Here in New England, the predominant type of grass is a mix of Kentucky blue, rye, and fescues. All those are cool season grasses. They grow well in early Spring, and Fall, usually mid April and mid September. Rye germinates in one week, when the day temperature is above 55 degrees for seven consecutive days. Fescues germinate in roughly 14 days, and Kentucky Blue in 21 days. Weed seed like crabgrass, will germinate when the soil temperature reaches 55 degrees. That usually happens by the beginning of June.
This is why it is so important to overseed your lawn as soon as the weather is optimal for grass seed germination. Since good grass will grow well in early Spring, we must make sure we take good care of our lawn–before the weed seed germinates in late May and the beginning of June.
Once the weather improves and the soil temperature increases, the microbiology in the soil will start digesting whatever is available and will produce available nutrients to the plants. During the summer, when the temperatures reach 85 degrees, the cool season grasses will stop growing and weeds will grow vigorously because the dry and hot days are the perfect environment for those weeds to grow. The cool season grass will go into dormancy, and if we are not careful, weeds will take over. The best thing to do in the summer is to let the grass grow to four inches preventing some of the weed seed from germinating, or at least delaying the germination rate. It is also important not to mow if it is not necessary.
Grass grows well in the Spring and Fall
By September, when the outdoor temperature gets colder, the lawn will grow back again, and the weeds will start to die back. This will also be a good time to reseed the lawn to encourage more grass growth.
Organic grass grows when the grass utilizes the nutrients released by the microorganisms. So it is always good to feed the soil, to keep those microbes happy, and feed them when they are most active. Early Spring and early Fall. You can also feed them during the summer. Microbes, can digest all types of products such as clippings, compost, seaweed, corn gluten, leaves, and they will even feed on other microbes.
The end result after a few years is that the lawn will be self sustainable. By doing soil tests, we can follow recommendations to increase pH, organic matter, and fertilizer rates, among others. This is the only way to know how much product is needed.
Remember, feed the soil and not the grass.