Irrigation Bags

Have you ever seen those big bags wrapped around the bases of young trees? They are irrigation bags.
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There are flattened versions used in garden beds, too. Those are called garden or watering mats.

Tree watering bags help young trees get a good start on life (Michael Trolove) CC BY-SA 2.0

A steady supply of readily available water is critical for young trees and other plants to establish new root systems. Water stress can kill a plant. If there’s not enough water, they usually shrivel up and die. If there’s too much water, fungal diseases, such as damping off, set in. Or, they may simply drown. Irrigation bags help prevent these problems.

How irrigation bags work

Irrigation bags and garden mats store water and release it slowly. They are handy if you are going to be away or if drought conditions exist. Irrigation bags and garden mats are tough UV-stable, tear-resistant tarp material. Some irrigation bags stand up against and get strapped to the trunks of saplings. Others are donut-shaped. Garden mats lay flat and provide spaces for plants to grow through. You simply fill the bags with water using a garden hose. Some irrigation bags have adjustable drainage holes.

Benefits of irrigation bags

Irrigation bags provide several benefits. A steady supply of water is only one. Irrigation bags can also stabilize soil temperatures, benefitting soil-dwelling worms and microbes that support your plant’s root system. Irrigation bags reduce erosion in sloped areas where water and soil might roll away. Irrigation bags can also serve as a weed barrier.

Zippered irrigation bag wraps around tree trunk (Caniceus) Pixabay

Irrigation bags should be removed each winter and sanitized between uses.

The downside to irrigation bags

Anything that comes into direct contact with a tree trunk or central plant stem for an extended period sets the stage for pest and disease problems. Insect pests, mice, and rats use irrigation bags and tree wraps as protection against predators and the elements. Here, they can gnaw, burrow, and procreate in relative safety, leading to bark breaches, infestation, and infection. As moisture stays close to a tree trunk or stem, fungal spores can take hold, leading to disease. If you use irrigation bags or something similar, be sure to check the integrity of your plant’s natural protections regularly.

Irrigation bags are great for young trees, at first. For as long as all the roots are near the base, that’s where the water needs to be. As a tree grows, its root system extends out horizontally. [Picture a goblet on top of a dinner plate.] This provides stability as well as access to nutrients and water. If all the water stays at the base, the roots will be less likely to extend outward, making the tree more likely to fall over as it gets bigger. As a tree grows, irrigation rings at the drip line create a healthier environment and better stability. Soaker hoses do a pretty good job, too.

Applying the same idea to other plants

Irrigation bags and garden mats work much like self-watering planters. You fill them up and watering is done. These products aren’t particularly expensive, but there are some DIY on-the-cheap tricks you can do at home. You can use some of those plastic shipping bags or trash bags. Put them where you want them, fill them with water, being careful not to over-stress the material. Then start poking holes in the bottom until the desired flow rate is reached. These bags won’t hold nearly as much water, and I don’t know if there are any chemicals that might leach from those materials. I’ll leave that to you to research. Some people use layers of water-soaked towels. When roots grow upward into the towels, they become permanent parts of the landscape.

You can also sacrifice a wheeled plastic trash can to act as a portable water source by poking a few holes in the bottom. Then wheel it to where water is needed, fill it with the hose, and close the lid. Watering done.

There’s also the trick of filling a glass or plastic bottle with water, flipping it over, and inserting it into the soil. Easier said than done, in my experience, but it does work. Sometimes. Sometimes all the water flows out all at once, and sometimes it doesn’t. I don’t know why.

The previous owner of my old house buried gallon milk jugs throughout the landscape for irrigating. She cut off the bottoms and buried them so that only the openings on top were exposed. It seemed very convenient at first. Then I realized that, unlike more durable pot irrigation, the plastic was degrading, and the space was filling up with soil, debris, and rocks, leaving very little room for water. I decided to remove them and fill the spaces with root-friendly, watering-storing soil. The plants seemed to like that plan.

Irrigation bags and watering mats can save a lot of time, and provide plants with important water, but you can’t forget about them completely.