Photo credit: Nancy Knauss
New and experienced gardeners sometimes follow advice without knowing if it is based on a myth or valid science. Here are a few of the untruths about gardening that I’ve heard over the years, followed by the facts that today’s gardener should heed.
Fiction: When using fertilizers and pesticides, if a little is good, a lot must be better.
Fact: An exact measurement of fertilizers and pesticides is crucial for a healthy garden. I cannot overstress the importance of reading the product label carefully and using no more than the recommended dose. Too much fertilizer can burn the roots and stunt the growth of your plants; overused pesticides can burn the leaves. Both fertilizers and pesticides can raise toxicity levels in the soil and cause serious health complications. The preferred strategy is to diagnose first to determine if the plant damage is caused by an insect, a disease, or lack of nutrients. If you need help with this, contact your Extension office. If it is pest damage, the second step is to decide how much you and the plant can tolerate. I don’t mind a few nibble holes in my leaves, but I need to know if the plant will die if not treated. Here are five strategies to reduce a pest’s impact:
- Create a physical barrier to deny the pest access.
- Keep plants healthy, so they can fight off diseases and pests.
- Let Mother Nature do the work by encouraging natural predators and parasites.
- Use mechanical controls, such as picking off pests from your plants (I drop Japanese beetles into a container of soapy water.)
- Use chemical controls as a last resort. Remember that pesticides are tools, not silver bullets.
Fiction: Fertilize all of your plants regularly throughout the growing season.
Fact: Much of the fertilizer you apply to plants washes away and into our local streams. A more environmentally safe approach is to feed the soil, not the plants. Provide nutrients to the soil by adding compost and organic mulch. A plant may become stressed if you add fertilizer when it is not nutrient deficient. Also, fertilizers can cause excessive growth. Base your decision to fertilize upon the health of the plant, the rate of growth you desire, and a soil analysis. It is a good idea to test your soil every few years. Purchase a soil test kit from your local Extension office, then follow the recommendations that come with the test results.
Fiction: An expansive lawn is a must for every homeowner.
Fact: Lawns have high maintenance costs with Americans spending $30 billion a year on the lawn care industry. They have a negative impact on the environment: the average riding mower emits the same amount of pollution in one hour as 34 cars; gas-powered garden tools cause 5% of all U.S. air pollution. While lawns provide little support to wildlife, lawn chemicals pose a risk to animals and humans. Water runoff, spiked with fertilizers, enters storm drains then pollutes our natural bodies of water causing harm to aquatic plants and animals. Homeowners tend to water their lawn excessively, especially during the summer when it starts to turn brown (it is actually going dormant and will revive.) Finally, lawns are boring compared with a varied, diverse landscape with year-long interest.
What to do:
- Consider reducing the size of your lawn. Plant islands of native plants including herbaceous perennials, deciduous trees, shrubs, vines, and grasses that offer ornamental value and adapt to our local environment. Once established they require less water, maintenance, and chemicals than lawns.
- Use groundcovers, especially in hard-to-grow and hard-to-mow areas.
- On the lawn you keep, avoid watering during its dormant period.
Fiction: Topping a tree will control its height.
Fact: Topping is the cutting back of large branches in a mature tree. Homeowners have their trees topped when they fear the height is unsafe and the tree may blow over. This fear is usually groundless, as a healthy tree has a root system sufficient to support it. Trees need leaves to manufacture food; when you remove the leafy crown, the root system starves. Rapid sucker growth occurs in an attempt to provide food for the compromised root system. The greatly weakened tree quickly regains the height it once had, becoming deformed and ugly. Insects and disease easily invade the large wounds caused by tree topping. The results may lead to a slow death of the topped tree. To keep a tree in healthy condition, a light pruning every three years is preferable.
Fiction: You should add sand to loosen heavy clay.
Fact: Gardeners often have to deal with heavy clay soil and rocks. Adding sand, however, is not the answer to the clay soil problem. Clay and sand, with the addition of rainwater, form a rock-hard substance resembling concrete. Instead of sand, dig in plenty of organic matter that will not only loosen the heavy soil but will also add nutrients.
Fiction: Go twice as wide and twice as deep as the root ball when planting shrubs and trees.
Fact: It is true that when planting shrubs and trees the hole should be twice as wide as the root ball; however, it should be no deeper. Ultimately, deep planting will slow root growth. You want to encourage the plant’s roots to grow out rather than down to make the plant more stable and enable the roots to better find water and nutrients. Look for the root flare where the roots spread laterally away from the trunk: the hole should be as deep as the distance from the root flare to the bottom of the root ball. Loosen the root mass and place the plant in the hole. Backfill with the soil from the hole, firming as you add it. Do not add fertilizer at this time because it can damage newly developing roots. When the hole is two thirds full, water to settle the soil. When backfilling is complete, water thoroughly and add two to three inches of organic mulch, keeping it away from the plant stem or trunk.
Fiction: Plant closely for an instant landscape.
Fact: When installing a new garden, it is so tempting to place plants close together to create an immediate landscape, but those plants will suffer from decreased light and air circulation. As well as being susceptible to stress and diseases, they will be in constant competition for nutrients and water. Closely planted trees and shrubs will need more frequent pruning and maintenance; they may even die if they overgrow the space you give them. Planting too close to buildings is similarly detrimental. Always check mature sizes before planting: the plant label, or a reference guide will suggest general spacing requirements. You should measure from the center of one plant to the center of the next. They will eventually fill in the gaps. In the meantime, you may grow colorful annuals between them until they become larger.
You cannot believe every bit of gardening advice you hear. Please don’t let superstitions and poor practices waste your time or harm your beautiful plants.