Hawai'i gardeners are going wild for the Thai hybrid crown of thorns. They are less thirsty and bloom for months. I'm happy to report that there will be quite a few of them for sale at the 19th annual Open House and Unthirsty Plant Sale at the Halawa Xeriscape Garden.

Inez Brunson of the Cactus and Succulent Society shared some great info about the crown of thorns plant: It's native to Madagascar, and more than 2,000 distinct varieties have been created and cultivated over the past 30 years. These hybrids, called poysean, were developed in Thailand.

It's a good-luck plant to most in Thailand. Poysean is a combination of two Chinese words meaning "eight saints." The eight legendary saints sacrificed all of their gold, assets, intelligence and spirit to promote righteousness and justice. By honoring the eight saints, one will be granted good luck in accordance with the specific mythic power of each of the saints: health, bravery, wealth, beauty, artistry, cleverness, poetry and victory over evil spirits.

It's believed that the more flowers there are in a cluster, the more luck the grower will receive. Initially, the ultimate goal of a grower was to get eight flowers on a plant. Now, as many as 132 "blossoms" per plant may be seen on several varieties.

Their popularity has also grown because they are thought to resemble the crown of thorns that tradition says was placed upon Jesus' head. The beautiful large flowers can appear continuously throughout the year with relatively little care.

Propagation is mainly by cuttings, as seedlings tend to not look like the parents. A very small percentage produce desirable flowers. The number of viable seeds produced is extremely limited — about three seeds per "flower." Scions of popular cultivars also are grafted onto more common rootstocks.

Environment-friendly, these plants are unlikely to escape into the wild and become rampant weeds.

The "flower" is not really a flower. It's an inflorescence, botanically called a cyathium. There is one pistillate (female) flower surrounded by three tiny staminate (male) flowers. Each of the staminate flowers consists of a single stamen. Glands surround the flower. Around the flowers and glands are two colorful bracts, or cyathophylls that look like they should be petals.

The well-developed bracts of Thai hybrids are much larger than those of earlier crown of thorns and come in an endless array of color combinations. They can last up to three months. Sun and temperature affect the colors, and some changes are observed as the "flowers" develop.

Crown of thorns is a good plant to choose for water conservation and ease of maintenance. Attractive and compact growers, they come in a wide range of colors for xeriscaping. They are a salt- and drought-tolerant ground cover. The thick, fleshy leaves and stems have evolved for water storage, and they can share areas with other plants that have similar growing requirements. Infrequent watering and virtually full sun will do for them, while bright, filtered light indoors stimulates flower production and is less harsh to the leaves. Strong sunlight promotes an abundance of flowers but will burn the leaves if they are not accustomed to it, and if heat is high and humidity is too low for prolonged periods.

Poysean, like many dry-climate plants, needs good drainage. If a chosen site in the garden does not drain well, a 12- to 18-inch raised bed of crushed rock and sandy soil may be made. Sandy, gritty soil combined with added organic material like compost is an ideal medium for these bedding plants. Space individual plants well apart for good air circulation. They may be watered regularly if growing media and pots drain freely.

Once established, crown of thorns can go without frequent watering. The top inch of soil may be allowed to dry out. Water pots until you see water drain out the bottom. They will survive drought, although they will drop their leaves under extreme dry conditions and recover when conditions are better. Pesticides are not needed to keep these plants attractive and healthy, but remove caterpillars, as they are voracious eaters and can kill the plants.

Apply balanced slow-release fertilizer every six months. Remove dead and yellowing leaves and flowers to prevent fungal rot in wet conditions. Debris that's allowed to remain on a plant can trap moisture and encourage the development of bacterial and fungal leaf spots, and stem and root rot. Check and keep plants clean during prolonged rainy weather.

PLANT DEALS IN HALAWA

A variety of drought-tolerant and native Hawaiian plants will be available at moderate prices at the annual open house and plant sale hosted by the Friends of Halawa Xeriscape Garden and more than 10 local nurseries and growers Aug. 4. Proceeds support educational programs and classes at the garden.

The open house includes a full day of free activities, including workshops and classes by garden and landscaping experts, tours of the three-acre demonstration garden and a free mulch giveaway (visitors must bring their own bags).

"Water for Life — Ka Wai Ola" is the message of the Honolulu Board of Water Supply, and is something we can all take to heart and put into practice in our gardens. We can all kokua by learning and understanding how we can preserve O'ahu's water supply through wise water use in our gardens. Plus, xeriscaping can save you money. An estimated 50 percent of water consumption in the average single-family home is used outdoors. Xeriscaping offers an ideal way to use 30 percent to 80 percent less water and includes growing native Hawaiian plants, and less-thirsty kama'aina plants as well as succulents and cactus. There are all kinds of drought-tolerant plants available to us.