Plant of the month: Ixora odorata

  • Pruning off some of the uprights and lower branches can make an ixora odorata shrub into a tree. (Kim and Forest Starr/Courtesy Photo)
  • Ixora odorata is well suited to being grown in containers either outside or as a houseplant. (mgonlinestore.com/Courtesy Photo)
  • Ixora odorata flowers last more than a week on the plant turning from white to cream colored as they age. (piergrossi.squarespace.com/Courtesy Photo)

Those of you looking to add fragrance to your garden might want to consider a somewhat rare species of ixora known as ixora odorata. Several ixora varieties grow well in tropical climates and are often found in Hawaiian gardens. The odorata, however, is the only one that has fragrant flowers. Odorata is a Latin word meaning perfumed and is often attached to plants that have a fragrant inflorescence like this one.

The word ixora comes from the Malabar deity, Iswara, to whom the flowers were offered. Several other species and common names define this plant. Sometimes known as ixora hookeri, this name honors Sir Joseph Dalton Hooker who was a British botanist and explorer in the early 19th century. Later, he took over his father’s job as the director of London’s Royal Botanical Garden. Since Hooker gathered plants from around the world, many of those he collected bear the name hookeri.

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A common name frequently associated with ixora odorata for unknown reasons is “jungle geranium.” Though the plant does prefer a jungle-like habitat it is not botanically related to geraniums. It is actually in the large Rubiacae family which includes around 7,000 species, several of which also have fragrant flowers, including coffee and gardenias.

This ixora is a large woody evergreen shrub native to Madagascar but now cultivated throughout the tropics. In ideal conditions it can grow to almost 20 feet and be pruned to a single stemmed tree. It is also tolerant of frequent pruning to keep it smaller. Pruning after the flowering cycle is actually recommended to maintain a desirable shape, especially when grown in a small garden or as a hedging plant.

The pollinator for odorata is not present in Hawaii, so it will not likely produce fruit with seeds. In this case, propagation from cuttings is the preferred method for producing new plants. Semi-woody cuttings dipped in rooting hormone and maintained in a moist mixture of half vermiculite and half perlite should root in a month or two. The cuttings will root best in a partial shade location.

The new plants prefer a location in either full sun or somewhat filtered light. They will also do well in partial shade, especially at lower elevations. They grow best in slightly acid soil around pH 6 with regular watering. Although they can tolerate short dry periods, moist soil that drains well to prevent standing water or soaked roots is their preference. These conditions can be achieved at lower elevations in Kona but usually occur naturally at elevations above 1,500 feet.

The older leaves of the odorata are dark green, ovate and shiny and can be up to a foot long with points at both ends. New leaves emerge in a red-orange flush and turn green as the mature. The leaves of this, as well as other ixora varieties, are particularly attractive to insects including scale, mealy bugs and aphids. These insects suck sap from the leaves and produce “honeydew” which can host a black sooty mold. Frequent treatments with a combination of Safer soap and neem oil can control these pests, however.

Maintenance of ixora odorata is fairly easy including pruning when desired, soap and oil applications when needed and fertilizing every few months with a balanced fertilizer or one that encourages blooming with a higher phosphorus content (the middle number ex: 10-15-10).

The outstanding feature of this plant is its fragrant inflorescence. The flowers appear several times a year as buds at the branch tips. They open into an umbellate cluster of white blossoms that can be up to 12 inches across with tubular flowers up to 4 inches long. The four-petaled flowers are sometimes tinged in pink and often age to a lovely cream color. Each inflorescence lasts for a week or more on the plant.

The versatility of ixora odorata adds to its appeal. It can be grown as a single specimen either in shrub or tree form. It is a great hedging plant and also a good candidate for container growing. Their fragrance can grace an outdoor location as well as a spot indoors. Because it can tolerate low light for a while it will do fine as a houseplant if occasionally moved outside in more direct sun for a short time.

Call around to local nurseries and to some big box stores to find ixora odorata. You can always check with Margo, formerly of Sunrise Nursery, to see if she can find one for you.

Hopefully, if you want to plant this uniquely fragrant ixora you can find one for your garden and enjoy many days and weeks of its sweet fragrance.

Diana Duff is a plant adviser, educator and consultant living in a dryland forest north of Kailua-Kona.

Gardening Events

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: “Hooulu 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

“Waimea Town Market” from 7:30 a.m. to noon at the Parker School in central Waimea

“Waimea Homestead Farmers Market” from 7 a.m. to noon at the Waimea Middle and Elementary School Playground

Sunday: “Pure Kona Green Market” 9 a.m. to 2 p.m. at Amy Greenwell Garden in Captain Cook

“Hamakua Harvest” 9 a.m. to 2 p.m. at Highway 19 and Mamane Street in Honokaa

Plant Advice Lines

Anytime: konamg@ctahr.hawaii.edu

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Tuesdays and Thursdays: 9 a.m. to noon at UH-CES in Kainaliu – 322-4893

Mondays and Fridays: 9 a.m. to noon at UH CES at Komohana in Hilo 981-5199 or himga@hawaii.edu