Jason asks: When the buds on my standard gardenia plant are about ready to open, they start to turn brown and many of them drop on the ground. What can I do to keep the blooms white, on the plant and encourage them to open?
Tropical Gardener answer: The problem you describe is often referred to as “bud drop” and can have several causes. The main cause for bud drop is usually inadequate sunlight. Another causal factor is overhead watering or rain that continually wets the developing buds. When buds that are ready to open get wet from frequent overhead water or rain, the white petals can turn brown and, in some cases drop onto the ground. Temperature variations can also cause bud drop. Maintaining a uniform temperature of 60-70 degrees with adequate sunlight and humid (not wet) air can reduce the frequency of bud drop.
Soil conditions that are less than ideal can also be a cause for buds to drop. Gardenias grow and flower best in soil that gets regular water and is more acid than alkaline. A pH below 6.5 is ideal. In alkaline soil conditions (above pH 7.0) gardenias will not thrive. If you are not sure of your soil pH, consider doing a soil test. Go to http://www.ctahr.hawaii.edu/oc/freepubs/pdf/SCM-9.pdf for information on soil testing and a form to fill out and submit with your sample. Call the UH Extension Service in Kainaliu (322-4892) for drop off times.
Areas at lower elevations, with low rainfall or cinder soil, are likely to be alkaline with pH readings of 7.0 or greater. You can acidify alkaline soil over time by adding organic matter such as compost (especially coffee grounds) to the root zone. Mulching with peat moss, shredded coconut material, decomposed saw dust or well-aged macnut hulls can also help acidify the soil. Introducing gypsum or elemental sulfur may achieve quicker results. A monthly application of one ounce of iron sulfate to two gallons of water will also work quickly. Sulfate fertilizers like ammonium sulfate as well as acidic fertilizers like ammonium nitrate, ammonium phosphate or urea can also help when used in moderation. Several commercial fertilizers for acid-loving plants are also available. Be sure to follow all application directions to avoid over doing, which is not desirable.
A bud mite infestation can also be a cause of bud drop. These mites are too tiny to see without magnification but will feed on gardenia buds. They can be treated with a pesticide containing carbaryl, like Sevin, but this should be applied in the evening when bees aren’t active. Another alternative is to remove the current buds, as the mites will probably move on once their food source is gone.
Check your plant to see if any of these issues may be the cause of bud drop and proceed with the recommended solutions.
Some questions that appear here were originally directed to Kona’s Certified Master Gardeners. You may contact them with questions at konamg@ctahr.hawaii.edu.
Diana Duff is a plant adviser, educator and consultant living on an organic farm in Captain Cook.
Gardening Events
Monday: “Hawaii Tropical Fruit Growers Meeting,” 7-9 p.m. at 81-6393 Mamalahoa Highway in Kealakekua. White wooden building on makai side across from the Department of Transportation yard. The topic will be propagation and members are asked to share their experiences with seeds, cuttings, air layers and grafting. Park in front or on the north side. For more information contact Brian Lievens at 895-8753 or greenwizard@hawaii.rr.com.
Wednesday: “Lease &Fee Simple Farming,” 4-6 p.m. at UH CTAHR Cooperative Extension Service office (across from the Aloha Theatre in Kainaliu). Information on buying, selling and managing Kona Farms sponsored by FarmWorks Hawaii. Free event with refreshments. For more information call 328-3441 or go to www.farmworkshawaii.com.
Saturday: “Waiwai Weekend: Supporting Local Food Security,” 2:30-6:30 pm at Kohala Center’s Ainahoi at Keawewai on Kohala Mountain Road with presentations by Nancy Redfeather, Jerry Konanui and Dr. Albie Miles. Cost is $75, which includes presentations, site tours, pupu, two drinks, T-shirt and gifts. Call 887-6411 or go to www.kohalacenter.org (events) for more information or register at http://koha.la/ww2 and get directions.
“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. 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
Wednesday: “Sunset Farmers Market,” 2 p.m. to sunset at the north makai corner of the Kmart parking lot.
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: “South Kona Green Market,” 9 a.m. to 2 p.m. at Amy Greenwell Garden in Captain Cook
Tuesday through Saturday: “U-Pick greens and produce,” 10a.m. to 4p.m. Tropical Edibles Nursery, Captain Cook.
Plant Advice Lines
Anytime: konamg@ctahr.hawaii.edu
Tuesday and Thursday: 9 a.m. to noon at UH-CES in Kainaliu, 322-4892
Monday, Tuesday and Friday: 9 a.m. to noon at UH-CES at Komohana in Hilo, 981-5199 or himga@hawaii.edu