Heat arrives early

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Carol O'Meara - Colorado State University Extension

Carol O’Meara – Colorado State University Extension

BOULDER COUNTY – This summer is shaping up to be known as the Slide Into Insanity season. After starting off with freezing snow in May, in a handful of weeks we’ve tipped the other way into broiling heat. To say this makes me grumpy is an understatement: my spouse was asking if I’d like a little cheese with my whine.

But the summer is heating up, and yards, vegetables, and trees are paying the price. The cabbage is showing scorch, lettuce is drooping, container plants demand water twice daily, and flowers are fading rapidly.

This kind of summer heat takes its toll on many plants, especially once the soil begins to dry. Trees with lush canopies from all the May moisture are now in water stress, their dense foliage too much to support because the soil doesn’t have as much moisture for all the leaves.

To deal with this, trees will thin canopies by dropping leaves they can’t support under hot, dry conditions. This is normal and particularly common in ash and cottonwood. Like most slimming regimens this doesn’t harm the tree, it simply helps it live within its means.

Shade cloth over vegetables prone to sunscald is a great way to prevent that problem. Peppers, tomatoes, lettuce, and any other crop, such as the cabbage, will benefit from a bit of shade. In studies conducted at Colorado State University’s Arkansas Valley Research Center in Rocky Ford, a 30-percent shade barrier is ideal for protecting these plants.

Shade cloth is a loosely woven material that can be placed over crops in a tent. It allows plenty of sun to filter through but takes the edge off its harsh rays. You can cut and sew it to size to fit whatever support you choose; I use a PVC pipe frame but others have hoops. Find shade cloth at the local garden centers, but because not all retailers carry it, call ahead to see if they have it.

One of the most obvious areas suffering from heat is our lawns. Brown spots are blooming everywhere, and sprinkler sections at local hardware stores are sizzling with action.

Most brown areas are due to poor watering of the lawn. Check the coverage of water on your lawn by conducting a catch-can test to check the amount of irrigation you’re putting down. Gather six to eight cans of the same size and randomly place them around the area you’re having problems in, making sure to place some in the green and in the brown areas. Run your irrigation like normal. Measure the amount you’ve put down to see how much the lawn is getting each time. In general, bluegrass needs two inches of water per week, spread out over two to three watering.

Don’t forget to adjust the run times on automatic sprinkler systems to deliver more water to lawns, flowers, vegetables and trees. Perennials and annuals that put on good growth since spring need to have water increased to accommodate their larger size. Trees planted years ago with drip irrigation should have the lines and emitters checked to make certain they’re delivering enough water for older trees.

Most herbaceous plants will look droopy in mid afternoon – much like gardeners do – but those with enough water will spring back once evening arrives. Plants that don’t rebound in the evening should be given a drink, and if this doesn’t help, check their stems for signs of disease.

With any change in irrigation, be alert to signs of trouble. Lawns don’t need water every day, and if you are running your sprinklers that often you may need professional help.

By Carol O’Meara, Colorado State University Extension. Colorado State University Extension, together with Boulder County Parks and Open Space, provides unbiased, research-based information about consumer and family issues, horticulture, natural resources, agriculture and 4-H youth development. For more information contact Extension at the Boulder County Fairgrounds, 9595 Nelson Rd., Box B, Longmont, 303.678.6238, e-mail comeara@bouldercounty.org or visit ext.colostate.edu/boulder.

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