Seeding of the lawn can be done at any time, although it is highly recommend to be done in the fall. The seeding process is all about timing in the pick or If you’ve just used weed killer in your garden, how long do you need to wait before you can start sowing grass seed?
The Seeding Process
Whether you are starting with an existing lawn or have some grass established, seeding is always a process that takes time and patience. The mix of weed control and seed is a very fine balance which usually involves picking one or the other. This process can go a couple different ways depending on the time of year that this process is set to start, it can also take several years to get the results expected.
Starting the process off in spring can be tricky. Spring is the time of year that weeds are most prevalent and the best time to control them or prevent them. Pre-emergent needs to be down in the spring before the soil temperatures reach a consistent 55 degrees to help prevent crab grass from germinating. In the spring months, we highly recommend using weed control over doing the seeding. A full season of the lawn care program will get the weeds under control before planning a fall seeding. The more weeds that are under control, the easier the seed will germinate and grow.
Spring Start – Fall Seeding
After the fall seeding has been completed, it is crucial to follow the recommendations given on caring for the newly seeded lawn. The quicker the seed germinates and begins to grow; the better off the lawn will be the next year. In the following year, TurfGator recommends continuing the lawn care program beginning with the pre-emergent barrier during the early spring application. Without mature enough grass, this barrier cannot go down until the second lawn application which could allow more crabgrass to germinate than if this barrier had gone down during the first lawn application.
Spring Start – Spring Seeding
While spring is a good time to seed, be aware that there will be a struggle with weeds throughout the year. With a spring seeding, weeds cannot be controlled at all until early summer. Our commercial grade weed control products will interfere with the new grass seedlings, as well as prevent seed from germinating. Once the grass is mature enough, our post-emergent weed control sprays can be used to help get the weeds under control.
First of all, we recommend doing the fall aeration and overseeding in the current year. We are not concerned as much with the weeds lingering from the summer such as crabgrass, spurge, and nutsedge because they are about to stress out and die from cool fall temperatures. These weeds are annual weeds meaning that just because they grew there this year, does not mean they will automatically grow there next year.
Also, if your home is a new build, the compacted bare dirt is a breeding ground for these summer weeds. The fall weeds that are present or popping up will only last a little while before the winter temperatures stress them out too. Also, by putting an aerator on the lawn our technicians will be puncturing and tearing up the weeds, which will also stress them out and kill them. Any “skeletons” left from dead weeds should be left where they lay, as they will act as a natural straw blanket and help protect your seed and new seedlings.
Our technicians will leave you a care sheet on how to take care of your newly seeded lawn, we recommend following this sheet as closely as possible to get the best germination this year, rather than the seed germinating next year.
Fall Start – The Following Year
In the following year, the full 7-application lawn care program of fertilizer and weed control in will get the weeds more controlled throughout the year. For the first lawn application (March through early April) we will apply a pre-emergent barrier which helps prevent crabgrass and other grassy weeds from germinating. The sooner we can get this down the better; this is why it is so important to follow our seeding care sheet to get the grass to germinate this year, rather than next. If the grass is not mature enough at the 1 st application, we will need to wait until the second application (April through early June) to apply the pre-emergent or spray for any weeds. If the pre-emergent barrier is not down before crabgrass starts germinating, some may pop and grow within the lawn which is more difficult to treat rather than prevent.
Seed, Treat, Repeat
Regardless of when the first seeding was done, we recommend aerating and overseeding again the following fall to help thicken the lawn even more and introduce new life into it. This will also help fill any bare or thin areas in the lawn where weeds have died off. The thicker the lawn, the fewer weeds are present.
We would recommend following the lawncare program in the future years to continue to control weeds and fertilize the lawn, we then recommend assessing the lawn during the summer months to determine if the lawn will need the aeration & overseeding yet again that fall. At this point, it may not be completely necessary if all the thin & bare spots are pretty well filled in, but it would still be highly beneficial to the lawn to introduce the new life and continue the thickening process. Once the lawn is well established, we recommend aerating every year to keep the soil loose and highly recommend seeding every year, or at least every other year to build or maintain the thickness.
The processes set out above should get you the results you are looking for over time, with care and patience. The owner of TurfGator has actually gone through this same process for their own personal lawn, as well as the lawns of their neighbors, and several other customers. Each of those processes averaged out to be about 3 years to get a full turn around.
Unfortunately, there is no seeding method that will give the lawn a sod-like appearance just from doing it once, seeding is a process rather than a one-time result so unless you are willing to pay the money for sod, growing a new lawn from scratch is a process, no matter which method is taken.
To Sum It Up
Seeding of the lawn can be done at any time, although it is highly recommend to be done in the fall. Timing is everything in the pick or choose balancing game of weed control and seeding. These recommendations are valid for new lawns, as well as for the reseeding established lawns.
It is always a good idea to consult with a lawn care professional and ask any questions you may have. Look around, ask friends or family, and research companies on the Better Business Bureau to find a company that you can trust.
How Long After Weed Killer Can I Plant Grass Seed?
If you are trying to spruce up your garden and cut back on the weeds you have to deal with, you might be wondering how long you have to wait after weed killer before you can plant grass seed.
The answer varies quite a lot depending on what kind of weed killer you use, but it’s important to know so you don’t end up wasting the seed you have bought, or affecting the weed killer and reducing its impact on the weeds.
We’ll take a look at how weed killers work and how soon you can plant grass seeds after using the various different options.
How Long Do Weed Killers Stay In The Soil?
The unwanted plants might die back fast, but the real answer to “how long after weed killer can I plant grass seed?” will lie in how long the weed killer stays in the soil for; while it’s there, it’s still active and could harm your grass seedlings.
The amount of time that weed killers can stay in the soil for is quite varied; many take months to stop having an effect, but because that can make planting impractical, some weed killers have been specifically developed to allow for quicker planting.
If you’re dealing with lots of weeds coming up in unwanted places, you might decide to use a herbicide that has been designed to stop weeds from sprouting and to kill young seeds before they really have the chance to germinate.
This can be effective for handling weeds, but it has a major disadvantage; it will affect any seeds you put down too, and may stop them from germinating or growing. This will set you back if you’re attempting to overseed your weedy lawn. Equally, the seeds may stop the herbicide from working as well, neutralizing some of the barrier that it sets against weeds.
If you are going to use pre-emergent herbicides, you will not be able to plant your grass seeds until after their influence has faded, which will depend on what herbicide you use. The packaging should give instructions about how soon after use you can seed; use these as your guide, and then plant your lawn as normal. These often take around four months before you can safely plant in the soil again; you must wait for the barrier that they create to completely fade before you sow your grass seeds, or they may germinate and be killed, wasting your time and money.
Try Scott’s WeedEx Pre-Emergent Weed Control – if applied in the early spring, this pre-emergent weed killer can work all season to prevent the growth of a number of weeds, including crabgrass, foxtail, spurge, oxalis, and other grassy and broadleaf weeds such as clover. Also, it can prevent the growth of winter weeds like poa annua, henbit, and chickweed, if applied during the fall.
Selective Weed Killers
Alternatively, you might use a selective weed killer to remove weeds from the spaces where you want to reseed your grass. These herbicides are used to kill quite a few different plants, and will target grassy plants and broadleaf weeds.
This herbicide may also harm any grass that you plant and the amount of time it can be effective for will depend strongly on what kind you use. You should read the instructions carefully before you apply it to the garden, and then use these as your guide for how soon you can safely plant. If you are planting anything that isn’t affected by the weed killer, you may be able to plant sooner, but many grasses will be affected by selective weed killers of various types.
Often, around a month will be long enough to let the impact of selective weed killers fade, but you should follow the instructions on the packet. If you’re planting flowers or vegetables, you can probably plant more quickly.
This easy-to-apply WeedClear Weed Killer from Ortho will get rid of any weeds that have grown in your lawn. It has been formulated to kill over 250 types of weeds right down to the root without causing any damage to the surrounding grass, as long as you take care when following the instructions.
Glyphosate Weed Killer
This is a particularly popular kind of weed killer that targets the roots of the plants, and works its way quickly through the whole plant, from the top to the base. It is not thought to leave any traces, and once it has worked through the plant, it is absorbed by the soil and stops having an effect. It works as a highly effective weed killer, but it’s important to note that it will also kill off any grass that it’s applied to.
You may be able to plant as soon as three days after using Glyphosate, although you should be careful and follow any guidance provided with the product to avoid wasting your grass seed.
Glyphosate can take around a week to kill the weeds fully, and you may wish to remove debris before planting, so that you can aerate the soil and maximize the root space for your new grass seedlings. Wait until the poison has taken full effect so you can remove the whole plant. You don’t want roots left behind; the Glyphosate may not reach them, and the weed might sprout back from the leftover scraps of plant, spoiling your grass and competing with the seedlings.
If you want to completely kill off weeds and grass plants using a glysophate weed killer, try the Roundup Max Control Vegetation Killer. It contains 18% glysophate and will produce noticeable results in the lawn in as little as 12 hours.
Err on the side of caution with all of the above herbicides; if in doubt, wait longer. This will reduce the chance of you accidentally killing off seeds that you are attempting to plant, or wasting your weed killer’s efficacy on plants that you want to keep.
Using Herbicides On Newly Planted Grasses
Newly planted grasses are very tender and can be delicate for quite some time, even if they look well-established and as strong as your older patches of grass.
That means that you need to be careful about using herbicides on grass that is young. You don’t want to kill off your carefully seeded new grass, so it is important to read the instructions that come with your weed killer.
Many weed killers will damage grasses that are less than three months old. Things like Weedol should not be applied until the grass has reached three months, while Resolva will take a full six months before it can be applied to grass.
Products such as MossOff are generally safe to use once grass seed has germinated properly, but should not be used on top of grass seed, as they may damage it. You should always double-check use instructions before adding a product to your lawn or letting it come into contact with your grass seedlings.
If you’re wondering how long after weed killer can I plant grass seeds, you should find that most weed killers have instructions to help guide you on waiting periods and the potential risks of planting sooner.
Traces of weed killer in the soil could massively reduce the seeds’ ability to germinate, or might destroy the seedlings, so it’s important to choose a weed killer with short-term impact, especially if you want to seed your lawn quickly, and not wait.
Sarah Kimbrell, our West Coast editor, is the owner and operator of LawnFertilizers.com. She has been involved in the lawn care industry for over 15 years, and is passionate about helping people achieve the perfect lawn. Sarah is a certified lawn care specialist with a degree in horticulture and many years of experience working as a professional gardener.