[VoodooChile]

I'm seeking recommendations on an herbicide that would kill dormant grasses before mulching.

The project is a large property with many recently planted trees and shrubs that need tree rings and beds defined. We are planning to mulch thickly, 4-6", but know from experience such a layer of mulch won't kill the more tenacious grasses, i.e. Johnson and Crab grass.

And yes the mulch layer will be less to nothing in the root-zones of the woodies.

Thanks!

[cutntrim]

I can't help you, I've only ever used Glyphosate (RoundUp).

[VoodooChile]

We, the client and us, don't want to wait until the grass is photosynthesizing since she has big plans, and we have the time right now.

[cutntrim]

Soil conditioner/landscape rake attachment on a skidsteer maybe?

[Greensmith]

torch it and put down a pre-emergent under the mulch?

[VoodooChile]

Chewing up the soil is iffy due to the potential for root-zone damage to the existing woodies, a big concern of this client. Plus, the more tenacious grasses just proliferate when pulverized...not so noticable in a new lawn, but definitely a problem when they come roaring through the mulch.

Torching would burn down the tops, but what about the root-stock?

Pre-emergents typically kill germinating seeds. Are some pre-emergents effective on existing, tenacious grasses?

[NCSULandscaper]

i dont think you will achieve what you are looking for, being dormant its not going to uptake anything systemically.

[johnkeegan]

Rent a sodcutter and skim off the grass, roll it up and make them a compost pile. That should spare the existing root systems. To prevent the crabgrass reseeding you could either spread some pre-emergent down or do your mulching and wait for the few stragglers to pop up and hit them with Round-up then.

[VoodooChile]

Own a sod-cutter and use that method for most of our installs, but this place runs to 300 acres, and I'll guesstimate 1/8 is planted in trees/shrubs, arboreteum like. I'll try to get some pix up, so you can appreciate the scale.

To ease mowing and reduce competition, the client wants to create beds around the plantings.

When I weigh the fuel/manpower cost of removing sod, versus the environmental impact of spraying, spraying seems more sound. If there is something that would kill the grasses (and we aren't talking turf-grass but more like let-go pasture grasses) without effecting the trees, I would like to go that route.

[cutntrim]

Originally posted by VoodooChile
this place runs to 300 acres, and I'll guesstimate 1/8 is planted in trees/shrubs, arboreteum like

Wow, that's big. How about one of those articulated scrapers that are used for grading in new subdivisions?

[cutntrim]

Like one of these guys. That oughta do it.

[VoodooChile]

Good one cutntrim!

Spiderlilly did some research on the web and couldn't come up with anything, so I thought I would ask here.

At this point we plan on doing the mulching, and then using glyphosphate on what comes through.

Yeah it's a big place. Fortunately it doesn't all need mulching.

[Mark Oomkes]

I'd say casoron or dyclomec (same thing) will do it, but there are too many downsides to it---like leaching. Also, it won't actually damage the trees\shrubs, but it sure won't help any newly planted trees or shrubs.

So while it would work, I don't think I would use it except for maybe large beds, if there are any, and if you do, keep it at least an arm's length in from the edge on flat ground, more on slopes to prevent or at least reduce leaching.

I think the mulch and Roundup is probably going to be the best way, unfortunately.

[LabourofLove]

I'm unclear about whether there will be other plants underplanted in this mulch under the trees.

If not, I would use about 20 page thicknesses of newspaper overlapped and fanned around the tree trunks then mulch and nuke whatever else comes up.

I've used this technique to establish large clumps of daylilies in a field. Worked very well. More stuff grew in the tops of the mulch (from windborne seeds) than came up through the newspaper.

Newspapers all use soy-based inks these days, so no leaching problems with the inks. I wouldn't use the colored supplement or magazine sections, though: don't know whether those are soy-based inks or not.