CAPTAIN COOK — In Hawaii where greenery surrounds us all year, variations in the shade of green can add interest to a landscape, especially when the plant is attractive in its own right. The silver buttonwood tree is one you might consider for its appealing growth habit and shapely trunk as well as the addition of a silvery green color to your garden’s palette.
This lovely plant is a member of the Combretaceae family which includes 20 genera and over 500 species. It is one of the two species in the Conocarpus (white mangrove) genera. One has dark green leaves and the other has silvery foliage. The two trees have the same botanical name, Conocarpus erectus, but some botanists refer to the silver form as a separate variety, Conocarpus erectus var. sericeus. As mangrove trees, they often grow along shorelines in tropical and subtropical areas of the world. They adapt well to harsh coastal conditions that often include salt water immersion in water logged mud as well as occasional heavy wave action. Mangroves are valuable trees as they protect coastal areas from erosion and from storm surges during hurricanes and tsunamis. Though silver buttonwoods are actually native to tropical America and the West Indies, they are considered a native and grow throughout Florida. They now grow up and down the Pacific and Atlantic coasts of tropical South America, throughout the Caribbean, in Melanesia and Polynesia and in some tropical parts of western Africa. Though they often grow close to the shore, they can be found now in wooded areas and private landscapes further up slope.
In 1946, Otto Degener brought seeds of the silver buttonwood to Hawaii from Nassau. The first trees grew in his beach garden at Mokule’ia on Oahu and spread from there. They are now growing throughout the Hawaiian Islands where they are used as street trees, windbreaks, hedges, container and bonsai plants as well as landscape specimens.
Silver buttonwood trees have many features to recommend them for West Hawaii landscapes. They grow at a moderate rate and, in cultivation, usually determine at about 20 feet. They can be used as wind breaks as well as providing light shade. In addition to their salt and wind tolerance, they can also tolerate a variety of soil conditions including sandy or nutrient poor soil. The trees also have several physical features to recommend them. As they age, their smooth gray bark becomes rough and furrowed and their twisting trunks become almost sinuous in appearance. The dark trunk then serves as a striking contrast to the soft silvery foliage of the canopy. The leaves of the silver variety are covered with tiny hairs that create the silvery green appearance. The hairs also serve to hold moisture so the tree can survive dry times.
The buttonwood name is obviously derived from the appearance of the flowers and fruit. The small button-like flowers appear, nearly fifty at a time, on long panicles. They develop into reddish-brown woody cones that contain the seeds. When fully ripe, the heads will burst, dispersing the seeds.
Though the green buttonwood can be easily propagated from seed the silver variety does not grow true to seed and should be propagated vegetatively. Woody cuttings of about four inches will usually root within a month in a mix of moist vermiculite and perlite. Once the cuttings have rooted and started to put out new leaves, you can plant them in a larger pot filled with soil and fertilize the tree lightly. Choose a sunny or partly sunny spot for your new tree once it is at least a foot tall. Trees can be kept in large pots for a year or more giving them time to take on a form and allowing you a chance to do some trimming. Silver buttonwoods have an attractive natural growth habit but can also be lightly pruned to determine height and shape.
When planting your tree, be sure to dig a hole twice as large as the pot it is in and the same depth. Fill the hole with native soil as well as some organic matter to increase healthy microbial activity. Insure that the crown of the plant (at the soil line) is not buried in the planting process. You can create a berm around the plant at the drip line to hold water in the root zone as the plant adapts to its new surroundings. A little top mulching within the berm can help hold moisture and keep competing weeds at bay.
Though silver buttonwoods have almost no pest or disease problems, you will want to monitor your young trees regularly to catch any issues before they become serious. The fun part is to watch the interesting shape that develops as the tree grows and to enjoy the beauty the soft silver green foliage adds to your landscape. Increase the pleasure, plant a few.
Though the silver variety of Conocarpus erectus is somewhat hard to find, Janice at Keauhou Gardens and Irrigation may be able to help. You can find contact information for her on their website: www.keauhougardens.net.
Diana Duff is a plant adviser, educator and consultant living on a farm in Captain Cook.
Gardening Events
Wednesday: “Little Fire Ant Control” from 5:30 to 8 p.m. at the UH Extension Office in Kealakekua. The Little Fire Ant (LFA) workshops instruct on ant control and offer vouchers to reduce the cost of ant bait and spreaders to those who complete the workshop led by the Hawaii Ant Lab. Free. Class size is limited and registration is required. For more information, visit http://www.hawaiicounty.gov/rd-agriculture. To register for one of the Kona Workshops go to http://bit.ly/2eYWIvx .
Saturday: “Work Day at Amy Greenwell Garden” from 9 a.m. to 12:30 p.m. Meet at the Garden Visitor Center across from the Manago Hotel in Captain Cook. Volunteers will be able to help with garden maintenance and are invited to bring a brown bag lunch. Water and snacks provided. Call Peter at 323-3318 for more information.
Farmer Direct Markets
Wednesday: “Sunset Farmers Market” 2 p.m. to sunset at the north makai corner of the Kmart parking lot.
Wednesday & Friday: “Ho’oulu Farmers Market” 9 a.m. to 2 p.m. at Sheraton Kona Resort & Spa at Keauhou Bay
Saturday: “Keauhou Farmers Market” 8 a.m. to noon at Keauhou Shopping Center
“Kamuela Farmer’s Market” from 7 a.m. to noon at Pukalani Stables
Friday & Sunday: “South Kona Green Market” 9 a.m. – 2 p.m. at Amy Greenwell Garden in Captain Cook
Tuesday–Saturday: “U-Pick greens and produce” 10a.m. to 4p.m. Tropical Edibles Nursery, Captain Cook.
Plant Advice Lines
Anytime: konamg@ctahr.hawaii.edu
Tuesdays & Thursdays: 9 a.m. to noon at UH-CES in Kainaliu – 322-4892
Mon., Tues. & Fri: 9 a.m. to noon at UH CES at Komohana in Hilo 981-5199 or himga@hawaii.edu