Tree Care Tips from Tiana, Part 3: Watering, Mulching, Composting and Pruning

Certified arborist Tiana George discusses the importance of nurturing your tree’s health with proper watering practices, composting, mulching and pruning. If you missed the start of the series, you can find it here: Tree Care Tips from Tiana, Part 1: Planting.

Tiana George is an ISA Certified Arborist and one of the primary consultants for Tree Shepherds. With ongoing education in horticulture, she is a huge advocate of organic gardening and tree care, and believes that urban renewal is not merely good for the environment, it’s good for our minds.

Correct Watering Practices

In the first part of this interview, you mentioned the importance of watering correctly. Can you explain that a little more for our readers?

Watering is the most important aspect to maintaining the plants in your landscape. Unfortunately, most people over water. Because it is hot in Texas, homeowners are tempted to run their sprinkler systems every other evening, or if we hit a particularly long streak of over 100 degree weather, homeowners might program the sprinkler system to run every night.

While you might need to drink frequently in hot weather, your trees do not. Overwatering can actually lead to roots being choked out, in a sense, by constant saturation. A tree’s roots need oxygen as well as moisture. And they can’t get oxygen if the soil is always wet, if they are being watered every day, or even every other day. It’s just not necessary.

How often should a tree be watered?

Ideally, a tree should be watered one day a week. Two days a week, if needed. The objective is to water deeply. You want to soak the roots, not sprinkle them. One to 1.5 inches of water in volume. This usually requires 30-40 minutes for dry ground to absorb.

Since most people in North Texas have sprinkler systems installed, can you explain how that might work? 

Typically want to run each section, 10 to 15 mins, for a total of 3 to 4 times, in one session. That will ensure that you’re getting 30 to 40 minutes of total watering time. By only watering 10 to 15 minutes at a time, it will allow the water to soak in before the section is watered again. This will guard against runoff as well.

You should experiment with your system, observing it in action, to make sure that you’re not wasting water.

A sprinkler system spreads the water out, usually targeting the grass, more than the tree. So, where should you water?

Whether you’re using a hose or a sprinkler system, you should target the root zone. Remember, your trees are not potted plants in your home. Their roots extend 2 to 3 times the height of the tree. You need to make sure the sprinkler system is programmed to hit the root zone of your tree or trees.

What about watering your grass? Doesn’t it need to be watered everyday to stay green?

Your grass doesn’t like to be watered every day. Sure, it might look green and happy, but then you start getting circular fungal spots in your lawn. St Augustine, a very widely used grass, is prone to fungal issues. To mitigate fungal problems, limit watering to once a week.

The only time water is really necessary is when we haven’t gotten rain.

How and Why to Use Mulch and Compost

What are the benefits of using mulch?

• Good for new trees
• Helps with moisture retention
• Cools the root zone
• Helps with weed control
• Adds nutrients to the soil

What is the correct amount of mulch to use for trees? And is it possible to use too much?

Two to 3 inches deep of mulch spread over the root zone is fine. But 5 to 6 inches deep is too much. And then, never lay mulch on any bark tissues. This will cause root problems.

When and how should compost be used with trees?

Unlike mulch, which takes time to breakdown, compost is ready to go. Think of compost as vitamins for the soil and the soil microbes which encourage root growth.

An inch of compost spread out over the root zone from time to time is a good way to build your soil health to help your trees thrive.

Good Pruning Practices

How important is it to prune your tree, since it’s not natural?

Especially with new trees, pruning is important to the structural development of the tree. It’s recommended that a tree have a central leader. This will better ensure long-term structure and maintenance in an urban environment. That means there is one stem that is clearly the dominant stem going straight up.

A lot of trees that you find at the nursery have several competing, main stems. And while they might look cute, like little lollipops, they are not structurally as healthy. So if you have a strong central leader you have less opportunity for breakage. You don’t have multiple stems competing with each other. Bradford Pears are a good example of this. The multiple stems competing with each lend to the development of weaker unions and thus allow for a greater chance for breakage. If you have a main central leader, then you can have stronger branch unions because they aren’t competing as much. So, you want to control the number of possible conflicting branches to make the tree safer structurally.

What is a bad prune job?

A bad pruning job is one that does not take into consideration the natural shape of the tree. You want to work with nature, not against it.

Pruning all the lower branches of a tree so that your house can be seen, for example, is not recommended. It could make the tree unsafe. Pruning a tree too aggressively, and without experienced consideration, will upset the tree’s natural balance. This could result in possible hazards, say if a strong wind comes along and tests the structure of the tree.