From the Fort Bend County Master Gardeners Tree Team

Last time we learned the importance of slow, deep watering of your newly planted and established trees. Today, we introduce slow-release watering via commercially available devices such as bags and rings.

Our Tree Trail re-development expert and Tree Team Co-Chair, Larry Fleming, gave a lot of consideration to how to best irrigate new trees being added to or replaced in the Fort Bend County Master Gardeners (FBCMG) Demonstration Garden's Tree Trail. As we shared in part one of this three-part series on irrigation, newly planted trees require deep, slow-release watering three times per week for the first month, two times per week for the second month, and so on until it has been one year since planting. Since watering of mature trees is only required in the absence of rain, Larry assessed that installation of any automatic watering system (such as scheduled sprinklers) would be an expense that was not needed long-term. But sending out Master Gardeners to hold a hose on each tree was equally impractical.

So, what works to deliver water slowly so that it soaks into the soil deeply? To avoid running pipes or hoses, Fleming chose to evaluate three types of durable plastic irrigation bags that all deliver water to the tree roots in a way that is most likely to soak in deeply. These are: • Gator bags: a vertical plastic bag that is available in 20-gallon capacity. Position them 6-12 inches away from the trunk and fill these to the level appropriate for your size of tree (two to four gallons per inch of trunk diameter). They will deliver water over a five-to-nine-hour period, allowing water to soak well into the soil.

• Ring bags: Fleming chose two types of plastic ring bags for his test. First is a bladder-type of 20-gallon capacity. It is deployed on top of the soil around the trunk of the tree, and releases water all the way around the root area over 5-9 hours. The second is a ring filled with water-absorbent gel. The user pours water on the ring or soaks it, or it rains, and the gel in the ring absorbs the water and releases it to the soil slowly over several weeks.

• Fleming’s observations about the pros and cons of each:

o Gator bags: be placed more strategically to water specific spots; can be zipped together with additional bags to ring the tree’s root area. The water hose can be easily inserted near the top of the bag and can be left to fill while the user does other tasks. Con – requires purchase of multiple bags to ring the tree, requires two or more feet of clearance under branches due to the height of the bag, may trap moisture against the trunk.

o Ring bags: Pro – covers the entire circumference of the tree’s root area with one bag; is low profile so it can be used easily under trees with branching close to the ground. The gel ring absorbs rainwater and releases it over several weeks. Con – the user must crouch down to insert the hose into the ring bag and

must monitor them while filling. The gel bags have small capacity. They trap moisture for long periods and may cause mold.

Before any irrigation plans were made, Fleming -- with the help of many Fort Bend County Master Gardeners -- followed tree care best practices by applying a thick layer of mulch, such as bags of dried leaves, from six feet to ten feet around the tree trunk (but always not touching the trunk) before applying irrigation. It’s been a hot summer, but under his care, the Tree Trail is expanding and thriving.

This is our final installment on the topic of best practices in irrigation and deep watering of new and existing trees.