Four Factors That Affect Grass Growth

Whether you’re planting cool- or warm-season grass this spring, it’s helpful to understand the factors that affect germination and growth. The following growing conditions determine when to plant which type of grass.

Soil Temperature

One of the most important factors for grass growth is soil temperature. Cool-season grass starts to germinate when the soil temperature reaches 50°F and grows most vigorously when the soil temperature is between 50°F and 75°F. Come late spring and summer, soil temperatures above 85°F will slow the growth of cool-season grasses. 

On the other hand, warm-season grass germinates well in soil temperatures between 65°F and 70°F. Warm-season grasses continue to thrive through the summer until soil temperatures dip back below 65°F in the fall.

Daylight

Grass can only grow when it has sunlight and carbon dioxide to trigger photosynthesis. Both cool- and warm-season grasses grow more with more sunlight. The longer days of spring make it a good time to plant cool-season grass if you want an alternative to traditional fall seeding. For warm-season grasses, late spring and early summer are the ideal time to seed.

Moisture Content

Turfgrass will never grow without proper moisture. Spring snowmelt typically provides cool-season grass with all the water it needs. Drier summer days require you to water more deeply and frequently, which helps the grass build a deeper root system. You should still water during fall when there’s less than an inch of precipitation per week. Don’t water after the ground has frozen because the water won’t reach the roots.

In geographies where warm-season grass is grown, the lack of snowmelt means you may have to water more. However, warm-season grasses require less water overall than cool-season.

Soil Nutrients

With the right conditions, soil can have many naturally occurring nutrients to support grass growth. Test your soil before seeding to determine if it has the proper nutrients. If there is some deficiency, you can choose a fertilizer to supplement what’s missing. This is a good practice to follow for both warm- and cool-season grasses.