Maui’s Blue Morning Glory: Ipomoea indica

Before I moved here I never gave the Morning Glory a second thought: to me it was just a colorful but mostly innocuous ground cover on the beaches of California where I grew up. However, on a small island like Maui they are kind hard to ignore because there are so many of them and they are seemingly everywhere you look. From the high-tide line on most of our white-sand beaches to almost 4,000 feet up Haleakala’s volcanic slopes, their cookie-cutter-perfect flowers and massive amounts of foliage and choking vines spill out over the landscape, engulfing everything from derelict automobiles to the headstones in cemeteries.

Flowers & foliage, the Blue Morning Glory, Ipomoea indica.
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The Morning Glories are plentiful in the Hawaiian Islands for two reasons: (1) they are able to adapt to almost any environment and (2) they propagate like oversexed rabbits. Their roots can absorb large quantities of seawater, they tolerate almost any kind of soil, and though they may be torn to shreds and small pieces they are still capable of taking root and flourishing. They choke off the saplings of competing species and shade-out established trees and bushes. On the other hand, Morning Glories can be important pioneer species that stabilize sand dunes and prevent beach erosion.

A solitary blossom of Ipomoea indica.
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The Blue Morning Glory (Ipomoea indica)

Ipomoea indica is a perennial vine native (indigenous) to Hawaii (“koali awa” in Hawaiian). It is variously known as Ocean Blue Morning Glory, Blue Morning Glory, and Blue Dawn Flower. It’s also called a “Dunny Creeper” in Australia (a “dunny” is an outhouse toilet), referring to its habit of covering everything in sight with its vines, including small out-buildings. Its geographic origin is uncertain: it may be native to the West Indies. It is now naturalized throughout the tropics and is found on all the main Hawaiian Islands. It is usually found at lower elevations (below 200 m) but has been known to grow at altitudes above 1,200 m.

Close-up of a mature Ipomoea indica plant. Note the characteristic 3-lobed leaves.
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Ipomoea indica prefers sunny open ground in a moist environment, but will tolerate seasonal dry spells once it is well established. It is a perennial that grows as a sprawling (ground-hugging) vine that produces a dense ground cover, but it is often seen climbing and twining over other plants. The vine itself (called a “stem”) is softly hairy and may grow to more than seven meters in length. The distinctively shaped leaves are large (as much as 15 cm wide and 17 cm long) and numerous. They may be heart-shaped when immature; mature leaves are 3-lobed to 5-lobed with pointed tips. The upper and lower surfaces of the leaf are covered by silky, short, closely-spaced hairs.

The flower is large (as much as 80 mm in diameter) It usually ranges in color from sky blue to purple-blue; less commonly it may also be light magenta and reddish-pink. It has paler mid-petal bands and a pink to whitish tube inside. The petals (3 to 15 per flower) are joined, which accounts for the distinctive trumpet-like shape of the flower. Ipomoea indica sets flowers all year, continuously flowering during warmer months. The short-lived flowers are replaced as they fall from the vine.

The fruit is a small (about 10 mm in diameter) 3-chambered spherical capsule. These are rarely produced by the plant. It has almost no self-fertilization and so grows vegetatively: its preferred method of propagation is by the production of numerous stolons, stems that grow above ground and are able to produce both roots and foliage. Individual stolons are readily detached from the parent plant and dispersed by mechanical means such as flooding, stream flow, landslides, or human activity (ground clearing and weed removal). Even when badly damaged, a plant can easily recover 4-6 m of its length in a single growth season. One theory about why Ipomoea indica evolved this unique reproductive behavior is that the species is a sterile hybrid and its genes are self-incompatible.

This species contains toxic alkaloids (including Ergonovine, which bears a strong molecular resemblance to Lysergic Acid Diethylamide, or LSD) that discourage ingestion by grazing animals. This defense mechanism contributes to its prevalence as a weed species.

Photo shows the tendency of the Blue Morning Glory to choke off sunlight from other plants by spreading its tendrils and vines in all directions, wrapping itself around anything from tree trunks to derelict automobiles.
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The Blue Morning Glory is a vigorous climbing vine that not only forms a dense ground cover but can easily extend itself high into the forest canopy. The twining stems can quickly choke off the growth of seedlings of other species and smother even older well-established plants. It also poses a significant shading hazard to other species.

Maui’s Beautiful Weeds: The African Tulip Tree

Atop the itinerary of most first-time visitors to Maui is a day trip to view the rain forests on the road to Hana… the Hana Highway. One of the first trees to grab your attention as you enter the rainforest canopy is a tall fellow with wide-spreading branches overflowing with impossibly bright-red flowers, the African Tulip Tree. But curb your enthusiasm, malahini… it’s a WEED!

The African Tulip Tree (Spathodea campanulata) is a shade-tolerant, evergreen tree native to equatorial Africa. It is a member of the Bignoniaceae Family, which includes the Jacaranda (also growing on Maui). It is also known as Flame Tree, Fountain Tree, Indian Cedar, and Santo Domingo Mahogany.

African Tulip Tree blossoms.
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Although it was originally introduced to The Islands as a domesticated ornamental tree, the African Tulip Tree has escaped cultivation and invaded agricultural land, forest plantations, and natural forests; it is now one of the dominant canopy trees in all of Hawaii’s rain forests and has become a serious threat to the biodiversity of that ecosystem.

An African Tulip Tree in full bloom along the Hana Highway.
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The African Tulip Tree is a tall tree, growing to more than 75 feet (30 m) in some habitats. It favors moist and wet areas from sea level to 1,000 m throughout Hawaii. The flower’s calyx is a leathery sack filled with watery sap (which attracts many ants, though the flower’s aroma is quite foul) from which blooms a bright scarlet-orange flower that grows in large terminal clusters. It sets flowers year-round, but the most prolific flowering occurs in Winter through Spring. The fruit consists of clusters of upright, canoe-shaped capsules about 10 inches long and 2.5 inches in diameter; these contain hundreds of small flat winged seeds that are easily disbursed by the wind. The seed pods are buoyant and so are easily carried off by streams and surf action to germinate far from the parent tree. The tree also propagates readily from root suckers, broken root pieces, and fallen branches.

Rain forests and drier mesic forests are very susceptible to invasion by this tree. Its high reproductive rate and capacity allow it to colonize disturbed areas (either created by human activity or by storms) at the expense of native plant species. Once established in an area, the tree grows rapidly and it can easily exceed the height of the native flora and shade it. Furthermore, this tree has no natural enemies in the Pacific region.

If the African Tulip Tree replaces native tree species, the effect on the biodiversity of Hawaii’s forests would be disastrous because so many of the native species support numerous tree-dependent flora, such as vines and epiphytes.