To get rid of weeds before laying sod, you should first apply a natural or chemical weed and grass killer to kill all existing weeds. Then, use a sod cutter to remove the old lawn and weeds. Finally, till the lawn, water it, and wait 1-2 weeks. This step is essential because it will cause any weed seeds to sprout. Treat these with a weed killer or herbicide to fully stomp out the invasion. Then, you’ll be ready to lay new sod with confidence that weeds will not return.
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6 Steps to Removing Weeds Before Laying Sod
The purpose of laying grass sod is to start new, with a fresh carpet of healthy, weed-free grass. Your beautiful fresh sod can be destroyed by old weeds and invasive grasses pushing up through the new grass, and all your time and effort sodding will seem wasted. The best way to prevent this fate, and ensure your new sod takes root, is to get rid of existing weeds before you lay down sod. To do so, follow these steps:
Treat Lawn with Weed and Grass Killer
When you are preparing to re-sod your lawn, unless you’re laying sod next to existing grass, you can attack weeds and existing grass with a no-holds-barred approach. You want to kill all existing weeds and grass, so you can use strong weed killers that act fast.
Glyphosate-based weed killers, such as RoundUp, are your best bet when prepping an old lawn for sodding. They work quickly, kill grassy weeds down to the root, and wash out of the soil within a few weeks, so your fresh sod won’t be harmed.
You can also use Atrazine for certain broadleaf weeds, or a 2,4-D weed killer, but consider the best option for your old lawn. For example, if you currently have Bermuda grass, 2,4-D will preserve most Bermuda, while Atrazine will kill it.
If you want to avoid using chemicals to help with weed control on your existing lawn before sodding, use a solution of horticultural vinegar mixed with a small amount of dish soap. This will also kill weeds and old grass but won’t cause long-term damage that will negatively affect your new sod. You can even buy commercial vinegar-based weed killers for this purpose.
Whether you choose Glyphosate or vinegar-based weed killers, use a pump or backpack sprayer to spray the lawn. Then, wait a week to allow the weed killer to fully kill any and all weeds.
Re-Treat Lawn as Necessary
After your initial round of weed killer, you may still see some new weed growth. This is because emergent weed killers do not kill seeds. If, after 2 weeks following your initial weed-killer treatment you still see weeds in your lawn, do a repeat treatment to kill these weeds.
Alternatively, if your yard is small, you can cover the grass with black plastic to block sunlight and moisture from the soil. This should kill weeds within 4 weeks, and prevent even a single weed seed from growing, but can be inefficient as it is slower than weed killer, unsightly, and not practical for large yards.
Cut and Dispose of Old Sod
Use a sod-cutter tool to remove your old sod layer. Sod cutters are available for rental at most hardware stores and are essential in the process of sod installation on a new lawn. If you don’t remove the old sod there is a huge potential for weeds and grasses to grow through your new sod. Removing your existing sod helps get rid of weed seeds, rootstock, rhizomes, crabgrass, and other dead grass.
Once you have cut your old sod, you should dispose of it for recycling. Your impulse may be to use it for compost, but keep in mind, composting weed-infested soil creates a large risk of reintroducing weeds. Most weed seeds can remain dormant in compost and sprout as soon as the compost is spread. It’s best to dispose of every old sod strip to prevent a future weed infestation.
Till for Soil Preparation
One of the main challenges of sodding a lawn is getting the new grass to take root in the soil below. Consider the pros of tilling the soil to loosen it and promote grass root growth. Otherwise, your new sod may wither and die, creating the perfect environment for invasive weeds to take root.
Buy or rent a tiller to work the soil to a depth of 6–12 inches. This will prepare the soil adequately for future sodding.
Water, Wait, and Kill Some More Weeds
The downside of tilling is that it brings dormant weed seeds to the surface. These seeds can lie in wait for decades, but once brought within 1 inch of the surface, they will sprout. Often, freshly tilled soil can become a weed haven.
So, it’s time to smoke those sneaky weeds out. Water your newly tilled soil surface daily for 1–2 weeks, which will help it settle into optimal conditions for sodding and encourage hidden weed growth. Once these weeds have made their presence known, treat them as you did in steps 1 and 2, spraying weed killer and waiting a week to make sure all the weeds are dead.
Time to Sod
Now that you’ve killed your existing weeds, removed as many as possible, and killed any previously dormant seeds brought to the surface by tilling, your lawn is ready for new sod grass. Apply the sod carefully and follow the best practices for caring for new sod. Your lawn will flourish and you’ll see no trace of the weeds that previously plagued your lawn.
Can You Lay Sod Over Weeds?
You should never lay sod over weeds. You will only prevent weeds for a short time. Weeds will quickly work their way up through even the smallest seams between pieces of sod grass or push up through the sod and topsoil. New sod is fragile because it has yet to form deep roots and combine with the soil. In this stage, it can’t repel weed invasion like a healthy, established yard. Your best course of action is to kill all weeds before sodding.
Also, do not apply pre-emergent on new sod until at least the following growing season. These types of herbicides can severely limit your sod’s growth if applied too early.
Best Way to Get Rid of Weeds Before Laying Sod
The trick to getting rid of weeds before laying sod lies in the preparation. In order to fully eradicate weeds that can otherwise invade your new sod lawn, you need to follow these steps:
- Kill existing weeds with weed killer.
- View results of the weed killer. Repeat application as necessary, or use a black plastic tarp to smother weeds.
- Cut old sod and get rid of it.
- Till the soil to prepare it for new sod.
- Water recently tilled soil and reapply weed killer to kill any weeds sprouted from seeds brought to the surface by tilling.
- Lay down your new sod
By following these steps you will not only prepare your soil for new sod and create a healthy yard, but you’ll also kill existing weeds, remove the means of their return, and snuff out any hidden, previously dormant weed seeds. This method will ensure your familiar pest weeds won’t appear in your new sod lawn.