Help Our Gardens Beat the Heat 
By Hilda M. Morrill
July 31, 2010

This summer has been one for the records on the East Coast. What to do?

To encourage gardeners who may be frustrated by the record-high temperatures and dry conditions that have been battering their vegetable beds, Sonia Uyterhoeven of the New York Botanical Garden has ten tips she and her fellow experts employ that will help our gardens beat the heat. We thank Sonia for her generosity, and we share her tips with our readers:

Plan your garden by grouping plants with similar cultural requirements. "Place together drought-tolerant plants such as many herbs to create low-watering zones," she suggests. Some leafy greens will grow fine in part-shade during the heat of the summer.

Amend your soil with organic matter such as compost or aged cow manure when preparing your vegetable garden for planting to improve the soil structure, increase water and nutrient retention, reduce runoff and compaction, and improve drainage. If you are starting a new garden, add 25 percent by volume. For an established garden, one to two inches of organic matter turned into the soil is sufficient.

Space your plants properly so they have enough room to grow but are not crowding each other and fighting for root space, light, water, or nutrients. Also, keep your garden well-weeded. Weeds compete with vegetable plants for nutrients and water.

Mulch your garden, not only to suppress weeds, but also to retain moisture. A two- to three-inch layer of mulch is sufficient for most areas of your garden. Shredded leaves, straw, or salt hay make good options for the vegetable garden. The finer your mulch, the more you can add.

Do not fertilize water-stressed plants. The salts in the fertilizers will burn the weakened, water-deprived roots. When the soil temperature gets too high and the moisture levels are low, plants start to shut down. This is not the time to encourage growth by feeding them. "At The New York Botanical Garden, we use fish emulsion or a combination of fish emulsion and liquid seaweed to feed the vegetable garden," says Sonia. "Be aware that fish emulsion contains oils that could potentially burn the foliage on your vegetables in warm, sunny weather," she warns. Use with caution or wait for a cooler, cloudy day.

Water early in the morning, before the heat of the day, to minimize evaporation. Watering by hand at the base of plants, with a soaker hose, or with drip irrigation is highly efficient. Oscillating sprinklers tend to be less efficient, but can be used early in the day.

Water deeply and less frequently as opposed to shallow and often. "Deep watering creates deeper and more efficient root systems, she says. Do not water a plant if it doesn't need it. Botanical Garden Vice President for Horticulture and Living Collections Todd Forrest says, "Whether by hose or Mother Nature, I water so that the whole garden receives about an inch of precipitation per week."

Let nature do its share. You do not have to water your garden after a substantial rain. However, sometimes in a heavy downpour rain falls so quickly that it's not absorbed into the ground. To check if your garden is well-watered, stick a trowel four to six inches into the ground to see if the soil is still moist. If the soil is cool to the touch, it is still holding water.

Some of your plants will wilt in the heat of the day. This does not necessarily mean they need water. It is a normal defense reaction to high temperatures. If the same plant is wilting in the morning, then it is suffering from water stress. Always check the soil for moisture levels. "Keep a watchful eye on newly planted areas," she cautions. "These plants are more vulnerable to water stress since they have not yet had time to establish a good root system."

Harvest herbs and vegetables in the morning, after the dew has burned off, but before the heat of the day. Plants suffer from heat stress as much as we do. They are fresher in the morning.

We know that many of our readers often travel to the Big Apple. The New York Botanical Garden has been motivating many to channel their inner vegetable gardener through "The Edible Garden," an exhibition about growing and preparing good food. Why not drop by if you are in the area?

Running through October 17, the exhibition presents locally grown and seasonal food. With celebrity chef appearances, daily cooking demonstrations, kitchen gardens, children's programming, a weekly Greenmarket, and home-gardening demonstrations, visitors will learn how to create their own edible gardens and transform bountiful harvests into healthful, exceptional meals.

For more information about "The Edible Garden" and to see Sonia Uyterhoeven's schedule of Home Gardening Demonstrations, be sure to visit www.nybg.org.

Happy Gardening!