Spray paint, not plants: How to keep a vegetable garden weed- and pest-free

The universal spray: It’s a fungicide! An insecticide! A floor wax!

Rick, who works in Laurel and lives all the way up in Westminster, writes: “I have a small raised-bed garden that contains tomatoes, peppers, cucumbers, watermelons, onions and corn. I am looking for a universal-type product I can apply to keep insects and disease away from my plants so that I don’t have to spray a lot of different things.”

Whoa there, Nellie! There is no such product. And the ones that purport to be can be impossibly toxic to you, and deadly to the beneficial insects that will otherwise control most of your potential pests and to the bees and other pollinators your cukes and watermelon require.

More importantly, you don’t go into a season planning to spray the heck out of everything just in case something might happen. You already have a raised bed, which will prevent a lot of potential problems. Feed your plants with compost instead of chemicals and you’ll prevent even more. (Chemically-fertilized plants attract insect pests and are much more vulnerable to disease.)

Then, just keep a close eye on things, pull off any discolored leaves and/or squish any bad bugs. Daily inspections of the garden have been shown to be a much better defense than weekly sprays.

Crowded gardens invite problems

One thing jumped out about Rick in Westminster’s garden description: “I have a small raised-bed garden that contains tomatoes, peppers, cucumbers, watermelons, onions and corn.”

To misquote a line from Butch Cassidy and the Sundance Kid: “You sure you put enough plants in there, Rick?”

This garden seems way overcrowded; that’s a lot of plants for “a small raised bed.” And when there isn’t good airflow between plants, disease is a virtual certainty. And no spray will prevent or cure it.

So I suggest taking a good, honest look at this garden. Now, imagine the tomatoes as they’ll look in August, when they be four or five times larger than they are today. Does it still look like a garden? Or a place you might catch Cheetah taking a nap while some loud guy in a loincloth swings by overhead?

Removing a few plants now will prevent disease better than any spray. Peppers are easy to move, and they grow very well in containers. And if there are fewer than 30 corn stalks, consider just pulling them out; you need a lot of stalks to get decent pollination. And corn is a real sun and food hog. A too-small patch will use up a lot of your resources and not deliver any decent-sized ears.

And if it’s still too crowded, maybe lose a tomato plant or three. You’ll get more and better fruit from three plants that have a good amount of open space around them than from a dozen that are collapsing into each other.


Ants and spiders aren’t pests

I asked Rick to describe his set-up. “It’s a U-shaped raised bed,” he replies, “no wider than 4 feet at any point. I used Leafgro for the soil and see no insect activity yet other than some small ants and a few spiders.”

Well, then, forget the sprays, Rick. The combination of raised beds that you don’t have to step into and that Leafgro (a fine compost made and distributed by the state of Maryland) will help keep problems at bay by growing super-healthy plants for you.

And spiders are a great insecticide; they dine on enormous numbers of pests and don’t harm plants. (Or people. Just because you’re scared of them doesn’t mean they’re a real threat.)

And ants aren’t a problem. In fact, they naturally aerate the soil with their tunneling activity, and they keep termites away. (The ants raid the termite colonies and consume their young, so termites stay away from areas with ants.)

So ix-nay the spray and just sit back and watch how well nature can protect your plants!

Wet feet can kill carnations

Lou in Rockville writes: “My wife’s carnations came up recently and now they all seem to be
dying. Is it the D.C. weather? Got any suggestions?”

Well Lou, there are lots of kinds of flowers that can be called “carnations.” All are members of the very large Dianthus family, commonly known as pinks.

But they all have the same needs. The first is an exquisitely well-draining soil. Poor drainage will kill them.

They are also one of the very few plants that need an alkaline soil. Our soils tend to be acidic, so Dianthus, pinks, carnations — whatever you want to call them — often benefit from a dusting of wood ash or lime. (A foolish application of peat moss or a fertilizer designed for acid-loving plants could also do them in.)

And finally, if a nearby lawn is treated with herbicides, it can be death to any plant. Remember: What you put on your lawn does not stay on your lawn.

Don’t mock those strawberries

Blair in Sterling writes: “I have a problem with Indian mock strawberries that have invaded my
healthy organic lawn. I tried pulling them out with only minor and temporary success before they returned in force. Do you know of a solution short of killing the strawberries along with the lawn, and reseeding?”

These plants, often called “wild strawberries,” are an escaped ornamental that was once sold as a very popular groundcover. The little red fruits aren’t poisonous, but they’re also tasteless.

Pulling slowly from soaking wet soil is the recommended control. If you were pulling during the recent dry times, it wouldn’t have worked. Try again with saturated soil, and pull slowly so you get all the roots out.

Then be sure to never cut that lawn lower than three inches. These weeds are generally only found on bare ground or very low-cut lawns.

If you have general success but a few stragglers, a second round of wet-pulling should finish them off. And if they’re the type with fairly large leaves (some varieties are essentially just runners with flowers), you can spray any leaves that reappear with one of the new iron-based herbicides. But use the herbicide only during a hot and dry stretch, not when the plants are well-watered.

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