Native Grass Restoration and Management
Timing of Native Grass Seeding
Time of Year
In the coastal region of California, the Fall is considered the best time to seed. Fall seeding projects take full advantage of the winter rainy season. The native grasses are almost guaranteed to germinate without requiring irrigation.
A disadavantage to seeding in Fall is that any weed seed on the site is also guaranteed to germinate. If there are any weed seeds on the site, you will be faced with weed competition. California is, unfortunately, one of the few places in the world where weeds have a competitive advantage over native grasses, so weed germination in restoration projects is a serious consideration.
According to state regulations, erosion control must be installed by October 15. This deadline applies to those sites where there is bare soil requiring erosion control, but it does not apply to seeding in general. If erosion control is not a consideration, then October 30 is a useful target date.
Seeding projects from November through February are at higher risk, because the seeds take longer to germinate, the seedlings are small and vulnerable for a longer amount of time, the rains are stronger while the seedlings are small, and there is a higher risk of mortality from fungal diseases.
If you have flexibility in your seeding date and you have overhead irrigation available, you may consider seeding in late January through early March. Weed seeds are less likely to germinate in late winter, so your site is more likely to be weed free or essentially weed free. With irrigation, you can take full advantage of the spring growing season. You must be particularly careful with erosion control while doing this, because at least for a few weeks, you will have a site without effective vegetative cover during the height of the rainy season. If you do this wrong, you can create an eroded mess. However, if you do this right, you may be rewarded with an essentially weed-free stand of native grasses in the first year after seeding. The risk of erosion goes down if you wait until March to do the site prep and seeding.
Timing for Germinating Rains
"Germinating rain" refers to a period of four or five cool, cloudy days with enough rain or drizzle to trigger germination. This generally happens in late October or early November. If you can time it, it is ideal to seed one day before the germinating rain. This minimizes the opportunity for the site to be disturbed before the rains come.
Seeding on Dry Ground
Besides wanting to take advantage of the early germinating conditions, you want to apply the seed before the ground gets wet. It is easy to rake seed into dry powdery soil, but difficult to rake it into a moist, firm surface.
Whenever we seed, we go crazy watching the birds attack the restoration site. And we wonder about the mice and voles at night. I haven't seen any data on how much seed the animals normally eat, but we figure that they are getting the obvious and easy pickings. They scratch around for the buried seed, and even get some of it, but most of the buried seed probably stays that way. I don't how much seed predation makes a difference between a successful or failed project, but this is just one more reason why you should take every effort to cover the seed with mineral soil.