The ‘Rhubarb and Custard’ dahlia is known for its unique yellow and red or pink blooms, which inspired its name. This dahlia variety is popular among gardeners.
Getting to Know the Rhubarb and Custard Dahlia
The ‘Rhubarb and Custard’ dahlia is a collarette type, with a distinctive bloom structure. Its flowers measure 4 to 6 inches in diameter, featuring a single outer row of broad, rounded petals. These outer petals are pale peach, transitioning to a deep purple-red at their base. An inner collar of shorter, narrower white or blush-pink petals surrounds a bright yellow central disc.
This dahlia forms a compact, bushy plant, reaching 27 to 36 inches (70-90 cm) tall with a spread of 20 to 24 inches (50-60 cm). Sturdy, upright stems support abundant blooms from mid-summer until the first frost. Its unique petal arrangement and bicoloration make ‘Rhubarb and Custard’ a standout variety.
Planting and Growing Rhubarb and Custard Dahlias
‘Rhubarb and Custard’ dahlias thrive in full sun, needing at least six to eight hours of direct sunlight daily for abundant blooms. A location protected from strong winds is also beneficial.
Well-draining soil is important for dahlias, as they are susceptible to root rot in waterlogged conditions. An ideal soil pH ranges from 6.0 to 7.0. Prepare the soil by incorporating organic matter like compost or aged manure to improve drainage and fertility, loosening it to a depth of at least 12 inches for tuber expansion.
Plant dahlia tubers in spring, after the last frost and when soil temperature warms to at least 60°F (15°C). Plant tubers 3 to 4 inches deep with the “eye” facing upwards. Space tubers 18 to 24 inches apart for proper airflow and spread. After planting, water thoroughly to settle the soil, but avoid overwatering until sprouts emerge to prevent rot.
Ongoing Care and Maintenance
Consistent watering is important for ‘Rhubarb and Custard’ dahlias, ensuring the soil remains evenly moist but not waterlogged. Deep watering one to two times per week is sufficient, though more frequent watering may be necessary in hot climates or for container-grown plants. Mulching helps retain soil moisture and regulate temperature.
For bloom production, dahlias benefit from regular fertilization with a low-nitrogen formula higher in phosphorus and potassium, such as a 5-10-10 or 10-20-20 NPK ratio. Apply fertilizer about 30 days after planting, or when new shoots are 3-4 inches tall, and continue every three to four weeks throughout the growing season. Over-fertilization, especially with high nitrogen, can lead to excessive foliage growth at the expense of flowers and may weaken tubers.
As dahlias grow, their sturdy stems may benefit from staking to provide support and prevent breakage from wind or heavy blooms. Deadheading, the removal of spent blooms, encourages the plant to produce more flowers. In colder climates, dahlia tubers are not winter-hardy and must be lifted from the ground before the first hard frost. After digging them up, clean off excess soil, air dry for a day or two, and store in a cool, dark, humid place between 40°F and 50°F (4°C and 10°C) to prevent drying out and rot.
Troubleshooting Common Dahlia Issues
Pests like aphids, slugs, earwigs, and spider mites can affect ‘Rhubarb and Custard’ dahlias. Aphids and spider mites cause distorted or yellowed leaves. Organic insecticidal soaps or horticultural oils control these pests, while physical removal or traps work for slugs and snails.
Dahlias are susceptible to diseases like powdery mildew and botrytis (grey mold). Powdery mildew appears as a white coating on leaves. Botrytis causes dark, fuzzy mold on buds and stems. Good air circulation, avoiding late-day overhead watering, and removing affected plant parts help manage these fungal issues.
Lack of blooms or poor growth can stem from several factors. Insufficient sunlight is a common cause, as dahlias require ample sun to flower. Improper watering, nutrient deficiencies, or too much nitrogen fertilizer can also hinder growth. Adjusting light exposure, watering, and fertilizer application can resolve these issues.
Displaying and Enjoying Your Dahlias
The ‘Rhubarb and Custard’ dahlia makes an excellent cut flower. For longer vase life, cut blooms in the early morning or late evening when fully open. Use sharp pruners for clean cuts, leaving long stems, and immediately place them into cool water.
These dahlias integrate well into garden designs. They are suited for planting in garden beds and borders, where their height and colors create focal points. Their compact size also makes them suitable for large containers. Complementary plants with contrasting textures or colors, such as ornamental grasses or annuals in shades of cream, deep red, or soft orange, enhance their appeal.