Fall Lawn Tasks: Here’s the Primer
In the northern half of the nation, the days are still warm, the nights are cool and Mother Nature usually provides plenty of rain. The humidity drops, biting insects take a break and garden centers start putting many products on sale.
Welcome, in other words, to the gardening utopia known as autumn. This is a great time to plant absolutely anything, other than maybe annual flowers and vegetables. Trees, shrubs, roses and all sorts of perennials will benefit from going into the ground in September and early October and having the remainder of fall to grow out a root system before winter.
I get most excited, though, about working on my lawn. Just after September 1st, I always trot out my checklist of organic lawn care tasks. If you’re looking to upgrade your lawn’s current appearance, here are just a few of the considerations:
MOWING — In the cool-season areas of the country, it’s getting safer to lower the mower blade if you’ve been using the proper methods and keeping the blade high all summer, at about three or more inches. From now until the final mowing of the year, you can get away with about two and a half inches — dropping to two inches for your final mowing in early November. If you leave the grass too high heading into winter, you may be creating a nice haven for field mice that can damage the lawn.
Gauge this carefully. If you live in a region of the country where you’re still getting 80- and 90-degree days, it’s too soon to lower the mower blade.
OVERSEEDING — In lawns with any thin areas, apply a layer of new grass seed. Be sure to scratch the soil first with a bamboo rake or mechanical machine known as a dethatcher. This will ensure good seed-to-soil contact. You can also cover the seed with a light layer of compost or healthy soil (a quarter-inch layer is plenty) to increase the germination rate of the seed. You’ll want to water frequently to keep this new seed moist while it germinates.
FERTILIZING — The goal in autumn is not to push out loads of growth; the idea is to establish healthy roots that can make it through winter. Early autumn fertilizers, therefore, should have potassium, phosphorus and calcium in abundance, with less emphasis on nitrogen. Alfalfa-based fertilizers are perfect this time of year, as are seaweed or humate-based products.
Avoid fertilizing at all when the ground begins to freeze in your area. Be sure to watch the weather, too. If a heavy rain is predicted, don’t fertilize in the days before the rain.
LIMING — I know many people who put pulverized dolomitic limestone on their lawns as a matter of course each fall. The product is recognizable by the heavy, white paper 40-pound bags. With our acid rainfall increasing in the Northeast, that might seem like a good thing to do. If you’re concerned about weeds, however, the dolomitic lime can be a problem. In ideal lawn soil, the ratio of calcium to magnesium should be seven to one; in dolomitic limestone, the ratio of Ca to Mg is three to two. The high level of magnesium compacts the soil and actually promotes weed growth.
It’s a good idea to have a soil test if you haven’t for a while prior to putting down any limestone or soil additives; most Cooperative Extension offices still offer basic soil tests, or you can contact the Soil Food Web laboratory on Long Island in New York or Oregon for a more comprehensive test. The state folks, though, often don’t know about the calcium-magnesium ratio, so you’ll need to trust us on this one.
Many garden centers sell high-calcium limestone with little or no magnesium. This a generally a great product for many areas of the country with low pH soils. Here is one example: http://www.natraturf.com/natrasweet-how-to-use.cfm. If you live in an area with inherently high pH in the soil, consider an application of gypsum instead. Here’s a post that clearly explains the difference: http://www.safelawns.org/blog/index.php/2010/11/guest-blog-the-difference-between-calcium-and-gypsum/.
WEED MANAGEMENT — If your lawn has a lot of crabgrass, plantain, or other seed-forming weeds, mow off those weeds with a bagging attachment if possible so that the seeds don’t have a chance to hit the soil. If you don’t have a bagging attachment, you may want to dig up or cut off some of the worst areas by hand, or spot spray with an organic weed killer (see below).
Crabgrass will usually be at its worst by the edge of your driveway or walkway where the soil is continually compacted.
If the seeds do drop to the ground after the first frost, cover the ground with a layer of compost or fresh soil, which will inhibit the crabgrass seeds from germinating (the crabgrass seeds need light to germinate). Be sure to overseed with grass seed this fall so the new grass growth will crowd out any crabgrass that does germinate next spring. You can also apply a layer of corn gluten in the spring just as the forsythia buds begin to pop open; the corn gluten will help inhibit the crabgrass seeds from germinating (but don’t over-rely on this product: http://www.safelawns.org/blog/index.php/2011/03/thinking-of-corn-gluten-meal-read-this-first/)
These days, it’s becoming popular to spot spray weeds with organic weed killers that are based in vinegar and often mixed with either limejuice or clove oil. You can sometimes find straight vinegar that is strong enough to kill weeds on its own; look for at least 10 percent vinegar in the solution. A friend of mine from the Midwest sells a 20-percent vinegar that will reliably burn out weeds (email firstname.lastname@example.org for more information).
A company known as Perfectly Natural also sells a pre-p
ackaged product that works well (www.perfectlynatural.com), as does Nature’s Avenger and Burnout II.
COMPOST TEA — Maybe you’ve tried organic fertilizers and expected the same quick green-up you obtained with chemical products. Chances are, you were disappointed. Whether you’ve been organic for years, or especially if you’re making the transition, applying compost tea will give you the best lawn results.
The tea, which contains the microbial life and nutrients of the compost suspended in a liquid solution, will stimulate growth and also fortify the biological processes of the soil. Applying compost tea is especially useful for folks making the transition to organic lawn care from synthetic fertilizers and pesticides. Synthetic fertilizers and pesticides kill off beneficial organisms in the soil; the tea will bring them back. Tea is also faster acting than dry compost because the liquid drenches down into the soil quickly.
Tea brewing kits are available now at many garden centers, as well as numerous on-line sources. With a kit that includes an electric aerator, it’s possible to have usable compost tea in about 36 hours. For lawns, try to start with compost that has been made with some amount of grasses in the pile; that way, the bacteria in the compost tea is more likely to match what is needed for good lawn soil. Visit SafeLawns.org for a free how-to video that shows the brewing process step-by-step.
PRE-WINTER CLEANUP — In addition to lower mowing, it’s a good idea to rake off any excess thatch, which shouldn’t even be present in an organic lawn system (thatch is caused by excess nitrogen applications). Rake up any excess leaves prior to winter to avoid dead patches next spring. Mulching the leaves with a mower is fine, provided the leaves aren’t too thick; a matted layer of mulched leaves can also cause dead spots.
If you do dethatch your lawn, it’s always a good idea to overseed at the same time so that the new grass germinates before any weed seeds.