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How wet to keep new grass seed?

Posted by spup345 NY (Z6) (My Page) on
Wed, Sep 26, 07 at 13:56

It's been very hot in NY the past 3-4 days, I've been watering around 8am, then around 1pm, then around 4:15pm every day to try & keep the seeds moist that I put down.

However, when I go out around 1pm after the midday sun, I touch the top of the soil and the seeds and they seem to be dry already.

My question is, how long does it take for a seed to 'die' when it has dried out? Is it like an instantaneous thing where once the water is gone, it is dead? Or do I have 1-2 hours of leeway to re-water? Does anyone know the mechanism for seed growth at the beginning stages, etc.?

I just hope I don't have to put down all new seed again....


Follow-Up Postings:

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RE: How wet to keep new grass seed?

I don't know all the answers to your post. I hope someone can elaborate but since this thread has been up here a while I will try to take a stab.
The best way to learn how moisture levels effect germination of grass seeds I have found is to use a clear plastic cup, coke or water bottle and fill said container with various types of soil and various types of seed and water at different intervals. I have done this indoors in a window sill and use a spray bottle so I could keep it moist all the time. If you can think back to the last time it rained, (in my area it's hard to remember when that was!) and what the ground is like after a good soaking rain. It's easiest to start from that and maintain moisture. You can go longer intervals by using some kind of mulch to keep the soil and seeds moist. It may be that you need to water longer to saturate the ground and more frequently to keep it moist. Your seeds are probably not ruined but will take longer without constant moisure. Try to relax and remember that nature wants this to work.

I too have being watering frequently with the hose trying to keep the seeds moist in 90 degree temps where the sprinklers miss. I paid a fortune for seed blankets and I'm nervous too.

As for the stages, if you do the plastic cup experiment you'll see that one minute it's a seed in a cup of soggy dirt then you go to bed and the next morning there's a few strands of grass there. Try to be patient and water more often and the seeds will eventually hatch. You need a cloudy day with light rain. Then it's a done deal.


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RE: How wet to keep new grass seed?

My question is, how long does it take for a seed to 'die' when it has dried out? Is it like an instantaneous thing where once the water is gone, it is dead? Or do I have 1-2 hours of leeway to re-water? Does anyone know the mechanism for seed growth at the beginning stages, etc.?

Missed this, sorry. Yeah, the weather's been a real delight this year for seeding--today was nearly 90. On September 22nd. Yuck.

Seed germination is such that the seeds don't die immediately upon drying out (or grass would never seed out in nature). If the seed remains dry for 24 hours, you lose 30%. 48 hours and you lose 60%.

That means if you water once a day the amount of time the seed stays dry is less than 24 hours (the water takes time to evaporate). Your losses should be less than 30% even doing it that poorly, which you aren't. Your 4:15 watering certainly keeps things damp in most areas until morning.

For natural grass, 1-2% germination is fine--in fact, that's probably high. For your lawn you want as close to 100% of viable seeds to sprout as possible.

The water absorbs through the (relatively thick compared to the soil/air interface) seed coat to the embryo. The embryo has to go dry before it has a problem, and that requires at least 24 hours.

You have more than 1-2 hours' leeway before there's a problem, but don't push it. The damper you can keep it the higher the germination percentage. Regrettably, very hot temperatures slow things down but it'll resume in a few days when temperatures cool back to near-normal again.


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RE: How wet to keep new grass seed?

morph & quirk, thank you so much for your replies, you both provided a lot of VERY useful info and made me feel a lot better. I decided to throw on some remaining seed today (I put the first batch maybe 3-4 days ago) just because I was paranoid about the germination rates and I remember last year I told myself I should have put more seed because it didn't fill out the way I had liked. Also it's supposed to finally cool down and start to rain on/off the next few days so I figured I might as well.

Thnx again, I think everything will work out great, interesting about the embryo, etc. That's what I was hoping for. Night!


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RE: How wet to keep new grass seed?

You might also check the soil just before your 8 a.m. watering, I imagine it will still be damp from the dew. 10 a.m. worked better for me for germination. I now start a bit later, but that is because I have started cutting down the frequency (I am at day 26 or so).


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RE: How wet to keep new grass seed?

+1 Paul. I'm at day 54 on the new lawn and the only thing still pumping away three to four times daily is the large area on the western face that the sun blasts and that decided not to sprout until temperatures went down. Right now, I have a few thousand sprouts. I'm waiting for them to invite friends.

Now, in late September with the weather about to break, 10 AM, 1 PM, and 4 PM would be great. The seed will stay damp overnight plus get any dew that's forming, and by the time it even thinks of drying out you're watering again.


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RE: How wet to keep new grass seed?

Got it, you are right about the morning dew, it certainly still is damp in the morning, but I trade stocks so 9:30am I need to be inside at this computer so 10am doesn't work for me. So I can push it back to around 8:45am since it takes me about 30-40 mins to spray everything.

Tnx & good luck with your lawns!


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RE: How wet to keep new grass seed?

Your lucky cause the only time I can water is 5am, before taking train into Manhattan, and 5pm when I get home. Still with that I'm have some pretty successful germination. I did however apply some topdressing mulch to help hold moisture. The soils not wet when I get home but it's the best I can do for now. Hopefully we'll get some rain.


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RE: How wet to keep new grass seed?

I just wanted to thank spup345 for asking the question to start with.

Everyday (several times a day) I look at my seed lying on damp earth and try to gauge "is it damp enough" or "does the seed look swollen" or "is my straw too dry" or "egads the sun is out"- it's been a stressful couple of weeks. I was wondering about the degree of moisture that a seed needed to stay viable and I am much heartened by the replies that it all just might work out OK.

Thanks guys!


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RE: How wet to keep new grass seed?

Everyday (several times a day) I look at my seed lying on damp earth and try to gauge "is it damp enough" or "does the seed look swollen" or "is my straw too dry" or "egads the sun is out"- it's been a stressful couple of weeks. I was wondering about the degree of moisture that a seed needed to stay viable and I am much heartened by the replies that it all just might work out OK.

We all do that. :-)

I use the knee test. I kneel on the edge of the seed bed for five seconds or so (usually pulling a particularly obnoxious weed I can't stand any more). If the trousers come up with the knee damp and definitely damping the skin of my knee, it's way damp enough. Somewhat damp is fine. Barely damp and it needs more water.

Seeds don't need that much water to sprout. Two waterings a day of 15 to 20 minutes is just fine. More won't hurt unless the water puddles without draining, in which case the seed may rot on you. That doesn't seem to happen all that often.


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RE: How wet to keep new grass seed?

spup345, I once overseeded a public park with winter rye and I had to 'load the dice' in my favor. There was no irrigation to the park so every day for about 4 weeks (Sat and Sun included) I turned up with a water truck, hoses and portable spike-mounted impact sprinklers. The whole area was sprinkled for 15 minutes daily (slightly less than 1/4"). I was trying to simulate the 'overnite soak' recommended for germinating blackeye peas.
The soil was all sand (St Pete. Florida, you understand?) and the weather was quite dry.

What I did observe is that adequate moisture is critical in the 10 to 14 days AFTER the seeds sprouted.


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RE: How wet to keep new grass seed?

Yes. AFTER the sprouting. A little moisture will get the seed to become a sprout. But it's a newborn baby, literally. It can dry out and die in a hot sun, or in a stiff wind. It has no root, so there's no sense in watering 'deeply'. The root hasn't grown yet. There's no sense in watering 'a lot'.....if a puddle forms, and floats that sprout, it's dead. But there's no root to hold it in place, yet. So just mist it, don't soak it. Don't float it, don't dry it, and don't walk on it. And, after it grows, don't mow it. For awhile. Let it get itself sturdier, and each day helps some little bit in that regard.


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RE: How wet to keep new grass seed?

I know it has been some years now...but how long did it take for your grass to germinate? Did it ever germinate?


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