I have had no previous experience with Cosmos but recently started a packet of seed under lights on my PVC lightstand. They germinated almost instantly. Were up and growing within 3 days. But they are the tallest, spindliest little plant I've ever seen, especially since they are only beginning to form their first set of leaves. They are under the same light as my tomatoes and other flowers but I had to keep moving the Cosmos because they grew so fast they would be touching the fluorescent bulb. I don't know if this is the usual growth pattern for Cosmos or not but they sure took off in a hurry !!
I'm no expert, but I've grown a lot of Cosmos and have found that they do germinate and grow very quickly, and they will self seed if allowed. Mine are definitely a full sun lovers, so yours may not be getting enough light with grow lights. I generally begin to pinch mine back as soon as they have their second set of true leaves, and they seem to branch out nicely. I give them just a small bit of diluted fertilizer once week after they've gotten several leaves. Their height will depend on cultivar, also. You can get Cosmos that grow anywhere from one to four feet tall. Hope this helps!
Rosey: Cosmos, even though they are annuals in your zone, will reseed fairly easily--so in that respect, you won't have to replant often. They do like some sun, though, and get pretty tall so I'm not sure they'll do well under your Blue Spruce tree.
If you have a place in the back of a sunny bed or border (most get pretty tall), they'll be very happy. Cosmos tend to bloom all season, so you'll have lots of color all summer.
If you want to start them ahead of time, but don't have room under your lights, try wintersowing them. Check out the winter sowing forum for lots of good information on how to do this. They'll also do well if you direct sow at the appropriate time for your zone.
Thanks Mom2, I'll have to give it some thought about the Hostas, and maybe with some shade loving annuals. I have
trouble with a lot of woody weeds. We had a nice day today, but storms are suppose to come in tonight.
It was beautiful here, today also. It's still 52 degrees at almost 10pm. However, some storms are moving in. My poor yard is so soggy!!!! I walked about today and noticed many plants have heaved themselves out of their spots due to all of the freezing/thawing. Hope all will survive until I can get them replanted.
Hi Mom2, I know what you mean about your yard being soggy, I have a couple of plants that heaved up also. Of course my yard has some places that feels like it has sunk while other place feels like it has raised up. Did you make it through the night ok? We had stroms all night, which means we got little sleep. I think we have had enough snow and rain to last us for at least a month. Thank goodness this is the last day of Feb. I saw some new green growth on one my plants yesterday. I cleaned up some dead neddles from my Spruce Tree yesterday, trying to get ready for some plants soon.
Hope you can make sense out of what I'm trying to say.
Most Cosmos have the most success when planted in situ, outdoors after the last frost. They will get tall and spindly if started indoors. That's good for me, since I never have very much room under my lights. Happy Gardening everyone!
Well, I have to agree with the advice given here. Last year I wintersowed some and they did fine. It takes longer to come up in the cooler temps, but they come up when they are ready. Also I sowed them where I wanted them. They really do like full sun, or mostly sun if you have it. They are really easy and only require thinning if needed.
I've always started cosmos indoors 3-4 weeks before planting out, so they will flower sooner than direct sowing. I've never seen much in the way of self sown volunteers even though I've always had them in my gardens, both on the east end of LI in the past and now in CT