Eucalyptus Care: Watering, Feeding, Staking and Keeping the Silver Leaves

Water hard for two seasons, then stop

A newly planted eucalyptus has a small root ball attached to a plant that wants to grow three feet (0.9 m) a year. Until the roots catch up with the top, it needs real water: five to ten gallons (20-40 liters) once a week through the first growing season, delivered slowly at the base rather than sprinkled over the leaves. Two or three light waterings a week are worse than one deep one, because shallow water grows shallow roots and this is a plant that already tends toward a shallow root plate.

In the second season, cut back to a deep soak every two to three weeks in dry weather, and only in dry weather. By the third season an established plant in open ground needs nothing at all in a normal year, and in a genuine drought it will drop some older leaves and carry on. Leaf drop in a dry summer is the plant managing itself, not a signal to start irrigating.

Container plants are a different case entirely and never become drought tolerant. In a pot the plant will use everything you give it and wilt within a day in summer heat, so check by pushing a finger two inches (5 cm) into the compost and water thoroughly whenever that depth is dry. What kills potted eucalyptus is the opposite mistake: a saucer of standing water underneath, which suffocates the roots within a fortnight.

Feed almost never

Eucalyptus evolved on poor, low-phosphorus ground and grows fast without help. Feeding it does not give you a better plant; it gives you a taller, softer, more brittle one that snaps in wind and loses the tight silvery color that makes the juvenile foliage attractive in the first place. In open ground, a plant in ordinary soil needs no fertilizer at any point in its life.

The exception is a plant in a container, where every watering flushes nutrients out of the drainage holes. Give a potted plant a half-strength balanced liquid feed once a month through the growing season only, and nothing from mid-autumn until growth restarts. High-phosphorus feeds and bone meal should be avoided; this genus is unusually sensitive to phosphorus and reacts with scorched leaf margins and dieback rather than with lush growth.

If the leaves on an in-ground plant go pale and yellow between the veins, suspect high soil pH locking up iron rather than a lack of feed. That happens on chalky ground and near new concrete or mortar, and adding fertilizer makes it worse rather than better.

The stake has to come off

A stem only builds taper, the thickening toward the base that lets a trunk hold itself up, in response to being flexed by wind. A plant tied rigidly to a tall stake never gets that signal, so it stays a uniform pencil from top to bottom. It looks fine while it is tied. It goes over in the first real gale after the stake rots.

Use a stake only through the first growing season, keep it low so the top two-thirds of the stem can move freely, and check the tie every couple of months because this plant thickens fast enough to strangle itself on a tie you forgot. Take the stake out at the end of that first season even if the plant leans a little; the lean straightens as the trunk thickens.

If a plant that was staked too long now cannot stand up, the fix is not a bigger stake. Cut it hard back to a low stool, which is covered under pruning, and let the regrowth build its own trunk in open air.

A leaning young eucalyptus that has never been staked is usually fine and will correct itself. A leaning eucalyptus with a rotten stake still attached is a plant that has learned nothing about wind, and the lean will get worse every year.

Cutting back is care, not surgery

The round, silvery, almost stemless leaves people grow this plant for are juvenile foliage. They belong to a young shoot, not to the plant as a whole. As the plant matures it switches to adult foliage: long, narrow, leathery, hanging leaves in a dull gray-green, and once a shoot has made the switch it stays switched.

The way to keep the silver is to keep making the plant produce young shoots, which means cutting it back hard, to a low stool or to a short framework, every one to two years. This is routine care for anyone growing eucalyptus for foliage rather than as a tree, and the plant regrows a mass of new stems from the base within weeks in the growing season.

If you have decided to let it become a tree instead, accept the foliage change and stop expecting the silver leaves back. The two goals are genuinely incompatible on one plant, and trying to split the difference by trimming the tips gives you neither.

Bark, litter and what is normal

Eucalyptus sheds. Long strips of bark peel off the trunk and branches, and older leaves drop all through the year rather than in one autumn flush. Both are normal and neither means the plant is sick. Rake the litter away from the base if it is piling against the stem, but there is nothing to treat.

Leaves also change appearance with the season: a plant going into cold weather often takes on a purple or bronze cast, and that color disappears when growth restarts. Persistent brown crisped margins in summer are a different matter and usually mean either drought in a container, or phosphorus from a feed the plant did not want.

The two records worth keeping

Write down the date you last cut the plant back and how far back you cut. That single record tells you when the silvery foliage is due to run out, because the interval between hard cuts is what controls it, and after two or three cycles you will know whether your ground wants a one-year or a two-year rhythm.

Also note the date the stake came off and the height of the plant at the end of each season. Height gain per year is the most useful number you can have for a plant this fast, because it tells you how many years you have before a plant you are letting grow as a tree reaches the size where it becomes someone's problem.