Editor’s note: Get Growing, written by the La Plata County Extension Office’s Master Gardener Program, appears every other week during the growing season. It features timely tips and suggestions for your garden and landscape.
By Melanie Palmer
Lurching from one climate extreme to another seems to be a characteristic of the short growing season in the Intermountain West.
It was only a few weeks ago that we had to worry about freezing temperatures dealing a setback to our vegetables and flowers. Now, we may be seeing the opposite problem: heat stress. When temperatures suddenly skyrocket above 85 degrees for days or weeks and fail to cool down below 70 degrees at night, plants will suffer.
When heat-stressed, plants’ photosynthesis process shuts down and they cannot draw sufficient water into their leaves. Keep an eye on temperatures and monitor plants for these signs of heat stress, which can appear suddenly:
Wilting, drooping and eventual browning of leaves.
Leaf scorch, an irreversible browning around leaf margins, particularly a problem in aspen.
Yellowing of interior leaves or needles.
Deciduous trees that begin to drop green leaves.
When temperatures exceed 90 degrees, classic summer vegetables such as tomatoes, peppers and squash may experience blossom or pollen death resulting in poor fruit set. Fruit that already is set may experience sunscald and blossom-end rot. Tomato foliage may curl.
The best remedy for heat stress is consistent watering. Container plants may need to be watered twice daily. Vegetables will need more water as they put on more leaf material, but check the soil and adjust amounts to avoid overwatering. Symptoms of overwatering often are similar to those of heat and drought stress.
Perennials that have not been established for several growing seasons will need extra water. Even the toughest of established xeric perennials in the landscape may not survive prolonged periods of high heat and drought without some supplemental water. Deep watering at less frequent intervals is preferable to frequent shallow watering.
For vegetables, particularly in high hoop tunnels and greenhouses, consider using shade cloth. Available in a variety of “shade percentages” from 30 percent to 90 percent, these can be ordered from agricultural supply companies in custom sizes.
Using good gardening practices year-round – choosing water-wise plants, using proper planting techniques, mulching to conserve moisture and watering into the late fall or even in winter depending on temperature and snow cover – will give your landscape the best chance of coming through the dog days of summer in good health.
Melanie Palmer has been a Colorado master gardener since 2012. She lives in La Plata County.