If you’ve laid new sod, don’t apply pre-emergent herbicide to your yard. Pre-emergent herbicides (including products labeled as “Crabgrass Preventers”) can hinder sod root growth. This makes it hard for new sod to establish itself, leaving it vulnerable to death by drought, high temperatures, and foot traffic.
If you’ve already applied pre-emergent to your yard and plan to lay sod, wait at least 6 weeks after herbicide application before laying sod. Then, prepare the soil by tilling in order to break the pre-emergent barrier and allow for healthy grass rooting.
Table of Contents
Will Pre-Emergent Kill Sod?
Applying pre-emergent on a new sod lawn can harm and kill your grass by stopping it from forming deep roots. The herbicide in pre-emergent prevents cell division. Although this is great for killing weed seeds as they sprout, it also attacks the new roots your sod attempts to send down into the soil.
- Pre-emergent inhibits sod root growth.
- Poor root growth in sod makes it prone to drying out, disease, and damage from use.
- Sod treated with pre-emergent may yellow, brown, and die.
Sod that doesn’t develop deep roots cannot reliably pull in water and nutrients. This weakens the grass, makes it prone to drying in hot temperatures, and increases the chance it will be damaged by mowing or foot traffic. Allow time for your sod to root before you apply pre-emergent, or you will risk killing your new lawn.
What if You Applied Pre-Emergent Before Laying Sod?
Most pre-emergents are applied in early spring, prior to the optimal time for laying new sod. So, you may find that you want to lay sod after you’ve already spread pre-emergent on your lawn. In order to stop existing pre-emergent from harming your sod, follow these steps:
- Wait 6 weeks after applying pre-emergent before laying new sod.
- Till the soil before sodding, to break up the layer of pre-emergent in the soil.
- Water daily after sodding, to encourage grass growth and wash out any remaining pre-emergent.
Most pre-emergents will have run their course in 6 weeks, so it’s safer to lay sod after this period. Additionally, it’s essential to till the soil prior to sodding. Pre-emergent forms a barrier just beneath the surface, which is what kills sprouting seeds and sod roots. By tilling, you break up this barrier and loosen the soil, both of which encourage healthy sod.
How to Prevent Weeds in Sod
Most types of sod are laid in mid-to-late spring or in fall, depending on the grass variety. Although fall pre-emergent applications are beneficial in some areas, most pre-emergents are applied in early spring. In essence, applying pre-emergents to sod doesn’t make much sense. By the time you’re laying sod, most of the weed seeds that will sprout have already done so. In order to keep your sod weed-free, follow these tips:
- Get rid of weeds before laying sod. This will prevent a weed invasion.
- Water and fertilize your sod to encourage fast rooting and choke out weeds.
- Never lay sod over existing weeds or grass.
Preparation is key for keeping your sod weed-free. Kill existing weeds and grass by cutting out the old sod, tilling the soil, and spraying any weeds that sprout with a post-emergent herbicide. Then, lay your sod and nurture it with a proper water and fertilizer plan. The faster your sod roots, the better it will be at resisting weeds.
How Do You Kill Weeds in New Sod?
If weeds are coming up in your newly laid sod, it’s too late for pre-emergents. Instead, use a post-emergent weed killer to spot-treat these weeds. Because new sod is very vulnerable, allow 3 weeks for your sod to establish itself before using any weed killer sprays.
- Avoid spraying weed killers until the sod is at least 3 weeks old.
- Spot-treat weeds with post-emergent weed killers, like Roundup.
- Hand-pull weeds growing through sod.
If you’ve properly prepared your yard for new sod, there should be very few weeds coming up through your sod. In many cases, these can be hand-pulled. This is the best method to keep your sod safe and prevent an application of chemicals that may harm your lawn.
Can Sod be Laid Over Weeds?
Never lay sod over existing weeds or grass, although you can lay it next to existing grass. This is a recipe for disaster. Your new sod won’t be able to take root without sod-to-soil contact and the weeds will come right through the sod.
- Avoid laying sod over weeds, grass, or other vegetation.
- Existing weeds will grow through sod.
- Sod will struggle to root on top of existing weeds and may die.
It’s incredibly likely that sod laid over weeds or grass will struggle and die. There’s simply too much competition and no chance for the sod to take root.
How Soon Can You Use Weed Killer on New Sod?
Wait 3 weeks after laying sod before you use any post-emergent weed killer sprays. The sod needs this time in order to put down roots and recover from the stress of being transplanted.
- Post-emergent weed killers can be used 3 weeks after sod is laid.
- If you are using non-selective weed killers (such as Roundup) spray weeds only, not your grass.
- If you are using a selective weed killer, make sure it is safe for use with your grass type.
Keep in mind that weed killers differ by type and brand. Non-selective weed killers, like Roundup, will kill any plant they’re sprayed on. This includes your sod. If you’re using one of these weed killers, spray weeds only and keep your grass protected. Selective weed killers, like 2,4-D, kill weeds without harming your grass. Check the product label to make sure these products are safe for use with your grass type.
How Soon Can You Put Pre-Emergent on New Sod?
Wait an entire growing season before applying pre-emergents to your new sod lawn. This gives time for your sod to develop deep roots that will not be damaged by the herbicide.
- Pre-emergents can be applied after your sod has experienced 1 full growing season.
- If sod was laid in spring, pre-emergent can be applied in fall.
- If sod was laid in fall, pre-emergent can be applied in spring.
For grass varieties sodded in spring, you can safely apply pre-emergents in fall. If you sodded your lawn in the fall, you can apply pre-emergents the following spring. This will protect your new lawn and stop weeds.
Can You Apply Pre-Emergent to New Sod?
Do not apply pre-emergent to new sod until it has been allowed to establish itself for an entire growing season (3–6 months). If pre-emergent is applied to a sod lawn before this time, it will damage sod root growth and potentially kill your lawn.
We all want beautiful lawns, and the best way to keep your sod safe is to prepare the ground beforehand to rid it of weeds. After that, sodding will be a breeze and weeds will struggle to invade. Keep the pre-emergents in the garden shed for a later date so you can enjoy your new grass.