‘Rancho Dahlia’ is a popular cultivar, known for its captivating appearance that enhances various garden settings, including borders, garden beds, and patio containers. As a tender perennial, it offers a burst of vibrant color from summer until the first frost. This dahlia distinguishes itself with a waterlily-type flower form, featuring fully double, open-faced blooms. These flowers display a lustrous apricot-yellow hue, often blending into warm shades of orange, and typically measure 4 to 6 inches (10 to 15 cm) across. The plant generally reaches a mature height of about 4 feet (90 to 120 cm), with an upright, bushy growth habit. This combination makes ‘Rancho Dahlia’ a stunning focal point or a beautiful cut flower.
Growing Rancho Dahlia Successfully
Planting and Soil
Plant ‘Rancho Dahlia’ tubers after the last spring frost, when soil temperatures have warmed to at least 60°F (15°C), typically from April to June. Choose a location that receives full sun for six to eight hours daily, though the plant can tolerate some semi-shaded conditions. These dahlias thrive in well-draining, rich, organic, humus-rich soil. Loosen the soil to about 12 inches (30 cm) deep and incorporate compost or an all-purpose granular fertilizer for added nutrients.
Plant tubers 3 to 6 inches below the soil surface, ensuring the “eyes” face upwards. Space individual tubers 12 to 18 inches apart, which allows sufficient room for mature growth. Water sparingly after planting, then wait until sprouts emerge before watering again to prevent tuber rot.
Watering and Fertilizing
Once established, ‘Rancho Dahlia’ benefits from deep watering one to three times a week, especially in hot, dry conditions. Allow the top inch of soil to dry out between waterings. Always water at the base of the plant to avoid wetting the foliage, which can help prevent disease.
For robust growth, apply supplemental organic water-soluble fertilizer every three to four weeks until September. Some growers recommend a high-nitrogen liquid feed in June, followed by a high-potash fertilizer from July to September. Cease fertilizing in September to prepare the tubers for overwintering.
Pinching and Staking
Pinch the main stem when the plant reaches 10 to 18 inches tall and has three to four sets of leaves. This technique, which involves removing the terminal bud, encourages bushier growth and more abundant blooms by directing the plant’s energy into lateral shoots, though it may delay the first blooms by a week or two.
Due to their height, ‘Rancho Dahlia’ plants often require staking for support to prevent brittle stems from breaking, particularly when heavy with blooms. Stakes can be placed at planting time or when the plant is small, around 8 to 16 inches tall. As the plant grows, tie the stems loosely to the stake, allowing some movement to prevent girdling. Alternatively, for multiple plants, a corralling method using t-posts and twine can provide collective support.
Overwintering Tubers
In colder climates (zones 3-7), overwintering the tubers is necessary as ‘Rancho Dahlia’ is a tender perennial. After the first autumn frost blackens the foliage, cut the stems back to a few inches above ground. Wait approximately ten days before carefully digging up the tubers.
Gently clean the tubers of soil and allow them to cure by drying for several weeks in a cool, dark, well-ventilated, frost-free location, such as a garage or basement. Once cured, store the tubers in peat moss, vermiculite, or dry growing mix within cardboard boxes, paper bags, or plastic bins. Ensure good air circulation and maintain a cool temperature between 40-50°F (2-10°C). Periodically check stored tubers for any signs of rot or shriveling throughout the winter.
Addressing Common Dahlia Challenges
Pests
Gardeners may encounter several common pests when cultivating ‘Rancho Dahlia.’ Aphids and spider mites are frequent visitors, sucking sap from the plants and leading to yellowed or distorted leaves and stunted growth. Horticultural soaps or strong water sprays can help manage these infestations, especially since spider mites thrive in hot, dry conditions. Slugs and earwigs can also damage tender leaves and flower buds, particularly in the early growing season. Maintaining a dry soil surface and utilizing repellents or traps can reduce their presence. Thrips, tiny insects that cause discoloration and distortion, can also transmit plant viruses.
Diseases
Fungal diseases like powdery mildew, appearing as a white coating on leaves and stems, are common in warm, humid environments. Preventing this involves ensuring good air circulation around plants and avoiding wetting the foliage when watering. Tuber and stem rot frequently result from overwatering or poorly drained soil, causing leaves to yellow and stems to become mushy. Proper drainage and careful watering practices are important to prevent these issues. Viral diseases, such as Dahlia Mosaic Virus, can cause leaf mottling and distortion, often spread by sucking insects. Unfortunately, infected plants usually need to be removed as there is no cure.
Environmental Stressors
Environmental stressors can also impact ‘Rancho Dahlia’ health. Overwatering often leads to symptoms like wilting, yellowed leaves, and a soggy appearance, potentially resulting in root rot. Conversely, underwatering can cause leaves to droop and dry, leading to stunted growth. A lack of blooms might indicate an imbalance in nutrients, such as excessive nitrogen, which promotes lush foliage at the expense of flower production, or it could be due to pest damage to developing buds.