Kaffir Lime Care – Harvesting Leaves
by Kasma Loha-unchit
15. Do Not Pick Leaves But Prune Your Tree
It seems so idyllic to be able to pick leaves fresh from a kaffir lime tree just when you need them for your Thai dishes. But if you do this all the time, you'll find that your tree starts looking a bit lean with few leaves left on the lower branches. That's because when you pick a leaf, the plant doesn't get a message to replace that leaf with another one in the same spot. The growth continues to take place on the end of the branches.
So the advice is not to pick leaves but to prune. When you cut a branch back to a leaf node, the tree gets a signal that it needs to replace the limb. New growth will emerge from that leaf node and pretty soon you'll have new leaves to replace the ones on the branch you cut. Sometimes the tree might even produce two new limbs, usually from the two leaf nodes closest to the cut. It's best that you do this kind of harvesting mainly during the growing season (i.e., during the warm months of spring and summer when the plant is still capable of putting out new growth) and refrain from doing so in the dead of winter, when the plant's energies are focused on survival. Pruning at that time, especially with a freeze coming, can be harmful to the plant. You shouldn't be picking single leaves either during the coldest part of winter as the leaves do serve as a blanket to protect life in the branches and the trunk of the tree. But of course, like everything else, this is just a generality for the Bay Area; if your tree is happy and warm in your garden even in the heart of winter when it continues to put out new growth, then you need not worry what time of year to harvest leaves.
Many inexperienced gardeners are very hesitant about cutting a branch of their precious tree. "What?! Cut a limb off my baby?" It's really not like that at all. Look at it more like giving the plant a haircut. Just as haircuts can improve the vitality of your hair, so can pruning do the same for your kaffir lime plant. But do this pruning during the warm months when the plant is in growing mode. In the winter, it needs its "hair" to keep its neck warm.
When you prune for your leaves, you may end up with more than you need for the meal you are cooking, but kaffir lime leaves do keep well in the refrigerator, for nearly a month, or longer if you freeze them. And they do freeze well without losing much in the way of flavor and aroma. So prune in the spring and summer and freeze the extra leaves for your winter Thai cooking.
Pruning will help your tree grow bushier and more lush with leaves, so you'll end up with more leaves in the long run for your cooking, as well as your friends', neighbors' and their friends' and on and on. It will also help you shape your tree into an aesthetically pleasing plant to fit the space you have allotted to it. You can prune a branch back by as much as a third of its length, even more if your tree has grown much taller or wider than you wish it to be. Don't just snip off the tips of tender branches as this will only make the plant grow top heavy. Top heavy branches can end up breaking off, tearing the bark and impairing the health of the tree.
Whether you need leaves or not, pruning can contribute to the overall health of your tree. You can open up the center of a tree that is thick with small branches and leaves in order to improve air circulation. A tree thick with leaves in the center may provide hiding places for bugs. Good air circulation during the hot, dry summer months can help ward off major bug infestation, as well as fungal diseases. Be careful when thinning a large tree as it has vicious thorns.
When you prune, try to cut back to an outfacing leaf node, which would direct new growth outward and away from the center of the plant. This not only will give the plant a more aesthetic appearance but will keep the tree from becoming too thick in the center, thereby closing off air circulation. Or, prune back to a node that faces the direction you wish the new growth to go. If your plant is bushier on the right side, you would want to cut back to a left-facing node to fill in the leaner side.
If the tree you've had for several years only has leaves on the end of the branches because you unknowingly have been practicing leaf-picking that has stripped the lower part of the branches, you might wish to rejuvenate your tree by pruning in stages. Cut one or two branches at a time back hard to a node (it'll be a bump or eye on the branch as the leaf is no longer there) from which you wish to see the growth of new leaves. When new growth emerges, you can choose another branch or two to prune back and so on until the entire tree has been pruned. This way the tree will not be completely without leaves, which it needs for photosynthesis.
Generally, spring pruning increases the vigor of a tree while fall pruning controls the vigor of an over-vigorous plant.
Of course, if your plant is still very young, you should neither pick leaves nor prune it until it has developed a good branch structure with sturdy woody branches. Let your baby grow some hair before you give it a haircut. In the meantime, buy the leaves you need for your cooking or get some from a friend who has a mature tree and way too many leaves than he/she can use.
If you would like a copy of this article in Adobe Acrobat (PDF) format for your own personal use, please contact Kasma.
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