Michelle asks: A new road has opened up at the edge of our property near the ocean. Are there any plants we can install that will deaden some of the traffic sound?
Tropical Gardener Answer: The best noise barrier, of course, is a rock wall. A wooden fence can also help especially if you put plants inside, outside or both in addition to the fence. Carefully selected noise buffer trees and shrubs can reduce noise by as much as 50 percent. Plant them close to the noise for the best results.
Probably the best noise-deadening plant is banana. Planting these is like putting in a wall of water. They absorb or deflect a lot of noise. You would probably want to provide irrigation to be sure they grow large and fast. As they grow you may also want to install a thick understory just in front of them that will fill in below and between them. The good news is that you’ll also have fruit to eat. Cut down the tree when you harvest. Keiki will grow from the parent corm.
Another “wall of water” plant is cactus. A supportive fence with the water-heavy, night-blooming cereus or pitahaya (dragon fruit) growing on it can work as well as the stand alone prickly pear cactus or the saguaro (tree-like) variety. The thorns on these plants can also protect your border from intruders. Add the low-growing carissa for more thorns and a full shrub understory. Some of these plants will also provide interesting edibles.
Though we often imagine that bamboo might help deflect noise, it must be planted very thickly to be effective. Only consider clumping varieties. Other standard hedging plants that can produce a thick wall of leaves include panax, privet and podocarpus. All would need to be pruned to keep them shaped into an attractive hedge.
Plants in the Cupressaceae (cypress) family are often recommended as noise barriers since they are evergreens and do not lose leaves. This family includes cedars, junipers and arborvitae. Most of them have dense foliage that can block lots of noise, though they vary somewhat in growth habit and leaf appearance. The supine shore juniper (Juniperus procumbens) is a good understory plant for a noise barrier planting. The taller cultivar “Pfitzeriana,” as well as the Hollywood juniper, are also worth considering.
The Italian cypress can be very effective at noise reduction, when planted closely. It will grow quite tall and has a somewhat narrow footprint. The Monterrey cypress is also a good choice with a shorter and broader growth habit.
In order to block out sound, you will need to put the plants closer than you might otherwise. In your selection, do be careful not to plant an invasive species. You can find a partial list of invasives at https://en.wikipedia.org/wiki/List_of_invasive_plant_species_in_Hawaii.
Email plant questions to konamg@ctahr.hawaii.edu for answers by Certified Master Gardeners. Some questions will be chosen for inclusion in this column.
Gardening Events
“Work Day at Amy Greenwell Garden,” 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.
The Kohala Center classes I mentioned in last week’s column are all full at this point. You can, however, go to koha.la.fsaworkshops or contact Hanna Bree at 887-6411 or at hbree@kohalcenter.org to get more information or on the waiting list.
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
Friday: “Pure Kona Market,” 9 a.m. to 5 p.m. at Amy Greenwell Garden in Captain Cook
Saturday: “Keauhou Farmers Market,” 8 a.m. to noon at Keauhou Shopping Center
“Kamuela Farmer’s Market,” 7 a.m. to noon at Pukalani Stables
Sunday: “Pure Kona Green Market,” 9 a.m. to 2 p.m. at Amy Greenwell Garden in Captain Cook
Tuesday–Saturday: “U-Pick greens and produce,” 10 a.m. to 4 p.m. at 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
Mondays, Tuesdays &Fridays: 9 a.m. to noon at UH-CES at Komohana in Hilo, 981-5199 or himga@hawaii.edu