Now’s the time to think weeds and lawns

August seems like the peak of summer – the dog days – with the heat and the humidity. But for plants it may signal winding down and getting ready for the dormant period ahead. That is because plants respond more to the hours of sunlight and angle of the sun than the temperature. Between the summer solstice (June 20) and the end of August we reduce our daily sunlight hours by  2 hours and 18 minutes and the angle of the sun at solar noon changes from 68.6° to 57.1°, which reduces the intensity of the sun’s rays. So plants sense that we are heading for the autumnal equinox and the winter solstice, and the trees and perennial plants are storing up nutrients to get them through the winter. That is why early fall (mid-August to mid-September) is a good time to pay attention to certain yard and garden practices.

If you are bothered by perennial broadleaf weeds, such as dandelions, early fall is the best time to treat them chemically if you are not able to keep up with manually removing them. Dandelions grow best in thin, sunny lawns and bloom in both spring and fall when days are less than 12 hours in length.

Since dandelions are a perennial weed, they must be removed or killed or they will sprout again next year, bigger and stronger. The best time to do this in September, when the plants are translocating carbohydrates to their roots for winter storage and the herbicide will move into the internal parts of the plant. Plants are most susceptible right after they bloom.

The most effective chemical for dandelions is 2,4-D, which you usually find mixed with other broadleaf weed killers such as MCPP (Mecoprop) and dicamba. Spray the herbicide on a calm day to avoid drift, when the temperatures are not expected to reach above the high 70’s and no rain is expected for 24-48 hours. Spray directly onto the leaves, so the herbicide can be moved into the plant where it will disrupt the growth pattern of the plant. Within 24 hours you may see the leaves begin to twist and curl. While you may not see any other effects it is highly unlikely that the weed will re-sprout in the spring.

Mid-August to mid-September is also the best time to overseed your lawn, because the environmental conditions are favorable, the weed competition is less than in early spring and seeding at this time allows for grass to be well established before winter. Before you spread seed there are several steps you should take to prepare the site.

  • Remove perennial weeds. You can remove them manually, but if you choose to use an herbicide before to do this 2-4 weeks before you reseed. Broadleaf weeds such dandelions can be treated as mentioned above. Grassy weeds such as quack grass can be treated with glyphosate (Round-up™ or Kleenup™), but be aware that this generally kills most green vegetation it comes in contact with.
  • If the ground is dry, soak the ground thoroughly 6-8 inches, once the weeds are removed.
  • Soft or spongy ground indicates a thick thatch and this should be removed in order to allow the seed to make contact with the soil.
  • Prepare the soil by vigorously hand raking or aerating with a commercial aerator. This is so that the seed can make good contact with the soil and set down roots.
  • Choose seed that is appropriate for your site. You may want to choose grasses that require minimum input: that is generally not watered, fertilized one time or less each year and mowed no more than once per week. For sunny sites a mixture of 50-60 percent common Kentucky Blue Grass and 40-50 percent fine fescues will produce a minimum input lawn, while  mix of 60 percent fine fescue and 40 percent shade tolerant Kentucky Blue Grass such as Eclipse, Glade, Touchdown, or Nugget is good for a shady site. To spread the seed mix 1 part seed to 4 parts sawdust. If the area to be seeded is less than 8 feet across, you can hand spread the seed. Spread in two directions – north to south and then east to west. If more than 8 feet across, a rotary spreader is the preferred method. If you use a drop spreader be sure to seed in two directions and overlap your rows.
  • Water lightly for good soil to seed contact. Water twice daily if the soil is dry. Keep the lawn moist but not soggy.
  • Once the grass is 3 1/2 inches tall mow it to 2 to 2 1/2 inches. Be sure that you mower blade is sharp.

Even the dog days of August are the right time for some yard and garden chores.