by Diana Duff
Special To West Hawaii Today
Sunday, December 5, 2010 7:40 AM HST
Many gardeners in Hawaii have become native plant enthusiasts. More and more people are awakening to the beauty of our native species and learning about them and the vigilance required to save them from harm or eventual extinction. Events like Arbor Day at Amy B.H. Greenwell Ethnobotanical Garden, offering free native plants and information on growing them, help folks learn ways to grow and care for native plants. Interest in these plants, which have thrived in our native forests for millennia, helps raise awareness of the threats a multitude of invasive species pose to them.
One particularly threatening species, the autograph, or signature, tree (Clusia rosea) caught the notice of Darcy Ames, who has witnessed firsthand the encroachment of this species on the ohia forests near her home.
“When I first bought property in Holualoa, I thought the autograph tree was quite lovely,” Ames said. “After a few years of experience, inspection and investigation, I began to realize this tree was capable of destroying the habitat of our ohia and other native species unless we began a proactive course against it.
“After witnessing the damage it can cause, I can honestly say that I hate what this plant is capable of doing. Autograph seeds can be dropped by birds and root as much as 20 or 30 feet in the air in the crotch of an ohia tree. The autograph seedling sends its long banyan-like roots toward the ground while establishing other roots into the interior of the host tree. Then the invasive, destructive autograph tree begins to suck the lifeblood from its host. Eventually, the trees this invasive alien has attacked, die.”
The tree that has aroused Ames’ ire is a familiar tree in Hawaii and one some gardeners still plant and enjoy without understanding its destructive downside.
The autograph tree is a known invasive species in Hawaii. Its habitat is so widespread and its growth habit so aggressive that those familiar with it and its impact on native species shudder at the mention of its name.
Native to the Caribbean islands, the autograph tree was brought into Hawaii as an ornamental plant but has achieved the unenviable distinction of being so invasive as to be listed in the Global Compendium of Weeds.
The autograph tree is best known for its stiff, thick, dark green, waxy leaves, which easily retain any marks, or “autographs,” written on them. The tree produces an attractive pink or white flower that develops into an apple-sized green fruit. As the fruit matures, it opens at one end into a star shape, releasing tiny red-orange seeds. These seeds are very appealing to birds that eat them and disperse them over large areas in their droppings.
Though attractive trees in some respects, their tendency to sprout and crowd out other less aggressive species in our forests qualifies them as a dangerous, invasive species. Learning to identify them and remove them where possible can go a long way toward slowing their invasive nature.
Conscientious gardeners are advised to remove autograph trees from their property and not to plant new ones. Spreading the word about the invasive nature of autograph trees can be very helpful in diminishing their numbers. By limiting the number of autograph trees in our gardens, we can certainly help reduce the number of seedlings that invade our native forests and pose a real threat to our lovely native ohia trees.
Duff is a plant adviser, consultant and an organic farmer living in Captain Cook.
Tropical gardening helpline
Kathy asks: I live at 3,000 feet on the wet side of Waimea and want to plant some fruit trees. Do you think I could grow mountain apple or mulberry on my property?
Answer: Mountain apple is definitely a tropical tree. It was brought by the Polynesians to Hawaii to provide a ready-to-eat, crisp and refreshing treat during long, hot workdays. Although you may find it growing in warm, moist valleys at upper elevations, it does best in moist conditions below 2,000 feet.
Less sweet, and best when cooked, ulu is another Hawaiian heritage plant to consider at your elevation.
Mulberry trees may do fine at your location. They are native to warm temperate and subtropical regions of the world and you can certainly find a variety that will grow and produce well at your elevation.
You are in a location that is ideal for some fruit that can’t be grown at lower elevations. Consider subtropical varieties of apples, pears and plums. Depending on how cold it gets at night you may even be able to plant varieties that grow in temperate zones, which need a longer chill. Check out their chill needs online or ask your nursery owner.
The Waimea University of Hawaii College of Tropical Agriculture and Human Resources experiment station has been testing blueberry varieties for Hawaii. Call them to see where you can get varieties that will grow well at your location.
You can probably grow most citrus varieties, as well as some of the Annona family, including cherimoya and its relatives. Persimmons will likely do well. Loquat, many guava varieties and star fruit are also worthy of consideration for your location. Check with local nurseries or visit plantithawaii.com (exotics) to get ideas for more fruit bearing plants you might consider.
– Thursday: Farm Record Keeping” meets 5 to 7:30 p.m. at the University of Hawaii College of Tropical Agriculture and Human Resources Cooperative Extension Service office across from the Aloha Theatre in Kainaliu. It offers free instruction on keeping farm records. Reservations are due Monday. Call Joan at 322-0166.
– Saturday: “Crop Swap” is held from 12:30 to 3 p.m. at Malaai Garden at Waimea Middle School. Bring surplus produce to swap and stay for talk story. It is open to all. Free. For more information, e-mail Nicole Milne at firstname.lastname@example.org or call 987-9210.
– Ongoing: Plant advice lines — consult with Master Gardeners and Tropical Gardening advisers from 3 to 6 p.m. Mondays at the Kona Outdoor Circle at 331-2426 or 9 a.m. to noon Thursdays at the University of Hawaii Cooperative Extension Service at 322-4892, and Tuesdays and Fridays at UH CES in Hilo at 981-5199.