Is October too late for overseeding after aeration?

For cool-season grasses like fescue and ryegrass, October is the optimum time to overseed after core aeration. This timing utilizes the cooler temperatures of autumn, taking advantage of aeration holes as protective pockets for seeds. Soil temperatures are most commonly above 10°C (50°F) during early October, creating favorable conditions for germination without the hot summer heat stress. The combination of the aeration has been shown to yield seedling success rates of 70-90% better than seeding alone. This method will prepare the turf for vigorous spring growth.

Monitoring soil temperature remains crucial for success in October. A probe thermometer should be used at a depth of 5 cm, aiming for steady readings above 10 °C (50°F). This temperature is necessary for the root establishment of the seedlings before frost prevents further growth. In northern areas, overseeding should be completed before the middle of October, while in southern regions, this is extended to the latter part of the month. When overseeding, also apply starter fertilization to accelerate root development. It is the addition of nutrients in this way that will enable the seedlings to tolerate frost before winter dormancy sets in.

The aeration-seeding method produces excellent seed-to-soil contact. Seeds that fall into open holes have the advantage of being completely sheltered from the elements while receiving subsoil moisture. This made-to-order environment is much more conducive to natural germination than surface seeding. After the seed has been broadcast, the lawn should be lightly dragged with a mat in order to allow the seeds to settle into the holes without being covered too deeply. When properly performed, the technique will provide maximum utilization of the aeration channels.

Post-over seeding care dictates survival rate through the winter months. It is essential to maintain constant moisture in the soil by light watering daily for 21 days. Foot traffic should be avoided until the grass has attained a height of 7 cm. A winterizing fertilizer can be applied 4 to 6 weeks after germination to fortify roots against the freezing temperatures. These measures will help babies establish themselves sufficiently to withstand the winter's stress, and burst forth with growth in the spring.

Lawn areas in October with overseeding are dominant in the next season, developing deeper roots during the cool spring months than turf seeded in the spring, which has better drought resistance. This is aided by the fact that a complete application of herbicides can be made in the spring when the newly seeded grass comes into maturity before the weed treatments are used. The resulting autumn investment is a happy one, which produces thicker and healthier turf, and less maintenance will be necessary for years to come.

Read the full article: 10 Benefits of Lawn Aeration Explained