You could divide them - it won't hurt the roots at all - but you don't really need to. Depending on the type, they will rapidly fill up that empty space on their own.

If the dropseed is Prairie Dropseed, it might have been better to not divide it. They are slow to reestablish and it will take a division 4 or 5 years to establish but you did get a lot of plants so if you are not in a hurry, its fine. Its a very long lived, slow growing grass that doesn't die out in the center so it needs no dividing. If you do divide it, you should take at least a two inch division. I wish I could find it in gallon sizes for sale around here!

Amen to that. I usually plant my mondo and monkey grass (liriope) in larger clumps and closer together than many recommend. This is because I, unlike some, very impatient about filling my beds and lawn spaces. Waiting for 6 months, much less two years just ain't me!

think lumberjack ... sing the old song in your head if you are old enough .. lol .. lumberjacks saw wet wood ... so the teeth are large and far apart.. with large spaces so wet sawdust can be raked out as you saw ... lumber.. as in house building ... is dry ... so you dont need to rake out wet gobs of sawn wood ... all that need be done is for dry dust to be pulled out ... using a lumber blade to prune is maddening ... the blade keeps binding because of the built up wet saw dust .... btw ... using them in the ground is not easy ... as your machine will make them bend .... when you hit roots or stone or clay .... pretty sure i do recall grass peeps lassoing their tall grasses.. binding them tight. and then using the saw to cut them done to a few inches or so ... ken