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Green Gardening: Environmentally Friendly Alternatives to Chemicals

By: Ministry of the Environment

Posted on: May 03, 08

Strategies for a Healthy Garden
Prevention is the best approach to maintaining plants. There are a number of ways to prevent pest problems before they occur. Preventative strategies include proper plant health care practices which promote healthy plants that are less susceptible to pest damage, drought, temperature extremes and other environmental pressures. Cultural, mechanical and biological control methods can also be used to manage pests at levels that will not impact the health of the plant(s).

Cultural Control Methods
Methods used to modify the growing conditions to boost plant vigour or impact a pest’s life cycle are known as cultural controls. Here are a few strategies for healthy gardens and pest management.

Landscape Planning-Appropriate Plants for Environmental Conditions
Choosing plants that are most appropriate for your garden environment can be the most important factor in growing healthy plants and avoiding pest problems. When planning your garden select plants suited to the soil type, drainage and pH, light and moisture conditions in your garden. Plants that are native to an area are the best choice for healthy growing. They are usually quite resistant to pests common to the area, and thrive in the natural climate.

Healthy Soil and Nutrients
Healthy soil is the basis for a healthy garden. Soil can include clay, sand, air, water and organic matter. The fungi, bacteria and other microscopic life forms in healthy soil are important because they break down organic matter, which, in turn, releases carbon and nitrogen into the soil for the plants to feed on. The more organic matter in your soil, the better for growing plants.
Properly composted plant material is valuable to the environment because it reduces materials going into the waste stream and provides a rich nutrient source you can put back into the garden. Synthetic fertilizers should be applied at the recommended rates. If you give your lawn or ornamentals too much synthetic fertilizer you may damage your plants. Be sure to spread the fertilizer only on the target area since any excess spillage on driveways and sidewalks can runoff into drains and eventually into lakes and rivers. 

Too much, too little or infrequent watering can cause diseases or the death of plants. A rule of thumb is to water deeply to encourage deep root growth of trees, shrubs and grass. When required, water in the morning so that plants dry before nightfall. Deep watering also helps to reduce drought stress. The frequency of watering will depend on the plant, soil conditions and the amount of rainfall.
Seasonal conditions and municipal water restrictions may also impact watering frequency. Avoid watering your lawn during summer drought periods when water reserves are low - let your lawn go dormant. Under severe drought conditions, beyond six weeks, lawns should be watered only about 1.5 cm every two weeks to hydrate but maintain dormancy. Trees, on the other hand, require water during drought periods. Soak the soil around the base of trees for up to two hours once a week. Younger, less established trees will require more frequent watering.

Plant Rotation
Rotating what you plant in a specific location from season to season can help prevent pest infestations. This is especially true for vegetables. Try not to plant two vegetables from the same family in the same spot in consecutive years. Use the following list of plant families as a guide.
• okra, beans, peas
• onions, leeks, garlic
• kale, cauliflower, cabbage, brussel sprouts, broccoli, kohlrabi, rutabagas, turnips, radishes, bok choi
• peppers, tomatoes, eggplant, potatoes
• celery, carrots, parsley

Cutting the Grass
Don’t cut your lawn too short when mowing in an attempt to reduce the number of times you need to cut the grass. Not only does the lawn look unattractive, it also places stress on the grass and allows weed seedlings to easily establish. Weed seeds need light to germinate; keeping the grass 6-8 cm in height reduces weeds. Raise the wheels on the mower and cut the grass so that no more than one third of the grass blade is removed. Make sure the blade is sharp as dull blades tear the grass making it susceptible to the entry of disease organisms whereas sharp cuts heal quickly. Also, use a mulching blade to return the nutrients from the clippings back into the lawn.

When you incorporate a large variety of plants into your yard you are more likely to create a balanced ecosystem. Annuals or perennials that produce pollen and nectar are attractive to birds, butterflies and other beneficial organisms. Provide water, whether it’s a jar or a bird bath, to attract beneficial organisms (ensure the water is replaced on a weekly basis to deter the breeding of mosquitoes). By having a diverse garden, you will minimize potential overall damage because most pests only attack specific plants.

Clean up Debris
By removing as much of the dead vegetable and plant debris as possible from your garden in the fall, you will eliminate a food and habitat source many pests need in order to survive over winter. This will minimize the potential for an infestation when you plant the following season. Clean up remaining leaves, stems and other plant debris in the spring. Plants and leaves can be disposed of by placing them in a garden composter. Avoid composting disease-infested plants, or weeds that have gone to seed.

Mulches are materials placed on top of the soil and are effective in reducing weed and insect pests. Materials such as landscape cloth, wood and bark chips, and plastic can be used to reduce weeds. Mulches also help retain soil moisture and warmth.

Mechanical Control Methods
Despite all your efforts to prevent pest problems from developing, sometimes they happen all the same. Many pests such as slugs and cutworms attack plants at night. It is essential that the pest be properly identified in order to take the appropriate action. If you detect an infestation in your yard or garden try some of the following mechanical or physical approaches that are environmentally friendly.

Hand Weeding and Pruning
Simply remove diseased or infested leaves and branches to control the problem. If the problem is still relatively contained, hand picking or pruning affected areas is an effective, environmentally friendly way of managing the pests, and most of the time does no harm to the plant. Use sharp gardening tools when cutting and removing branches or stems to avoid ripping. Proper pruning will allow plants to heal quickly and keep pests from entering.
Taking some time to pull weeds from your yard or garden is another great method of management. Hand pulling or using hand weeding tools gives you a chance to get to know your garden better. When you are familiar with your garden, you are likely to notice pest problems early enough to manage them through chemical-free methods.

A Blast from the Hose
A strong stream of water has a lot of force and is ideal to use on trees or shrubs to flush out insects. A blast of water can wash away small colonies of pests before they infest your garden. This method can be used to control aphids on ornamentals, but to be effective it must be done repeatedly.

Keep pests away from your plants by using barriers. Fine screening or row covers can be used as a barrier when placed over plants. They allow light, air, and sun to reach the plant, but can block out many pests. Knowing the life cycle of the pest and when to cover plants is important for effective control.
Garden centres sell coloured sticky lures (yellow to lure whiteflies and aphids and blue to lure thrips). Barrier tape can be used around trees and shrubs to prevent many pests from climbing up the tree. Copper strips can be used along garden edging to deter snails and slugs.

A trap is similar to a barrier, and is just as environmentally friendly. You just need to attract the pest to a container that it can’t escape from. Here are some ideas for different traps.
• If slugs or snails are your problem, then beer is your solution. Fill a dish with stale beer and place it somewhere in your yard or garden. The pests will climb into the dish and drown.
• A good way to control earwigs is to place a hollow tube in your garden overnight. Cut the tube from an old hose. Earwigs will gather in the tube, and in the morning you can remove the tube and tap out the pests into warm, soapy water to drown. The more tubes the more earwigs!
• Garden centres and other stores sell wasp traps which are used to collect scavenging yellow jacket wasps when placed between a nesting site and a food source.
• Sticky and pheromone traps are used to monitor insect populations rather than control insect pests such as Japanese beetles, Gypsy moths, Apple maggot, Codling moth and numerous other cutworms, armyworms and borers.

Biological Control Methods
Let nature do its job. Many insects in your garden prey on other insects. A few insects will not damage plants and they will provide a food source for beneficial insects as well as birds.

Ladybeetles are among the most beneficial insects you can have in your garden to help control harmful insect populations. Ladybeetles can be purchased for release into your garden (these varieties are not the multicolored Asian lady beetle (Harmonia axyridis) that has invaded Southern Ontario these past few years). You can also attract ladybeetles to your garden by providing a food source of pollen or nectar for them, a source of water and shelter.
Other beneficial insects such as bees, soldier beetles and parasitic wasps can be attracted to your garden using lures. Pollinating Mason bees can be attracted using cedar nesting sites. Lures and cedar nesting sites may be available at garden centres, or ask about suppliers in your area.
Parasitic nematodes can also be purchased to control some species of lawn grubs such as June and Japanese beetles and should be applied according to label rates.
Consider placing bird and bat houses, bird feeders and toad houses in your garden to attract these insect-feeding predators. Butterfly shelters will also attract pollinating butterflies to your garden as will planting ornamentals that attract butterflies such as butterfly bushes.


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