Native Trees Kou & Milo

When the high heat of summer is overwhelming, there is nothing quite like being in the shade of a big tree. There are a number of popular shade trees that we carry, but we wanted to highlight two native trees, Kou and Milo, that you might consider for your space.

Kou – Cordia subcordata
I have a special place in my heart for kou because I grew up with one in my backyard, where I climbed its branches and relaxed in its shade. While this tree can reach heights of 30-40 feet, it is easily pruned and shaped between 15-25 feet to fit into a backyard. They are relatively quick growing when they are young, so kou is a great option for creating shade quickly! They produce beautiful orange trumpet-shaped flowers that are prized by lei-makers.

Kou does best in lowland coastal areas in full sun, though they can handle some shade. It is relatively drought-tolerant, and can handle some sea spray, but not too much (Salt tolerance Zone 2). It can handle occasional water logging of soil during wet times. It prefers sandy or limestone soils. It can handle clay, but it does not like acidic soils. Once established, it can make a nice wind-break, though care should be taken to keep it staked when it is younger so that it doesn’t become bent to one side overtime. Care should be taken when transplanting kou due to high-susceptibility to root injury that can lead to disease.

Until recently, it was believed that kou is a canoe plant, that it came to Hawaii via the voyaging Polynesians. In 1997, pollen studies at ancient sites near Maha`ulepu have shown that kou was here on island before the canoes arrived, so it is considered indigenous. Ancient Hawaiians preferred kou for their food bowls and plates as its wood did not contain any resins or sap that would impart a flavor on the food. Today, the wood is highly prized as it often is light colored with red and purple stained heartwood. The wood is also very termite-resistant!

Some things to consider prior to planting kou are the deciduous nature of the tree, and the kou leaf worm. Kou is one of the few deciduous native Hawaiian plants, so it will at some point drop most of its leaves. In addition to the leaves, the tree flowers throughout the year, and eventually produces small round fruits that drop en masse. Kou should be planted in a location where it can freely drop this biomass, or it needs to be cleaned up consistently, especially in windy areas. It also isn’t suggested that kou be planted near a walkway or driveway as the seed drop can create hazardous walking or driving conditions. The kou leaf worm will occasionally defoliate the tree. On younger trees, this could be enough to kill it, but older specimens are usually resilient and will grow its leaves back quickly.

Milo – Thespesia populnea
Milo is another native tree that is near to my heart, as these trees lined the playground of the elementary school I attended on Oahu, called Kamiloiki (the little milo tree). Milo stays a bit smaller than kou, topping out around 25 ft. It can grow as wide as tall, so it makes a great shade tree! This is partially due to its more sprawling growth habit, though trees can be selectively pruned and supported to ensure a more “tree-like” shape. They do however recover slowly from pruning, so care should be taken before removing any parts of the tree.

Milo produces a hibiscus-like flower that closes at night. It starts out yellow with a maroon center, and as the day progresses, they become red, purple, or pink. The seed pods produced are flat and brittle and contain 5 fuzzy seeds that can germinate easily under the right conditions. There is a fair amount of clean up that is required with milo, though not as much as with kou.
Milo prefers full sun and thrives in rocky and salty coastal areas. It does not do well in heavy clay or acidic soils. It is drought- and wind-resistant and makes a great wind break along coastal areas, and it will grow relatively quickly. Its prolific seed production and easy germination create the potential for milo to become invasive.

It is not known if milo existed in Hawaii prior to the arrival of the voyaging canoes. The Polynesians likely brought milo with them, but it is now known that milo seeds can germinate even after one year of floating in salt water, so its possible that the seeds arrived here on their own and proliferated. Milo was second only to kou, its wood was highly prized for food bowls and utensils. Milo is still in demand by wood workers due to its attractive light-colored grain with occasional pink shades, however the darker tones of the heartwood fade over time when exposed to the sun. Milo used to be more prolific along coastal areas in Hawaii but harvesting for timber has reduced its population in the wild.

We have both milo and kou available in the nursery in 5 gallon pots, as well as a few larger specimens (15 gallons) of milo.

This blog was written by Alli, Kauai Seascapes Sales Associate.

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