The number one reason flowering crabapples are planted is for there attractive flowers that appear in the spring. The colors range from white to pink to red to rose. The flowers usually have 5 petals that are small and the complete flower will range in size from a dime to a quarter. Other characteristic of the trees are; low mound-like shape between 15-25', they offer tremendous winter architecture because of unique and art like branching, the bark on older trees will be a shiny gray-brown color and exfoliated. Fruit from the trees are called pomes, and if fruit is 2" in diameter or less, it is a crabapple, if fruit is larger than 2", then it is classified as an apple.
Practically all flowering crabs are self-sterile and are propagated by budding, grafting, from softwood cuttings or tissue culture. Crabapples are often grafted, using a whip graft, or are budded in summer. The most common root stock used to graft to are; M. x robusta, M. sieboldii and also where hardiness issues come into play M. baccata. A problem with crabapples is that they have a history of being known as a tree that sends up little trees around that base, commonly known as suckers. There are certain rootstock which are being introduce to prevent this problem.
Now that you have a small background of flowering crabapples, I will focus on how to propagate them. The particular clone of crabapple I will focus on is the Spring Snow Crabapple.
Spring Snow Crabapple: Flowers are white, fruits are few to none, has a dense, upright oval tree form, 20 to 25' tall. Spring Snow is severely susceptible to scab; slightly susceptible to cedar apple rust and also to fireblight. In the discription of the Spring Snow I mentioned that the fruits are few to none. That is the characteristic that sets this tree aside from the other clones. In the spring this specimen turns into a white snow ball on top of a stick, then in the fall when all the other trees are full of fruits and dropping them on lawns and side walks, there is little to no mess with this particular specimen.
Here now is a discription along with an illustration of how to propagate Spring Snow Crabapples.
Whip Graft (also known as whip and tongue)
In this particular type of grafted you first need to make a diagonal cut on your scion(a), about 1 1/2 to 2"long. Then cut back up in the middle of the first cut about 3/4"(b). Next take the root stock and make a cut with the same angle of degree(c), once you do that, make a cut down the center of that as you did in b, (d). The last step then involves interlocking the two stems (e). It is important in this step to line up the cambium layers to achieve a successful graft.
In this graft the main factor that will play a part in a successful graft is weather or not the bark on the rootstock is slipping, meaning will pull away from twig without ripping. Step one is to cut your scion at about a 60 degree angle around an 1 1/2" to 2". Next on your rootstock make a vertical cut around 2". Then make a horizontal cut at the top of your vertical cut, making a "T". Peal open the bark just enough to slide your scion into your rootstock. Once again the main factor is lining up the cambium layers to insure a successful graft.
When performing a cleft graft step one is taking your scion and making to sloping cuts once again about 2" long, so they come to a point (a). After you do that take your rootstock and make a cut directly in the center also about 2- 2 1/2" and spread the rootstock open (b). Insert your scion with the bark facing out, making sure the cambium layers line up, (c), and (d) inustrate this. The final step involves wrapping or putting a rubber mixture on the union to protect it until it begins to grow (e).
The side graft is similar to both the bark graft and the cleft graft. The first step involves taking the scion and again making a sloping cut about 2" (a). Then taking your rootstock cut downward at about a 60 degree angle 2-2 1/2" (b). Next insert the scion into the slit on your rootstock with the cambium layers lining up (c). Image (d) shows how the front view looks. For your final step either wrap the union, or coat it with a mixture of wax, or rubber (e).
Hopefully the previous information will help you with the propagation of your woody plants, and if your looking for a great ornimental tree the Spring Snow Crabapple is one of the best. Here are a few pictures of the Spring Snow Crabapples outside the Horticulture Greenhouse located on the NDSU Campus.