10

I feel stupid to ask this, as there are many posts on Google about this, and I can't tell, if people are writing these stories for fun or it is real.

Some claim that if you have a many old lemon trees they can become orange trees if you are not careful, whatever that means.

Question

Could it be that pollen from an orange tree could convert a lemon tree?

Or is this whole thing a hoax?

15

Most citrus trees are grafted onto a different rootstock, usually sweet orange these days, even if the fruit from the top graft is going to be lemon or lime. The only way a lemon tree can completely turn into an orange tree is if the grafted part has died and the rootstock then grows on its own, producing the fruit its programmed to produce, depending on the rootstock used. That might be sweet orange (most likely) or sour orange, or even, on older trees, rough lemon. The grafted part might die for various reasons - infection or even over rigorous pruning, right down to the base, which is likely to encourage the rootstock to take over instead.

The other possibility for partial change is if a sucker arises from the rootstock (below the scion, or graft point, at the base of the plant, usually) and is allowed to grow - because rootstocks are generally more vigorous than the grafted parts, this may well grow strongly and produce its own, different fruit. More suckers may arise, and they take over the growing process, and the grafted part dies or fails to produce.

Chimerism is somewhat different - this might be something that happens in very old trees, but citrus stock has, for some years, been produced by cloning, which means chimerism, unless it occurs naturally (rare), isn't really an issue via grafting. Even if it did occur, it wouldn't make the whole tree an orange instead of a lemon.

9

I'm not an expert on the subject, but here is my understanding. In nature, a lemon tree will never turn into an orange tree as they are completely different species:

Lemon - Genus: Citrus Species: C. × limon Orange - Genus: Citrus Species: C. × sinensis

There does exist a hybrid cross called a Meyer Lemon:

Meyer lemon - Genus: Citrus Species: C. × meyeri

With that said, it is partially possible due to the way many fruit trees are grown. Often fruit trees are grafted rather than grown from seed. During the grafting process a part of a tree is is cut off and grafted onto the other tree. They do this so that, for instance, a weaker orange tree can be grown on a stronger, healthier lemon root/trunk. It also allows them to make many more trees using branches from a single tree.

If you have a tree that was grafted originally, it's possible under certain conditions for the tree to grow a branch or part on the top that is from the original base trunk (aka rootstock.) This is called graft-chimaera:

http://en.wikipedia.org/wiki/Graft-chimaera

http://en.wikipedia.org/wiki/Chimera_(plant)#Plants

Hope that helps explain things!

protected by kevinsky Jan 26 '16 at 10:51

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