I bought a small, inexpensive Everred maple at Costco. I don't know if it has much in the way of roots, and I don't know if I should leave it in the pot it came in for now or transplant it into a larger pot. Suggestions appreciated
Leave it in the pot it is in now. I presume it was a cutting, so no, it doesn't have much going in the way of roots, yet. Next year at this time, it may be a different story.
Owl are you prescient? Is 'Everred' normally propagated by cutting? Cutting grown plants could be root bound.
I think it's improbable that costco is selling cutting grown cultivars but I may be mistaken.
Dev you could take a look and see if there is a graft mark on your tree and determine how it was propagated. You could also gently lift the plant out of the pot and check on the roots. If the pot is very full of roots you could pot up and tease the roots apart a little bit in to new soil. If the roots have room to grow maybe check again in Fall and repot then.
I will take a look at the roots. Thanks for the advice.
I would go ahead and repot your maple now. I have successfully repotted containerized JMs throughout the year without ever losing a tree. Most trees sold in garden centers are already root bound when you buy them and benefit from replanting in a larger pot with good potting soil. Keep the tree in a shady spot for at least a week and water it well.
Again, Dawgie - there is a distinct difference between repotting and potting-up. While there is no harm in potting-up whenever it's convenient, there is very good reason to avoid repotting, which includes a soil change and root work, because of the probability of severe set-back or death of the plant. You should always avoid repotting deciduous trees while they are in leaf except in the case of extreme emergency.
On the other hand...
Here is a link that might be useful: Fragile roots.pdf
"To every thing there is a season, and a time to every purpose under the heaven:"
I'm aggressive with Acer p. roots when I repot in spring. The tridents roots are often even reduced to where the plant is at near cutting status and all the other Acers are totally bare-rooted with the roots pruned back hard at repot time, but it is very unwise to undertake major root work while the tree is in leaf. I agree the roots are not fragile.
The Dr. in the 'fragile roots' link is talking about 'transplanting'. I am guessing she is discerning enough to delineate between planting and transplanting. If you called her and asked if she recommends bare-rooting and correcting root problems when transplanting a deciduous tree while in leaf, her answer will be a resounding "NO". If you ask her if performing this work on a dormant/quiescent tree at transplant time, her answer will be "YES".
The group most skilled at maintaining healthy trees in containers are probably experienced bonsai practitioners. Ask ANY one of them if you should do any significant disturbance of the root mass while the tree is in leaf, and they will answer, "Only in a dire emergency - perhaps as a last alternative when the viability of the tree hangs in the balance."