Tim Johnson: Senior Director of Horticulture at Chicago Botanic Garden

Tim Johnson, senior director of horticulture at the Chicago Botanic Garden, advises gardeners on eradicating invasive grasses in garden beds, a challenge exacerbated by Chicago’s humid summers and compacted soil. The methods, tailored to regional conditions, aim to prevent ecological disruption while preserving desired plants.

What Methods Are Effective for Removing Invasive Grass?

Johnson emphasizes mechanical removal as the first step, using tools like a broadfork to loosen soil without disturbing root systems of nearby plants. “Grasses like quackgrass spread via rhizomes, so cutting them at the root is critical,” he says. “But it’s a labor-intensive process—gardeners should focus on small sections to avoid soil compaction.”

The Chicago Botanic Garden’s 2024 study on invasive species highlights that chemical herbicides, while effective, risk harming beneficial organisms. “We prioritize organic solutions,” Johnson adds. “Vinegar-based sprays or boiling water can kill grasses on contact, but repeated applications are often needed.”

Why Does Grass Invasion Matter to Chicago Gardeners?

Invasive grasses threaten biodiversity in urban gardens, competing with native plants for nutrients and water. The City of Chicago’s 2025 Environmental Impact Report notes that 68% of residential gardens face grass encroachment, costing residents $120 million annually in maintenance. “It’s not just about aesthetics,” says Dr. Maria Lopez, a local ecologist. “Invasive species disrupt pollinator habitats and reduce soil health.”

Local ordinances, such as the 2023 Chicago Lawn Care Standards, encourage sustainable practices. Gardeners are advised to use compost instead of synthetic fertilizers, which can fuel grass growth. “The goal is to create a balanced ecosystem,” Lopez says. “It’s a long-term investment.”

How Can Gardeners Prevent Grass Regrowth?

Johnson recommends mulching with 3-4 inches of wood chips or straw to block sunlight and inhibit seed germination. “Mulch also retains moisture for desirable plants,” he explains. “But avoid piling it against stems—this invites rot.”

The National Gardening Association’s 2026 guidelines emphasize soil testing to address nutrient imbalances. “If soil pH is too low, grasses thrive,” says Dr. James Carter, a soil scientist. “Adjusting it to 6.5-7.0 can deter invasive species.”

What Local Services Help with Grass Removal?

Chicago residents can consult [Local Horticultural Society] for free workshops on organic weed control. [Chicago Lawn Care Services] offers customized removal plans, while [Regional Gardening Cooperative] provides bulk compost at reduced rates. For legal guidance on municipal landscaping laws, [Chicago Municipal Law Firm] advises residents on compliance with city codes.

“It’s about understanding your garden’s unique needs,” Johnson says. “A one-size-fits-all approach rarely works.”

What’s the Long-Term Impact of Grass Control?

Effective grass management supports Chicago’s 2030 Green Infrastructure Plan, which aims to increase urban green spaces by 15%. “Healthy gardens improve air quality and reduce heat islands,” says Mayor Lori Lightfoot’s office. “Every yard matters.”

Gardeners like Sarah Mitchell, a Chicago resident, attest to the benefits. “After using these methods, my garden’s biodiversity has skyrocketed,” she says. “Bees and butterflies are back—It’s magical.”

How Can Residents Access Expert Advice?

The Chicago Botanic Garden’s website hosts a free, downloadable guide on grass removal. [Local Extension Office] offers free soil testing, while [Chicago Community Garden Network] connects residents with volunteer-led restoration projects. For legal or regulatory questions, [Chicago Zoning Department] provides resources on landscaping permits.

“This isn’t just about ridding your garden of grass,” Johnson says. “It’s about fostering resilience in our urban ecosystems.”