CORVALLIS, Ore. — With so many sources of gardening advice — from books and magazines to social media — it’s easy for misinformation to spread. Oregon State University Extension Service experts are setting the record straight on some of the most persistent myths in home gardening.
For more answers, contact your local OSU Extension Master Gardeners or submit questions (with photos, if possible) through Ask Extension, the university’s online question-and-answer service.
MYTH: Lime will remove moss from your lawn.
REALITY: Lime won’t solve a moss problem. Moss thrives in wet, shady conditions and infertile soil. Increase sunlight through pruning or thinning nearby trees, and apply nitrogen-rich fertilizer four times a year (two in fall and two in spring). Healthier, denser grass will outcompete moss.
— Alec Kowalewski, Grover Family Endowed Sustainable Urban Landscapes Specialist
MYTH: Pine needles make the soil too acidic for plants.
REALITY: Pine needles have a low pH when fresh, but as they decompose, soil microbes neutralize them. They make an excellent mulch that conserves moisture, suppresses weeds and adds nutrients over time. Difficulty growing under evergreens usually results from root competition and shade, not acidity.
— Amy Jo Detweiler, OSU Extension horticulturist
MYTH: Topping a tree controls its height.
REALITY: Topping only causes problems. Trees are genetically programmed to reach a certain height, and topping triggers weak, fast-growing suckers that increase hazards and stress. The large wounds caused by topping often lead to decay and a slow decline.
— Al Shay, former site manager, OSU Oak Creek Center for Urban Horticulture
MYTH: You can’t add too much compost.
REALITY: While compost improves soil health, too much can create nutrient imbalances. Excess organic matter (above 8%) can raise phosphorus to harmful levels and increase soil salts, both of which can stunt plant growth.
— Brooke Edmunds, OSU Extension horticulturist
MYTH: Bee houses boost native bee populations.
REALITY: Most native bees nest in the ground, not in cavities. Studies show bee houses are often colonized by wasps, which still provide pest control benefits. Bee houses can be useful but are not a solution for conserving native bee diversity.
— Gail Langellotto, OSU entomologist and professor, College of Agricultural Sciences
MYTH: Tree roots only grow to the drip line.
REALITY: Tree roots often extend well beyond the canopy. Depending on species, roots can reach two to four times the spread of the branches.
— Neil Bell, retired OSU Extension horticulturist
MYTH: Epsom salts make tomatoes thrive.
REALITY: Epsom salts (magnesium sulfate) should only be used if a soil test shows a magnesium deficiency. In most gardens, they can harm plants rather than help them.
— Brooke Edmunds, OSU Extension horticulturist
MYTH: Always add soil amendments to planting holes.
REALITY: Amending only the planting hole can stunt root growth. Roots may stay within the amended soil instead of expanding into native soil. Instead, amend the entire planting area before digging holes, or skip amendments altogether if soil is healthy.
— Neil Bell, retired OSU Extension horticulturist
MYTH: Brown recluse and hobo spiders are common in Oregon.
REALITY: The brown recluse does not occur in Oregon, and the hobo spider does not cause necrotic bites. The Centers for Disease Control and Prevention removed the hobo spider from its venomous species list in 2015. The black widow is the state’s most harmful spider to humans.
— Heather Stoven, OSU Extension entomologist and community horticulturist
MYTH: Watering on hot, sunny days burns plants.
REALITY: It rains in summer all over the world — and plants do just fine. Sunlight doesn’t scorch wet leaves. The real issue is evaporation, which reduces watering efficiency. (Cold water can damage sensitive indoor plants like African violets, though.)
— Brooke Edmunds, OSU Extension horticulturist
Previously titled Myth vs. reality: What’s the truth behind some common gardening practices?
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