Most visitors who see a rainbow eucalyptus for the first time stop walking. The bark looks wet, like someone took a brush to it. Patches of pale green sit next to streaks of blue, orange, maroon, and gray, all on the same trunk, all real, none of it painted.

Where to actually see them in Hawaiʻi:

• Maui: Keʻanae Arboretum on the Hāna Highway (free), and Garden of Eden Arboretum at mile marker 10.5 (paid). - Kauaʻi: Keahua Arboretum at the top of Kuamoʻo Road in the Wailua Forest Reserve (free). - Big Island: Hawaiʻi Tropical Bioreserve & Garden on the Onomea Bay scenic route, about 7 miles north of Hilo (paid). - Oʻahu: Hoʻomaluhia Botanical Garden in Kāneʻohe (free) and Foster Botanical Garden in downtown Honolulu (small fee).

The rest of this piece walks through each spot, the bark science behind the color, and how to photograph the trees without getting a muddy shot.

The species is Eucalyptus deglupta, native to the Philippines, Indonesia, and Papua New Guinea per the USDA Plants Database. It is the only eucalyptus that occurs naturally in the Northern Hemisphere, and it grows fast and tall in wet tropical climates. A handful of older plantings around the islands stuck around long enough to become visitor attractions.

The painted look is not decoration. It is the tree’s normal bark cycle. As explained by the U.S. Forest Service, the outer bark sheds in long thin strips at different times of year, and the freshly exposed inner bark starts out bright green. As that new layer ages and oxidizes in the sun and air, it darkens through blue, then purple, then orange and red, and finally brown before it sheds again. Because the strips peel off at different times across the trunk, the colors all show at once.

That is the whole trick. The colors come from age. A young patch is green; an old patch is rust. Same tree, same minute.

The most popular public stand of rainbow eucalyptus on Maui grows at the Keʻanae Arboretum on East Maui. The arboretum sits along the Hāna Highway just before mile marker 17. According to Hawaiʻi DLNR, it is free, with no formal facilities. A short paved path winds through plantings of tropical fruit, timber, and ornamental trees, with the eucalyptus stand rising up on the right.

Practical notes before you go:

• The pullout is small and the road is curved. Cross carefully and don’t park in a way that blocks the highway shoulder. - There are no restrooms at the arboretum. The closest public restrooms are at the Keʻanae Peninsula lookout area down the road. - Conditions can shift after winter storms. Check current Hāna Highway advisories on the Hawaiʻi DOT goakamai page before driving out, and be prepared to skip it if the road is restricted. - The trees photograph far better in soft midday light or under thin overcast than in harsh full sun. The colors blow out in direct light and look muddy under flash.

A second public stand sits at the Garden of Eden Arboretum at mile marker 10.5, which we cover in our Maui gardens roundup. Garden of Eden charges $20 per adult. The trees there are grouped near the entrance and are easier to photograph in flattering light, with some paved paths through the property — check current accessibility on their site if you’re relying on it for wheelchair or stroller access. If the Keʻanae stop feels too rushed or the road too tight that day, this is the friendlier alternative.

On Kauaʻi, the easiest public spot is Keahua Arboretum at the top of Kuamoʻo Road in the Wailua Forest Reserve. From Wailua, turn mauka onto Kuamoʻo Road and stay on it for about 7 miles until the pavement opens into a small picnic area with tall painted-bark trees standing along the lawn.

Logistics matter here:

• The arboretum sits in front of a stream crossing. Reaching the parking lot does not require driving through it, but the unpaved road that continues past the lot does, and that crossing is impassable in normal cars after rain. Stop at the arboretum, look at the trees, and turn around. Do not gamble on the crossing. - Kuamoʻo Road is the same approach used for the Kuilau Ridge Trail. If you are already hiking that trail, the rainbow eucalyptus add maybe ten minutes to the day. - Mosquitoes are real here. Wear long sleeves or bring repellent. - Cell coverage drops out before you reach the arboretum. Pre-load your map on the way up.

The Keahua trees are not as tall or as dense as the Keʻanae stand on Maui, but they are easier to walk around and photograph from multiple angles, and the picnic tables make a calm coffee stop on the way back from a Wailua-area hike.

The windward side of the Big Island is wet, low-elevation rainforest, and rainbow eucalyptus do well in it. The most reliable visitor stop is the Hawaiʻi Tropical Bioreserve & Garden on the Onomea Bay scenic drive about 7 miles north of Hilo. Adult admission is $35 and covers a self-guided loop through the rainforest down to the coast. Several large rainbow eucalyptus grow on the upper part of the trail, with name plates and benches.

A few details worth flagging:

• The trail is paved but steep and humid. Wear shoes with grip. - The Hilo side of the island is famously wet, and showers can roll through at any time of day. Bring a small rain shell and don’t count on a clear afternoon. - This is one of the better spots in Hawaiʻi for someone who wants to see a rainbow eucalyptus, take a clean photo, and leave with their visit measured in hours rather than half a day.

You will also catch wild specimens scattered along the Hāmākua Coast between Hilo and Waipiʻo. Most are not formally signed and most are on private agricultural land, so don’t trespass to chase one. The roadside ones along the 4-Mile Scenic Route (the same loop the Tropical Bioreserve sits on) are the safest pull-off targets.

Oʻahu has rainbow eucalyptus, but not the postcard stands of Maui, Kauaʻi, or the Big Island. The reliable spots are cultivated:

• Hoʻomaluhia Botanical Garden in Kāneʻohe (free, accessible, well-marked). - Foster Botanical Garden in downtown Honolulu (small fee, urban setting).

A few specimens are reported on Tantalus Drive above Honolulu and around the upper Mānoa Valley, but they are unmarked and easy to walk past. If rainbow eucalyptus is the goal, bake the visit into a day on Maui, Kauaʻi, or the Big Island instead. On Oʻahu, treat it as a nice surprise inside a botanical garden rather than the headline.

Most visitor photos of rainbow eucalyptus look duller than the trees in person. A handful of fixes go a long way:

• Light is the whole game. Bright direct sun blows out the highlights and crushes the colors. Thin overcast or filtered shade through the canopy is ideal. Mid-morning to early afternoon under cloud cover is the sweet spot. - Get close. The colors are most saturated at eye level. Step in 3 to 6 feet and shoot a single section of trunk rather than the whole tree. - Mist helps. A light rain wakes up the colors. The trees look most “rainbow-y” right after a passing shower. This works in your favor on the Hāna Highway and the Hāmākua Coast, where passing showers are normal. - Skip the flash. It flattens the bark and adds a yellow cast. - Don’t strip the bark. Stripping bark can damage or kill the tree. Touch and look, then leave it attached.

For phone shooters, tap to focus on a colored section, drag the exposure slider down by a third or so, and shoot. The default auto-meter usually overexposes against the surrounding green canopy.

Rainbow eucalyptus is a 10-minute stop on a day you were already going to spend on the Hāna Highway, the Wailua side of Kauaʻi, or the Hilo side of the Big Island. It is not worth a long detour on its own. If your trip is built around West Maui resorts and the Lahaina coast, or Waikīkī and the Ko Olina side of Oʻahu, you are far from every reliable stand and the math doesn’t really work.

But if your itinerary already runs through East Maui, the Wailua corridor on Kauaʻi, or the Hilo side of the Big Island, build in 15 minutes for the trees. The colors are real, the light is good, and a four-color living trunk is the kind of thing visitors remember years after the resort details fade.