If you want the crabgrass gone next week you will need chemicals and keep the dog off the lawn (if you applied a pre-m last spring I'm not sure why your averse to chemicals). Or, you can outcompete it with a nice healthy stand of grass. Core aerate, overseed, and fertilize routinely. Mulch mow at your mowers highest setting. Water 1" per week in the growing season (includes mother nature). Consistent application of the basics is key to preventing crabgrass.

HI Soccer dad, thank you for taking the time to answer my post. The pre-m I put down was in my front yard only (the dog only goes in the fenced in back yard). I don't mind putting chemicals on the front lawn but don't do it in the back yard.

I just cut my lawn yesterday and didn't bag it. I had it on my regular setting. So what is my next step? Do I core aerate now? Or do I cut the grass lower and bag it?

Thanks for your help!
Maureen

If you intend to overseed then you want to cut your existing grass as low as possible. This is called scalping. You want to do it in phases and not all at once so the existing grass isn't so stressed. Then rake, bag or otherwise rid the lawn of as much of the debris as possible. Your trying to get to the soil. Then core aerate, fertilize, seed and irrigate.

There are some hand tools sold as core aerators and there are pull behind models for lawn tractors, but renting a machine or finding a lawncare professional to do it is probably your best choice.

If your back yard is half weeds, I think the only way you'll be able to get them under control is to spray them. Most weeds are going to seed right now, so even if you spray, you'll have a new crop next year from all the seed.

I understand your concerns about your dog. What I would do is next spring, when all the new weeds are germinating, and all the perennial weeds are coming back, I would go ahead and spray and keep your dog on a chain on the side of the house or the front yard for a few days. Or, ideally, many weed sprays are rainfast in 4 hours, so spray when rain is expected that night or the next day. That way, the weeds absorb the chemical so they'll die, then the rain will wash it off so your dog can go back in the yard.

A non-toxic weed preventer is corn gluten meal. However, it will not prevent the perennial weeds from coming back. Many weeds are perennial, like dandelions. It only suppresses the germination of new weed seed if applied at the right time - when the soil is 60 degrees or when the forsythias bloom in your area. Incidentally, that's also when you need to apply crabgrass preventer.

Then in the fall, reseed your backyard so the grass is thicker, making it more difficult for weeds to get well established to the point of taking over the whole yard.

By the way, if you spray your crabgrass, you have to wait 3 weeks before seeding, which would mean you're seeding awfully late. Pulling it is probably your best bet (I know, that is a lot of work). And is your backyard really 100 x 4, or was that a typo?

Deanna

1. I bought and used some weed-b-gone/crabgrass killer earlier this year..you can buy it at the big box stores. It worked well in my weed infested back yard(disclaimer, the weeds were not my fault, it's a new house for us) You just attach it to your hose and spray the yard and watch those weeds fade away...it won't kill them all though...keep hand pulling...not sure what to do about your dog.

2. Absolutely aerate...it is so good for your lawn in so many ways. You can hire someone to do this for you..it costs about $80 for an average size lawn in MN, not sure on NY...when they come to do it, I would insist that they go over the lawn twice(front to back side to side) so that there are more holes for seed to fall in when you overseed. If possible, you're probably better off doing it yourself because then you can go front to back, side to side, and diagonal, which will really be an aggresive aeration, which means more holes and soil cores for your seed to germinate in. You should mow the grass down very low and bag it before you aerate. Then mow it again and mulch it after they aerate...then seed...then water twice a day..if your lawn gets plenty of sun, I'd recommend a higher quality Perennial Rye / Kentucky blue mix. Though you should know that you must keep Kentucky Blue moist for an entire month after you seed it.(alot of work if you don't have an irrigation system)..you only need to keep Perennial Rye moist for about two weeks...so maybe just the Per Rye mix unless you don't mind twice a day watering with sprinklers for a month...you probably already have some K blue in your lawn so if you just follow the lawn basics mentioned below it will start to flourish.

3. I personally enjoy hand sowing the seed...put it in a big bag or bucket and grab it and throw throw throw yourseed to a nice new lawn. Yes, do the entire lawn if you've aerated the entire lawn. Some of the seed will fall into the aerated holes, and some will get in contact with the mulched up soil cores that are now laying all over the top of your lawn. The seed that lands in the holes will grow the best, so again, more holes better results.

After doing this, follow soccerdads advice about mulch mowing on the highest setting for your lawn mower once a week, fertilize spring, summer, and fall(if you have a shady lawn, only fertilize once a year) put out a pre emerge for crabgrass next spring, aerate and overseed each fall for the next few years, and water once a week about an inch of water. Aerating, once a week watering, and mowing on the highest setting will promote deeper root growth and a strong and dense stand of grass....this is how you keep the weeds and crabgrass away, if there is no room for them to grow, they don't.

By the way, if you have a shady lawn, you need a shady mix of grass seed instead of the Per Rye/ K blue. The best shade grass in my opinion is chewings fescue...when you buy shade grass seed make sure there's chewings fescue in it.

Irish rose grower,

I've got an idea for your backyard, and don't know why I didn't mention it before. Renovate it in sections instead of the whole thing at once. Do one area every year and fence it off. I have dogs, and that's what I do. Not for the purpose of weed spraying, but for the purpose of seeding. I can't seed the whole yard at once, because the dogs would destroy the grass seedlings. So I renovate one area of my backyard every fall, and keep it fenced off until spring so they won't be pottying on it all winter.

You could fence off an area for the purpose of weed spraying, and just do one area at a time. That way your dog doesn't get exposed to the chemicals. Then next fall you could start seeding one area at a time, and eventually, your whole yard will be greatly improved.

Deanna

Even for Long Island, it is starting to get late for seeding now. The crabgrass will die with the first frost.

That all said, if you really want to kill the crabgrass without using poisons, put vinegar on the center of the clump of crabgrass (it's a bunch-grass). It will die pretty quickly. It will also kill any good grass within about 4 inches of where you put it. Salt also works, but Long Island gets all of the drinking water from shallow wells, so that's not good in your area.

The best move might be to save your money and effort for April.