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Landscaping classes coming up

March 9, 2014 - 8:18pm

The Hawaii Island Landscape Association, working with the University of Hawaii Extension Service, is holding classes for those who would like to learn about installing a new landscape or maintaining an existing one.

The series of 10 classes will cover a range of topics of interest and value for homeowners interested in gardening as well as professional landscapers and landscape workers seeking ways to improve their knowledge and service to their clients. The classes are open to the public as a series or individually and are offered from 2 to 5 p.m. Wednesdays at the Kaupulehu Interpretive Center, located north of the old Kona Village Resort.

March 26, Erin Lee, landscape director at Hualalai Resort, will review basic botany and identify about 75 groundcovers and shrubs that grow well here. I will continue with more plant identification the following week, covering additional shrubs, tropical trees and common weeds. Included in this class will be a review of herbicides that can help control weedy pests in Hawaii.

On April 9, Derek Shigematsu from the Hawaii Department of Agriculture will discuss the safe and effective use of pesticides. Ty McDonald from University of Hawaii College of Tropical Agriculture and Human Resources will discuss soil health and its importance April 16. If you want to install or maintain an existing irrigation system, Brian Burke from Grass Busters Landscape will share helpful information in his “Irrigation Basics” class April 23.

Learning to prune properly is essential for maintaining healthy, productive plants. I will review the basics of pruning and offer hands-on practice April 30 in “Pruning Tree and Shrubs.” Chris McCullough’s “Turf Care” will offer lots of information on mowing, fertilizing and maintaining healthy lawns May 7.

Valuable information on the planting, transplanting and upkeep of a healthy landscape will be offered in “Establishing and Managing a Landscape” by Keone Au from Island Greenscapes on May 14. Learning to identify pests and control insects in Hawaiian landscapes will be covered in UH’s Chris Jacobsen’s “Insect Pest ID and Control” on May 21.

The final class, “Plan Reading and Calculations,” will be of interest to homeowners as well as professionals who need to follow a landscape architect’s plans. Since ordering supplies as well as calculating pesticide and fertilizer application rates is also part of all landscaping work, a special section of this class will be devoted to math. Garrett Webb, from Kalaoa Gardens will help simplify the task.

Classes are offered to members of HILA for $35 each or $325 for the complete series. The public is invited to attend at $40 per class or $375 for the series. More information is available through Ty McDonald at the UH-CTAHR office in Kainaliu. Contact him at or 322-4884. Schedules and registration forms are available at The deadline to register is March 19.

HILA offers this series of classes annually to help homeowners and landscapers gain new information and review the basics of good landscape maintenance practices. With so few gardening and landscaping classes available in West Hawaii, you may want to take advantage of the opportunity these classes offer.

Additionally, a landscape maintenance certification test preparation intensive will be offered June 7. Information on the test and preparation are available through the contacts for Ty McDonald.

Tropical gardening helpline

Phil asks: I have been given a koa tree that is about 17 feet tall. We live at 3,500 feet elevation on the wet side of Waimea and want to know where and how to plant our new tree. What are the best conditions for growing koa trees?

Tropical Gardener answer: You are lucky to get a koa tree. The Acacia koa is endemic to Hawaii, meaning that the species originated here and nowhere else. The Hawaiian word koa means brave, bold, fearless or warrior, so you have acquired a hardy tree for your landscape. They grow quickly into lovely, large specimens so plan on giving your young tree lots of room to grow.

Your location is a good one for koa. They are native to upland forests and will do well at your elevation and enjoy the frequent rains. Since you are on the wet side of Waimea, you may want to plant the tree in a sunny spot where it will get full sun on nonrainy days. That will allow it to grow rapidly and develop an attractive shape.

Dig a hole for your new tree that is twice as wide as the pot it is in and the same depth. You want to mix native soil with about 30 percent organic matter to fill the hole once the tree is in place. Carefully plant the tree so the soil line that is established in the pot remains the same in the ground. You do not want to bury the “crown” of the plant which is right at the soil line. Be sure the tree does not sink once planted.

For the first week or two, water the tree deeply every second or third day if you have no rain. You can water less once you see new leaves appearing. Though koa can get root rot and other diseases at lower elevations, it will probably be fine with only rainwater and occasional watering during dry spells.

Because koa is a nitrogen-fixing plant, it will do fine with little fertilizing. Applying a fertilizer with low nitrogen and micronutrients two or three times a year should be plenty. You can prune your tree as you like to help it develop an appealing shape, but its natural growth habit is tall with an attractive, spreading round head. Left alone it will probably do fine. In favorable conditions your tree can grow as much as 5 feet per year.

Email plant questions to for answers by Certified Master Gardeners. Some questions will be chosen for inclusion in this column.

Diana Duff is a plant adviser, educator and consultant with an organic farm in Captain Cook.