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By: Jennifer Schutter, Field Specialist in Horticulture, University of Missouri Extension
Vegetables: If hot, dry weather is making it difficult to grow vegetables, provide plenty of moisture and use straw mulch around plants. Keep gardens weeded so weeds are not competing with vegetable plants and flowers for moisture. Weeds attract insects, so another good reason to keep the garden weeded. Knowing when to harvest sweet corn and vine crops like watermelon can be tricky. Corn is ready for harvest when silks begin to turn brown and dry. After silks are mostly brown, pick out a thicker ear from a row. Peel back the husk to get a peek at the kernels and see if it is ready to pick. Okra grows quick, and should be picked daily. Pick okra pods when they are 2 to 3 inches long. Watermelon should be harvested when the underside of fruit turns from whitish to yellowish. Do not pick winter squash too early. Butternut, spaghetti, acorn and other winter squashes should be picked whenever the fruits have turned a deep, solid color and the rind is hard.
Fruit: Many fruits ripen in July and August. Most fruits are ninety percent or more water. Supplemental moisture and mulch during the hottest, driest months of the year, will help fruits like blackberries, develop with a sweet taste. Lack of moisture causes small, tart berries. If you notice tan or white areas on your berries, this is a type of solar injury, which usually occurs under hot, dry conditions. Solar injury is caused from ultraviolet radiation from the sun that appears when there has been an abrupt increase in temperature along with a drop in humidity. Keep your plants well irrigated and if this is a problem, try using a shade cloth to provide some protection. Grapes start to ripen in July in northern Missouri. As grapes ripen, sugar, color and pH increase, although, sugars accumulate more and grapes tend to be sweeter during dry, hot weather. Summer rains can delay sugar accumulation. Water increases berry size and dilutes the juice in the berry reducing the sugar. Cloudy days reduce photosynthesis and the production of sugar. In order to avoid the birds beating you to them, use netting to protect ripening clusters.
Ornamentals: Butterflies need both a nectar and larvae source. Bright colored flowers that are tubular hold the most nectar and are attractive to hummingbirds. Through the years, I have tried many butterfly and hummingbirds plants in my gardens. Zinnias, are one of my favorite garden flowers. They tolerate heat and dry conditions fairly well. They make excellent cut flowers to arrange and bring into the home. I grow both ‘California Giant’ and ‘Profusion’ zinnias, which have become popular in recent years due to their compact size of 12-15”. They make great border plants. Both types of zinnias, grow best directly planted in a garden bed or border. Lantana is an annual flower that blooms profusely from May until the first hard freeze, which is usually late October or early November. Cleome also known as spider flower, petunias, impatiens, parsley, dill and fennel are just a few of the annuals that attract butterflies, their larvae, and also hummingbirds. Columbine, cardinal flower, coreopsis, coneflower, yarrow, goldenrod and aster are just a few perennial plants that attract butterflies and hummingbirds. Butterfly and hummingbird gardens also need rocks so butterflies can rest and soak up the sunshine, bird feeders (leave out the red food coloring for the hummingbirds) and bird baths as a water source.
Disease, Disorders and Insects: Be on the watch for Japanese beetles. Japanese beetles feed on the leaves, flowers or fruit of more than 300 species of plants. They were first found in the United States in 1916 in a nursery in New Jersey. They are native to Japan, where their natural enemies keep their populations in check and they are not a serious plant pest. In the United States, however, the beetle does not have any natural enemies. It found a favorable climate with an abundant food supply. Hand pick and place in a bucket of soapy water.
Cucumber beetles and Squash bugs are a pest on cucurbit crops. Companion planting with various herbs and flowers, like marigolds, help repel them to some extent. Their populations tend to decline as fall approaches. Diseases like Septoria Leaf Spot and Early Blight may be a problem on tomatoes from improper watering practices or if there has been a lot of rainfall. Replenish straw mulch under each tomato plant by mid-summer, take off leaves touching the ground, and if necessary spray the plants with a fungicide containing ‘chlorothalonil’. Be sure to follow label directions and observe the pre and post-harvest intervals. Blossom end rot is a tomato disorder that may appear in hot, dry weather. A lack of calcium in the soil or more likely inefficient uptake of calcium by the plant is the culprit. Cucumber plants that are stressed from lack of water or heat may produce bitter fruit. Keep all vegetable plants well-watered and mulched to hold in moisture.
Trees and Shrubs: Shade trees can provide much enjoyment during the summer months and create fond memories. I remember climbing the mimosa tree in my grandparent’s yard, and picking the pink flowers off of it. Mimosa trees do not grow well here in northeast Missouri, and I miss seeing mimosa trees during the summer. I also remember a big, old American Elm tree in our backyard in Texas county and having picnics with my sisters under that old tree. Unfortunately, Dutch Elm disease killed it in the 1980s.
Trees create memories for many families, so we need to take care of our trees. In a hot, dry summer trees and shrubs need additional water to alleviate stress. We saw this during the summer of 2012 when many trees died, particularly evergreens like spruce and arborvitae. Fruit trees even benefit from additional water during dry spells. Be careful not to waterlog the soil though, as this can also create problems, particularly for fruit trees like cherries. Be sure to mulch around new trees to help hold in moisture and keep out weeds. Large, established trees like the oaks can usually get by with no watering, but if you see signs that the tree is under stress, watering will help reduce that stress. You may notice at this time that some shade trees may have insect damage from leaf feeding insects such as the leaf skeletonizer or various leaf-feeding caterpillars. Often control is not necessary, particularly if it is a large, mature shade tree. For young trees, you may need to apply a product labeled for such insects.