Hi Jean - I`ll start the discussion off. Others will chime in and elucidate. Most citrus for sale by nurseries
or big box stores are grafted citrus. In your case a key lime bud was grafted to a sour orange rootstock or a trifoliate rootstock. The graft is usually about 6 to 8 inches up from the soil level. It looks like a gnarl or it may evenlook like an `L`. i.e. branches off in another direction. There are other ways to propagate citrus, but I believe grafting is the most common used for retail sales Look for the graft gnarl or L shape. If any shoots are popping out below the graft, they are the rootstock, which you really don`t want. You clip those off, otherwise you will get a fruit which is not a Key Lime. If the tree was not grafted, and was started from seed,(not likely)you may have to wait 10 years for your limes. Look for the graft and let us know. Others will jump in and give you more info.

Bill

If the tree is grafted you will see a scar on the main trunk coming from the soil line. Where the scar would be is anyones guess but its usually 6" above the roots.

I would prune any growth from below or on this scar line unless you want to grow the rootstock from cuttings.

If you can find no sign of a scar it would mean that your tree was either grown from a cutting or on its own roots from a seed. You can prune the growth along the main trunk to give it a tree shape or leave the branches for a shrub look.

Since key Limes(aka Mexican Lime) are easy to grow from seed and fruit early(2 or 3 years), it could very well be a non grafted, grown from seed plant. Pruning would depend on what you want the plant to look like.
Andi

It may be a rooted cutting. Limes and lemons are very easy to root. If it was from a bearing tree it should bear in two to three years.

I've never seen a non-grafted citrus tree for sale here in CA, but I am guessing this may not be the case for trees from non-citrus producing states. Many people seem to post about having purchased cutting-grown trees or seedlings.

A grafted tree is simply a tree that was created by planting and growing a selected rootstock--mostly from seed I believe--and then taking another piece of tree from a known, producing variety and attaching it to that rootstock so that now the roots of the tree are from one variety and the canopy is from another. The limbs from the rootstock are generally removed soon after successful grafting (provided you do not want production from it), and so the rootstock just provides the roots and lower trunk. Done in many different ways on many different plants, but particularly on fruiting trees.

Citrus is grafted for many reasons, but the main reasons for growing grafted trees are to assure more rapid production of a particular fruit and to impart certain characteristics such as increased disease resistance or improved tolerance to environmental factors. A tree from seed can take many years to flower and fruit, and sometimes will not produce a fruit that is the same as the mother plant (though Key limes and most lemons should be ok according to this forum). Cuttings will give you a tree that produces a reliable variety--in that it is genetically identical to the parent--but it will not have the resistance/tolerance that another rootstock may provide. You can also graft many cultivars and types to one tree, so that you have a "fruit cocktail" tree or a mulit-graft.

Occasionally, the rootstock portion will try to produce limbs and branches, and it is generally recommended to remove these so that energy can go to the main canopy of the tree and not to these useless suckers. Though, I am attempting to harvest them and root them to produce my own rootstock without seeds. Seems to work--got 2 trifoliates rooted and putting out new leaves. So they are not useless to me.

Billy1had described a grafted tree nicely--I generally find them about 2-10" off the soil surface, and there is often a diagonal line or a knob in the main trunk. Often there is a change in the bark texture, but it *can* be hard to see--usually not, but look carefully. Check out the pics below.

As gardener dragon said, you can prune for shape if you want. The natural habitus of many citrus is really more shrub-like than standard tree form.

Sounds like you took good care of your Key lime :)

HTH.

Here is a link that might be useful: Suckers--not suckas