Many of us who live in Hawai'i have postage-stamp-sized house lots that limit us to growing smaller trees and shrubs.

One of the reasons a botanical garden is special is that it provides a place to nurture trees that are not only unique, but huge!

Take, for example, the kapok tree. Foster Botanical Garden is home to two of the massive giants, which are about 75 feet tall. In their native range, from tropical Central to South America, they can grow to 200 feet or more.

According to plant records, the garden's trees were planted by Dr. William Hillebrand, a distinguished botanist and physician, between 1850 and 1871, making the trees around 150 years old. Due to their age and historical significance, the kapok are designated as "Exceptional Trees," two of 24 such trees at Foster Garden.

If you visit the garden now, you would find that the trees have dropped their leaves (they're deciduous). However, small flower buds are beginning to develop and will soon produce half-inch-long, pinkish-white flowers, followed by oblong, dark brown, dry fruits.

During April and May, mature fruits, woody capsules up to 6 inches long by 3 inches wide, create quite a stir. The dry fruits often break apart while still on the tree. The capsule parts quickly fall to the ground, but clouds of tan-colored hairs (floss) containing small, dark brown seeds can be seen floating in the air throughout the garden and beyond.

Visiting school kids love playing with the soft, silky floss, which lands everywhere. It's a little like playing in snow, Hawaiian style.

The floss that lines the seed capsules is actually individual hollow hairs that are coated with a waxy layer called cutin. The hairs are very light in weight and water-resistant. In the past, the floss was used as filler for mattresses, pillows, upholstery and life preservers. Today, kapok has been replaced commercially by synthetic materials.

Kapok trees have impressive fin-like projections, or buttress roots, at the base of the trunk. They are thought to provide increased stability in areas of high rainfall and wind, but school kids seem to think they are the ideal place to play hide-and-seek.

The two trees at the garden usually mirror each other's growth habits, dropping their leaves, flowering and fruiting at the same time. Sometimes, however, one tree will have a full crown of lush green leaves, while the kapok growing close by is completely leafless. Go figure.

Winnie Singeo is director of the Honolulu botanical gardens. Reach her at hbg@honolulu.gov or 522-7060.