I plant mine close enough together that there is no space between the plants later in the season...they form a hedge, basically. But then I have a different climate...so I can't say for sure that it wouldn't be a problem for your area.

Spacing depends on the size of the dahlia flower. The larger the flower, the more space they need. I have been planting in double rows that are 6 inches apart. The plants are planted 12 to 18 inches apart in a zigzag pattern so that two plants are not close to each other. The double rows are spaced at 7 feet apart so that my small Kubota tractor can till the weeds between the rows. If you are using a small tiller, you can space the rows at 5 feet. If you space them closer than 5 feet, you will not be able to walk between the rows late in the season. If you are growing for show flowers, you should space the plants at least 18 inches apart. If you are a back yard gardener, the best way to plant dahlias is to put a heavy stake in the ground(rebar or a T post) and plant 4 dahlias around the stake about 12 inches from the stake. The stakes should be at least 4 and preferably 5-6 feet apart.

I already have quite a few planted and theres lots of space between them so I was hoping to maybe squeeze some in the open spaces and see how they do. I tried using stakes and then tying the plants loosely to the stake but didn't work to well for me. I tried a couple tomato cages this year that worked pretty good so gonna try that again next yr. I have them mingled in with roses and lilies so I don't plant them in rows but if the cages don't work out I will def use the post and try it that way. Thanks, Judy

Regular dahlia plants that reach 4,5 feet or more should be plantes 24 inches apart in any direction. At least in my garden

Santiago Rolland