Eliminating coarse grasses

[Dr Mike Oxgreen]

I have a lawn of about 300 square metres, which is in reasonable health except that large areas of it are dominated by really coarse, ugly weed grasses. I'm 90% sure that the worst offender is "Yorkshire Fog" as it's known in the UK - a Holcus species.

I'd like to know what lawncare regime I should be following to make life as difficult as possible for the coarse grasses and encourage the finer ones - with a view to shifting the balance of power and gradually ending up with a nicer lawn. None of the books I've found go into much detail about this.

The only thing I've read consistently about Yorkshire Fog is that it doesn't like being over-grazed - and therefore I've decided to mimic this by mowing as frequently as I can during this summer: every third day if possible, mowing at a moderate height (not too short). Will this work?

Some time in September I plan to spend a weekend scarifying, aerating and then overseeding with fine grasses. I did this last year in the spring, but I think I understand now that autumn is better. I also think I could scarify a bit more aggressively.

So... do you think this regime will have a significant impact on shifting the balance in favour of the finer grasses?

I don't think I feel brave enough to glyphosate the whole lot and seed it from scratch. Or is that what I should do?

[mike]

I've had some small success mixing detergent with roundup and using a brush to paint it on individual blades of offending grass. One horror story, tho... I did this on a species that propagates by sending underground shoots to the next patch. I painted on the roundup. Some days later, I had a yard that looked like a roadmap. The dead patches of grass were connected by brown patches that followed the shoots between patches.

[Dr Mike Oxgreen]

Thanks for replying!

Unfortunately I've got large areas of grass that are dominated by Yorkshire Fog; at a guess I'd say at least a quarter to a third of the lawn, in large patches. So it won't be practical for me to be so selective with the glyphosate. I think my choice is between nuking large areas and reseeding, or finding a long-term cultural regime that favours the fine grass at the expense of the Fog.

Something I didn't mention in my opening post was that I did glyphosate some of the very worst patches last year, where the Fog had formed particularly dense tufts. I then reseeded with fine grass. So I now have patches of very fine grass mixed in with the patches of very coarse grass, which admittedly looks a bit daft but at least it's a step in the right direction!

[Frank]

There are some new herbicides available. Google them up. They may just hit the course grass and leave the good stuff alone.

[trader4]

Being in the US, I don't know about Yorkshire Fog, but undesirable grasses are a big problem and share many of the same issues. The biggest one is that for many of them, there is no selective herbicide. I'd do what Frank suggested, ie google and see if you can find one. The next issue is that many of those are regulated, not sold to consumers, or if they are they come in sizes and costs targeted for commercial use. The real problem here is that, well, it's a grass. So, it's a lot harder to make a herbicide that will kill the undesirable, but not the desirable grass. If you can find one that will work and that you can get, it's going to be your best solution.

The other unfortunate thing you're usually up against is that the undesirable is a rough, tough grass, grows fast, etc. Meaning in a war between it and the turf grass, the undesirable is usually going to win. Another factor is how that particular grass spreads. If it's via rhizomes, even more trouble. In short, I have not had much success in trying to deal with it in any way other than killing it with herbicide.

In my experience, if there is a substantial infestation, the best course is to kill it off and renovate. It's not that hard. Essentially you kill it off with glyphosate in very early Fall. Then when it's all dead, mow it short, rake up debris. You could core aerate at this point. Then rent an over-seeder, which is a gas powered machine that cuts grooves in the soil and drops the seed. Apply starter, keep it constantly damp and in 2 months you'll have some decent cover. It won't look real good though until Spring.

If you have just a few spots, you can do the kill on just those, again, I'd do it in early Fall.

[Frank]

I had googled out of curiousity and did get hits indicating such stuff is a= vailable in the UK. Did not have the time to look at the details. I've be= en in a situation with Japanese Stilt Grass here and going through same typ= e stuff. In this case, outside of Round-up the only thing that works are p= re-emergents. Older crabgrass killers with arsenic would have worked but a= re now banned. There is a newer crab grass killer that also takes out abou= t 200 undesireable grasses and weeds but a call to Ortho said not the stilt= grass. This is another potential avenue for our UK inquirer, is to call t= he big herbecide producers and ask them about his problem.

[Dr Mike Oxgreen]

A couple of weeks ago, I did find an online reference to a selective herbicide that targets coarse grasses but leaves fine grasses intact. It's called "Rescue", and is obviously intended for golf course managers. It sounds very exciting, but unfortunately it costs about £350 (about $540) for a one litre bottle (about a quart) treating 10,000 square metres (about 2 and a half acres). I'm not sure if you can even buy it unless you have a licence. It's very new, so I'm guessing the manufacturer is at the "make as much money as possible before the patent runs out" stage.

Let's hope that this product becomes available in a quantity and strength that's more suitable for the home gardener. But for the moment, it's a bit out of reach.

I think I will probably do as some of you are hinting: kill off larger areas and reseed. At least I have established some confidence at this, because the small patches I reseeded last year are looking quite good. If I do spray glyphosate a couple of weeks before I do my planned renovation work in September (scarify, aerate, maybe top-dress and then reseed) then the scarifier will do the job of removing the dead grass for me.

[mike]

Depending on how the stuff propagates, you may need to kill it ALL. I get a lot of weed influx from my neighbor. Only long-term solution is to nuke her yard.

At least I have established some confidence at this,

[trader4]

:

available in the UK. =A0Did not have the time to look at the details. =A0I= 've been in a situation with Japanese Stilt Grass here and going through sa= me type stuff. =A0In this case, outside of Round-up the only thing that wor= ks are pre-emergents.

Pre-emergents only work to eliminate what's already there if it's an annual grass that can produce seeds in a turf environment. The Yorkshire Fog is a perenial. I don't know if it's capable of producing seeds when it's being kept mowed either, so the seeds may not be an issue to begin with.

=A0Older crabgrass killers with arsenic would have worked but are now banned. =A0There is a newer crab grass killer that also takes out about

200 undesireable grasses and weeds but a call to Ortho said not the stilt grass. =A0This is another potential avenue for our UK inquirer, is to call the big herbecide producers and ask them about his problem.- Hide quoted text -

[justinh]

Try using a stanley knife and slash patches of it in a criss-cross pattern. Leave it a week or so then rake, you'll be left with bare patches ready to reseed.

Just> I have a lawn of about 300 square metres, which is in reasonable health