Here’s another followup to my posting on GardenWeb about caring for Japanese maple seedlings. I think I’ll try this. I already had the same idea with two other young trees last summer — I took a seedling from my Autumn Blaze maple and a Golden Rain Tree seedling and put them in a shaded corner of my veggie garden area. They like it better than the pots. I also put two Clematis seedlings in the bed, but kept them in the small pots, buried up to the rim. I hope those little guys are surviving the winter OK, because I didn’t pile any mulch on them. Anyway, here’s the reply from GW:

I transplant my JM seedlings outside in early to mid-summer in a nursery bed, placing the seedlings about 6″ apart. In late fall, I mulch the bed heavily with oak leaves (several inches) which I hold down with plastic netting, and uncover them in early April the following spring. Depending on their parentage, I get anywhere from 50-90% survival. I live in zone 4 Minnesota so am pretty happy even with a 50% rate. I transplant the survivors later on that year if they are 1′ or more in height, those that are shorter get mulched for a second winter and then are transplanted to their permanent location the following spring/summer.

I asked a few followup questions and got this reply:

I water them in with a low dose of water-soluble fertilizer or fish emulsion when I plant them. I don’t feed them after that as I don’t want to encourage too much growth later in the season that won’t have any chance of hardening off.

Rainfall is usually pretty regular here so I water them only if there is extreme drought. As long as there is no leaf scorch or drop, I leave them alone. I think it results in less but stronger growth.

I don’t root prune my JMs. I try to move them during a cloudy day—just before a rain if possible. If I can’t wait for that, I water them a couple of hours before I move them–it seems to help the soil stay on the root ball better.

I am a big fan of nursery beds–it makes tending young plants easier (they are all together, can be mulched, watered, fed, protected from critters), and it is easy to compare the characteristics and growth rate of the seedlings.