Dahlias are celebrated for their diverse forms and vibrant colors, bringing striking beauty to gardens from midsummer until the first frost. The ‘Hemisphere’ dahlia stands out among cultivars with its unique coloration and elegant bloom structure, enhancing any landscape.
Understanding the Hemisphere Dahlia
The ‘Hemisphere’ dahlia is recognized for its double, water lily-shaped flowers that present a captivating blend of colors. Its petals typically feature a white base overlaid with reddish-pink or magenta, often displaying delicate white veins and pinkish-red edges on the inner petals.
Individual blooms generally measure between 3 to 5.5 inches across. The plants grow to a height of approximately 3 to 4 feet, creating a notable vertical element in garden beds. They bloom continuously from July through autumn.
Planting and Growing Hemisphere Dahlias
Plant ‘Hemisphere’ dahlias in locations that receive at least six hours of direct sunlight daily. While they can tolerate some partial shade, bloom production might be less prolific.
The soil should have good drainage and a rich, humus-filled composition. Amend the planting area with compost or well-rotted manure to improve soil structure and fertility. Plant after the last spring frost, when soil temperature consistently reaches 60 to 65 degrees Fahrenheit.
Dig a hole 4 to 6 inches deep and place the tuber horizontally, with the growing eye facing upwards. Cover the tuber with a few inches of soil. Space tubers 18 to 24 inches apart for proper air circulation and growth, which helps prevent disease. After planting, avoid watering until green shoots emerge, as excessive moisture before sprouting can lead to tuber rot.
Ongoing Care for Hemisphere Dahlias
Once ‘Hemisphere’ dahlias emerge, consistent watering is important, especially during dry periods. Deep water two to three times a week, ensuring moisture reaches 8 to 10 inches deep. This encourages deep root development. Apply water directly to the soil surface, rather than overhead, to help prevent foliar diseases.
Regular fertilization supports vigorous growth and prolific blooming. Apply a balanced, low-nitrogen fertilizer periodically throughout the growing season, about once a month. As plants mature and set buds, switch to a fertilizer higher in phosphorus and potassium for more abundant blooms. Removing spent flowers, known as deadheading, redirects the plant’s energy to new blooms, extending the flowering period.
Due to their height, ‘Hemisphere’ dahlias require staking to support their stems and heavy blooms. Place stakes, such as bamboo or metal rods, near the tuber at planting time to avoid damage. Tie growing stems to these supports as the plant gains height. Good air circulation also helps deter common fungal issues like powdery mildew.
Winterizing and Storing Hemisphere Dahlias
In regions with freezing winters, ‘Hemisphere’ dahlia tubers must be lifted and stored indoors. Begin this process after the first hard frost, when the foliage blackens, signaling dormancy. Cut stems back to 4 to 6 inches above ground, then gently dig around the plant to lift the entire tuber clump.
After lifting, remove as much soil as possible. Some gardeners rinse tubers with water, being careful not to damage the skin. Tubers require a drying period of several days to a few weeks in a cool, well-ventilated area to cure and prevent rot. Once dried, store them in a cool, dark, dry location where temperatures remain consistently between 40 and 50 degrees Fahrenheit.
Store tubers in breathable containers like cardboard boxes, mesh bags, or crates for good ventilation. Packing them in peat moss, sawdust, wood shavings, or vermiculite helps maintain optimal humidity and prevents desiccation or excessive moisture. Periodically check stored tubers throughout winter for signs of rot or shriveling, removing affected ones to prevent spread.
Propagating Hemisphere Dahlias
Propagating ‘Hemisphere’ dahlias is most commonly achieved through tuber division, which increases plant stock and can improve vigor. The best time for division is early spring, just before planting, as the “eyes” or growth points become more visible. While fall division is possible, spring often makes identifying viable sections easier.
Each division must include a section of the “crown” (the base of the old stem) with at least one visible eye and an intact tuber. The tuber provides the necessary stored energy for the new plant. Use a sharp, clean knife or pruners to separate the tubers, ensuring each piece has these components. Discard any tubers that are soft, show signs of rot, have a broken neck, or lack an eye.