....Forgot to add, it's funny how the warm-season zoysia and the cool-season bluegrass begin to bloom at about the same time. You'd think the zoysia would bloom towards the end of the summer, like the warm-season crabgrass does. But for some reason, it doesn't work that way with zoysia.

Well, according to a Fairfax County site, Kentucky bluegrass blooms from May to August.

They also say, "Flowers are tiny, growing on small spikelets in clusters at the end of the stems. Each spikelet is 1/4 inch long; a cluster can be six inches long. Tiny reddish fruits take the place of flowers and provide seeds for many animals. Kentucky Bluegrass spreads by rhizomes, stems that grow sideways underground."

But they don't say how long it takes the seed "to set." Here's GardenWeb's definition of "set seed":

"To produce seeds after flowering. In some cases a gardener wishes to prevent this in an effort to prolong flowering, or continue harvesting the foliage of an herb." [end quote]

Nice, but I'd like to know how quickly Kentucky bluegrass seed can set, because I would like to wait to mow my lawn (without the bag) until after the seed has fully formed, so that when the mower drops the seed to the ground, the seed has a chance to germinate in the future, whether this year or next.

Tomorrow will be 13 days since I've cut the bluegrass. It's really tall now with lots and lots of inflorescenses.

We all know bluegrass can take up to 4 weeks to germinate, but I want to know how long it takes for bluegrass seed to set in the flower, or perhaps in the fruit after flowering . Tough question I know.

Well, after a half-hour of reading, I found the answer at
http://www.americanlawnguide.com/lawn-types/37-bluegrass-seed-heads.html

Here's what they say:
"Once correctly identified, mulching clippings and the seed heads they contain can often be seen as a good idea to overseed the existing Bluegrass lawn. The main problem with this is that it will most often not work. This is because the Bluegrass seed heads will need to fully ripen and mature before they actually become viable seed.

The full process will often take around 8 weeks for the seed to mature and dry out before they can be used. Leaving a lawn for such a long period of time between lawn mowing would obviously cause the lawn to grow too high and then become scalped and damaged from when lawn mowing resumes, so this is obviously not a good idea."
Other Reasons To Mulch Seed Stalks

While we may not be able to mulch our seeding Bluegrass lawns for the purposes of re-seeding the turf, we can still mulch the clippings into the lawn. This is a great time of the year to recycle the abundance of nutrients which are found in seed stalks, especially Nitrogen. These mowed seed stalks will quickly break down into the soil and release all their nutrient goodness in the process.

They also have this to say:
"Bluegrass sends out masses of seed heads usually around May and June each year. Bluegrass seed heads have a tough green stalk topped by a red set of the seeds themselves.

Many people who see these masses of seeds suddenly appearing in their lawns believe that they may be a new infestation of weedy grasses. This usually isn't true and the difference between weedy grasses and the Kentucky Bluegrass re-seeding itself is easily spotted.

The obvious and best way to spot Kentucky Bluegrass seeds is by the way they look, the red tipped seed stalks are a dead giveaway."

Well, I can't wait 8 weeks to mow the bluegrass. Guess I'll mow it tomorrow after 13 days :-)

Forgot to add this to the prior message just posted:

So the tiny bluegrass flowers are blue but the fruit containing the seed is red. I don't think I've ever seen red bluegrass fruit. I may leave two square feet of bluegrass unmowed for 8 weeks to see the red fruit. Anyone ever tried it?

Here's an update posted 5 weeks after the previous post:

So it's June 19 now, and while I didn't leave a whole 2 square feet of bluegrass unmowed for 8 weeks in order to see the red bluegrass fruit, I did let the bluegrass (and tall fescue) grow super tall along my fence and walls by simply not using the string trimmer there for a long time. Wow, I have now seen and recognized the red fruit of bluegrass. I had been expecting bright red fruit, but it's not bright at all. It's more of a rustic red, and they're tiny fruits just like the pale blue flowers of bluegrass are tiny, so don't expect to see nectarines after leaving some bluegrass unmowed or untrimmed [Lol] :-)

The Rebels Tall Fescue fruit doesn't look red; it looks yellow if I'm interpreting what I've seen correctly. After all, these are grass fruits, which don't look like what we'd normally expect fruits to look like--they ain't peaches or nectarines [chuckle].

I actually started seeing the bluegrass's red fruit a week or two ago, maybe more. The last few days or week, I'm seeing actual seeds that have taken the place of the fruit. Just like the site above mentioned, the seeds are dried out. The seeds I've seen from my 1970's bluegrass and 2012 Rebels Tall Fescue range in color from brown to whitish grey. The bluegrass seeds are significantly smaller than the tall fescue seeds.

The whitish grey bluegrass seeds I took from some bluegrass seed stalks today along my fence are really small seeds. I guess they're about the same size, or probably even a little smaller than the Bewitched Bluegrass seeds I bought from WLS many months ago (perhaps even they're half the size of the dwarf Bewitched seeds, but I couldn't say with certainty if that is a correct average). Kind of surprises me that the 1970's regular-height variety of bluegrass I have would produce smaller seeds than a dwarf-height variety of bluegrass (Bewitched), but maybe the Bewitched grass was grown in more ideal conditions in Oregon or Washington, thus allowing the seeds to grow bigger. Or it just may be a paradox that dwarf bluegrass seeds are bigger than regular-height varieties of bluegrass seeds. Don't really know.

So bluegrass has pale blue flowers, rustic red fruits, and brownish to whitish-grey seeds.

It's pretty wild to see grass seeds in your hand that you grew yourself.

I have a question, how can grass from the 1970s still be going? I understand lawns to last no more then 10 years, and more likely 8 years is an old lawn. Did you manage to get the 1970s blue grass that seeded to regrow? If it is really that old, maybe people would like to buy it? The problem is that other grass, the fescue, how could one separate out just the blue grass for sale? On the downside I believe having the grass set seed means the 70s bluegrass would then die and if the germinate failed, then that is end of that 70s grass. Lots of things could cause a failure in germinate like temperature. So, I would set some aside, to plant later in case of failure. And the seeds would be viable for only a few years. It sounds just too risky, if you can't replace those seeds again to let the lawn go to seed.

This is a really old thread, so I doubt the OP will be back. But maybe!

>>I have a question, how can grass from the 1970s still be going? I understand lawns to last no more then 10 years, and more likely 8 years is an old lawn.

Bluegrasses regenerate off rhizomes, so although each individual grass plant isn't of advanced age, the lawn as a whole is. It's like the old question, if you have a shovel and replace the handle, is it the same shovel? What if you later replace the blade?

I was never much one for philosophy (I don't care if it's the same shovel or not, I just care if it can do its job). But I'm willing to call this the same lawn, even though the plants are cloned great-great-granddaughters of the original plants at the absolute closest.

>>On the downside I believe having the grass set seed means the 70s bluegrass would then die and if the germinate failed, then that is end of that 70s grass.

It'll be fine. Grasses are perennials, happily setting seed year after year just like the columbine, lilacs, and so on in my gardens. Removing the seed will grant more energy to growth and spreading, but not doing so won't kill the plant.