The heat is on! The string of 90-plus degree days is forecast to continue and climb into triple digits before Memorial Day, which means time in the garden should be limited to just a few hours in the morning or evening to tidy things or harvest. If your garden, like mine, sprouted lots of weeds after the last rainy day, I figure they will suffer from the heat too but will still be there when the heatwave breaks.
The effect of heat is usually seen much later in the season, but some plants, like hydrangeas, are quick to show that they are conserving energy. This is usually seen as leaves that droop badly during the day making the inexperienced gardener think that they are dying. This is not always the case, and if you look at the plant first thing in the morning or after the sun has gone down, the plant will usually look fine.
The pores underneath the plant leaves – stomata – are usually open to allow moisture and gases into the plant’s system. When the temperature goes up, these pores close to conserve moisture. The effect on the large leaves of hydrangeas is that the lower surface of the leaf contracts while the upper side stays the same – giving the wilted look to the leaf and plant overall.
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If you water the plants every time you see this wilting, you will not only waste time and water because the plant doesn’t need it, but you are also likely to drown the root system and kill the plant.
However, after a week or so of high temperatures and no rain, the garden will start to look forlorn. The high maintenance areas (containers, annual beds and the vegetable garden) need to be watered at least once per day and most will benefit from twice-daily watering. The next group is the more drought tolerant perennials and shrubs. With the exception of newly planted material, these are probably going to show signs of drought stress after about 10 days of heat. I like to use the hydrangeas as a signal plant because it shows signs of stress from heat and drought before many other plants. When the hydrangea is looking sad at 7 in the morning, I take it as an indicator that the whole garden is likely in need of watering. Your lawn is also in this category and should not get to the crisp, straw-like stage before you water it. To keep in good shape, a lawn needs about 2 inches of water each week, so sometime in the near future, you are going to have to water that too. Well-established turf can survive longer than newly planted grass, but neither should be so stressed that you leave an imprint when you walk across it.
When the temperatures are in the upper 90s and above, the plants conserve moisture, which results in less flowers being produced and often poor fruit development in the vegetable garden. Hold off on fertilizer in all areas of the garden as well until temperatures return to a more moderate level.
So, keeping the garden hydrated is the key to surviving this early heatwave. Restrict garden work to early morning or late afternoon and takes lots of breaks.
Enjoy the Memorial Day weekend!
Kate Copsey is a garden author, writer and speaker now living in eastern Orangeburg County. Her book, "The Downsized Veggie Garden," is available from bookstores everywhere as well as her webpage, www.katecopsey.com.