By John Fech, UNL Extension Horticulture Educator
Generally, there are 3 categories of lawn reseeding:
- Total renovation - if less than 50% of the lawn is comprised of desirable species
- Lawn Overseeding - if 60 to 70 % is desirable
- Lawn Thickening - if the current lawn is mostly desirable, but just a little thin.
With total renovation, step 1 is to spray the entire lawn with a non-selective herbicide such as glyphosate. Once the herbicide has taken effect, you can move on to Step 2.
Step 2 is powerraking to create a seedbed. It's wise to think of this step as the platform on which the new grass will grow, much like new carrot seeds in the veggie garden.
Next, it's time for step 3, to rake off the debris. You may need the help of a Boy Scout troop for this, as it is fairly labor intensive. While you are raking, think of the dead grass as a potential addition to your compost pile; it may help with the motivation necessary to finish the task. As hard as it may be, it's well worth it in terms of creating a seedbed that facilitates seed to soil contact.
Step 4 is to apply grass seed with a drop spreader; seed is light and can easily be carried off site with a light wind. Divide the amount of seed in half and apply it in a north/south direction and then an east/west path. For Kentucky bluegrass turfs, apply a total of 2 -3 lbs of seed per 1,000 sq. ft. and 9-10 lbs of seed for turf type tall fescues lawns.
The goal after the seed is in place is the same as it is for routine lawn watering - to water to the depth of the root system and to keep the roots moist. The difference with rehabilitation is that the new roots are shallow. To create a suitable environment for germination and initial growth, it's best to irrigate several times per day and keep the upper inch moist, but not soggy or dry. For Kentucky bluegrass lawns, this will take about 3 weeks; for turf type tall fescue, about 2 weeks.
It's very important to keep watering lightly and frequently until all the seed has germinated, or else the resulting lawn will be thin and clumpy. After the new turfgrass plants are a half inch to an inch tall, apply a starter fertilizer at label rates to encourage thickening and provide for the next few weeks of establishment.
If lawn overseeding is called for, the procedure is much the same as it is for renovation, except that the spraying of the lawn is skipped.
In the case of caring for a mostly desirable, but slightly thin lawn, apply 0.5 to 0.75 lbs of a slow release nitrogen fertilizer product and spot spray broadleaf weeds that may have invaded due to the voids in the lawn. Products such as Weed-Free-Zone, Weed B Gone Maxx or Trimec are suitable for this purpose. As with all pest control agents, be sure to read and follow all label directions.