You'll definately get larger clumps faster if you don't thin them. However, a lot depends on the type of grass you've sown. If it's a grass with distinctive characteristics, like color, you may want to grow plants from individual seeds, and select for the strongest characteristic representation. In other words, if you sow Blue Fescue, and grow clumps from multiple seeds, there will be blades within the clump which are more or less blue in color. You also need to be careful how you do the thinning. If you just cut off the blades of some Fescues, they'll grow right back, with more blades than before.

Most grasses will germinate with one or two blades, but will quickly, during the first growing season, expand the number of blades. You should sow more than one seed in each cell, or to each square inch of an open seed flat. Check the web for specific instructions on the number of seeds per cell for the varieties of grass you are sowing. Jelitto, linked below, is one source for such information. If I can't find appropriate information, I use the ultimate width of the grass blade as a guide. If it's a fine-bladed grass, I sow more seeds per cell, and if it's a wide-bladed grass, fewer seeds. When I grow grass from seed, I transplant the small seedling clumps to nursery pots, usually 4" or 1 quart pots, to grow them on for at least the first season. Then they go into nursery beds for at least another growing season, before eventually being moved to display beds as almost mature plants. What grasses are you sowing? Here is a link that might be useful: Jelitto

I have winter-sown six types of grasses this year. Most of them are native prairie grasses. Androprogon gerardii - Big bluestem Bouteloua curtipendula - Side oats grama Chasmanthium latifolium - Northern sea oats or River oats Lagurus ovatus - Bunny Tail grass Schizachyrium scoparium - Little bluestem Sorgastrum nutans - Indian grass I winter-sowed them April 12, in 1 and 2 liter bottles, with little hunks of seeds. The plan was to get plugs of grasses going this year. After an unusally warm stretch in mid-late April, most were sprouted by the end of April. Still waiting on the Chasmanthium, which has not sprouted yet. Supposedly it can be a good reseeder, so I'm not expecting it to be difficult to sprout, and the seeds are commercial purchased this year. Maybe it just needs warmer temps than the others.

Hi, I'm growing grasses from seed this year. I got some nice ones from "Pase Seed" @ only $2.50 per packet (average). Each packet only contains about 20 to 50 seeds but unless you want a lot, this is fine. They had many that would work in your zone. Jelitto is a highly rated seed source with the best choices but they are rather expensive and the site is difficult to order from as you have to change euros to dollars and order a minimum amount. The packet prices are expensive. I read recently that you can experiment with grasses listed as hardy to certain zones and try some a zone warmer than yours because often you will have success as there are many factors involved. Zones are just a sort of average gauge to go by. With seeds, you can afford to do this. I sowed a couple of types listed as zone 8 in some sources while other sources has the same grass as low as zone 6. In other words, don't be intimidated. I have many natives growing that are listed as zone 8 growing successfully for years now. So much for strict zonal laws. Another source is "Plants of the Southwest" which offers some really nice natives that are quite decorative especially when mass planted. They are only $2.50 per package and usually you get 200 seeds. There is no shipping cost. Make sure your medium is sterile, non-soil potting mix, they tend to damp off otherwise. Cover your pots with clear plastic until they germinate and then uncover and give them some good light. Don't ever let them dry out completely. One day can kill. I am using a large south window to have good sized plugs by spring. I thought I'd started too soon but some are germinating and coming around so slowly, I'm glad I started early now. If every seed comes up within three days or so and grows very fast, I consider it a probable invasive and don't plant it. Some need warm, then cool, then warm again. These would be best done as winter sowing. Cool season grasses are especially good to start now. Warm season grasses are better started in Spring. I broke that rule too. Also, some seeds take quite some time to germinate and then come up at different times so don't ever throw out your pots too soon. I have some Deergrass Muhly doing that. I sowed them in early October and I am still getting sporadic germination and very tiny, slow growing plants.