Being rooted to one spot has disadvantages, like not being able to evade others that want to eat you or crowd you out, but how much help should we give our garden plants?
For a sustainable garden, we need to balance what our plants need to survive with what we want them to look like. This is likely to mean embracing diversity in the lawn and enjoying some holes in leaves as indications of caterpillars that will become butterflies, food for insect-eating birds, and construction materials for native leaf-cutter bees. But if aphids overrun new rose growth, or your citrus gets whitefly or sooty mold, should you spray? What if dandelions and plantains start to invade your lawn?
The first thing to keep in mind is that pesticides and herbicides are almost all toxic to people too, and can affect beneficial insects and desirable plants as well as invaders, and can contaminate water. It’s safer and cheaper to avoid them whenever possible. So how can you minimize the use of chemicals in your garden?
Lawns: Weeds are generally the problem in lawns, but regular dousing with herbicides can be avoided if you have healthy, thick turf since that will make it harder for weeds to grow.
- First, choose a grass that will be happy with your light conditions. If your lawn area becomes more than a little shady, reduce the shade, replace the lawn with a more tolerant variety, or make a flowerbed.
- Next, watering your turf to a depth of about 6” once a week is usually enough. Less frequent, deeper watering encourages roots to grow further into the soil reducing the loss to evaporation that occurs with shallow watering. Step on the grass and if it doesn’t spring back in about a half hour, it probably needs water.
- Fertilizing in spring will help replace the nitrogen used for leaf growth, but doing this regularly will encourage growth during dry times of year, which means more watering.
- Keep the lawn on the long side, 2-3”; don’t remove more than ¼ of the height at a time; use sharp blades; and let the clippings sift down to the ground and compost there. Rake out dead grass once a year.
- When you see a weed, pull it out.
Annuals, perennial, shrubs: How can you reduce your garden’s pest load without using poisons?
- Grow plants or varieties that are naturally resistant; for instance, some roses are not subject to black spot or rust.
- Be sure the plants have good growing conditions: my euonymus with afternoon sun is fine but the one with too much shade gets mildew.
- Keep a sharp eye out for little invaders. Take a tour around the garden every few days. Remove infested leaves and toss them in the trash; squash aphids; wash off upper and lower surfaces of leaves with a heavy spray of water; handpick snails; put sticky barriers on trunks to prevent ants from farming aphids and scale whose secretions lead to sooty mold growth.
- Include plants that provide food and housing for beneficial predators like ladybugs, praying mantises, parasitic wasps, and lacewings.
- If you’ve tried to grow a plant and it keeps getting eaten or diseased no matter what, replace it with one that is tougher.
- Cover the ground with plants or mulch so that weed seeds have trouble getting to the soil.
- Pull weeds as soon as you see them and never let them go to seed.
And if you do decide to resort to chemicals? No matter what you use, be sure you follow directions and check to see that it is safe for the plant you want to treat (and not too bad for you!). Also, to avoid killing bees, don’t spray when they are out foraging and don’t treat the blooming plants they are visiting.
These pesticides are not too bad: (these all smother the insects)
- Insecticidal soap
- Horticultural oil (petroleum-based).
- Neem or canola oil (plant-based)
But these should be avoided:
- Pyrethroids such as permethrin (toxic to aquatic organisms).
- Organophosphates such as malathion (toxic to many beneficials).
- Carbaryl (kills bees, beneficial predators, and earthworms)
- Metaldehyde snail bait (toxic to other animals such as dogs)
- Neonicotinoids such as imidacloprid (move throughout the plant into the flowers and kill pollinators– ask local nurseries to stop selling plants grown using these common pesticides).
Demystifying Sustainability is an initiative of Sustainable Claremont (sustainableclaremont.org).