john greenlee's guide to:
killing your lawn
Key Takeaways
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Overview & Supplies
The most important step in successful meadow making is starting with a clean palette - one with no weeds and no lawn grasses. The best way to do this is with successive applications of weed kills on actively growing lawns. Otherwise known as grow-kill cycles.
The best weed killers for eliminating old lawns are glyphosate weed killer types, such as Roundup®. Currently, these are the safest weed killers you can use. In order for the chemicals to work, the plants you are trying to kill must be actively growing.
A dry, old lawn may look dead, but it is more than likely just drought dormant.
It is best to water and fertilize the lawn you are trying to kill weeks before you spray although this may seem counter-intuitive.
But trust me, this is important.
The best weed killers for eliminating old lawns are glyphosate weed killer types, such as Roundup®. Currently, these are the safest weed killers you can use. In order for the chemicals to work, the plants you are trying to kill must be actively growing.
A dry, old lawn may look dead, but it is more than likely just drought dormant.
It is best to water and fertilize the lawn you are trying to kill weeks before you spray although this may seem counter-intuitive.
But trust me, this is important.
The First Round
If it's an old lawn you are trying to kill, fertilize it with any standard lawn fertilizer at a rate of 5 lbs. per 1000 sq ft. And water it well. It will take some time for the fertilizer to kick in, so keep watering and keep the soil moist.
If an old lawn is very dry, it may take many waterings to really get the soil wet (especially for clay soils). Continue to water after spraying. Water as if you wanted the greenest lawn in town! It may also help to mow the lawn and if weeds are really tall, they should be mowed as well.
If this is the case, continue to water and fertilize to encourage new growth.
Remember: The more actively growing the plants are, the more effective the kill cycle.
Always be sure to follow the directions on the label of any chemical that you use. The instructions are there by law for a good reason. When properly used, these can be the last chemicals you'll ever need for your meadow, with little consequence to the environment.
Remember: Meadows are far better for the environment than conventional lawns.
If an old lawn is very dry, it may take many waterings to really get the soil wet (especially for clay soils). Continue to water after spraying. Water as if you wanted the greenest lawn in town! It may also help to mow the lawn and if weeds are really tall, they should be mowed as well.
If this is the case, continue to water and fertilize to encourage new growth.
Remember: The more actively growing the plants are, the more effective the kill cycle.
Always be sure to follow the directions on the label of any chemical that you use. The instructions are there by law for a good reason. When properly used, these can be the last chemicals you'll ever need for your meadow, with little consequence to the environment.
Remember: Meadows are far better for the environment than conventional lawns.
In 7-10 days after spraying (depending on temperatures), you should notice a distinct kill or halt in growth. Areas that you missed should become apparent - spray them again immediately. Wait a day, then resume watering as before.
Soon, any seeds, rhizomes, or stolons that are in the soil should begin to germinate - some weeds can take 30+ days.
Because of this, it usually takes x2-3 successive grow-kill cycles to thoroughly "clean" the meadow palette.
Note: Rototilling or turning the soil may cause even more weed seeds to germinate. Adding mulch can add weeds as well (depending on the kind).
The length of a grow-kill cycle will depend on soil, moisture, fertilizer, temperature, and time of year. I've found that the fastest cycles are with warmer temperatures, good soil moisture, and fertilizer.
Soon, any seeds, rhizomes, or stolons that are in the soil should begin to germinate - some weeds can take 30+ days.
Because of this, it usually takes x2-3 successive grow-kill cycles to thoroughly "clean" the meadow palette.
Note: Rototilling or turning the soil may cause even more weed seeds to germinate. Adding mulch can add weeds as well (depending on the kind).
The length of a grow-kill cycle will depend on soil, moisture, fertilizer, temperature, and time of year. I've found that the fastest cycles are with warmer temperatures, good soil moisture, and fertilizer.
Timing
The time of year that you attempt to kill your lawn is important as well.
Warm season grasses start to go dormant in the fall, meaning that they no longer are actively growing and spraying them will not work. An early frost will also shut some grasses down and prevent a thorough kill cycle so start well before your first frost in cooler zones and regions.
Depending on the species and temperature in cold climates, warm season grasses may not start actively growing until May, or even June. Dormancy can be shorter in the hot southwest regions, but it's best to kill these grasses from May to September.
Bermuda grass can be particularly hard to kill if its not actively growing. This is yet another reason to employ successive grow-kill cycles to clear your meadow-to-be of these aggressive competitors. Remember: It can be very costly to re-spray after your desirable meadow grasses have been planted. I know of many projects that tried to shortcut their grow-kill cycles and they ended in disaster. This step can be particularly problematic on sites where irrigation cannot be provided until late in the construction process.
Warm season grasses start to go dormant in the fall, meaning that they no longer are actively growing and spraying them will not work. An early frost will also shut some grasses down and prevent a thorough kill cycle so start well before your first frost in cooler zones and regions.
Depending on the species and temperature in cold climates, warm season grasses may not start actively growing until May, or even June. Dormancy can be shorter in the hot southwest regions, but it's best to kill these grasses from May to September.
Bermuda grass can be particularly hard to kill if its not actively growing. This is yet another reason to employ successive grow-kill cycles to clear your meadow-to-be of these aggressive competitors. Remember: It can be very costly to re-spray after your desirable meadow grasses have been planted. I know of many projects that tried to shortcut their grow-kill cycles and they ended in disaster. This step can be particularly problematic on sites where irrigation cannot be provided until late in the construction process.
A typical grow-kill cycle on an actively growing lawn during the growing season is usually 3-4 weeks. |
Applying Bark Mulch
I have found it helpful to cover the newly-killed lawn with a thin 1"-2" layer of bark mulch to prevent planting sites from becoming muddy while grow-kill cycles are in process. Mow any tall weeds or dead lawn before top dressing with bark and continue to look for germinating weeds in the mulch.
Without a mulch cover, weed seeds will continue to blow into the site. New plants being planted on the site often introduce weeds. Field grown material and specimen trees are notorious sources for contamination. Often noxious weeds are surface cleaned from new nursery plants when they arrive with underground stems and roots just waiting to grow.
Be careful when importing topsoil to your site. Make sure your additional topsoil is clean and your contractor knows where it is from. It's best to apply grow grow-kill cycles to any additional topsoil brought to the site to assure it is truly weed free.
Without a mulch cover, weed seeds will continue to blow into the site. New plants being planted on the site often introduce weeds. Field grown material and specimen trees are notorious sources for contamination. Often noxious weeds are surface cleaned from new nursery plants when they arrive with underground stems and roots just waiting to grow.
Be careful when importing topsoil to your site. Make sure your additional topsoil is clean and your contractor knows where it is from. It's best to apply grow grow-kill cycles to any additional topsoil brought to the site to assure it is truly weed free.