Dirty Fingernails: Don’t get worked up over bugs

horn worm
Credit: ravallirepublic.com

Q: Do you recommend using landscape cloth when planting a new flower bed?

A: Only for a year or two of weed control, if you think that the weed problem will be severe and that no one will have time to weed. I recommend leaving landscape cloth in place not more than two years. By that time weed seeds will have blown in, and their seedling roots will have pierced the landscape cloth. Meanwhile, grass stems will have infiltrated from below. In another year the landscape cloth will have become the center of a weed carpet. Another problem is that landscape cloth prevents perennials and shrubs from their normal ability to spread sideways.

Q: What do you do about bugs that you don’t recognize but which are eating holes in leaves?

A: Most of the time I do nothing. I look once a day or so, to make sure that the number and/or size of the holes are not increasing at some astonishing rate. As long as the plants are staying ahead of the damage, I let plants and bugs deal with their own problem.

I believe that healthy gardens include healthy insect populations. If I interfere unnecessarily, I am likely to upset the ecological balance, just because I do not understand the complexity of what is happening in the garden. I do not mind seeing a few holes in leaves. For instance, I love having a variety of butterflies throughout the summer. But it is not possible to have butterflies without having the caterpillars which grow up to be butterflies. And caterpillars eat holes in leaves.

This is not to say that all leaf-eating bugs are welcome in my garden. There are a few kinds which cannot coexist with garden plants. Like biblical hordes of locusts, they would strip the countryside of all its green. But these are truly rare occurrences. Many years ago my garden was visited by a few tomato hornworms, and one hornworm can strip a leaf to its skeletal veins in less than an hour. I picked off the worms and disposed of them, and I have not seen a hornworm since.

Every summer when white butterflies appear around the broccoli and cabbages, I move to protection mode. Either I cover all the plants with netting, or I spray them weekly with Bt, the bacterium which kills caterpillars but nothing else. And I spray Bt only on plants in the cabbage family. I know that they would be eaten out of existence by cabbageworms. Other caterpillars I do not spray, because the damage they cause is not fatal to plants. They munch, not devour.

After years of gardening in the same place I have fewer and fewer problems with damaging insects. Though I cannot prove the connection, I think that interfering as little as possible has increased the beneficial insect population while decreasing the enemies. It has allowed birds to eat their fill of bugs, for one thing, so that I get to watch more birds. I am reminded of the old dictum that most garden insects are good news to a gardener; only a few make trouble.

Whatever I do about insect control, I never use a product that is designed to kill many kinds of insects. Simply because of the natural insect distribution, these “broad spectrum” insecticides kill far more good bugs than bad. They kill many insects which would otherwise be eating the bad ones. There are a few insecticides like Bt and neem which target only some bugs. These are the ones I use, but still I employ them as a last resort. I spray only an out of control problem, perhaps once a year.

I also use a forceful spray of water to knock bugs off the plants they are eating. I consider water to be a fairly benign weapon.

Q: If I want to save seeds from any of my vegetables, to grow next year, how can I be sure that they will grow the plants I expect them to be?

A: Growing a true variety from seed is so complicated that few gardeners try it. Plants making seeds for the next year must grow in isolation from any other varieties; their location must also be rotated regularly if the true variety is to be maintained. If seeds are grown in the same place two years in a row, the second year’s crop will inevitably contain some plants from the previous year. Seeds drop to the ground before harvesting. Unless it is the same variety which is always grown,  the two varieties are mixed into a new one.


Complications like this explain why commercial seed production was such a boon to gardeners when it first appeared. In this country a few Shaker colonies in New York pioneered the growing, packaging, and sale of vegetable seed. Gardeners were so excited to buy their dependable seeds that the Shakers could not keep up with the demand. Soon commercial interests got into the seed business, and the movement has only increased from that point.

Another problem, obviously, is cross-pollination. To keep a strain of any vegetable pure, it must be grown far enough away from other strains that bees will not travel between them. Sometimes plants grown to produce seed are kept under cover, so that flying insects cannot reach them.

All this makes it understandable why growing one’s own vegetables to produce seed is done for fun. It can be very pleasurable, but it is a labor of love and experimentation. Growing vegetable seed to sell to seed companies is a specialist’s business.

Q: We bought some foxgloves several years ago, but most of them lasted only two or three years. Is there a way to keep foxgloves in our garden, or is it necessary to replace them every few years?

A: Foxgloves survive our winters easily, so cold weather does not prevent their being a lasting presence in our gardens. However, most foxgloves are biennials or short-lived perennials. They must be continually replaced from seed. Since foxgloves are champion seed producers, an easy way to ensure seedlings is to let a few flower spikes make ripe seed, or to leave the bottom few inches of most flower spikes until seeds ripen and scatter.

Because foxgloves are fussy about their growing conditions, try letting some of the seeds fall around the existing plants. Then offer them a choice of other locations by scattering some seed in likely places. Do not clean up the area so thoroughly that the scattered seeds are removed. The foxglove seeds will want soil that does not dry out and is shaded for part of the day. You may discover that the foxgloves prefer some new location to their original one.

Watch for baby foxgloves in spring, and do not weed them out. Seedlings will show up as tiny rosettes of quilted leaves, densely packed together. The crowded seedlings can be left to thin themselves. They will make only ground-hugging leaves the first year. Tall flower spikes will appear in the second summer.

Credit: ravallirepublic.com