What's Up In The Garden

 by Jackie Dohlman, Franklin County Master Gardener

Tips on Hardening Transplants, Using Newspaper as Mulch in the Garden, and Controlling Iris Borer

What is meant by the term hardening?

Flower and vegetable plants purchased from greenhouses or garden centers should not be planted directly into the garden. The intense sun and strong winds may damage or kill the tender seedlings. Bedding plants should be "hardened" (acclimated to outdoor growing conditions) before transplanting them into the garden. Initially place the plants in a shady, protected site. Then gradually expose the plants to longer periods of direct sun.

Closely watch the plants during this period. If possible, check on them at least once or twice a day. Thoroughly water the seedlings when the soil surface becomes dry to the touch. Move the plants indoors if strong winds, a severe storm or an overnight frost threatens them. After several days of hardening, the flower and vegetable plants should be ready for planting.

Can newspapers be used as a mulch in the vegetable garden?

Yes, shredded newspapers or whole sheets may be used as a mulch in the vegetable garden. Newspapers use organic inks so gardeners need not worry about lead contamination. When using newspaper sheets, place a layer of two to four sheets between plant rows in the garden. Water the sheets so they stick to one another and to the soil surface, then place a layer of dry grass clippings, shredded leaves or straw over the newspaper.

How do I control the iris borer?

The iris borer is a serious pest of bearded irises. The mature stage of the iris borer is a grayish moth. Female moths lay eggs on iris foliage and other nearby plants in late summer/early fall. The eggs hatch the following spring. The small larvae (caterpillars) bore their way into the foliage and feed on leaf tissue. Over time, the larvae tunnel down through the leaves and into the rhizomes. The caterpillars continue to feed inside the rhizomes and eventually destroy much of them. When fully grown, the larvae move into the soil and pupate. Adults (moths) emerge in late summer.

Bacterial soft rot often invades rhizomes damaged by iris borers. Rhizomes infected with bacterial soft rot become soft and foul-smelling.

Iris borers can be controlled by sanitation and the timely application of insecticides. Remove and destroy dead iris foliage in fall or very early spring. This will eliminate many of the iris borer eggs. An insecticide should be applied when the new shoots are four to six inches in length. An application of an insecticide at this time should destroy small iris borer larvae before they have the opportunity to tunnel into the iris foliage. Products that contain acephate, permethrin or spinosad should be effective. As always, carefully read and follow label directions when using pesticides. 

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picture courtesy of flickr.com