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Organic Lawn Strategies- August-September:


A lawn is really thousands if not millions of individual plants.

Now is the best time to improve your lawn! It may seem odd since you are beginning to think about packing up the croquet set and patio furniture for winter storage. Like your outdoor activities, annual weed seeds burst forth in May and fade away in late summer, but turf grass just keeps on growing through October and into November. By improving it now, you give it the best start for spring.

Lawn Strategies for Fall – printable PDF version

So if you want to

  •  aerate the soil,
  •  spread fresh compost or lime,
  •  overseed,
  •  fertilize,
  •  prevent insect & weed pests and
  •  even start a lawn,

then do it now while seedlings have less competition for nutrients and moisture!
Luckily these are the perfect steps to improve your lawn organically. Feeding the turf grass and boosting its environment to optimal growing conditions in the fall will encourage grass plants to crowd out weeds and make the lawn more resistant to all sorts of pests.

To aerate the soil and/or improve the soil’s absorbing qualities:

If your soil is compacted, heavy clay – water just sits for days on the surface without being absorbed— try renting an aerator to open up the roots to more oxygen. Also raking in a thin layer (1/4” to ½”) of compost will increase the bulky organic texture of your soil, increasing pore size and will allow better water exchange. Supply list: Compost & Rent an Aerator or Slicer/seeder.

Why compost and/or lime?

Compost will increase the living bacteria and nutrient level of the soil which depletes over time.

Lime is helpful if your soil test shows a pH of 5.8 or lower.

  • The soil’s pH affects a plant’s ability to take up the nutrients that are available in the soil.
  • Ideal pH for growing grass is 6.0-6.8.
  • Soil test kits and instructions are available at the garden center and local Master Gardeners provide soil testing in May and September at area Farmer’s Markets.
  • If you need to bring pH down, you’ll want to spread sulfur. Spreading rates and quantities for adjusting pH are explained on the product bags. If you need to adjust pH once, chances are you’ll need to do it again. Test every couple years.
  • Supply list: Soil Test, Lime or Sulfur and Compost.

How do I overseed a lawn?

With the soil aerated, loosened with more organic material and pH adjusted; you can spread fresh seed over your existing lawn. To germinate effectively, grass seed needs to be in firm contact with soil. Rake the area to loosen the soil and make it easier for new roots to sprout and spread. By overseeding, you encourage grass to use the space that weed seeds would normally find. Use a quality perennial seed mixture recommended for your conditions whether they are full sun, part shade or dry. After seeding, water the seeds in and keep the area moist until the seeds have germinated, about 2 weeks. The increased and regular rainfall typical in September will help you! Supply list:  The Right Seed Mixture and Spreader or Slicer/seeder if you’re aerating in the same step.

Can I start a new lawn now?

Absolutely. If your property lacks topsoil due to new construction, spread a 4-inch layer of compost mixed with topsoil. If re-seeding smaller areas, just rake in compost to improve the organic structure. Check the pH of your soil and add lime if indicated as above. Then, as in overseeding, rake and loosen the soil surface preparing it to receive the seed. Spread seed at recommended rates in a criss-cross pattern to achieve the best coverage. A light mulch of straw helps keep the seed in place while maintaining soil moisture. One bale per 1,000 square feet is enough and won’t need to be removed after grass germination. Supply list: The Right Seed Mixture and Straw

What kind of fertilizer is good for fall?

An organic slow-release fertilizer provides a long-lasting nutrient base that feeds your lawn as needed. Leaving grass clippings on the lawn surface with a mulching mower returns nitrogen to the lawn regularly. But as grass grows more slowly into fall, the slow-release nitrogen of an organic fertilizer is helpful. The phosphorus, potassium, iron and trace elements found in organic fertilizers all boost the health of your lawn in a steady long-lasting form. If you fertilize just once a year, do it in early September while grass is still actively growing and weed plants are slowing down. Choose a fertilizer that is in a ratio by weight of 2-4-2 or 2-3-4, Nitrogen – Phosphorus – Potassium. (Could be 14-28-15; 6-12-7; 10-16-20 etc.) This will feed the blades as well as the roots and strengthen the grass for winter weather. Supply list: Slow-release, Complete Fertilizer and Spreader

Organic Lawn Maintenance & Problem-Solving

Regular Mowing Matters:

In addition to the practices above, regular mowing should continue through October. Keep grass blades tall—3.5 inches- by maintaining a high mower height. Remember if you use a riding mower, your weight lowers the cutting blade—adjust accordingly! To keep the grass healthy, don’t cut more than 1/3 of the blade at a time. Healthy grass grows faster so plan to mow at least once a week. For your last two scheduled mowings, lower your cutting blade one notch each time. This helps prevent fungal disease during the lawn’s next big growth spurt in spring—when it will probably be growing vigorously but be too wet to mow.

Late Summer is Best Time to Control Grubs (and Future Beetles):

Grubs destroy lawn areas, and in late August and September, they are small, actively feeding and still at the warm soil surface. This is the best time to start organic controls if necessary. Grubs eat the roots of grass plants and you can identify the problem when large patches of brown grass can be pulled back easily. Treat soil with Milky Spore or other appropriate B.t. product (a naturally occurring bacteria that affects grubs) by spreading product around the edges of the dead area. Grubs are moving to the green sections; they’ve left the dead area. Or try beneficial nematodes species: Heterorhabditis bacteriophora (HB) have achieved acceptable levels of control against Japanese beetle, oriental beetle, and European chafer grubs, but most effectively against Japanese beetle. These need to be timed carefully and well-watered in. Use dried nematodes  once damage is noted after grubs have hatched – late August around here. Apply before 9:30 a.m. or after 3 p.m. and water with about ½ inch of water to allow nematodes to move through the soil and enter grubs.

Stop Weeds:

Weeds take over where grass is not healthy or thriving. By increasing the vigor of your grass, you are making your best defense against weeds. For persistent and perennial broadleaf weeds, like  plantain and ground ivy, spot treat with an organic herbicide and completely remove by hand, then overseed the area. For large weedy areas, remove the weeds; and use a pre-emergent weed control like corn-gluten. After about 4 weeks, seed the area with new grass as indicated above. Try to schedule your new seeding by mid-September to ensure good grass growth before cold weather sets in.

Regardless of Weed or Not, Ground-cover Is Important for Insect Diversity:

Not all broadleaf groundcovers need be considered weeds.  Grasses with a mix of other flowering groundcovers will encourage more pollinators in our landscape.  If your lawn serves as a green backdrop and not a carpet for your bare feet or a putting green, consider mixing in clover or thyme seed with your grass mix.  Even let the dandelions have their moment to shine.  The flowers will benefit bees and other pollinators.  And, all insects serve as an important food source for birds.

Doing the Above Will Prevent Diseases:

Problems arising from diseases are most likely brought on by improper soil aeration, inadequate or too much fertilization, overwatering, or mowing too low. Diseases are usually brought on by fungi in the soil so the best defense is prevention. Plant resistant turfgrass mixtures suited to the site and alter your lawn care practices to favor plant growth.

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