Tree Care: Mulch and Water

MULCH

Mulching, a tree's best friend...or worst enemy. Trees are like people: they need food, water and shelter to survive. Thankfully, mulch can help provide all of these (for trees, of course!).

HOW TO MULCH A TREE

The easiest way to remember how to mulch a tree is to follow the 3-3-3 rule: 3 feet wide, 3 inches deep, and 3 inches away from the trunk.

FOOD

Organic (i.e. made of biodegradable material, not rubber or plastic) mulch is an excellent source of food for a tree’s roots. Over time, mulch will decompose, improve the surrounding soil, and benefit the tree by providing nutrients.

WATER

When applied correctly, mulch can help direct water towards the tree’s root system and will also act as a barrier from evaporation and prevent the roots from drying out.

SHELTER

Mulch is a great security blanket for a tree. A layer of organic mulch will suppress weeds that attempt to grow up close to the tree and compete for nutrients. A ring of mulch around a tree’s trunk will prevent mowers and string trimmers from getting too close and causing damage. Mulch will also – literally – act as a blanket. An extra layer of insulation on top of the root system will help protect the tree from extreme temperatures.

WATER

Why we water

Most people don’t think about watering trees—especially since mature trees rarely need it—but newly planted trees require consistent watering to survive and thrive.

When a tree is transplanted, its root system isn’t yet established enough to efficiently absorb the water it needs. Plus, roots dry out much more quickly when they’ve been out of the ground, meaning newly planted trees often start off already stressed and dehydrated.

Watering all the way out to the drip line—the area beneath the outermost branches—encourages healthy root growth. Absorbing roots will grow toward the moisture, helping the tree get better established and supporting growth throughout the rest of the tree.

When to water

Newly planted trees need to be watered every week during their first growing season. A good rule of thumb is to give them about 10 gallons of water per inch of trunk diameter (measured at ground level) each week from May through October, or any week when daytime temperatures stay above 70°F.

The only time you can skip watering is if your area gets more than an inch of rain in a 24-hour period. To check how much rain your neighborhood received, you can use the MSD Rain Gauge, a handy online tool that tracks rainfall amounts by location across the city.

In their second growing season, water trees every other week. By the third season, once a month is usually enough. However, during extreme heat or drought, even mature trees can benefit from supplemental watering to avoid stress.

To make watering easier to remember, we suggest creating a set watering schedule - watering on the same day and time each week. This not only helps build a habit, but also ensures your tree is getting water during cooler parts of the day, when it’s most effective.

How to Water

• Water slowly and deeply so moisture has time to soak into the soil. Tree roots that absorb water are shallow—just a foot or so below the surface—and spread out beneath the drip line (the outer edge of the canopy).
• Focus watering where the roots are. For mature trees, water under the branches. For newly planted trees, concentrate near the trunk where the root ball is still developing.
• Water in the early morning for best results. This minimizes evaporation and gives the soil time to absorb the moisture. Evening watering is okay, but can promote fungus or root rot if water sits overnight.
• Avoid spraying leaves. Always direct water at the base of the tree. Wet foliage can lead to leaf scorch, which causes browning and stress.

You can water several ways:

HOSE

One easy method is to set your hose to a slow trickle and place it on the ground near the base of the tree. Let it run for about 30 minutes, then move it a few feet around the trunk. Repeat this process until the hose has run for about an hour - or up to two hours for larger trees.

If you’re short on time, you can water more quickly by turning up the hose and spraying around the base of the tree for a minute or more, depending on the tree’s size. While this method is faster, it’s less effective than a slow, deep soak.

Larger trees need more water and more time. You’ll also need to move the hose around more to reach the full spread of the root zone.

SOAKER HOSE

Another great option is to use a soaker hose, which slowly releases water along its entire length. Simply lay the hose on the soil around the tree, turn the water on just enough to see tiny beads of water forming on the hose surface, and let it run for at least an hour to deeply soak the soil.

SPRINKLER

You can use a sprinkler, but turn it down so the water doesn’t splash on the leaves. The tree needs the water in the soil, where its roots are.

BUCKET

If a tree is too far from the hose, you can use a bucket. Pour the water slowly on the area all around the trunk. For a young tree, try to deliver at least 10 gallons every time you water. Mulch will help hold the moisture in the soil.