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Landscaping and pests topple hardy mock orange

By Heidi Bornhorst

POSTED:
LAST UPDATED: 02:25 p.m. HST, Aug 05, 2011


Mock orange hedges, once the toughest thing in town, are dying; they are drying up. What's going on?

Mock orange is one of Hawaii's best drought-tolerant and attractive hedge plants. It is in the orange family, Rutaceae, and comes from driest parts of India. For years it has been "bulletproof" -- a durable and versatile plant that doesn't need much care or precious water once it's well established in the ground.

It grows slowly, and this is a positive attribute as far as landscape maintenance and garden care. It doesn't need lots of trimming and makes a perfect hedge for privacy, wind buffering and screening.

New, pretty, fresh green growth appears after a big rain, and sometimes this makes it flower as well. Mock orange flowers are fragrant, and the perfume is too strong for some sensitive people.

Mock orange is known to plant scientists as Murraya paniculata. It is also called orange Jessamine. The Hawaiian names are alahee haole and walahee haole. (Alahee is a lovely fragrant native Hawaiian plant in the gardenia family.)

The plant called mock orange on the mainland, Philadelphus, is an entirely different plant. It also has nice, fragrant flowers reminiscent of

citrus blossoms. This is why we plant scientists like Latin names; we can be sure about the exact plant.

Grow mock orange from seeds to get a strong plant. The fruit with seeds inside is red when ripe. Birds will "plant" them in your garden, and you can transplant these to a pot or the place where you want a hedge. With time they can become a 20- to 30-foot tree. Large, gorgeous old hedges carefully sculpted can be seen up in old gardens in Nuuanu Valley.

I have been seeing entire old mock orange hedges dry up and die. My clients have been asking me what is going on.

One reason is the way many gardens are now cheaply maintained. Some call it "mow, blow and go." Weedeaters might be damaging and debarking the trunks. Using a blower can blow away all the fine organic matter. You can see gardens where blowers are misused and the soil itself is being blown away. Even a tough xeric plant can take having its very "skin" chopped off only every two weeks.

The soil is also being ruined. Lawn mowers and rakes are often better tools for professional gardening. Keeping lawn grass out from under the hedge and using organic or stone mulch to keep the weeds and grass out from under your mock orange hedge is another way to sustain your garden plants. Keep 'em separated!

Overpruning or pruning with the wrong tool is also damaging. It's best to selectively trim with a sharp lopper. Mock orange wood is very hard. Cutting with a machete is not good for the plant. Let the hedges grow tall and you will have more privacy and a healthier plant.

A new pest that attacks citrus and relatives like mock orange was reported in 2006. It is the Asian citrus psyllid (ACP). Eggs are laid on new shoots and hatch into nymphs, which are green or dull

orange. The nymphs feed on the young leaves and stems, and this causes stunting and twisting.

If there are lots of nymphs, the leaves develop severe curls. The deformed leaves are ugly and also make less chlorophyll and food for the plant. The insect attacks, along with drought and poor maintenance practices, all lead to less healthy, stressed or even dead plants.

Keep your plants healthy and practice akamai, sustainable landscape practices, and tough pretty plants like mock orange will thrive in our Hawaii gardens.

Heidi Leianuenue Bornhorst is a Hawaiian horticulturist, arborist, food gardener and sustainable landscape designer. Email her at heidib@hawaii.rr.com.






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