maple tree problems.
• White pines: Established specimens handle drought reasonably well, but young pines struggle. More in our white pine problems guide.

Watering During Water Bans

Many towns in our service area implement outdoor water bans during drought, typically restricting lawn watering to certain days or banning it entirely. Here is the good news: most water bans in Massachusetts exempt hand-watering of trees and shrubs. Check your town's specific ban language, but generally you can hand-water trees even during an odd/even or total lawn watering ban.

If your town does restrict all outdoor water use:

• Redirect gray water from dehumidifiers and AC units to trees
• Collect rainwater in barrels during storms (check local ordinances, but most MA towns allow this)
• Prioritize young trees and high-value specimens. If you can only water three trees, pick the ones that cost the most to replace.

Mulch Is Your Best Friend in Summer

A proper mulch ring reduces soil moisture evaporation by up to 70 percent. If you only do one thing from this article, mulch your trees correctly. Two to four inches of hardwood mulch from the drip line inward, keeping it 3 to 6 inches away from the trunk. Mulch volcanos piled against the trunk do more harm than good. For a refresher on proper mulching technique, read our spring tree care checklist.

What NOT to Do in Summer

Summer is the wrong time for several common tree care activities:

• Do not heavily prune in July and August. Heavy pruning during peak heat stresses the tree further. Remove deadwood anytime, but save major structural pruning for late winter or early spring.
• Do not fertilize drought-stressed trees. Fertilizer stimulates new growth, which demands more water from an already depleted root system. Wait until fall or the following spring when the tree has recovered.
• Do not compact the soil around the root zone. Avoid parking vehicles, storing heavy equipment, or doing construction near trees during drought. Compacted soil holds even less available water.

When Drought Damage Becomes a Safety Issue

A tree that has been severely drought-stressed for two or more consecutive summers may become a hazard. Dead branches in the canopy can fall without warning. A tree with significant dieback may not be worth saving if the damage exceeds 50 percent of the crown.

We assess drought-damaged trees throughout Bedford, Concord, Acton, and all 18 towns in our service area. If you are not sure whether your tree is recoverable or needs to come down, read our guide on when to remove a tree or call us for a free assessment.

Get Help With Summer Tree Care

If your trees are showing signs of drought stress, if you have questions about watering, or if you need dead or hazardous branches removed, call McDonald Tree Service at (978) 375-2272. We provide tree health assessments, pruning, deep root fertilization, and removal when necessary. Serving Billerica, Lowell, Dracut, Westford, Andover, Waltham, and all of Middlesex County.