University of Vermont Extension 
Department of Plant and Soil Science

Summer Article

Charlie Nardozzi, Horticulturist
Vermont Botanical Garden, and
Dr. Leonard Perry, Extension Professor
University of Vermont

Proper mulching, preventing pest problems and slug damage, and sufficient watering are some of the important gardening chores this month to keep your garden healthy and thriving.

Some gardeners report success controlling rose foliage diseases by spraying plants with a solution of compost tea, made by mixing one part mature compost that contains some manure with 5 parts water. Let the mixture sit for 2 weeks, then filter and spray at 2-week intervals. The tea also provides nutrients.

If you haven't already done so, spread a layer of organic mulch, such as straw, around the base of vegetable plants. This will help keep weeds at bay, conserve soil moisture, and prevent soil from splashing up onto plants. Keep the mulch an inch or two away from plant stems to minimize disease problems.

New ornamental plants should also be mulched to help control weeds, and to conserve moisture.  Most gardeners use shredded bark mulch for this purpose, but other organic materials such as shredded leaves or pine needles also work well. If mulching around shrubs or trees, you may wish to place a weed fabric down first.  Shape the fabric with scissors, then cover with about two inches of mulch.

Avoid the "volcano" method of piling mulch deeply around trees into a cone shape.  This will smother the trunk, and harbor moisture and diseases which will rot the trunk.

If the weather is dry, water young ornamental plants deeply once a week to ensure that they grow well through the summer. Apply water until it sinks down at least 2 feet into the soil. On newly planted trees, flood the reservoir around the tree with a few inches of water to make sure it sinks in deeply where the roots are growing. Consider investing in soaker hoses or other irrigation equipment to make your watering easier, and more effective.

Plants should receive the equivalent of an inch of rain a week.  Water well, and deeply, when watering. It is better to apply more water, less often, than just sprinkling plants every day.

With the humid weather upon us, slugs are having a field day. They eat holes in the leaves of many vegetable, annual, and perennial plants. There are many chemical and nonchemical controls for slugs, but a new one I've used successfully contains iron phosphate as the active ingredient. The slugs eat the pellets and die, yet the iron phosphate doesn't harm other wildlife or the environment.

Support single stems, such as delphiniums, with stakes.  I like to use green plastic-coated metal ones, or iron rods, as these don't rot as wood does.  Use soft twine, foam cord just for this purpose, even old panty hose, to tie stems to stakes.  These avoid cutting into and harming the soft stem tissues.

If using narrow stakes such as bamboo or iron rods, place some form of caps on top to avoid possible eye damage. (Such caps can now be found in some mail order supply catalogs, or complete garden centers.) One cap I use on such stakes is a wood filial (the kind placed on decking rails), with hole drilled part way through the center.

Other tips for June include keeping a bucket of sand soaked in mineral oil handy.  Use this for cleaning garden tools.  Use row covers over young vegetables to prevent pest problems. Now is also the time to lightly fertilize lilacs after bloom, and to prune spring flowering shrubs now that they are finished. If the weather is hot, or dry, and lawns grow more slowly, mow them higher and less frequently. Make sure you use a hat when gardening, and plenty of sunscreen with an SPF rating of at least 30, to avoid sunburn.

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