Tuesday, January 22, 2008

Coastal Native Plants for Xeriscaping

There aren't many words that begin with the letter X, so here's one to put into your secret arsenal of high-scorers for your next game of Scrabble: Xeriscaping.

The term probably scores bigger points with you if you're a gardener who wants to design a landscape that uses less water. Xeriscaping often includes natives that have adapted to such conditions. If you live near the shore, the plants you choose for your garden should be tough against hot, windy, dry conditions with salt spray. Hawaii’s coastal natives are perfectly suited to sandy and rocky beach areas and thrive with little fertilizer or water once established. Many are shallow-rooted and low to the ground, making them excellent ground covers and container plants.

Take a hike and compare leeward and windward shorelines to get a feel for how you can use coastal natives in your garden. It’s a good idea to go with someone who knows native plant identification; your local chapter of the Sierra Club and other hiking clubs also welcome non-members on most of their trips. Take photos of the plants you see, and then ID them. An excellent resource to ID native plants and learn how to use them in the landscape is Heidi Bornhorst’s book, Growing Native Hawaiian Plants: A How-to Guide for the Gardener (Bess Press, 2005).

One of my new year’s resolutions for 2008 was to hike to Mahana Beach, the famous green sands beach at Ka Lae, South Point, on Hawaii Island, so I tagged along with a group from the Moku Loa chapter of the Sierra Club. Along the windy, dusty, gritty trail to the beach we saw sprawling mats of orange-petaled ‘ilima papa (Sida fillax), and pa’u o hi’iaka (Jacquemontia ovalifolia subsp. sandwicensis), a tiny blue-blossomed beach morning glory. Also in great profusion were succulents like the creeping ‘akulikuli (Sesuvium portulacastrum) which up until 2007 was used in phytoremediation in the Ala Wai canal on Oahu, and that favorite H-1 freeway landscaping shrub, naupaka kahakai (Scaevola sericea).

It was exciting plant-geek stuff to see the endangered 'ohai (Sesbania tomentosa) growing naturally in its wild arid enviroment. No wonder the one I planted in my wet, rainy Hilo garden developed powdery mildew and simply croaked! (A gardener’s act of hubris, I’m afraid.)

In stark contrast to this stunningly beautiful place, we also experienced firsthand the ugly reality of marine debris on Hawaii’s shores. Although this area was recently cleared of several tons of marine debris, more was already accumulating – a disturbing reminder of the tremendous amount of plastics that pollute the North Pacific Gyre off the Hawaiian Islands.

Toward the end of our trip we had a serendipitous encounter with an endemic Hawaiian monk seal, an endangered mammal, contentedly basking in a rocky cove. Fewer than 1,400 of these seals exist. This one appeared to be somewhat young, judging by its silvery gray fur. I think all of us felt our heartbeats slow while we watched it dozing. Occasionally it would half-open its eyes to gaze at us, perhaps to acknowledge our blatant gawking. Then it would peacefully shut its eyes again and drift off into a pinnaped dreamland that most certainly did not include us.

Overall, Mahana Beach can be considered one entire rare and endangered site. Sparkling green olivine sand, yellow iron oxide deposits, and sheer lava cliffs carved smoothly and gracefully by centuries of wind and water are so striking they remain in memory long after the visit. However, visitors to Mahana Beach need to be mindful of how important it is to preserve its unique features. Remember, no matter how tempting, take nothing home with you – except photos, and all of your trash.


jbfriday said...

Aloha Janice,

Another good field guide to Hawaii's coastal plants is by Mark Merlin, UH Manoa botanist and naturalist:

Merlin, M. 1999. Hawaiian Coastal Plants (4th edition). Pacific Guide Books, Honolulu, Hawai`i. 72 pp., 140 color photographs.

JB Friday

mudita said...

Thanks, JB! Also in my library is "A Guide to Hawai'i's Coastal Plants" by Michael Walther (Mutual Publishing, 2004).