Dahlias bring vibrant color and unique forms to any garden space, and the ‘Kona’ dahlia stands out. This captivating plant offers a stunning visual display, making it a favored choice for adding dramatic flair to landscapes. Its striking appearance and prolific blooming habit transform garden beds into lively showcases of floral beauty.
What is a Kona Dahlia
The ‘Kona’ dahlia is a distinctive cultivar with tightly formed, ball-shaped blooms. These flowers typically exhibit a cool white or buttery cream color. Individual blooms generally measure between 4 to 6 centimeters across, showcasing a dense, intricate petal arrangement. While some sources describe it as a ball dahlia, others refer to it as a pompon type, both indicating its characteristic spherical and compact flower structure.
Mature sizes vary, from 50 centimeters (20 inches) to 1.8 meters (6 feet) tall. Its growth habit is more “shrub-like” than some other dahlia varieties, producing numerous elegant stems throughout the blooming season. ‘Kona’ dahlias are known for their abundant flowering, consistently producing blooms from July through November, making them a productive addition to garden beds or cutting gardens.
Planting Kona Dahlias
Successful cultivation of ‘Kona’ dahlias begins with proper planting, considering timing, location, and soil conditions. Plant tubers outdoors in early spring, after the last frost has passed and when the soil temperature consistently remains above 15°C (60°F). Planting too early in cold, wet soil can lead to tuber rot.
Selecting an appropriate site is important for healthy growth and abundant blooms. ‘Kona’ dahlias thrive in full sun, requiring at least 6 to 8 hours of direct sunlight daily. The soil should be well-draining, loamy, and rich in organic matter. Amending heavy clay soils with compost, peat moss, or sand can improve drainage and fertility, ensuring tubers do not sit in waterlogged conditions. A neutral soil pH of 6.5 to 7.0 is suitable.
When planting tubers, dig a hole 10 to 20 centimeters (4 to 8 inches) deep, wide enough to accommodate the tuber. Place the tuber horizontally with the “eye” or sprout facing upwards, then gently backfill the hole with soil. Space tubers 30 to 45 centimeters (12 to 18 inches) apart to allow for adequate air circulation and growth. After planting, avoid immediate watering unless the soil is exceptionally dry, as too much moisture before sprouts emerge can encourage tuber rot. For taller varieties, install stakes at planting to provide support as the plant grows, preventing damage to the tuber later on.
Caring for Kona Dahlias
Ongoing care is important for ‘Kona’ dahlias to ensure continuous blooming and plant vigor. Once established and visible above ground, consistent and deep watering becomes necessary. Dahlias benefit from receiving about 2.5 centimeters (1 inch) of water per week, with deep watering of 20 to 25 centimeters (8 to 10 inches) reaching the tuber roots. Water 3 to 4 times a week during dry spells, or more frequently in hot weather, using soaker hoses or drip irrigation to deliver water directly to the soil and minimize foliar moisture. For dahlias in containers, watering may be required once or twice daily, as container soil dries out more quickly.
Fertilizing plays a significant role in supporting abundant growth and flowering of ‘Kona’ dahlias. These plants are heavy feeders, benefiting from a low-nitrogen fertilizer that is high in potassium and phosphorus. A balanced fertilizer can be used early in the season, switching to a blend like 5-10-10 or 10-20-20 about 30 days after planting, and then reapplying every 3 to 4 weeks for in-ground plants or every 2 to 3 weeks for container-grown dahlias. This nutrient balance promotes prolific blooming rather than excessive leafy growth.
Regular deadheading, the removal of spent blooms, encourages continuous flowering and maintains the plant’s appearance. When a flower fades, cut the stem just above a leaf node or where it joins a main stem. This action redirects the plant’s energy from seed production back into creating more flowers. ‘Kona’ dahlias also benefit from pinching when about 25 to 30 centimeters (10 to 12 inches) tall; removing the central growth tip encourages branching, resulting in a bushier plant with more blooms.
Dahlias are susceptible to pests and diseases, requiring proactive management. Common insect pests include aphids, slugs, snails, spider mites, earwigs, and caterpillars. Aphids can be managed with neem oil or insecticidal soap, while slugs and snails may be deterred by copper barriers or traps.
Diseases such as powdery mildew and botrytis (gray mold) can occur, especially in humid conditions. Good air circulation through proper spacing and removing affected plant parts helps prevent these issues. Maintaining overall plant health through appropriate watering and feeding also enhances the dahlia’s natural resistance.
Overwintering Kona Dahlias
In regions with cold winters, particularly USDA Zones 7 and below, ‘Kona’ dahlias are not winter-hardy; their tubers require protection. Overwintering involves digging up tubers before the ground freezes, typically 10 to 14 days after the first hard frost blackens the foliage. This waiting period allows tubers to “set eyes” for next season’s growth and toughen their skin for storage. It is important to dig them up before a severe freeze, as frozen tubers will not be viable.
Cut dahlia stalks down to 10 centimeters (4 inches) from the ground. Carefully loosen the soil around the tuber clump using a pitchfork, taking care not to damage the delicate tubers. Gently lift the entire clump from the soil. After digging, brush off any excess soil from the tubers; some gardeners prefer not to wash them unless the soil is particularly heavy clay, as leaving some dirt can help with moisture retention during storage.
Once cleaned, tubers need to be cured for a few days to two weeks in a cool, dark location out of direct sunlight, often by turning them upside down to allow excess moisture to drain from hollow stems. This curing process helps to toughen the skin, preparing them for dormancy. After curing, store tubers in a cool, dark place where temperatures remain consistently between 4°C and 10°C (38°F and 50°F). The storage area should also have a relative humidity of 75% to 85% to prevent the tubers from shriveling or rotting.
Tubers can be stored in various mediums such as peat moss, vermiculite, or shredded paper, placed in ventilated cardboard boxes, plastic crates, or large paper bags. Ensure that tubers are not touching each other directly if using a medium. Periodically check the stored tubers throughout the winter for any signs of mold, rot, or excessive drying, making adjustments to humidity or ventilation as needed. Gardeners in warmer climates (USDA Zone 8 and above) can often leave their dahlia tubers in the ground year-round, as the soil provides sufficient insulation. Even in Zone 7, some success can be achieved by leaving them in the ground with a thick layer of mulch, though indoor storage is generally more reliable.