The only way to grow Kaffir lime in a cold climate is in a pot, either forever staying inside the house or moving it in and out when the weather permits. In a warmer climate, when Kaffir lime is grown in the ground, it’s a mid-size tree that can grow to 25 feet high and 6 feet wide. But it can adapt to live in a pot. One of mine, over 20 years old, has to be pruned twice each year to a manageable size (around 6′ tall) that I can put it back in our basement.
Annual pruning is an easy task. Getting poked here and there with very sharp thorns is expected. Feeding it well after a good annual haircut will keep it healthy. But, what’s more important than pruning is repotting.
Kaffir lime can be root-bound pretty fast since it’s a small tree being kept in a pot. It will not be happy having its feet bound for years… imagine Chinese foot binding. I repot mine every couple of years. The smaller ones is easy to do but the larger ones give me a back ache for a few days.
How to repot:
First, do not water the Kaffir lime for a couple of days. The potting soil should be on the dry side so it will be much easier to loosen the roots. Grab the main trunk and pull the whole plant out.
I just pull my smaller one, picture on top, out of its pot. This is only two years in this pot but the roots are already packed at the bottom. Though the soil is pretty dry, the roots still hold it in a pot shape.
Next, shake the soil off the roots. You can do it with your hands or use a trowel. Make sure not to damage the main root-the larger ones. Use a clean, sharp clipper to trim off the finer roots.
If you want it to grow bigger, you can put it in a larger pot with new soil. I keep my smaller ones in the same pot for five years then give them a little more room with a slightly larger pot. The twenty-plus year old, I put back in the same pot since that is the largest size I can manage without hurting myself. Both of the larger ones are still happy in their pots.
I put a couple of inches of new soil at the bottom, mixed with organic fertilizer, placed the Kaffir lime in, then added soil mixed with fertilizer around and on top. Use a small trowel to probe the area between the plant and the pot to make sure that new soil fills any air pockets. Water deeply. I water it and let it sit on a tray so the soil can absorb excess water back later on.
Use a clean clipper to trim damaged and dry branches. I prune it down to a desirable size and cut branches that rub against one another only after it starts to bud new leaves. I think root pruning is traumatizing enough so I wait for it to settle and get used to a new space first. But that’s just me.
That’s it. The Kaffir lime should be very happy for a few years before the leaves start to get smaller and take longer to sprout new leaves. That’s when it’s telling you that it needs to stretch it feet.