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David Ross's Garden

Dwarf Citrus in Containers

Copyright © 2004, 2006-2009, 2011 by David E. Ross

I used to have my dwarf citrus planted in redwood tubs. These were cylindrical, not tapered. They were about 18 inches in diameter and 18 inches deep. Even with the tubs raised on bricks (regular bricks, not the thinner pavers that I now use) and despite the durability of redwood, the tubs would eventually begin to rot and require replacement. Not only was repotting a real bother, but the large redwood tubs were becoming very hard to find. So I finally replaced them with large terracotta flower pots, about 22 inches in diameter at the top, 17 inches at the bottom, and about 20 inches deep. Mixing sufficient potting mix for each container was quite an effort.

I now have four dwarf citrus trees, three in containers:

Each pot sits on three, thin paver bricks arranged in a triangle. The bricks sit on an 18-inch concrete round set on the back lawn near a walkway. This elevates the bottom of the pot above the soil to allow excess water to drain.

Each pot is wrapped by several strands of copper wire to prevent snails and slugs from reaching the plant. Snails consider citrus bark a great treat and can kill a tree by eating away the bark all around the trunk.

The citrus is watered by drip irrigation tied to my automatic lawn sprinklers, which runs every third day. This is far more often than citrus in the ground should be watered. However, with their roots constrained in containers with a fast-draining potting mix, the soil must be keep moist. Even then, the foliage on my lemon sometimes outgrows the ability of its limited roots to provide moisture; when I see repeated wilting, I prune some of the excess growth.

I also have a dwarf 'Minneola' tangelo (Citrus reticulata × paradisi), a cross between a tangerine and a grapefruit. This is not planted in a container but in a raised bed in the back yard. To protect the tree from snails and slugs, I made a braid of thin copper wire and wound it around the trunk tight enough to prevent even a small snail from crawling under the braid but loose enough to allow the trunk to grow. It is too new to give any details yet about flowering or fruiting.

I feed my citrus every three weeks from early March until early October. Citrus prefers an acidic soil and requires much nitrogen, iron, and zinc. I alternate feedings with a commercial citrus and avocado fertilizer and ammonium sulfate. The commercial fertilizer is acidic and contains extra iron. The ammonium sulfate is merely nitrogen in an acidic compound; when I use it, I also add a large pinch of iron sulfate. With each feeding, I apply a pinch of zinc sulfate. Having learned a serious lesson with the original lemon, I feed only when the soil is moist. Growing in containers with fast-draining soil and frequent watering, the trees need frequent (but light) feeding to replace nutrients that quickly leach away. Feeding tends to promote tender new growth that would be damaged by the night frosts that generally begin in December. Thus, I stop feeding in October to allow any resulting new growth to mature and harden.

From March to September, I repeatedly prune the dwarf citrus, removing dead twigs and weak branches and pinching new shoots to make them bushy. This is a very light pruning, intended primarily for aesthetic purposes and — as already mentioned — to keep the foliage commensurate with the constrained roots. Citrus does not require pruning to promote fruiting (as, for example, is done for peaches). I do not prune from October to February because I don't want to encourage tender new growth.

I constantly check the trees for pests. Aphids are not usually a problem because, by the time they appear, ladybugs are also present to eat them. Spider mites and scale can be problems, but I don't see them every year. I use malathion if aphids, mites, or scale are a problem. Occasionally, I find a snail that somehow crossed the copper wire that is supposed to protect the tree; I hand-pick them.

Lately, a citrus leaf miner has attacked my trees. While their damage would not be severe on a full-sized, mature tree, they can defoliate and kill a dwarf tree. When I see the start of damage, I've been using imidacloprid (a systemic insecticide applied as a soil drench). Although its use on fruit-bearing trees is definitely not approved, studies indicate that imidacloprid is harmless to mammals.

29 March 2004
Updated 20 March 2011

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