Dave, Just found this older post of yours and thought I'd add a few thoughts not addressed by oneeyeluke or in my post regarding "when to transplant rooted cuttings into individual pots." From your photo it appears you are using different size pots for your cuttings and are sticking each woody species in its own pot(s). These are definitely preferred practices. I would reserve the larger pots for the more reliable species you have some experience with. Use the smaller pots for the species which root more weakly, less reliably, or later in the season. Wait until you see roots in the drain holes in the small pots to transplant those species. If you are attempting to root any species which set buds in the late summer or fall for the next year, don't be fooled by early bud break in those species; they may bud out before any rooting has taken place. Water cuttings which have leafed out with a gentle spray, preferably from a can. Treat these cuttings like softwood and move them into dappled to full shade until rooted. In my opinion, it's best to pot those (early to leaf) species in smaller pots and wait for visible roots in the drain holes before potting up. Don't worry about roots intertwining; roots separate readily in damp (not wet) sand; that's a big advantage of that media. So you can stick many cuttings in a sand filled pot; I often use 3/4" spacings. And don't be afraid of breaking tertiary or secondary roots or even intentionally pruning roots while potting-up your cuttings. In my opinion, root pruning is a better practice than coiling long roots around in the bottom of a pot. Of course, you should reserve severe root pruning for late fall to v. early spring, during dormancy. It's a bit species dependent I've discovered. Many badly damaged plants can be nursed back to health, if necessary; plants are amazingly resilient.
Are you using a rooting hormone? Varying the IBA concentration by type (season) of cutting?
I see that you've successfully rooted Viburnum ssp. I'm attempting some semi-hardwood Viburnum lantana cuttings now (stuck mine on 8/3). My Viburnum cutting stems have very prominent lenticels and I'm wondering if new roots will emerge from them. Have you observed that behaviour?
