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The Best Time to Plant Cool-Season Grasses

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As I sit down to write this (June 12), a commercial comes on my music streaming service and tells me, “now is the time to get out there and work on your lawn.” How do they know where I live to be able to tell me this? Perhaps if I lived in south Georgia, now would indeed be the time to fertilize and seed my lawn, but I don’t live in south Georgia. I live in Kentucky and now is certainly not the time to seed (or even fertilize) my lawn. Each spring, as I visit various stores and garden centers, I see massive displays of seed awaiting the uninformed consumer. Unfortunately, a lot of those displays remain out as spring transitions to summer. So why all the spring seed displays and advertisements when university extension documents across the country point people away from this? All I can come up with is the weather is turning warmer, people are sick of being inside, and want to make their yard pretty after it may have been off-color for a few months. Also, farmers are out planting at this time, so it’s gotta be the right time to plant lawns, right? Well, not really. In my former position as a university extension specialist, I would tell people the best time to seed is this fall. The second-best time to seed? Next fall…

I think most professional grass growers know why it’s so important to plant in the fall because they are highly educated in agronomic practices. But as I mentioned above, many homeowners are uninformed.

So why am I so adamant on fall plantings of cool-season grass seed? There’s a whole bunch of reasons. But first, because fall ranges from September to December, let’s narrow down what I mean by ‘fall’ seeding. Ideally, seed should be put in the ground while it’s still warm, but with a chance of cooling temperatures on the horizon. Usually, this means that late summer into early fall is ideal for planting. In the far north, this may mean mid-August to mid-September, while in the lower transition zone, it may mean mid-September to mid-October. Of course, each year is slightly different, so you always need to pay attention to the weather and make your best guess.

Reason number one to plant in the fall—weed pressure. In late summer/early fall, there’s not a whole lot going on weed-wise. Crabgrass and goosegrass can still germinate and emerge in late summer, but as soon as the first frost comes along, they will be shut down. Annual bluegrass and winter annual broadleaf weeds begin to germinate as temperatures and light levels begin to decline, but they usually don’t blow up until spring, giving us a pretty good window to get our seed going and be successful without massive competition from weeds.

The second reason to plant in the fall is because of ideal conditions. As temperatures begin to decline, we get into perfect weather for cool-season grass growth, and instead of going into hotter and hotter conditions like we would in the spring, temperatures continue to decline. This favors optimal growth for these grasses (optimum top growth for cool-season grasses is between 60 and 75°F; optimum root growth for cool-season grasses is between 40 and 60°F). Soil temperatures are also cooling during fall, which improves germination and results in a better stand of grass.

In many areas of the country, as we head into spring, rainfall is not prevalent, and conditions become increasingly dryer. So, the third reason I recommend planting in the fall is for timely rainfall. As fall progresses toward winter, precipitation often increases, which benefits fall seedings. Seeds need to imbibe water to be able to germinate. Following germination, due to a lack of a root system, seedlings need plenty of water to continue to grow. This is one of the steps where I often see spring seeding failures–people will irrigate until germination occurs, and then cut off the water, resulting in a poor stand.

The fourth and last reason to plant in the fall is also the most important. With fall plantings, seedlings are able to grow for a month or two in the fall and continue for a few months in the spring before the summer heat kicks in. This allows the seedlings to mature and send down a deep root system before they are hit with hot and dry conditions. Think of this in terms of your weed control strategy—large, mature weeds are difficult to control with herbicides, while small weeds are much easier. The same is true for turfgrass, larger and mature usually equals tougher.

Now, can you seed in the spring and be successful? Of course. Will it be harder to get a good stand of grass? Unfortunately, yes. The big concern with spring seedings, as I mentioned above, is that the immature seedlings may not fare all that well when the summer conditions arrive. There are a couple of ways to get around this. One way is to plant as early as possible. When soil temperatures at the 2-inch depth get to around 50°F, get the seed in the ground. A good indicator plant for seeding timing is forsythia. Once forsythia begins to bloom, it’s time to seed. As the blooms begin to drop from forsythia, conditions are usually right for crabgrass germination. This leads me to the second issue with spring seeding—summer annual grassy weeds. Crabgrass and goosegrass are such voracious growers that they will quickly overtake cool-season grasses and will outcompete them for light, space, nutrients, and water. To have any chance of spring seeding success, be sure to use a pre-emerge herbicide such as mesotrione at planting. This chemical will impede crabgrass germination but will not affect cool-season grasses. Depending on the year, irrigation may need to be supplied to reduce heat stress on the immature plants and supplement rainfall.

We live in a day and age where people are watching every move we make. One of the reasons turfgrass gets a black eye is the general public thinks we apply too many inputs to keep grass looking good. If we can reduce our inputs, even slightly, it is better for us all in the long run. Fall plantings can give us this—less water required, healthier plants come summer (potentially less pest issues), and less need for pesticides.

Finally, quality seed is an important component of a successful planting and a good starting point for reducing inputs. Plant seed that is as fresh as possible. Fresh seed is much more likely to be successful than older seed. You’ll also want to choose the proper species for your climate and pay close attention to the variety as not all grasses are created equally. Look for a grass that has gone through extensive testing and will do well with reduced water, fertilizer, and pesticide. And lastly, pay attention to the seed tag. The tag will tell you when the seed was tested (how old it is), as well as how much of the seed in the bag will germinate, how much of the bag is actually seed, and if there are weeds in the bag. You can then take this information and calculate pure live seed, but that is for another day…

Gregg Munshaw, PhD
Director of Agronomy
Mountain View Seeds