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Dividing Grasses and Other June Gardening Tips
by Leonard Perry
by Leonard Perry


In extension I serve as an advisor and consultant to the greenhouse and nursery industry, primarily in Vermont but throughout the region and beyond as well.

I give presentations on my research to the industry, and to home groups. In Research, my focus is "herbaceous perennial production systems".

His website is at  Leonards zone of gardening: home with my trials, generally USDA 4a. Campus in Burlington is 5.

June 12, 2018

Dividing ornamental grasses, supporting flower stems, and moving spring-flowering bulbs are some of the gardening activities for this month.

Support single stems, such as delphiniums, with stakes. I like to use green plastic-coated metal ones, or iron rods (like used to reinforce concrete), as these don't rot as wood does. Use soft twine, foam cord, plastic plant tape or Velcro plant tape 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. One cap I use on thick stakes is a wood filial (the kind placed on decking rails), with hole drilled part way through the center. Less attractive is a small piece of old garden hose. For bamboo stakes, pencil erasers work well on tips.

If large clumps of Siberian iris or ornamental grasses, such as maiden grass, have hollow centers, this is a sign they need dividing for best growth. Large clumps can have massive roots and be quite heavy, so we find it easier to just divide pieces off the sides rather than to lift the whole clump. A square-tipped spade works best for this. You may even need to get such divisions started with a hatchet!

If you want or need to move some spring-blooming bulbs to another spot, wait until the foliage has turned yellow, then carefully dig them up and let them dry in a shady spot for a few days. Store the bulbs in a cool, dry place for the summer until it's time to plant them in fall. Or, you can plant them now. Unless daffodils are flowering less each year, they shouldn’t need dividing. Unless tulips are labelled as “perennial”, they’ll only last one year and so should be treated like annuals after bloom—dug up and discarded.

Check apple, cherry, and other fruit trees for nests of tent caterpillars. Blast low-lying nests with water to destroy them, or knock them to the ground and destroy them. A spray of Bt will kill emerging caterpillars but is not toxic to beneficial insects, birds, or humans.

Grubs are short, squat white larvae that feed on roots of lawngrasses and other plants, and eventually turn into beetles that feed on leaves. While you’ll see recommendations and ads for products to apply now for these, the best biological controls are beneficial nematodes. These are best applied in late summer during the young stages of new grubs.

Milky spore is another organism that attacks grubs, but only those of the Japanese beetle. There are other types of grubs, such as those of the rose chafer and Asiatic garden beetle, so before using this product make sure you know which grubs are present. Your state Extension diagnostic lab can identify grubs ( Milky spore is often not recommended in New England as it is less effective and spreads more slowly in cold climates and soils, needs to be applied over a larger area than a home landscape to be very effective, takes 2 to 4 years to work, has variable results, and only will keep populations of grubs lower and not eliminated.

Each year the American Hosta Growers Association ( picks a hosta of the year, to help growers and gardeners choose the best from among the hundreds available. The winner for this year is ‘World Cup’— a bright gold-leaved hybrid reaching about two feet high and three feet or more wide. Leaves are deeply cupped, corrugated and moderately wavy. It grows better with brighter leaves if in at least part sun.

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