As I’ve been driving around the area, I’ve noticed that a lot of people have weeping cherry trees in their landscape. These trees can be beautiful with their large, arching branches covered with light pink blooms this time of year.
But for every 5 or 6 large stately trees that I see, there’s one that looks terrible. Sometimes it’s misshapen. Other times only half of the tree’s canopy is healthy. And then there are the trees that have some arching branches but also have large upright branches that don’t have many flowers.
After a little searching online, I learned that most weeping cherries are grafted trees. Grafting is process where tissue of one kind of plant is inserted into tissue of another plant and the two grow together, developing a shared vascular system. In botanical terms, these grafted plants are call chimeras or graft chimeras. The Chimera is a mythical animal that combines a lion, goat and serpent A graft chimera is a plant that combines two or more different plants into one single plant.
One of the most common kinds of grafted plants are tea roses. The wanted rose variety (called the scion) is inserted into the base of a rose variety with a better root system (called the rootstock). The result is a chimera, a grafted plant with a strong root system and beautiful flowers.
I’ve also been noticing that some places are offering grafted tomatoes. In this case, an heirloom is the scion and the rootstock is a stronger, better rooting tomato variety. It’s said that a grafted heirloom tomato will produce twice the fruit of the same variety grown from seed with its own root system – I’m a little skeptical but maybe it’s true!
All of the weeping cherries that I’ve seen are grafted varieties. You can tell because all of the branches develop from one spot about 5′ above the ground. To make this tree, one variety of cherry (a non-weeping variety) is used for the rootstock. The top is cut off, leaving a single trunk about 5′ tall. Then a ring of twigs of the weeping variety (scion) are grafted into the top of the trunk. If all goes well, the vascular systems of the rootstock and scion merge and you have a grafted weeping cherry tree.
If some of the weeping cherry scions die, the tree can look deformed or lopsided. When the rootstock sends out a shoot and it’s not removed, you can get a tree that has weeping branches and upright branches.
I saw this latter problem in a tree growing at the local school’s administrative building. The tree has nice weeping branches but there is also a large, upright branch growing in the middle of them. A closer look showed that below the graft site, a branch had grown out of the trunk. Since this branch has the genes of the rootstock and not the scion, it’s upright and doesn’t flower very much.
This unsightly problem could have easily been avoided if the shoot below the graft site had been removed when it was small. But this branch has been growing for a number of years and will take some major sawing to remove it.
With any grafted plant, you always have to remember that it’s a chimera – two or more plants in one. The graft site has to remain above the soil line – not an issue with a weeping cherry but important for roses. (If the rose is planted too deeply, the scion will develop roots and the benefit of a vigorous rootstock will be negated.) Also any shoots growing from the rootstock have to be removed or the chimera will start to show the characteristics of both the rootstock and the scion.
I really like weeping cherry trees. There’s an elegance about them that’s appealing. But if I ever grow one, I’ll be sure to remove any shoots that develop below the graft site. If I’m growing a weeping cherry, I want it to weep, not grow upright!