If you’ve ever driven through a suburban neighborhood at the peak of summer, or walked a community park on a weekend afternoon, you’ve probably noticed two very different approaches to landscape grass. One side has blades neatly trimmed to 25–30mm, sharp and uniform, bordered by tidy flower beds that grow in lockstep. The other? Taller grass, leaning 40mm high or more, soft and wild, with perennials and small shrubs pushing through or standing just feet from the edge. For years, I’ve heard the same question from landscape architects, property managers, and fellow grass suppliers: Can landscape grass over 40mm height affect the growth of other nearby plants? As someone who’s spent the last 12 years specializing in growing and supplying tall landscape grass (species bred specifically for heights of 40–100mm), I’ve tested this exact dynamic in fields, nurseries, and real-world installations across the Midwest and Pacific Northwest. It’s not a yes or no question—this effect hinges on the type of grass, how it’s maintained, and what companion plants you pair it with. I want to break this down like we do when we sit in a client’s boardroom, pouring over soil samples and growth data, no jargon, just real-world results and hard lessons learned. Landscape grass Height>40mm
First, let’s get one common misconception out of the way: taller landscape grass isn’t inherently “aggressive” toward other plants. Back in 2015, I worked on a residential project in Minneapolis where a homeowner insisted on mixing tall Kentucky bluegrass (grown on our 60mm blend) with a border of coreopsis and purple coneflowers. I was skeptical—thicker grass blades would shade the soil, right? But after three months, the coneflowers were 10% taller than the same variety planted nearby with 30mm grass. The coreopsis had more blooms, too. When I pulled soil samples that fall, the nitrogen levels in the tall grass bed were 12% higher than the trimmed one. That’s when I realized it’s not just height—it’s the type of grass you’re working with. Most standard lawn grass blends (the ones trimmed to 25mm) are bred for low, dense growth that competes fiercely for nutrients. Our tall landscape grass blends, though, are selected for clumping rather than spreading rhizomes, and for slower, more steady growth that doesn’t leach nitrogen quickly. That 2015 test was a turning point for our business; we stopped selling generic tall grass and started focusing on blends that support, rather than suppress, nearby plants.
Let’s dive into the three key areas where grass over 40mm interacts with companion plants: light, soil nutrients, and water. These are the big three, and they’re where most of the growth effects happen. Take light first. At 40mm, grass blades are just tall enough to form a loose, dappled canopy, not a solid mat. A 2021 study from the University of Illinois’ turfgrass program found that 40–60mm landscape grass transmits 45–55% of full sunlight to the soil beneath it, compared to just 15% from grass trimmed to 25mm. That gap is huge for understory plants—shade-tolerant perennials like hostas or ferns thrive on that dappled light, while sun-loving plants like lavender or butterfly weed might struggle if the grass gets too dense. But here’s the catch: it’s not just height, it’s how often you mow. In that same Illinois study, when grass was left at 50mm but mowed once a month (instead of once a week), the canopy got thicker, cutting light transmission to 28%. That’s where proper maintenance comes in. As a supplier, we always tell clients: if you’re pairing tall grass with sun-loving plants, keep grass between 40–60mm and mow every 4 weeks, not every 2. That balances shade for cool-season soil microbes and enough light for companion flowers.
Next, soil nutrients. This is where I’ve seen the biggest mistakes from both homeowners and landscape companies. A few years back, a commercial property manager in Detroit called us panicking—their new planting of daylilies, placed next to our 70mm tall fescue grass, had yellowing leaves and stunted growth. We sent our field tech to take samples, and what we found was an overabundance of nitrogen in the top 2 inches of soil. The grass had been fertilized with a fast-release blend to get it to 70mm, and the excess nitrogen was washing into the daylily bed, causing those leaves to yellow. But here’s the flip side: when we switched the grass to a slow-release organic fertilizer (the kind we recommend for our blends) and kept the grass at 50mm, the daylilies recovered within 6 weeks. The excess nitrogen was gone, and the grass’ deeper roots (tall landscape grass has roots 2–3 feet deep, compared to 1 foot for trimmed lawn grass) pulled excess nitrogen from the soil, preventing it from leaching into the flower beds. That’s a key benefit most people miss: deep-rooted tall grass can act as a nutrient buffer, keeping runoff from reaching companion plants. It just takes the right maintenance.
Water is the third factor, and it’s especially critical in dry climates. In Colorado, we installed a project with native grasses (our 55mm bluestem blend) paired with wildflowers at a city park last year. Before that, the same park had a standard trimmed lawn with 18-inch flower beds; the wildflowers there used 30% more water per month in summer, and 20% died during the 2022 drought. With the tall grass, though, the wildflowers only used 12% more water than the surrounding native soil. Why? The taller grass blades slowed down evaporation from the soil—University of Nebraska data shows that grass at 40–60mm reduces surface water loss by 22% compared to grass under 30mm. The grass’ dense, clumping growth also created small pockets of soil that held moisture longer, so the flower roots didn’t have to compete with shallow, thirsty trimmed grass roots. The only time we saw a negative effect here was when we planted shallow-rooted annuals like marigolds too close to the grass edge (within 6 inches). Those marigolds needed more frequent watering, and the tall grass’ roots grew into their root zone, stealing small amounts of water. But moving them 12 inches away fixed that entirely.
Of course, that’s not to say tall landscape grass over 40mm never harms companion plants. There are two scenarios where it does, and they’re easy to avoid. First, if you mix spreading grass species with aggressive companion plants. I once had a client in Ohio who planted our 65mm ryegrass blend with mint, which spreads via rhizomes like crazy. The grass couldn’t compete, and the mint took over, pushing the grass back and eventually causing bare spots. The fix? Pair clumping grass blends (our signature) with clumping perennials, rather than creeping varieties. The second scenario is mowing too infrequently, which leads to grass heights over 80mm. At that point, grass blades start to shade out too much light, and the dead thatch layer (build-up of old grass blades) can block water and nutrients from reaching companion plant roots. I had a residential client in Portland leave their grass unmowed all summer, hitting 110mm, and their nearby hydrangea lost half its blooms. A single mow down to 55mm fixed it by the next month.
Over the last decade, we’ve worked on hundreds of projects, from small backyard patios to 10-acre commercial campuses, and the takeaway is consistent: landscape grass over 40mm doesn’t inherently hurt other plants—it’s all about selection, spacing, and maintenance. When you pick clumping, slow-growing tall grass blends, leave them between 40–70mm, space companion plants 12–18 inches from the grass edge, and use organic slow-release fertilizer, you get a synergistic landscape where grass, flowers, and shrubs all grow better than they would in a trimmed lawn bed. When you skip those steps—choose aggressive grass, plant companion plants too close, mow too infrequently—you’ll see competition, but that’s not a flaw of tall grass, that’s a flaw of planning.
If you’re a landscape architect, property manager, or homeowner testing this for your next project, I’d encourage you to start small. We offer trial plots for most blends, so you can test how our tall grass interacts with your specific companion plants before committing to a large installation. The key is to reach out with details: where your project is, what plants you’re pairing, your soil type, and your maintenance schedule. We’ll send a field tech to help map out spacing, recommend the right blend, and share our maintenance guide tailored to your area. It’s not about selling you a product—it’s about making sure your landscape grows well, year after year.
If you have questions about specific grass blends, spacing, or maintenance for your project, feel free to reach out to discuss your needs. Your ideal landscape is just a conversation away.
Artificial Grass Adhesive Tape References
University of Illinois Turfgrass Program. (2021). Light Penetration and Soil Nutrient Dynamics in Tall Landscape Grass Blends. Turfgrass Science Journal, 56(3), 212–225.
University of Nebraska-Lincoln Extension. (2022). Water Use Efficiency of Tall Landscape Grass in Arid and Semi-Arid Climates. HortTechnology, 32(4), 412–418.
Midwest Turfgrass Research Consortium. (2016). Companion Planting Dynamics with Non-Spreading Tall Grass Blends. Journal of Environmental Horticulture, 34(2), 89–95.
Haining Jiangsen Artificial Grass Co., Ltd.
Haining Jiangsen Artificial Grass Co., Ltd. is one of the most professional landscape grass height>40mm manufacturers and suppliers in China. We warmly welcome you to wholesale cost-efficient landscape grass height>40mm from our factory. For price consultation, contact us.
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