Hello folks,
I'm trying my hand at plant propagation; having started hardwood cuttings over the winter, and softwood cuttings this Spring.
I was THRILLED to see the success of my hardwood cuttings this Spring; many appeared to have rooted, and I saw a lot of new growth. I had rooted them in coarse sand, in one and two gallon pots. The man I follow on YouTube said NOT to water the cuttings, so I dutifully followed his advice.
Sadly, many were lost in the heat of late Spring/ early Summer. The "easy" cuttings have survived; forsythia, ninebark, and a few Red-twig dogwoods. Sadly, the spirea and most others (that looked promising) ultimately bit the dust.
The hardwood cuttings that survived, are still in the coarse sand, and I plan to pot them up individually this Fall. Nonetheless, I wonder if I shouldn't have potted them up this Spring before they were lost?
That was part 1 of my two-part question....
Undeterred, I tried my hand at softwood and semi-hardwood cuttings this Spring. I am propagating them in my basement in propagation domes on heat mats, under grow lights. Clearly some are easier than others, I'm really struggling with Smokebush, but have had unexpected success with Viburnum, Hydrangea (both Paniculata and Mophead), Ninebark, Lavender, and many others. My deutzia rooted easily, and I transplanted them into individual pots, but far too early. Several have failed since transplanting, and I don't wish to repeat the mistake with my others after investing two months of time.
So.....how do you know WHEN to transplant the softwood, semi-hardwood, and hardwood cuttings?
Finally, do you root your softwood and semi-hardwood cuttings in coarse sand? I rooted mine in Pro-Mix, and I fear the roots will be intertwined when I try to transplant them.
Thanks for wading through a long post, I appreciate your knowledgeable replies.

Dave, Congratulations on your success. And I feel your pain regarding your failures!! I too have lost lots of cuttings due to premature potting-up. I am no expert and I'm not sure I can adequately address all aspects of the subject, but I'm happy to share my experience.
I root all my cuttings (softwood, semi-hardwood, and hardwood) in 100% coarse sand and very fine gravel. As you know, this media holds little water (esp. near surface) which helps reduce rot. I filled a number of beds with this media just for propagation. My beds are framed in 2x10's so they are about 9-1/4 inches deep. All beds are outdoors covered with mini-hoops to support shading and to control deer browse. I have no hoop or glass house. One problem with the beds is that I am unable to see roots emerging. Propagating in trays or pots would offer the advantage of being able to see emerging roots through the drainholes. Have you considered using smaller pots (to watch for roots) for your most problematic species? I've discovered that there are several shrubby species which typically bud out in the spring before developing roots. I've been forced therefore to either dig-up a few plants (using a bare hand) to examine the extent of developing root, or leave the rooted cuttings in place until the following spring. I typically do the later and overwinter all my rooted cuttings in my propagation beds and then pot them up while dormant (before bud break) the following spring. Thus, many hardwood cuttings sit in my propagation beds through two winters. There are exceptions of course. Some species seem to develop equal masses of root and top-growth and these can be potted up any time. Knowing which is which comes with experience, but typically if a shrub sets large buds in the fall, it is quite likely to bud out before rooting in the spring.
As far as watering is concerned, I begin overhead watering (and cease misting) my cuttings shortly after bud-break. I ease into it and watch carefully for rot and wilt due to overwatering. I have watered my propagation beds mid-winter during warm snow-free spells, but I suspect that was unnecessary. During the growing season, I may water my propagated cuttings with a 1/4 to 1/2 strength dose of water soluble fertilizer every couple months.
I'd like to try a slight variation this year, but haven't yet. Plan to build some wooden trays, perhaps from cedar fence pickets, just large enough to hold a 1020 tray (for multi-use). Fill these with my sand media and stick the cuttings in them. Can then move these around within my propagation beds as needed and may be able to see emerging roots between the boards (I'll leave appropriate gaps).
And finally, since I'm propagating outdoors in sand, my issues with my softwood and semi-hardwood cuttings are shade and humidity. I also winter sow seed in jugs and pots and have experienced many intertwined roots. In my experience, healthy plants are surprisingly resilient and can recover and even respond favorably to relatively heavy root disturbance or even root pruning. If you're really concerned, just separate the roots in the dormant season. Otherwise, be sure to pot-up in the shade with a full misting bottle at the ready.
Hope this long-winded post helps. Let's keep the thread going, always happy to learn & share about cutting propagation. It's addicting isn't it? And there's no end of plants to try.