Question: During the heat of summer, the plants on our deck need to be watered daily. Summer is such a busy time; I cannot keep up with it. Do water globes work? How about moisture-control potting soil or self-watering containers?

Answer: Keeping outdoor container-grown plants watered during the summer can be a chore even in our mild climate. As temperatures and plant water needs rise, many container-grown plants must be watered once, if not twice, a day.

Is there anything a gardener can do to lessen the burden? Let’s start by reviewing the three products you mentioned.

Water globes are typically blown glass reservoirs with long slender stems that are inserted into the soil. The globes are designed to hold water for slow release into the soil as it dries out.

Although water globes are attractive, they do not work as intended for most gardeners. The stems tend to be delicate and crack if not inserted carefully into the soil. They also become plugged with soil, requiring additional work when refilling the globe.

More importantly, the globes typically hold only a cup of water or so, less than what most outdoor plants need with each watering. Many gardeners also report that the globes empty almost immediately when they are inserted into the soil. Wetting the soil thoroughly before inserting the globe can slow the release of water from the reservoir, but the small amount of water in the globe still lasts only an extra day or so.

Moisture-control potting mix is a potting soil that contains amendments that are intended to absorb water and release it slowly as the soil dries. Polyacrylamide gel (commonly referred to as water crystals or hydrogel) is a commonly used material because it absorbs many times its weight in water.

According to the University of Massachusetts at Amherst, these products reduce the need for watering and are useful in many settings, but they have limitations.

Moisture-control potting mix remains relatively wet, especially when temperatures are cool or there is plenty of rain. Consistently wet soil can contribute to root rot and encourage pests that thrive in moist soils such as fungus gnats.

Moisture-control potting mix is typically more expensive than other potting soil. It must be replaced every year because the polyacrylamide breaks down and loses effectiveness with exposure to heat, fertilizer and ultraviolet light.

Finally, there are theoretical concerns that although polyacrylamide gels are safe, they might break down into more toxic substances that could be a health risk to humans, animals and the environment. When used in containers, however, this risk is minimized unless the soil is discarded into the compost pile or landscape.

Self-watering planters consist of a soil-filled growing bed that sits on a reservoir of water. A wicking system such as a piece of rope, strips of fabric or columns of soil carries water from the reservoir to the plant roots by capillary action, obviating the need for external watering.

Self-watering planters work well for many gardeners because the water reservoir only needs to be refilled every one to two weeks, but they have disadvantages. They tend to be more expensive than other containers and heavier once filled with water. The water in the reservoir can become stagnant and a breeding place for mosquitoes and algae.

In addition, self-watering containers might not be well-suited for all plants. Since the wicking system typically pulls water from below, the top portion of the soil stays relatively dry, which is not good for plants that like a lot of water. They also are not good for plants such as succulents that like the soil to dry out completely between waterings.

Bottom line: Water globes are plant ornaments at best, but moisture-control potting mixes and self-watering containers might lessen your watering chores. Test out these options to make sure your plants are not being under- or over-watered before abandoning your daily watering routine. Their effectiveness can vary depending on the plant, container, and growing conditions.

For more watering tips, see the sidebar.

Jeanette Stehr-Green is a WSU-certified Clallam County Master Gardener.

Watering tips for container-grown plants

Avoid unglazed clay containers because they draw water out of the soil causing it to dry faster. Plastic pots retain soil moisture better.

Use potting soil that is high in organic matter that naturally enhances the soil’s ability to hold onto water. Peat, coir (fibrous material from coconut husks) and bark retain water to varying degrees without making the soil soggy.

Mulch the surface of the soil in your container to conserve moisture. A layer of pebbles or wood chips will help prevent water evaporation from the soil.

When you irrigate, apply water until it comes out the holes in the bottom of the pot. It may take as much as a gallon of water to thoroughly water a large container.

If water runs right through the container when you water it, it could be that the plant has outgrown the container (i.e., its roots have replaced most of the water-retaining soil) or the soil has become overly dry and hydrophobic. If the plant has outgrown the container, transplant it to a slightly larger container (a process also known as potting up or up-potting). When up-potting, use a container that is only a couple inches larger in diameter than the original pot and break up any roots that encircle the plant.

If the soil has become overly dry and repels water, you will need to rehydrate it. Set the pot in a shallow container of water, allowing the soil to slowly absorb water from the bottom. Rehydration might take an hour or more for the surface of the soil to again become moist. Do not leave the container sitting in water after the soil is rehydrated.