With temperatures soaring well above 90 and even 100, backyard edibles can struggle to grow and produce. Mary Sipe of the Garden Club of Weddington offers some pointers on how to help your plants beat the heat.
1. Less is more. The first thing to say about watering in our climate is that it is always best to water infrequently but deeply. It is also best if at all possible to water in the very early morning hours so that your plants absorb the water before the heat of the day. There are many vegetables that can take heat but consistently moist soil is needed by most. Most will stop producing fruit during extreme heat, but bounce back when it returns to our normal temperatures.
2. Get to the root of the matter. It is always better to water the roots of plants and avoid the foliage because the wet foliage can invite fungus and other diseases, but it is difficult to do this without drip lines. When water comes from above, the foliage will actually deflect it away from the root zone in some cases, which does the plant little good. If you must use overhead watering, run it early in the morning preferable before sun rise.
3. Know when the plants are really thirsty. It sounds simple, but only water when the soil is dry. Plants will wilt in heat naturally and that is not always a sign of dehydration. I don't rely on the finger test anymore and use a probe that tells me on a scale of dry to wet the moisture level. These are fairly cheap at about $12 and can be found in garden centers. It is important to check your garden daily if possible so that it doesn't get too dry. Not every plant has to be checked (unless in pots), just general areas. Check as close to the base of the plant as possible.
Plants in the ground are much more able to withstand dry periods. If you see a plant wilting in the heat of the day, it does not mean that it has dried out and it is just temporarily having issues staying hydrated. However, plants wilting early in the morning are a sure sign of needing immediate watering. Resist watering unless the soil is dry or the roots may rot. Frequent shallow watering is only necessary for seedlings.
4. Low and slow. I like to use a simple sprinkler attached to a hose that I leave on an area for at least 30 minutes before moving it on to the next area. It is best to put these at a fairly low water pressure so that the least amount of water gets on the foliage and still covers about a 3 to 4 foot area. For areas soaked in this way, it should not require watering again for at least 3 days even in extreme heat given our high level of clay, which will hold water longer. If your soils are deeply amended, they may dry out a little more quickly.
5. Mind the sensitive plants. You also want to monitor some vegetables more closely that will not recover if they become too dry. Two in particular are tomatoes and squash. I find that these plants also need a deep soaking in a much wider area, so drip irrigation doesn't work very well. I sometimes use lattice that I cut from 4' x 8' sheets propped against posts for shading from afternoon sun on particularly exposed plants.
Container-grown plants are even more impacted by extreme heat. I find that drip irrigation works best for these with timers because it is difficult to get a hose to these on a daily basis. During extreme heat, I also find that I must water these twice daily if they remain in the afternoon sun. Water in the early morning and again around 2:30 p.m., or move your containers to areas where they are protected from afternoon sun if you cannot water a second time in the afternoon.
Mary Sipe was raised on a farm and has gardened for the past 25 years in both Atlanta and Charlotte. She is a member of the Garden Club of Weddington, which meets from September to May.