Grass in Your Flower Beds


Grass is Nice

Grass has swallowed up the tall bearded iris in this bed

Most homeowners crave a beautifully manicured, lush carpet of turfgrass. The sea of thick, green grass surrounding the Viette home is the envy of visitors who come to wander through the extensive gardens surrounding their home.

Yes, grass is nice – when it is growing in your lawn! It’s not so nice when it invades your flower beds and mixes in with your perennials, shrubs, and trees.

What do you do then?

One of the worst of the grassy weeds is Bermudagrass; aka wiregrass. This  warm season, perennial grass is often used as a turfgrass in southern zones because it is tough and durable and quite drought and heat resistant. The problem is that it is a very aggressive grass and can quickly spread into flowerbeds if it is not kept under control. Even if you don’t have a Bermudagrass lawn, this invasive grass can take hold and overrun your gardens.

Other perennial grasses that can infiltrate cultivated areas are Johnsongrass, quackgrass, and perennial ryegrass.

Annual grasses like crabgrass, barnyardgrass, foxtail, and annual ryegrass can also be major headaches in flower gardens.

How do we get rid of it?

Sethoxydim selectively targets grass but will not kill broadleaf weeds like this field pennycress.The problem is killing the grass but not the desirable ornamentals. Glyphosate (Roundup) can be used but it is non-selective and you have to be exceedingly careful not to get any spray on your plants. This is difficult to say the least and impossible in cases where the perennials are growing (or trying to grow) through a sea of invading grass.

Luckily, there is an answer – a selective herbicide containing the active ingredient sethoxydim. It can be found under the trade names Poast, Segment, and Vantage, among others. Bonide Grass Beater contains sethoxydim and can be found in most full service garden stores.

When applied according to the label instructions, sethoxydim can be sprayed over the top of most non-grass perennials, shrubs, and trees without harming them. It does not kill broadleaf weeds or sedges (sedges are not grasses), but it is ideal for post-emergent control of both annual and perennial grass weeds in your flowerbeds.

Grass growing throughout a row of dayliliesAn example of how it works …

At Viette’s, we have had some serious problems with grass taking over a few large sections in several of our daylily fields. Grass came up right in the middle of the rows completely surrounding the clumps of daylilies. It was pretty bad! We had to do something or the grass would crowd out the plants.

Our field manager and his helper used Segment (13% sethoxydim) to spray these patches of grass in the fields. Because daylilies are listed as tolerant to sethoxydim, they were able to spray right over the daylilies without harming them. This is ideal for post-emergent grass control in our fields.

The label on this herbicide is extensive and it is important to read and follow the instructions. The label includes a long list of tolerant species of perennials, shrubs, and trees. It can even be used in the vegetable garden when applied according to the label directions. As with any pesticide, be sure to read the label and follow the directions carefully.

The results were pretty striking

After three days ...

After three days








After fourteen days ...

It did a pretty good job eliminating the grass!

The daylilies are healthy and are growing well.

Luckily I can’t say as much for the grass!