By Scott Calhoun
Striking a balance with nature is what gardening is all about. In my own yard (which is almost entirely organic) that means creating plantings that are easy to maintain and not prone to pest infestation. Even so, sometimes infestations happen, and when they do I always try to use the least-toxic option. Below are a few of my favorite design tips and remedies for organic gardens.
Organic design: defensive gardening. When designing a garden that naturally resists pest problems, diversity rules. In gardens such as the front courtyard planting pictured above -- with a mix of trees, shrubs, agaves, cacti, and tough characters such as lantana and rosemary -- the pests have less chance to get a foothold. Most bugs are specialists: They eat a narrow range of plants. Therefore, if you mix in a bunch of plant species, you minimize the chances of an infestation that moves from plant to plant.
Water, water, and soapy water. Even when you take precautions, you still may end up with a pest problem now and then. When you find a problem, ask yourself, “Is this likely to be fatal, or is it just cosmetic?”
I’ll use a case-in-point: Cochineal scale often infest purple prickly pear cacti. The signs, which you can see in the photo, are white, cottony dots on the plant’s pads. The infestation can go on for years; although unsightly, it is rarely fatal. However, it is unsightly enough that I want at least to minimize it. I control the scale by spraying it with a strong jet of water from a hose-end nozzle until the scale is gone. Typically I have to repeat this several times.
Again, I start with the best nonchemical practices. Adding a few drops of dish soap to a spray bottle also kills a good number of insects. It is amazing how many pests you can control or eliminate simply by spraying them with water or soapy water. You can control spittlebug on rosemary and salvia, and even reduce stubborn pests, such as whiteflies, that can invade your lantana.
Stuff you eat. I become a little fanatical about organic gardening when it comes to my veggie garden. I don’t want to take a chance feeding my family any suspect chemicals. For me this begins by making my own compost with veggie scraps and coffee grounds, supplemented with bat guano, organic blood, and bone meal. That is it. No extra additives.
If I do get a serious problem -- say, a mass infestation of worms wiping out my tomatoes -- I first try to pick them off by hand. Failing that, I may resort to the natural bacteria Bt (Bacillus thuringiensis), which kills soft-bodied insects, including mosquito larvae!
You can employ the same tactic -- using diversity as a defense -- in the veggie garden. The photo illustrates how you can tuck in lettuce around artichokes, and mix it with onions and irises to discourage pests. Again, less monoculture (one-crop) planting is good for preventing big pest problems.
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