Kaffir Lime Care – When to Water
by Kasma Loha-unchit
13. How Often Should You Water Your Kaffir Lime Plant
How often to water your kaffir lime tree depends on many factors. Is it grown in the ground, or in a planter? If it is in a planter, it depends on whether the planter is made of plastic or terra cotta and on how big the planter is in relation to the size of the plant. It depends on whether the plant is in full sun, part sun or shade and on the changing sun patterns through the seasons. If it is in the shade, is it dry shade or damp shade? It depends on whether the plant has companions to create humidity for its surroundings. It depends on how well draining and moisture retentive the soil is. It depends on the season and the weather. It depends on whether you live west or east of the Caldecott Tunnel. It depends on whether you live in the fog belt or in a sunny district in San Francisco. Etc., etc., etc.
I had a student once who eagerly reported that she never had to water her kaffir lime plant and it did great... before she moved and her plant almost died from thirst. That's because she formerly lived in the fog belt of San Francisco where the plant was getting sufficient moisture from condensed fog to thrive in the shady garden. Her new home, on the other hand, had a sunny garden most of the year.
Of course, if there's a heat wave, you would want to water your container-grown kaffir lime tree daily, especially if it is in full sun and you live in the East Bay. Keep in mind that full sun in the spring is very different from full sun in the summer in the same location. The needs of the plant will change and you should adjust your care schedule accordingly. If mornings are mostly overcast in early spring or late fall when the days are shorter and evenings cooler, you might be able to get by with watering only once a week. And during the dark, rainy winter months when the plant goes semi-dormant (i.e., not producing any new growth), you won't need to water at all if there's a drenching rain at least once every two weeks and mostly cold days in between. In short, you have to determine what your particular plant needs in its particular location, with particular weather conditions, at a particular time of year. By no means should you stick to a rigid once a week or twice a week schedule the year round.
The best way to find out when your plant needs water is to check the soil. Scratch the surface of the soil and if it has dried an inch below the soil surface, then give the plant a drink. After a while, you may not need to check the soil any more and will automatically know how often to water based on the time of year or particular weather conditions in your area.
Make sure each time you water to give the soil a good soak. This means you should see water draining out from the drain holes if the plant is in a container. But at the same time, if the pot is on a saucer, make sure it isn't sitting on standing water for any prolonged period of time, as this can cause root rot. If your kaffir lime tree is large, my advice is to put the planter on a stand with wheels. This way you won't need to use a saucer and it'll be easier for you to move the planter around. If you must use a saucer to protect your wooden deck, a simple solution is to raise the container from the saucer with bricks. The water that collects in the saucer beneath the bricks will provide some humidity for the plant without the roots becoming waterlogged.
Garden soil generally holds moisture longer so you won't need to water as frequently. You can also cover the surface of the soil with a couple of inches of mulch to reduce water loss from evaporation, making each watering last longer. You usually have less of a chance of over-watering, especially when there are other plants and trees nearby to help use the water. Of course, a lot depends on the condition of the soil in your garden. Heavy clay soil stays very wet for a long time and is easily compacted which restricts root growth. On the other hand, sandy soil drains swiftly and holds little moisture, so roots can dry out quickly. Loamy soil containing a good amount of organic matter is the best for growing most plants as the organic matter contributes to both the moisture retentiveness of the soil and to proper drainage that keeps roots from being waterlogged. In loamy soil a kaffir lime tree will develop a stronger, deeper and more drought tolerant root system.
Larger, more mature kaffir lime trees actually are pretty forgiving if you occasionally over-water, so don't let yourself get too insecure about whether you are doing things right. For years, I watered my pot-grown kaffir lime tree on the sunny brick patio daily from mid-spring to mid-fall on sunny days and every other day during strings of overcast mornings. It did just fine and looked healthy, putting forth several sturdy new branches each spring and producing sizable crops of three to four dozen good-size fruits each year. A few of the limes grew as large as small tangerines. But last autumn when a group of advanced students and I visited Four Winds for an annual kaffir lime picking party, a serious discussion brought up over-watering as a primary cause of problems for amateurs trying to grow citrus and a cautionary advice was given that pot-grown kaffir lime trees shouldn't be watered more than twice a week.
So I got a little insecure and starting in the spring this year I cut down on my watering frequency to about twice weekly, checking the soil each time before I watered. Guess what! this was the first spring my tree flowered pitifully and had barely fruited at the start of July when in previous years it would already have limes the size of plump cherries. This was also the first spring I saw occasional leaf drop and the plant looked a little less happy. So I resumed daily watering despite what the experts say! In just a few brief weeks, the new leaves came in much larger and the tree bloomed profusely and had limes the size of peas by July's end. In spite of its temperate climate roots, my tree seems to behave more like the kaffir lime trees in Thailand which are drenched by monsoonal rains daily during the warmest half of the year. It lives in a terra-cotta pot which I think is much more forgiving about being watered frequently.
My other kaffir lime tree, planted in the ground in a shady border along the side of the house, gets watered once every three days on the same drip irrigation line as other plants on the narrow strip. It is as happy as can be although by textbook accounts it could be said that I am giving it too much water. So the standard advice to water pot-grown citrus twice a week and ground-grown citrus once a week doesn't seem to hold water with my trees. That's why I started this guideline saying that you need to observe and determine for yourself what your particular tree likes in your particular garden.
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