I live close to Ottawa, ON. I have a beautiful Harlequin Maple in my front yard. The tree was there when I purchased the house and no one told me about pruning the solid green leaves. I would say that ¼ of the tree is now solid green I would to rescue it back to two-tone green, but am not sure about cutting so much of the tree off. A landscaper told me it was too late, but I would ruin the tree's looks and shape. Also, last Spring, I found seedlings under it. I dig them up and planted them in a pot where it was kept outside. I don't know what to do with them now as we are in the Fall! I have brought them in from the cold, as I fear they won't survive Winter outside in a pot. I couldn't plant them on my property, as it is very small and no one wanted the seedlings. They're now in full sun inside the house and they seem to like it. My last problem with this is they ARE Harlequin, as I did see a two-tone leaf open up. Since then, it's all turned full green. Can I trim these down somehow to save the two-tone? I know.... lots of questions, but I'm new at this.
It will just keep going green, maybe you should give up. Botanically Acer platanoides 'Drummondii', a variegated Norway maple. Norway maple is a pest species in North America so I would not keep the seedlings. And if many more come up maybe the parent tree should be removed also - even out here, where the tree has so far not usually been the problem it is back East I have seen one urban ravine park where what must have been millions of seedlings were surviving under the canopy of native alders and big-leaf maples etc.
If you cut out the green part the rest of it will stay variegated. It is true as Ron points out that you have to keep a close eye one it and cut out reverted (green) twigs as early as possible. However it is possible to keep maintain given proper care, in which case it is a very beautiful tree. The seedlings will likely be green though, even if they show variegation at the beginning, and are not really worth bothering with. If the pruning is too major and will ruin the shape completely, you're probably better off starting over.
