As the gardening season gears up, it’s time to bust some myths. Myths tend to stick around, no matter how many times they’re corrected. Once you know the truth, pass it on.
Myth: Add gravel to the bottom of plant containers to improve drainage.
Reality: This practice makes the soil more waterlogged. Instead, make sure your pots have drainage holes and use high-quality potting media specific to your needs. Mixes with smaller particles and high components of vermiculite, peat or compost hold water for your water-loving plants better than a mix with larger particles such as bark, which will have more drainage for plants that don’t like wet feet.
Myth: Add sand to loosen clay soil.
Reality: A resounding “no” is the answer. When sand is added to claylike soil, it will set up into rock-hard adobe once it is watered, making it even more difficult for plants to grow.
Instead, add compost to clay soil to loosen it. The addition of organic matter to this type of soil improves the soil structure, creating more pores and thereby improving the drainage and the capacity for plant roots to work their way through the soil.
For a new garden, work 3 to 4 inches of compost into the soil with a shovel or spading fork. This organic matter also helps feed the millions of microbes in the soil, helping to drive the soil food web.
Myth: Drought-tolerant plants never need irrigation.
Reality: A drought-tolerant plants is one that, when established, requires no supplemental water and will still grow and flower normally. It gets by on what falls from the sky. If you are considering native plants for the garden, most of Oregon’s native plants (streamside or wetland plants excepted) fit that definition.
Many non-native plants may also be grown without supplemental irrigation. However, these plants require irrigation to get established. If planted in the spring, they may require irrigation at planting and periodically through the first summer.
In mild areas, the best way to establish drought-tolerant plants is to plant them in the fall and water until it starts to rain. This results in a truly drought-tolerant plant established by the following summer.
Myth: Grass clippings cause thatch.
Reality: Clippings don’t cause thatch. Thatch is caused by lateral growth of the grass—more specifically, by rhizomes, which are the below-ground lateral growth, and stolons, the above-ground lateral growth. Turf such as creeping bentgrass and Kentucky bluegrass produce rhizomes and stolons. The dominant lawn grass in the Willamette Valley is perennial ryegrass, which does not produce rhizomes or stolons, and therefore does not accumulate excessive amounts of thatch.
Returning your grass clippings when mowing makes grass greener because you are recycling essential nutrients such as nitrogen, phosphorous and potassium back into the soil.
Myth: Coffee grounds in the soil help plants grow better.
Reality: Coffee grounds may benefit some plants—as they break down, they add some great organic byproducts—but in many cases, they harm the plant. Use coffee grounds sparingly around plants or in your compost pile. Mix grounds with another organic product if using it as a topical mulch.
Coffee grounds create an acidic environment in the soil. Research shows coffee grounds may increase or decrease soil pH, and this change may be short lived. Do not depend on spent coffee grounds to keep a lower soil pH (more acidic soil). You are better off using elemental sulfur if the goal is to consistently keep a lower soil pH.