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  • March garden tips & tasks

    If your fescue lawn looks a little skimpy, overseed early this month. Fescue grows best when the weather is still cool.

    Clip dead stems from perennial herbs – thyme, sage, lavender, rosemary. Pruning encourages vigorous new growth.

    Prune nandinas, flowering quince and other airy shrubs by reaching in and removing about a third of the branches at ground level.

    Remove mulch or leaves that may be covering perennials in garden beds.

    Prepare a new garden bed: Have the soil tested (check with your county’s Extension service). Remove grass and dig or till soil 8 to 10 inches deep and mix with soil amendments and organic matter to improve drainage.

    Add fertilizer lightly to perennials as soon as you see new growth. Too much fertilizer may result in lanky growth.

    Herb transplants that don’t mind cool weather -- parsley, cilantro, sage, oregano – can go in the ground now.

    When you cut daffodils to bring inside, cut the stems at an angle and place them in water right away. Change the water in the vase daily to keep them fresh longer.

    Save the date - Middle Tennessee garden events

    The Perennial Plant Society's annual Plant Sale will be April 8, opening at 9 a.m. at The Fairgrounds Nashville. The sale offers newly released and hard-to-find perennials from top local nurseries -- more than 450 varieties of perennials, vines, grasses, shrubs and annuals. The event supports local scholarships for Tennessee horticulture students and monthly gardening programs, open to the public, at Cheekwood Botanical Gardens. For information visit www.ppsmtn.org.

    The Herb Society of Nashville's annual Herb Sale will be April 29, 9 a.m. - 2 p.m. at The Fairgrounds Nashville. The sale will offer heirloom vegetables, rare varieties of perennial and annual herbs, handmade pottery herb markers and more. To learn more, visit herbsocietynashville.org.

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Good bugs vs. Bad bugs

Question: I have found several big green caterpillars covered with something that looks like white eggs on two of my tomato plants. What are they? How can I get rid of them?

A tobacco hornworm covered with wasp cocoons, and one without.

A tobacco hornworm covered with wasp cocoons, and one without.

What you are seeing is a good example of Nature helping you to control some of the pests in your garden. The green caterpillars are tobacco hornworms, which can chew up big portions of a healthy tomato plant before you even know they’re there. The white things are the cocoons of braconid wasps, parasitic wasps whose larvae feed on the hornworm, ultimately killing the caterpillar. The wasps, which are very small and not a stinging type, are considered beneficial insects in large-scale agricultural production and in home gardens.

Here’s how it works: A female braconid wasp lays eggs under the skin of a hornworm. The eggs hatch, and the larva begin eating the caterpillar’s insides and chew their way out through the host’s skin when they mature. On the outside, they spin the little oval cocoons along the caterpillar’s back and sides. By the time the adult wasps emerge, the hornworm is weakened and will soon die.

If you see a green hornworm on tomato plants – and they’re hard to spot, being exactly the color of tomato leaves! – pluck it off and dispose of it. But if you find one with white cocoons all over its back, leave it in place. It’s hosting another generation of parasitic wasps that will seek out and destroy hornworms on your tomatoes.

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