How to Grow and Care for Rainbow Eucalyptus Trees

The tall, evergreen rainbow eucalyptus tree (Eucalyptus deglupta) gets its name because of the unique streaks of green, red, orange, gray, and purple that run along the trunk and branches when the tannin-filled bark peels. Outside of its native tropical setting, the rainbow colors aren't usually as pronounced. However, it's a striking gum tree regardless, and after the first year or two can produce small clusters of white flowers in different seasons depending on the location. Popular in places like Hawaii, where the humid, warm weather suits this species, it's often grown as a large focal landscape tree and can be seen providing shade along the edges of streets.

If you have a compact yard, this fast-growing tree won't be for you. Outside of its native habitat, it can still reach heights of over 100 feet and, when the conditions are right, it can grow at least three feet every year.

Rainbow Eucalyptus Trees Care

Transplanting these trees is not a good idea—they aren't fans of root disturbance. If you want to start seeds indoors, you'll want to grow your rainbow eucalyptus in a large container that can be easily transplanted outside. You'll want to select a warm, sheltered site as these trees don't like cold, drying winds.

Because of their fast growth rate and size, choose a site that is far enough away from structures, foundations, power lines, and drainage systems as the sprawling roots could cause problems.

Light

Rainbow eucalyptus trees need plenty of sun, so plant in a position with access to unfiltered light.

Soil

This species thrives in deep sandy, loamy soils that are fertile, moist, and well-drained. It doesn't appreciate high alkalinity in the soil, fairing better with neutral to slightly acidic pH levels.

Water

Although established rainbow eucalyptus trees can tolerate some drought, they need regular watering during their first year. The trees can't handle prolonged flooding or waterlogged conditions, but keeping them moist will encourage the trunk and the bark to swell, encouraging more defined color stripes. Mulching around the tree can help conserve moisture, but make sure you don't place the mulch up against the trunk.

Temperature and Humidity

These trees grow best in temperatures of around 70 to 85 degrees Fahrenheit and appreciate high humidity levels. Unsurprisingly, rainbow eucalyptus trees are not tolerant of frosts. Temperature, humidity, and airflow all have a considerable influence on how distinct the coloration of the tannins in the tree bark will be.

Fertilizer

Unless you plant your rainbow eucalyptus tree in highly infertile soil, it shouldn't need feeding. They aren't fans of phosphorus—plus, without fertilizer, you can slow down their infamously fast growth rate.

Pruning

Your established rainbow eucalyptus tree won't need a lot of pruning unless you want to shape it, manage its height, or maintain a strong leader. The leader becomes less dominant as the tree ages and the branches start to curve up at the ends so that a flat, spreading crown develops. Removing any branches suffering from damage or disease can be done in late winter or early spring.

Propagating Rainbow Eucalyptus Trees

Rainbow eucalyptus trees can be propagated only from very young trees. A study showed that cuttings taken from seedlings and trees younger than five years rooted well, but cuttings taken from older trees failed to root due to a chemical that inhibits rooting within the older specimen. Propagating in a humid, warm environment produces fast results, especially when dipped in a rooting hormone and selecting a stem node with a leaf segment.

How to Grow Rainbow Eucalyptus Trees From Seed

With the right conditions, this species also propagates easily from seed. Follow these tips for a higher success rate:

1. Make sure that temperatures around 90 degrees Fahrenheit are optimal for germination.
2. Surface sow the seeds in a sunny position with moist soil.
3. Keep the soil moist and wait for germination to occur, usually within 1-3 weeks.
4. Plant seedlings outside when they are around 12 to 15 months old.
   

Common Pests & Plant Diseases

Rainbow eucalyptus trees are relatively hardy and not prone to leaf spot disease, which is common in humid, warm environments. Their peeling bark also helps them get rid of certain parasites. However, they can suffer from root rot in waterlogged conditions and are susceptible to the root fungus Armillaria. Beetle borers and termites have also been known to attack this hardwood tree.