All through my youth, I visited my grandparentsвЂ™ in the summer and swam in their pool, and beside the pool was a kumquat tree that I snacked on. This is sad because a person might buy such a tree, plant it in their yard, and get some fruit in a couple years that is sour or seedy or ugly and wonder what kind of crazy mutation has occurred: вЂњI bought a blood orange tree, but this fruit never gets bloody or sweet!?вЂќ One example of citrus rootstock fruit.ДЄlso, rootstock suckers can take over old citrus trees.

Blood orange tree at nursery with rootstock sucker. IвЂ™ve seen rootstock suckers growing on citrus trees that are still in pots at nurseries. They can grow even before a tree is planted in your yard. Rootstock suckers on citrus trees are indeed little devils, and they often sneak by even the most knowledgeable and attentive gardeners. Here is an example of the severe, obvious bump, which citrus people often call a вЂњbench,вЂќ on an old Valencia orange tree in my grandparentsвЂ™ yard:Д«eware: If a branch emerges on the trunk from below the graft union, then it is rootstock - often called a rootstock sucker - and it will be vigorous and it will take over the whole tree if you donвЂ™t stop it. Here is a graft union that looks like a bump all the way around the trunk:ДЄs a citrus tree gets older, the graft union either almost disappears or it becomes a severe and obvious bump, depending on the kind of rootstock used. HereвЂ™s a graft union that looks like a diagonal line: Usually you can spot the union where the rootstock and scion were grafted together because the bark has a change in shape there. (How do they graft citrus trees? See this video of one method used at Four Winds Growers.) (Why do citrus trees have a rootstock? See my post вЂњFruit trees are grafted - Why? And so what?вЂќ) The scion is the part that gives you the fruit you desire - Washington navel orange, Tango mandarin, Eureka lemon, Oroblanco grapefruit, and so on. There is a rootstock on the bottom, and there is a scion on top. ItвЂ™s not a branch of my orange tree itвЂ™s rootstock.ДЄlmost every citrus tree you buy from a nursery is actually two trees in one.

That branch growing from the base of the trunk - thatвЂ™s the little devil. My orange tree above looks fine, right? ThatвЂ™s what I thought until I crouched down and noticed this little devil:

Actual size kumquat