Every once in awhile we get a question or comment from a fruit gardener that their citrus fruit tastes terrible. This week, Paul Marini wrote in to Ask Gardenerd with a different question that is related: “I know the Meyer lemon tree is a combination of lemon and mandarin orange. I am pretty sure there are orange branches growing out of the bottom half [of my tree]. Is it OK to leave them on, or should I cut them off?”
Thanks for this question, Paul. It leads to a larger subject that will provide an answer. Let’s talk about rootstock.
What is Rootstock?
Rootstock is essentially the bottom part of a tree, below the graft union. It’s the root system upon which a desired fruit tree variety is grafted. The rootstock controls the mature size of the tree, and is always in the same family (i.e. a stone fruit rootstock is used to graft plums, nectarines, peaches, etc. While a citrus rootstock is used to graft lemons, limes, oranges, etc. Pome fruits like pears, apples, and quince have their own sets of rootstock suitable for the job.) Rootstock is also chosen based on its ability to fight certain diseases, or tolerate heavy, poor-draining soils in areas known for those issues.
Generally speaking, the rootstock variety, on its own, produces unpalatable fruit. If shoots develop from the rootstock, those grow into branches and eventually produce fruit that is very different from the desired variety you planted. Some people move to a new home and find an old citrus tree with fruit that tastes terrible. The most likely reason for this is not that it hasn’t been fed properly, but that the rootstock took over the tree (probably after the desired branches died off).
What to Look For
Take a look at your fruit trees and identify the graft union. The graft union should be slightly swollen in diameter and you may find a curve right above it. That’s where the scion from the desired fruit was grafted to the rootstock.
Check for any branches growing from below that graft union.
Remove those branches. They are stealing energy and nutrients from your desired fruit. If the whole tree is now rootstock, call a time of death and pull it. No amount of fertilizer will make this fruit taste sweet.
NOTE: a few fruit trees are rarely if ever grafted: figs and loquats being two. If you can’t find the graft union, do a little research on your type of fruit to see whether it is a grafted tree or not.
So the answer to your question about whether to leave those wayward branches or not, Paul, is–remove them. Find a sunny location to plant that orange tree you want and enjoy the benefits in a couple years.
For more information about growing fruit trees, grafting your own, and much more, check out Grow Your Own Mini Fruit Garden.