Kaffir Lime Care – Graft Location
by Kasma Loha-unchit
9. Where to Site Your Kaffir Lime
Kaffir lime trees can take full sun if there is sufficient humidity. They can also do quite well in partial shade and probably prefers it in hot inland areas where humidity can be very low while the sun is scorching hot in the summer. Keep in mind that full sun in Walnut Creek is not the same as full sun in San Francisco, where morning and evening fog brings moisture to the air and daytime temperatures are generally much lower. They can even do well in dappled shade if there's a lot of bright reflected light. One of my kaffir lime trees, for instance, is as happy as can be in a narrow border in between my house and the next door neighbor's. It gets maybe two to three hours of direct sunlight a day in summer and none at all from late fall to late spring when the angle of the sun is low, but is exposed to plenty of very bright reflected light all day long from the white paint of the two houses. In this sheltered location with warmth radiating from the walls of the two houses, it doesn't even look unhappy during the winter and begins its growth spurt very early in the spring when most of the garden has barely awakened. It puts out plenty of long thick branches lush with huge leaves that now supply most of my classes with the leaves we need to make scrumptious Thai feasts.
From my own experience, I find that my kaffir lime trees actually do better in partial shade in Oakland and like to be surrounded by companion plants, whether it is grown in the ground or in a planter. That's because grouping plants together creates more humidity for the plants, which is especially important for tropical plants. A kaffir lime tree in a planter on a hot patio in full sun all by its lonesome self will most likely not have a very long, happy life even if you water and feed it properly. As mentioned earlier, the 'mother' trees at Four Winds in Winters, CA (near Davis) from which branches are cut and grafted to make new kaffir lime plants, are under the shelter of a tall, open-sided shade-cloth tent year round. I think it is 30 percent shade and certainly not full sun. The shade cloth protects the trees from the extremes of arid summer heat and damp winter cold.
I think the ideal location would be one where the tree gets morning and mid to late afternoon sun, with dappled shade during the middle part of the day when the sun is hottest. In such a location there would be less fluctuation in temperature for the tree during the day and the mid-day shade gives a little more humidity to the plant during the hours when it's driest. Humidity levels generally are higher in the shade than in the sun.
Because the tropical kaffir lime resents the cold, some people have suggested planting it against a south-facing wall which would give out radiant heat at night to keep it warm during the winter. South-facing walls also get lots of hot, direct sunlight during the summer months, so make sure not to plant your kaffir lime tree too close to the wall as this can reduce air circulation and humidity. Air circulation is particularly important on hot summer days inland when there is little humidity, or else you might find your plant succumbing to insect infestation and outbreaks of fungal diseases. It's best to site the plant at least a few feet out from the wall, close enough to get warmth during the winter months but far enough out so that the wall does not overheat the plant during summer heat waves, dry out the air surrounding it and block off gentle breezes it needs to breathe properly. Your tree will also need space to spread out and grow into, so think ahead before you plant. A fully matured tree can be as tall as 10 feet even on dwarf rootstock and can have a spread of as much as 5 feet. Of course, you can always prune the tree down to the size you wish it to be if space is limited in your garden.
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