Either by seed, or grafting. Not cuttings. If growing from seed, note that many of them hybridise freely, and identity of seedlings may well not be the same as the tree they were collected from, particularly if the seed was collected in an arboretum with numerous species present.
Seedlings of any other birch. Over here, that would usually be Silver Birch (Betula pendula), but you could use whatever species is native locally for you.
If you're not familiar with grafting you'd be better off growing from seed, unless you are trying to duplicate a specific individual tree with unusual characteristics. Or you have an assortment of different birch species growing in the vicinity and don't want to end up with any hybrid seedlings. The learning curve and gear needed for grafting requires quite a bit more of a commitment than raising these from seed.
It somewhat depends on which type of Birch you are talking about. If you are inquiring about Weeping varieties they are usually propagated by grafting on European birch seedlings (B. verrucosa). Most other varieties of Birch are usually grafted on seedlings of B. papyrifera or B. pendula. Otherwise you can start Birch from seed by planting in the fall or late in the winter where they are allowed to freeze for a couple months before germinating. Softwood cutting will root fairly well if they are treated with a rooting chemical and then put under mist. lastly, low growing limbs can be layered successfully, but be sure the limb used is on a young tree. - Millet
Thank you all! i have a weeping birch which isn't fareing too well, it was already here newly planted 15 years ago, whenwe bought our home, and hadn't done much because it shares an island bed with a huge blue spruce and a ponderosa pine. It didn't start to show new growth until I planted clematis around it and rock garden type plants. i guess the extra watering and fertilizer is spurring it on... I would get rid of the spruce and pine trees but they provide such valuable shade in the hot summer months that it is hard to give that up to wait for some type of trees to grow large enough to provide this shade cover. Then I bought what I thought was a single trunk white bark birch, and this one keeps pumping out other trunks, I guess it is a clumping white birch, not the kind with brown peeling bark. Last one was called 'Heritage' I guess I bought because it was hardy and bore resistant and the bark peels. This tree is the weirdest growing tree ever! It can't decide what it wants to be. So I do get lots of seeds I guess, new to where they are even though they are hanging all over the trees and looks really neat in the winter. I wouldn't mind trying mine hand at grafting as I'm gearing up to graft Japanese Ornamental Maples. So what do you guys think now? What should I try to do?
Heritage = 'Cully' is a highly popular cultivar of B. nigra. Multiple trunks are typical for this species.
But that isn't the one putting out multiple trunks, the one that has more trunks, the white bark doesn't peel much or at all. Although the heritage tree grows upward into a leaning position, then there are branches that grow out horizontally, and a couple that just come out of the trunk midway up the tree and shoots up toward the sky and just 3 inches away from the tree trunk. The bark is beautiful, though.
Many kinds of trees fork where exposed to full light and grow mostly vertically where shaded. Numerous survival advantages can be assumed from this, including successful competition with other trees for light in a crowded stand, or forming one's own little thicket of protective multiple stems and low branches where in the open and subject to browsing (or sun scald).
Thanks again for all the info. I will see if DS 16 will take a picture of it or myself as it is a matter of finding the working camera. LOL And then we have to put the photos on DS's computer and/or server since my computer doesn't want to upload pictures from the memory card (which sad to say but I had to ask him what the card was called again) Oy! :-( Maybe you guys might tell me how to prune it. It never seemed to have a leader, just one that flopped over never straight up, just that one sidebranch! My son tied a wire to it, which I don't think it helpd much and I think the wire needs to be cut off, as being 14 at the time he did not put a protective barrier around the apparent leader. It is planted in a very open space where it gets plenty of sunshine and water.
Well, I decided to search the web...duh! I put in How to grow birch trees from seed Voila! Eureka! Yahoo! There are several websites just for this purpose. I guess for people like me! Yippee!