Hi'iaka's Healing Herb Garden

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Let's Abolish the Term "Weed Tree"

Even before I moved to Hawai`i, I heard people using the expression "weed tree." Although I understood what it meant -- a tree that is undesirable, drops seeds everywhere and creates an entire forest of its keikis in no time -- it just didn't seem quite right to me that any tree was thought of as a weed. They're all good for something, like providing food or shelter for birds, shade for humans, and building materials for shelters or boats, as the early Polynesians discovered. The "weed tree" attitude indicates that people are thinking about tidy little human-controlled garden spaces that do not include the forces of nature. Even trees that are considered undesirable can be ground up and used as nourishing mulch after sitting for a couple of months under a sheet of black plastic to discourage any seeds.

This month I'll talk about some plants that thrive nicely here, but which you might not have considered keeping or planting in your yard. And I'll talk about ways of controlling the plants you don't want to keep.

Everything Is Something

I choose to use the word "undesirable" instead of "weed tree."

Many undesirables have been introduced to Hawai`i by well-meaning people who thought they would look pretty in landscapes or would provide a useful fruit. Then some of those plants "went bad," or rather wild, because they liked it so much here that they joyfully reproduced. They were so well suited to this new environment that they became very successful in forming whole populations of themselves. That's fine with some plants, like coconut palms -- if you want them. But others, such as maile pilau ("stink" maile vine), can strangle a tree, and plants such as Tibouchina can crowd out other plants in an area, making it impossible for many native plants to thrive. So they are things that you definitely want to get rid of, or at least control as best as possible.

I welcome volunteers of many species that can survive in my rocky environment. Here are some "undesirables" that I like:

Kolomona, or scrambled egg tree (Senna spp.), is an introduced ornamental evergreen shrub or small tree to 20 feet that sports pretty yellow flowers year-round. It has escaped to roadsides, pastures and waste places at lower elevations and is often used as a hedge plant. It is reported that the bark is medicinal.

Scheffleras ("octopus tree") are attractive and birds love to eat their berries. Although they naturalize fairly easily, I have never seen an invasive schefflera forest on any of the islands.

Trumpet trees are weird and tropical looking, and provide both shade and a place to attach the chain across my driveway. Again, I've never seen entire forests of these, as you see with Albizia, an undesirable you definitely do not want to keep on your property.

Noni babies occasionally pop up and they are a blessing because of their medicinal properties and the fact that I can pot up the youngsters and sell them.

Autograph trees aren't bad looking and the leaves are fun to use as placeholders and nametags. Just be sure to keep them cut back from the base of valuable trees because they can strangle their host tree in time.

Smaller plants, those we really consider "weeds," include species such as the native ko`oko`olau (bidens species), plantain (lau kahi; plantago species), purslane (akulikulikula; portulaca family), gotu kola (pohe kula; centella asiatica) and many others. These are all edible and/or medicinal and I consider them "wonderful weeds." The last two are groundcover plants, which can prevent other weeds from growing.

Controlling Undesirables

You can control many undesirables by simply keeping them pruned back, but if those plants are over 10 or 15 feet tall, it is best to hire a professional arborist. Pruning is both a skill and an art, according to the Sunset Western Garden Book. "The skill is in making cuts that heal properly and minimize the chance for decay. The art is in making cuts in the right places so the plant takes on a handsome form and is prolific if grown for flowers or fruit." Here are the pruning rules that both they and I recommend:

You can prune undesirable trees to keep them under control. You might try to change your attitude about some of your undesirable trees: if a tree wants to grow on your property without fertilizer or additional water, it is well suited to the elevation, climate and so forth. It will be a carefree plant for years to come and you can manage its sprouts or keikis more easily than you can the parent tree. So learn to recognize the keikis and pull them when they pop up. Live and let live.

Remove dead or diseased wood as soon as possible. Take this to the recycling center's compost operation rather than composting it on your own property.
Cut off branches that rub against each other.
If a tree is less than 10 feet tall and less than 6 inches in diameter, you can coppice it, which is a simple method of chopping off the top half of the tree, leaving a "stump." You can do this with wiliwili: chop up the top part and stack it around the base of other plants, serving as mulch and nutrient.

Tips for Pruning Trees and Selecting an Arborist

Be careful! Pruning in itself is not dangerous, but saws and lopping shears are sharp. I don't want to harp on this, but if you've got a big tree, get a professional tree trimmer. Arborists are professionals who do tree care safely, help minimize injuries and liability, and promote your trees' use and beauty, according to the U.H. College of Tropical Agriculture's fact sheet, "Selecting a Tree Care Professional." The Yellow Pages has listings for arborists under Tree Service and Arborists. Better yet, get referrals from friends or neighbors who have used tree care professionals in the past.