Keeping grass from going to seed is similar to deadheading flowers before seed heads can form and release seed to the wind and soil. Preventing seed development altogether drives all of the grass' energy to producing new root, rhizome and green blade growth. This foliage-oriented growth produces a healthier and more lush-looking lawn turf. The key to keeping a lawn from going to seed is regular mowing and using a catch attachment to capture any seed that has managed to develop. Different varieties of grass develop their seed heads on different schedules, but many produce seed heads in the late summer and fall which then typically mature and distribute their seed within a month's time.
Mow your lawn regularly, keeping it within the range of preferred blade length for your specific varietal of grass and your climate. Regular mowing takes off bloom stalks before they can develop seed heads and also takes off young seed heads before they can mature. Keeping your grass within the recommended range keeps the production of seed heads in check. Keeping your lawn at the lower end of the recommended blade length range ensures that grass flowers and seed heads are even less likely to develop.
Use a catch on your mower to collect clippings each time you mow your lawn. This prevents any errant seed heads from falling back down on the lawn to reseed or overseed. With the hybrid grass seed in use today, you cannot be certain that the seed your grass produces will even be the same variety of the grass the seed comes from. Hence, catching the seeds can also prevent your lawn from being overseeded with an unwanted variant of your original grass seed. In addition, using a catch can also minimize thatch buildup from cuttings and prevent crowding or choking off of healthy rhizomes.
Monitor the lawn very closely for production of seed heads, particularly in the late summer and early fall. More frequent mowings of every three to five days may be required to capture all seed heads that have developed or are cycling into maturity during this period. Moisture, climate, grass type and varietal all play into when seed heads develop. Carefully observing your lawn grass for seed heads will teach you when your grass is in prime seed-producing mode each year. This information will help you plan your mowing regimen to prevent seeding from occurring.