Adding some flowers to your summer garden will likely put a smile on your face. You can even brighten a partially shady spot with a small flowering shrub like the New Guinea impatiens. This impatiens offers colorful blossoms almost year-round and presents a choice of flower and leaf colors to suit your preferences.
The New Guinea impatiens (Impatiens hawkeri) is a member of the Balsaminaceae family and is native to the island of New Guinea, located just north of Australia. The first New Guinea varieties were collected during a plant exploration visit in the 1970s sponsored by the U.S. Department of Agriculture.
Though the original varieties collected in New Guinea were somewhat different from one another, they were all members of the same species. Crosses with related species from Java and the Celebes Islands have expanded the number of varieties available. Hundreds of the newly released cultivars have wide variations in flower and foliage size and color. Those available today include some that are more compact and have greater tolerance to heat and water stress. These attractive qualities have made the New Guinea impatiens very popular as potted plants as well as installed in the landscape.
Several cousins of the New Guinea impatiens are well known and often grown in Hawaii. The more common Impatiens walleriana is an herbaceous plant that is well established in areas of dependable rainfall. Though occasionally used as a bedding plant, it is extremely sensitive to direct sun and heat making it a poor choice for lower elevations in Kona.
Because it seeds profusely, it has become invasive in some areas. Impatiens sodenii is a more erect, taller plant, with bigger pale pink or white flowers. It has also become invasive. The New Guinea relative, however, is low on the invasive species list mostly because propagation is done asexually and cuttings can take up to a month to become established.
The New Guineas have flower colors that range from cool purples and lavenders to warm salmon, coral and deep red and even include several hot pink and bright orange varieties. A crisp white variety is also a stunning accent to the dark green foliage that is characteristic of many of the New Guinea varieties.
Some of the recent introductions include bicolored and variegated flowers but the color variety in the leaves adds to the interest in these new impatiens. Some varieties have deep bronze leaves while others have dramatic color combinations with white variegation, red mid ribs, green edges and purple undersides. Add that to a cacophony of bloom colors and you have a nearly full palette available in a single species.
New Guinea impatiens are useful as a colorful base under larger shrubs or trees. They also make attractive mass plantings in beds that get afternoon shade or in shaded patio containers or baskets. Some varieties can tolerate a bit of heat and dry weather and can be grown successfully in a shady location at lower elevations.
As indoor plants, New Guineas do well when placed near a window with partial sun exposure. They will thrive almost anywhere in moist soil and a shady area. Well-placed, healthy plants can reach a height and width of 18 to 24 inches.
Propagation of New Guinea impatiens is best done by collecting 4-inch cuttings with several nodes, applying rooting hormones to the cut end and placing them in a combination of moist perlite and vermiculite. They will likely establish roots and put out new leaves in about a month. At this point they can be ‘hardened off’ by placing them out into their new home for a few days before trans-planting.
Before planting out, be sure to loosen the soil and add some organic matter. Soil with a pH between 6 and 6.5 (slightly acid) will improve nutrient uptake for your plants. Putting a small amount of fertilizer high in phosphorus into the planting hole will help the roots get established.
Though good composting and mulching practices can reduce the plant’s need for fertilizers a balanced fertilizer with micronutrients can help the plants in marginal soil conditions. Do check the directions to avoid over fertilizing.
Providing shade and wind protection during hot afternoons will generally produce the healthiest and best flowering plants. Too much sun can cause pale and burnt leaves and flowers that are small and hidden in the foliage. New Guinea impatiens grow best with day temperatures of 70 to 85 degrees and night temperatures of 55 to 65 degrees. These plants also prefer soil that is consistently moist but not soggy. Avoid letting the soil dry out which can cause wilting and loss of flowers.
Adequate irrigation is best accomplished using a drip irrigation system that waters the base of the plant in the root zone rather than wetting the tops. Sprinkling the foliage from the top does not provide enough moisture to constitute proper watering when the soil is dry.
New Guinea impatiens can be kept attractive by trimming the foliage to maintain their compact bushy shape and by removing old flowers periodically. Though the plants shed their flowers, deadheading by hand can prevent the arrival of Botrytis, a fungal gray mold that can develop on old, fallen flowers.
The most common insect pests include aphids and spider mites that often appear on the underside of the leaves. Using horticultural oils and soap sprays can control these insects. Circular holes on the leaf margins or freshly chewed flower stems are evidence of caterpillar damage. Any insecticide formula containing bacillus thuringiensis will eliminate caterpillars.
Because impatiens prefer moist soil, they are occasional susceptible to fungal root and stem rots. Reducing standing moisture can avoid this problem. In severe cases, using an environmentally friendly fungicide can often successfully address these issues.
Though New Guinea impatiens may require some special attention at lower elevations in West Hawaii, the rewards of their colorful presence in shady locations will likely overshadow the extra care lowlanders might need to provide. Above 1,000 feet they should thrive and provide a lovely landscape addition with little care.
New Guinea plants are available in several local nurseries. Call around to find them. Even when small, the plants may already be covered in blooms and ready to plant out. Do install them wherever their size, shape and colors can be fully appreciated.
Gardening events
Saturdays: “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. Snacks, tools, and gloves are provided. Bring plenty of water and sun protection. Call the Garden at 323-3318 for more information.
Help is available to South Kona farmers affected by the May 22 earthquake.
Submit a Residential or Commercial Damage Report through Hawaii County Civil Defense at hawaiicounty.gov/departments/civil-defense or call Civil Defense at (808) 935-0031.
Also, through them get assistance from Vibrant Hawaii: bit.ly/vh-rfa.
Catchment tank repair at Keadin Fujii keadin.fujii@usda.gov (808) 933-8338. They reimburse 75-90%. Keep receipts. The Honaunau Rodeo gates are open daily 7am–7pm for water spigot access.
FEMA disaster assistance. Apply online at disasterassistance.gov.
American Red Cross can help with disaster needs. Local support at redcross.org/local/hawaii.
Thursday, June 11: “Market Smarter” from 1 to 4 p.m. at the Hilo Food Hub and online. Register to attend by contacting the Hub at (808) 353-5376 or anthony@hawaii commercialkitchens.com.
2026 Coffee and Orchard Crops Webinars with LIVE Q&A. If you missed his or any previous presentations you can find them on the Kona Extension YouTube channel.
Information on flooding and farm food safety: View on UH CTAHR Google Drive at tinyurl.com/3m6upwdm.
Current: “Kona typica” grafted trees available for purchase. First come, first served basis. 20 “Kona typica” grafted (on C. liberica rootstock) trees are available for $15 each.
Tissue cultured “Ito” trees available at $15 each. Contact Andrea at andreak@hawaii.edu if you are interested.
Still available: CLR Resistant Coffee Trees. Go to youtu.be/11-vtPT2jRU or call (808) 322-4892.
Continuing: Ka‘u Coffee Farm Field Day Events, in person in Ka‘u, from 11 a.m. to 1 p.m.
June 25 (R&G Farmspear tree location). Mid-season sanitation and desuckering field day.
A free event. Lunch included for registrants. Spanish translator on site. Register at www.HawaiiCoffeeEd.com/kau. Contact Matt at (808) 322-0164 with questions.
Ungoing: Tuesdays through April 2027: “E Ulu Kakou” on Zoom at 5:30 p.m. Register at go.hawaii.edu/iR3. Recorded on YouTube channel go.hawaii.edu/KKi. Questions at ugc@hawaii.edu or call for full schedule (808) 453-6050.
Save the date: June 14-20, 17th Annual Ka‘u Coffee Festival. Go to KauCoffeeFestival.com for more information.
Farmer direct markets
Wednesday: Ho‘oulu Farmers Market at Sheraton Kona Resort and Spa at Keauhou Bay.
Saturday: Keauhou Farmers Market, 8 a.m. to noon at Keauhou Shopping Center. Information on their online market at keauhoufarmersmarket.com/onlinemarket.
Kamuela Farmer’s Market, 7:30 a.m. to noon at Pukalani Stables.
Waimea Town Market, 7:30 a.m. to noon at the Parker School in central Waimea.
Waimea Homestead Farmers Market, 7:30 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 Hwy 19 and Mamane Street in Honoka‘a.
Plant advice lines
Anytime: konamg@hawaii.edu
Tuesdays and Thursdays: 9 a.m. to noon at UH-CES in Kainaliu, (808) 322-4893. Or walk in Mondays, Tuesdays and Fridays 9 a.m. to noon at UH CES at Konohana in Hilo, (808) 981-5199.
Diana Duff is a plant adviser, educator and consultant living on Oahu and working part time in Kona.
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