Gardening and optimism go hand in hand with the likes of Martha Stewart and the colorful compost ponds. One day we sit in the shade and eagerly plant a small tree. We enjoy tulips in the fall to enjoy spring flowers. We believe that our yards and gardens will always be a little better next year with stronger growth and less weeds.
Despite this year’s heat and drought, optimism has spread. The most striking effect on our courtyards is the clear brown landscape. But they are deeper than the grass that causes drought and heat.
Drought effects are quite straightforward — plants need water, and without it they will suffer or die. Heat is a secondary component of hot, dry summers, and its effects on plants may be more subtle than those of drought.
Physiological leaf bundles are common in the summer heat. Michael Wosberg / Forum Photo Editor
Here are some ways in which summer heat can seriously harm plants.
- Most plants grow well at 60 to 80 degrees Fahrenheit. If air and soil temperatures are kept warm for long periods of time, chemical activity is impaired and plant growth slows down.
- Even when plants are well watered, prolonged summer heat can damage and kill the photosynthesis system of a plant. Even when the soil is moist, the edges of the leaves may turn brown and clear.
- Heat can burn leaves and twigs on trees and shrubs, causing pre-leaf fall and branch rot.
- The roots of the tree can move away from the soil by crushing heat and drought, reducing the tree’s ability to absorb water.
- Fruits stored on tomatoes, peppers, and eggs are reduced when the temperature rises above the selected range.
- Heat can reduce pollen, which can lead to abortion and fruit falling.
- Cucumbers, pumpkins, pumpkins, and melons produce many male flowers during the hot summer months at the expense of female flowers. Female flowers can be distinguished from these crops by their successful flowering of small pollen grains.
- Bulbs, such as onions, stop growing at high temperatures, even when moisture is sufficient.
- Root crops, such as carrots, are more likely to become dull, hard, cracked, and sweet when exposed to high temperatures.
- Cold-loving vegetables struggle with heat. Radish will be fruitful, lettuce will produce unwanted seeds and become bitter, and peas, cabbage and broccoli will lose their quality.
- Spider mites and certain insects thrive in heat and lack of rain.
- Tomatoes grow easily in hot and dry climates, and cracks eventually ripen.
- Although tomatoes enjoy the heat, the longer the temperature above the selected threshold, the slower the ripening.
- Tomato leaves often roll in when heated, called a physiological leaf bundle.
- Apples, tomatoes, peppers, and other fruits are exposed to warm sunlight on their vulnerable areas, causing large yellow or white sores.
- When trees try to conserve resources to survive heat and drought, many unripe apples fall prematurely.
- On many annual and perennial flowers, the size and quantity of the flower decreases during the summer, and the flowers wither quickly. Burnt leaves are common, even after many years of cutting and watering.
Temperature stress causes many annual flowers to burn leaves. Michael Wosberg / Forum Photo Editor
- Trees, shrubs, flowers, and vegetables draw nutrients into their roots. Plants cannot absorb nutrients from hot, dry, and dry soils without sufficient moisture. As a result, malnutrition weakens plants and depletes stored energy.
- It is well documented that certain insects, such as copper birch borer, are attracted to trees and shrubs, especially those affected by heat and drought.
- Winter trees, shrubs, and shrubs that fall into a weakened, anxious state often suffer death or injury.
- Late summer and early autumn provide an important window to improve the health of our lawns, landscapes, and flowers for many years to come. In two years, this column will discuss how we can help our gardens recover from this year’s heat and drought.
Long-time gardener Don Kinzler is a horticulturalist with North Dakota State University Extension in Cass County. Readers can be reached at email@example.com.