Question: When should I water my plants during the summer heat? Is it true that I should only water my plants in the evening or very early morning?
Answer: This is a very common question as summer heat waves settle in. It is usually deep rooted in a garden myth that plants should never be watered during the heat of the day because the water droplets would act like tiny magnifying glasses and burn the leaves. It is also thought that the soil temperature being so high and water temperatures high from the water hose that it would actually boil the plant roots, killing them.
The myth seems plausible, but the reality is that plants need water to produce and to survive. Postponing watering dry plants until the evening or the following morning could damage your plants and leave them more susceptible to pests and pathogens like mites and fungal leaf scorch. Leaving the plant leaves damp overnight can encourage fungal growth.
While it is true that you can kill or at least deter the growth of plants with boiling water (weeds in the cracks of your driveway), we can easily dispel the myth of boiling our plants by simply watering them during the middle of the day. Steam coming up from the ground can occur even after a rainstorm in the summer. The rain is cooler than the surface temperature. Water coming out of a hose is hot and should be run for a short time to get the hot water out before turning it on your plants, but it is unlikely that it is at the boiling point (212 degrees Fahrenheit) and it quickly cools as the water runs through the hose. In fact, if your plants are dry, watering them may cool the roots, which they will welcome.
Here are some tips for watering during hot summer days:
1. Water well and water deeply. Plants need plenty of water going to their roots. Deep watering encourages deep roots. By watering with less water and more often you encourage shallow roots and weak plants. If water puddles on the surface at first, move to another spot, but come back to be sure plenty of water has soaked down into the soil.
2. Check container plants often as they may need to be watered daily during extreme heat.
3. Water in the morning when water is more likely to go into the soil before evaporating. But if you notice your plants showing signs of stress from drying out during the day, give them some water.
4. Avoid watering in the evening when you can. Plants left with wet leaves overnight are more likely to develop fungal and other diseases.
5. Choose an indicator plant, a plant that is the first to wilt when the soil gets dry. In a vegetable garden, this is your plants with large leaves, such as squash or melons. Their leaves lose moisture fast and will droop first. Watching your plants for signs of wilt is very important. Once they are past the point of terminal wilt, no amount of water is going to save them.
6. Spread a little extra mulch around the base of your plants to keep moisture in. An extra inch or two will help shade the soil to keep moisture from evaporating as quickly and help keep roots cooler. You can use hay, straw, mulched leaves or finely mulched bark.
7. In your vegetable garden, it is crucial to water your plants consistently. Tomatoes are especially unforgiving if allowed to get over-dry and then wet again. This opens them up to blossom end rot and cracking. Cracking is what happens when water follows drought and the fruit expands suddenly, splitting the skin.
8. Do not overuse fertilizers and pesticides. It is wise to cut back fertilizing to about every 2 weeks.
For more information on heat stress in plants and proper watering, you can contact your local extension office. Atlantic County residents can contact the Master Gardener Helpline at 609-625-0056. Cape May County Residents can call 609-465-5115, ext.3607.
Events: Atlantic County Master Gardeners will be available to answer gardening questions and take samples for plant identification or diagnoses throughout the county this summer. You can find us at the Ventnor City Farmers Market: July 19 and Aug. 8; Galloway Green Market: July 25; Brigantine Farmers Market: July 13; Atlantic County 4-H Fair: Aug. 8, 9, and 10; and Brigantine Green Fest: Aug. 24.
Do you have a gardening related question you would like answered here? Please forward your questions to Belinda Chester, Master Gardener Program Coordinator, Rutgers Cooperative Extension Office, 6260 Old Harding Highway, Mays Landing, NJ 08330. You can also submit questions at Rutgers-atlantic.org/garden or email them to email@example.com; please include “garden question” in the subject line.