Overseeding too early? - Ask Extension
I need to reseed/overseed my lawn. I live in Montgomery County and really need to do so this week. I'm a teacher, and I'm about to go back to school...
Knowledgebase
Overseeding too early? #880987
Asked August 10, 2024, 11:47 PM EDT
I need to reseed/overseed my lawn. I live in Montgomery County and really need to do so this week. I'm a teacher, and I'm about to go back to school (I won't have time after school starts). How bad will it be to reseed mid-August? I'll also be overseeding a lot of bare spots from pulling weeds. I plan to put compost on top of the seeds. I also have a bale of straw which I can spread on top if that will help.
Thanks!
Montgomery County Maryland
Expert Response
If our weather cooperates and doesn't get too excessively hot again, it might be successful. The key factor regardless of exact timing will be to keep the germinating seed moist, which usually involves several irrigation sessions per day (in hot weather...maybe only one or two daily if the temperatures are milder). The germinating seed cannot dry out too much during establishment or it will die. A programmable hose spigot timer that a sprinkler is hooked up to may help. If compost is used on top of the seeds, use a very fine layer, as seed should not be covered too much or it will block light needed for germination. (If compost is needed to level-out divots in soil or to improve soil texture, put it under the seed instead and tray to lightly rake it into the soil surface.) Straw mulch probably won't have a greatly significant affect on soil moisture retention, but a light layer should be fine to use, and might also discourage seed-eating birds from pilfering some of the seed.
If you haven't done so in the past few years, it would have been ideal to have a laboratory soil test performed prior to overseeding, so you know what kind of fertilizer to use (and if any lime would benefit the lawn). A good default assumption without test results would be to use a phosphorus-free fertilizer (zero P in the N-P-K analysis) and to not apply lime, as it could always be added later. You can always take soil samples now, just prior to seeding, and use the results obtained in a couple weeks to inform future fertilization and liming practices, since the test results are fine to use for about two or three years at a time.
These pages provide more information, if useful:
Miri
If you haven't done so in the past few years, it would have been ideal to have a laboratory soil test performed prior to overseeding, so you know what kind of fertilizer to use (and if any lime would benefit the lawn). A good default assumption without test results would be to use a phosphorus-free fertilizer (zero P in the N-P-K analysis) and to not apply lime, as it could always be added later. You can always take soil samples now, just prior to seeding, and use the results obtained in a couple weeks to inform future fertilization and liming practices, since the test results are fine to use for about two or three years at a time.
These pages provide more information, if useful:
- Lawn Renovation and Overseeding, which includes a section at the end about repairing bare spots
- Care and Maintenance of a Lawn After Seeding
Miri
This is great, thanks. I just got the results from my soil test (from U. Delaware). Ph is 6.4. Magnesium and calcium are WAY high. Everything else is good. UD also gave me fertilizer recommendations. For now, I think I need to focus on planting more grass seed. There are a lot of bare patches which (I think) are letting weeds come in. I know that won't fix everything, but it's what I've got the time/energy for. I think I'll push back the seeding until later. It's just hard once school starts. I've also got a lot of your (Extension) links bookmarked. They've got a lot of great info.
Thanks again,
Rich
You're welcome.
It's not uncommon for Maryland home lawn tests to have high or off-the-charts magnesium and calcium levels. It's okay, as nothing needs to be done to remedy that; it only means that adding more of either of those nutrients will not benefit the plants at all since they already have plenty at their disposal.
If you have the opportunity to do so, seeding sometime in September would be ideal, and hopefully the weather will be cooperative and some rains will ease any irrigation needs. (Early October would be the final window of opportunity for the recommended seeding timeframe.)
Miri
It's not uncommon for Maryland home lawn tests to have high or off-the-charts magnesium and calcium levels. It's okay, as nothing needs to be done to remedy that; it only means that adding more of either of those nutrients will not benefit the plants at all since they already have plenty at their disposal.
If you have the opportunity to do so, seeding sometime in September would be ideal, and hopefully the weather will be cooperative and some rains will ease any irrigation needs. (Early October would be the final window of opportunity for the recommended seeding timeframe.)
Miri
