Family: Boraginaceae

Kou is a part of the forget-me-not family (Boranginaceae), which includes hinahina (Heliotopium anomalum), tree heliotrope, and comfrey. Kou trees can grow more than 25 feet tall and across. They have smooth broad leaves, showy orange flowers, and small fleshy fruits that ripen to a brown-black color when dry. The native kou can be commonly mistook for the introduced geiger tree (Cordia sebestena). Geiger trees instead have sandpaper textured leaves and the flowers are redder with more constricted petals compared to the native kou.

Although initially believed to be a Polynesian introduction, fossil evidence found on Kauaʻi indicates that kou was present before the arrival of early Polynesians. Which makes sense as the hardy seeds of the kou can float and survive on the ocean until it reaches another shore. Kou was so culturally important in the Pacific that it was also brought on voyages as a canoe plant.

Habitat & Uses

Naturally you can find kou growing along coastlines in full sun across most of the Hawaiian islands where it typically grows up to 1000 feet elevation. This tree is tolerant to drought, wind, and saline. Kou trees are relatively small in stature, resilient to harsh conditions, and make an excellent shade tree. This is why you can see kou planted in parking lots and within commercial landscaping. Kou has non-invasive roots making a good street tree. However, flowers and seeds can create debris under the tree that may need to be maintained.

Kou wood is very useful. Although soft, when freshly cut, it dries hard and produces a beautiful grain. Kou was more highly prized in old Hawaiʻi than koa because it is easily carved with non-metal tools and kou containers don’t leave a resinous flavor on contained foods. Flowers are perfect for lei-making and kou was traditionally used to treat ʻea or thrush in young children.

Landscape & Cultivation

Kou is easy to propagate and grow, especially in dry regions. You can often find volunteer seedlings within the leaf litter of the kou. Those seedlings can be easily transplanted into a pot with well-draining soil until you are ready to plant it somewhere. Remember that kou needs ample space to grow (~25-35 ft mature canopy spread) and may not be suitable for urban yards. They have non-obtrusive but shallow roots which do not like to be damaged too much. However, once they’ve established in the perfect spot, they require little maintenance. Before you know it, you’ll have a lovely shade tree to have picnics, read a book, or to do your hobbies under!

Name Origins

The genus name Cordia refers to German botanists and pharmacists Euricius Cordus and his son Valerius. The species name subcordata literally means almost or not completely cordate. Cordate is a type of leaf shape where there are two equal rounded lobes at the base. Therefore, subcordata is interpreted as meaning almost heart-shaped leaves.

Plant Uses:

• Cultural significance
• Lei flower
• Medicinal
• Ornamental
• Shade
• Specimen
• Windbreak
• Woodworking

Plant Dangers:

• No dangers