Urban Gardening

Summer Watering Strategies

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Watering is usually the top summer chore for gardeners. From June through August, evaporation and plant transpiration (together termed evapotranspiration) reach their peaks. Water is quickly lost from the soil, from the leaves, and even from pots made of terra cotta and wood. Keeping moisture levels adequate can be tough.

Evapotranspiration is especially hard on hanging baskets, which are exposed on all sides. In a sunny location it is not uncommon for hanging baskets to need watering twice a day. Small pots fare no better. Of course, large containers can hold more water, but even they require watering every couple of days when exposed to the summer sun.

Equipment and Techniques

Summer watering presents special challenges to the gardener with a balcony, patio, or roof deck. Sprinkler or drip systems are usually impractical. Lugging buckets or watering cans gets tiring. For one or two plants it's not a problem, but when you have dozens like I do, carrying water is not the best option.

I recently bought a connecter that links my bathroom faucet to my new decorative 50-foot curly hose via a quick connect hose fitting. The inventor of that connector is a genius! Now soaking all my pots takes less than half the time with less than half the effort. I recommend this system to anyone who has outdoor gardens without access to an outdoor spigot. (As always, add extra washers to the connections to eliminate drips and sprays.)

Regardless of your watering system, always soak the pots and baskets thoroughly and deeply. Water in the early morning or early evening when the least amount of water will be lost to evapotranspiration. Watering close to dark can promote fungal and bacterial diseases, unless you have an automatic drip system that wets only the soil, not the foliage. Also avoid watering during midday sun because drops of water can act like magnifying lenses and scorch plant leaves.

Be diligent about monitoring soil moisture in your pots. Ideally, you want to water after the soil begins to dry but before the plant wilts. Most plants are very forgiving, but some will rot if kept constantly moist. It can be a tricky balancing act.

Water-Absorbing Crystals

You can help your container plants become more drought resistant with soil additives that help conserve water. Polymer crystals are tiny granules that absorb water and expand to many times their size. The expanded crystals resemble globs of clear jelly. When the crystals are mixed into potting soil, plant roots are able to absorb moisture from them when the soil is dry. This may buy your plants an extra day or two without water before they begin to wilt.

The use of polymer crystals in the garden is controversial because they often are washed away into rivers and lakes where they create issues for wildlife. However, in an enclosed container they are very useful. If using polymers, be sure to recycle the potting mix instead of dumping it outside.

Compost, manure, peat moss, and other organic materials also hold onto water molecules, although they are less effective than polymers. If the plant has high water needs, add extra organic matter to the planting mix.

Vacation Watering

When you're on vacation, the best solution for plants that need daily watering is to work out a trade with friends -- you water their plants when they are gone, they water yours. If this isn't possible, try making mini drip irrigation bottles out of empty, plastic, quart-size milk or juice jugs. Poke several tiny holes in the bottoms and then set the jugs on top of the soil so the water slowly leaks out. This requires some trial and error until you get the right number and size of holes so the water drips slowly. Use one jug for smaller pots, more than one for large planters.

Before leaving, group all your pots together to reduce exposure and conserve humidity. If you have a shaded or protected spot, place them there. Your plants will likely be fine, and if they look worse for the wear, you can deal with it when you get back, relaxed and rejuvenated.

From August 2007 E-newsletter

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