Hardy annuals tolerate frost


Q. I was ordering some calendula seed for my flower garden and noticed that it was listed as a hardy annual. What is meant by the term hardy annual?

A. I assume that you are ordering Calendula officinalis, or pot marigold. An annual is a plant that completes its life cycle in one year or less and does not return the following year. The term hardy annual is somewhat subjective. It refers to an annual plant that tolerates frost. They will continue to grow and bloom after a night of frost. Other plants may be termed half-hardy or tender. Half-hardy plants will tolerate light frosts but are killed after a heavy frost. And tender plants will not tolerate frost at all.

Q. I have seen cypress mulch for sale at local garden centers and had considered buying it for its nice red color. Does it work as effectively as hard bark mulch in the garden?

A. I have only limited experience in working with cypress mulch, but it should be effective mulch. Yet there are several good reasons to buy hard bark mulch. First, hard bark mulch is natural to our area. Whether it comes from Maryland or from a nearby state, it will be composed of bark from the trees of our Eastern deciduous forest. The bark of cypress trees comes primarily from Florida and in my opinion does not belong in our gardens. Cypress trees are a dwindling natural resource, and the demand for mulch is accelerating their depletion.

Cypress mulch also bleaches out after several months of exposure to the sun. It then becomes a bleached orange in color. In addition, cypress mulch is generally more expensive than hard bark mulch. Hard bark mulch has its problems, but why buy mulch from Florida when our local mulch is a superior product and is less expensive?

Q. English ivy has taken over our yard, and we would like to get rid of it. Do you have any suggestions?

A. English ivy is an invasive plant and can be very difficult to get rid of. Hand pulling, digging and cutting can be very tiring and frustrating. But chemical control is not always effective, either. It will take a persistent effort on your part to get rid of the ivy. It will not disappear on the first try, no matter what method you use. This is another place where I have made my peace with herbicide use, and I would use glyphosate (Round-up) to kill it. Because the leaves of English ivy are covered with a waxy cuticle, herbicides have difficulty penetrating the leaf surface and entering the plant. Also, mature plants are less susceptible to herbicides than are young plants. Knowing this, I would cut the vines back with a string trimmer, allow them to re-grow some young leaves, and then spray the young leaves and cut stems with glyphosate. You will have to repeat this several times.

Dennis Bishop is an urban horticulture educator for the Baltimore office of the Maryland Cooperative Extension Services. If you have a gardening or pest problem, you can call the Home and Garden Information Center hot line (Monday through Friday, 8 a.m. to 1 p.m.) at 800-342-2507. You can also e-mail questions, order publications and diagnose plant problems by visiting the Web site, www.agnr.umd.edu/users/hgic.

This week's checklist

1. Fruit trees can be pruned now, but it is best to wait until late winter, right before bud break. This is especially true for peach trees. Pruning on mild winter days may stimulate growth and cause a premature loss of dormancy.

2. Allow potting soil to dry out before watering your houseplants. Over-watering is a major cause of houseplant problems during the winter months.

3. Remove and discard the egg masses of the Eastern tent caterpillar from the branches of crabapple and cherry trees. The egg masses resemble black Styrofoam.

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