Personally, I pretty much follow all the advice given in this brilliant article:
So far, the advice given in that article hasn't totally prevented my crabgrass problem. I'm still battling crabgrass, especially when summer heat really kicks in here (St Louis Missouri), constant mid 90's°F (30's°C) to tomorrows forecasted high of 115°F (46°C).
From everything I've read, been told, and from 4 years personal experience with doing battle with this annual weed, I have come to the conclusion it's a slow battle that takes years to get under control (win), especially if going with an organic approach. Each year I have definitely seen an improvement, meaning less crabgrass, and yes I'm getting a little tired of this battle, but because I've decided to go into battle with an organic approach, I keep telling myself, "Perseverance and time is the answer in winning this battle".
Here is what I basically do each year, keep in mind I have a cool-season grass, a "Tall Fescue" lawn:
I have one lawnmower and two blades for it. I get both sharpened at the end of the cutting season (sometime in November for me). I install a sharp blade immediately before the first cut of the cutting season (sometime in April for me). I then swap out that blade with the other sharpened one about halfway through the cutting season (end of July, beginning of August for me).
When installing the sharp blade on the lawnmower for the first cut, I also:
- Fill it up with fresh fuel (petrol, gas), the fuel has been treated with a suitable fuel stabilizer.
- Fill it up with new oil.
- Put a new spark-plug and new air-filter in.
Mow high and when doing so only remove approximately ⅓ of the grass blade height. In my case, 3inch (75mm) is my final cut height, that is as high as my current lawnmower will cut. My next lawnmower will be able to cut to at least 4inch (100mm).
Seeing as my lawnmower is a mulching mowing, I leave all the grass clippings on the lawn (free, natural fertilizer), except with first cut and last cut of the season. I collect up those cuttings and dispose of them via a community yard waste pile.
Fertilize the lawn with corn gluten meal (by Bradfield because I can get it easily locally) in very early Spring, when I see the Forsythia shrub in flower in my area.
For the first time this year I also decided to fertilize the lawn with corn gluten meal in mid June. Why? See "Table 4" here: Cool-season grasses: Application schedule for organic fertilizers
- Corn gluten meal isn't a "magic bullet" for controlling unwanted weeds (plants). I've read and been told that it can take at least 2 to 3 years (following recommended application rates on yearly bases) before seeing any results with this method.
Once or twice a week, I walk the lawn and pull out by hand all the weeds (unwanted plants) I can see, roots and all. The first year I did this (4 years ago), I would be out there for at least an hour doing that (wife would continually tell me it was more like two). This year, I'm out there 5 minutes (10 minutes at the very most).
I make 5 gallons of compost tea each week (from late Spring to earlier Autumn "Fall") and apply the 5 gallon batch to the front garden one week, then the following week apply a new fresh 5 gallon batch to the back garden. I repeat that cycle for the period given previously. I have been doing this for 2 years now, and without question I have noticed a massive increase in worm activity e.g. lots of worm castings on the surface of the soil.
- I spread the 5 gallons of Compost Tea via a watering-can over approx 1800ft² (170m²). Lawn area is about the same front & back for me. So one week the front lawn gets treated, then the following week the back lawn gets treated, repeat, repeat...
2010-05-11, 5 gallons of Compost Tea brewing away nicely. (click image to enlarge)
During dry, hot spells (generally July & August here in Missouri), I water the lawn approximately once a week. I water deeply, at least 1inch (25mm) of water. I don't have an in-ground watering system, instead I use a sprinkler connected to a hose on the front lawn and the same again on the back lawn. I move the sprinklers once the areas currently being watered have received its 1inch (25mm) of water. I do this by timing, as I've worked out how long it takes my sprinklers to deliver that amount of water to an area.
During dry, hot spells (generally July & August here in Missouri), when temperatures are constantly over 90°F (32°C) I never go out and cut the lawn. A cool-season lawn hardly puts on any new growth in those kind of temperatures (will start to enter dormancy). Once the temperatures have dropped back into the 80's°F (mid to high 20's°C) for a few days, I will go out and cut the lawn, but only if it needs a cut. If it doesn't, I just wait until it does and temperatures are right for cool-season lawn cutting.
2011-08-10, Front garden (North facing) after 4 weeks of continuous +95°F (35°C) heat, almost zero rain, watered once a week (per above) and not mowed during that time. (click image to enlarge)
2011-08-11, Back garden (South facing) after 4 weeks of continuous +95°F (35°C) heat, almost zero rain, watered once a week (per above) and not mowed during that time. (click image to enlarge)
2011-08-11, Front garden (North facing) after being mowed for the first time in 4 weeks (due to excessive heat). (click image to enlarge)
2011-08-11, Back garden (South facing) after being mowed for the first time in 4 weeks (due to excessive heat). (click image to enlarge)
- Around "Labor Day" (beginning of September, early Autumn "Fall") here in the US, I prepare any bare spots for reseeding. Reseed using an appropriate seed for my lawn type. Cover the whole lawn with ½ to 1 inch (12.5 to 25mm) thick layer of STA-certified compost (bought in bulk locally). Water as needed, ie Amount needed for good germination to take place.
2010-09-26, Front garden after working through the above Autumn (Fall) lawn maintenance program. (click image to enlarge)
2010-09-26, Back garden after working through the above Autumn (Fall) lawn maintenance program. (click image to enlarge)
Fertilize the lawn with Ringer Lawn Restore (by Woodstream Corp) at the end of September, early October.
After the last cut of the cutting season (sometime in November for me), I service my lawnmower for the winter:
- Run the lawnmower to empty the tank of fuel (petrol/gas).
- Remove the spark-plug and dispose of it.
- Remove the blade, gather up my other blade, and go get both of them sharpened, so they are ready for the following cutting season.
- Remove the air-filter and dispose of it.
- Drain the oil and dispose of it in an environmentally safe way.
- Give the lawnmower an overall clean and wash down, especially making sure I give the underside cutting deck a thorough clean.
- Oil all the moving parts.
- Give it a pat and a kiss for the winter.
While I fully realise the above does not give you a "magic bullet" for dealing with crabgrass, I hope it does proves somewhat helpful.
Good luck, and please let me know if you find that "magic bullet."
I've now been maintaining a cool-season lawn for 5 cutting seasons, prior to that I had no "real" experience with that lawn type. Therefore I've made mistakes, learnt a lot and still have a lot to learn.
Mistakes I've made:
1st cutting season - Was cutting far too low, 1 to 1½inch (25 to 37.5mm) finished cut height.
1st cutting season - Was collecting the clippings (via mower bag) every cut.
1st cutting season - Did not water at all.
1st cutting season - Did not collect up all the fallen leaves in Autumn (Fall).
1st & 2nd cutting season - Did not apply any kind of fertilizer.
2nd cutting season - Reseeded bear spots in Spring (late April, early May).
Things I've changed, learnt:
Cut high, I would say 2½ inch (62.5mm) is the absolute minimum for a "healthy" cool-season lawn.
If you have a mulching type mower, leave the clippings on the lawn (free natural fertilizer).
Apply some kind of fertilizer, even if you only apply once a year (do so in the Autumn "Fall").
During hot, dry spells, water deeply (approx 1inch/25mm) once every week or two.
I think we can all agree, pulling weeds from wet ground is a lot easier and more effective, seeing as we get the whole weed (plant), root an all out of the ground. But today (2011-07-22) I finally noticed that if I look at my lawn immediately after watering (or a good rain), I can very easily see any young (small) crabgrass that's within my lawn. How? The young (small) crabgrass has a very different green colour from my lawn grass, I believe the water on the lawn helps magnify that difference in colour. In my lawn it looks luminous ie Light, bright green. Where as my lawn grass is a dark green.
Reseed in early Autumn (Fall) ie Performing major cool-season lawn maintenance at this time of year, will give you the best results (reap the rewards the following cutting season).
Pick up all the fallen Autumn (Fall) leaves, be careful with Black Walnut leaves & diseased leaves, for the "average" gardener it is "generally" considered best practice to dispose of them separately (don't put them in your compost pile). Shred them up if you can, put them into bags, store the bags in a shed or garage for the Winter, then at the very beginning of Spring empty those bags into your compost pile.
Organic lawn care (organic anything) is a long, slow process, not a "miracle" instant fix. Each year you build on the previous year, some years you will move forward more than others, but you should see at least some forward movement each year (unless you're really unlucky).
An organically maintained lawn isn't going to be totally weed (unwanted plants) free. Period. You can't control outside conditions eg Birds dropping seeds into your landscape. Weed (unwanted plants) seeds being blown into your landscape by the wind.
Nothing to do with crabgrass control, but hopefully you will indulge me if you've gotten down this far (if it proves "unwanted" I will happily remove this section), as a "bonus" (for myself) for taking an organic approach to lawn maintenance, I planted some Spring bulbs in the front lawn last year (November 2010):
- 50 Crocus "Lawn Mix".
- 12 Scilla "Siberica".
I am so glad I did, the wife loved them, a few of the neighbours made some nice comments...
Fingers-crossed, I'm hoping to see more of them next year, as they should hopefully start naturalizing.
Below are a few photos of those Spring bulbs, taken April 2011 (click images to enlarge):