Gardening Plant Encyclopedia Perennial How to Plant and Grow Delphiniums This elegant perennial produces spires of blue blooms. By Viveka Neveln Viveka Neveln Instagram Viveka Neveln is the Garden Editor at BHG and a degreed horticulturist with broad gardening expertise earned over 3+ decades of practice and study. She has more than 20 years of experience writing and editing for both print and digital media. Learn about BHG's Editorial Process Updated on January 10, 2023 Share Tweet Pin Email In This Article View All In This Article Where to Plant How and When to Plant Delphiniums Care Pests and Problems Propagation Types Companion Plants Garden Plans FAQs Most commonly grown for its beautiful, tall spires of blue blooms, delphiniums have long been planted in perennial gardens. These elegant plants add a strong vertical element. Because some varieties can grow up to 7 feet tall, plant these at the back of a garden border. If blue isn't your color, you can choose delphiniums in a few other colors, too! Delphiniums are sought after and planted for their blue flowers. These beautiful blues come in a variety of shades and forms. Many feature a white center, which adds a bright contrast to the deep, rich blue. Most delphiniums are in the blue and purple range, but they can also be found in pinks and reds. There are some stunning coral-colored varieties and rare yellow ones. These plants have attractive foliage in a pleasing green, with palm-shaped leaves like a fern. Delphinium plants and seeds are toxic. Plant them in a location away from children and pets. Delphinium Overview Genus Name Delphinium Common Name Delphinium Plant Type Perennial Light Part Sun, Sun Height 1 to 3 feet Width 1 to 3 feet Flower Color Blue, Pink, Purple, Red, White, Yellow Foliage Color Blue/Green Season Features Summer Bloom Special Features Cut Flowers, Good for Containers Zones 3, 4, 5, 6, 7 Propagation Seed Problem Solvers Deer Resistant Where to Plant Delphiniums Delphiniums prefer cool summers and moist soil, so they don't tend to do well in hot, dry weather. Plant delphiniums in well-draining soil in an area that receives 6 to 8 hours of sun daily. A location that provides some shelter from strong winds protects the tall flower stalks. How and When to Plant Delphiniums Spring and early autumn are the best times to plant delphiniums. They enjoy rich soil, so add compost to the planting holes. Position each plant so the top of the root ball is level with the soil surface. Space the plants 2-3 feet apart, depending on variety, and water them. Don't let them dry out completely. Delphinium Care Tips Delphiniums are well-loved, but they can be fairly short-lived and picky when it comes to garden conditions. Light Delphiniums should be planted in full sun for the best blooms and sturdiest stems. Soil and Water Plant delphiniums in well-drained soil with plenty of organic matter. While it's important to keep the plants consistently moist (they don't handle drought well), be sure that the soil has proper drainage. Standing water can lead to crown rot, which causes the whole base of the plant to rot and will eventually lead to death. Temperature and Humidity One of the most important things to keep in mind is that delphiniums don't like hot summers; they perform best in mild, humid weather. When it does get hot, the plants might die back to the ground. If you're lucky, they may come back as it cools back down. In anything warmer than Zone 7, these plants are typically treated as annuals. Fertilizer Fertilize delphiniums in the spring when the plants begin to grow and again while they are flowering using a granular 10-10-10 fertilizer. Pruning Once the delphinium blooms are finished, deadhead them and remove the stalk to encourage a small second bloom. Big Perennials for Big Impact Pests and Problems In too much shade, especially in humid climates, fungus issues can arise on the foliage. Powdery mildew, botrytis, and leaf spot are all common problems that delphiniums struggle with. The best fungal control method is prevention, so make sure the plants are in well-ventilated areas and full sun to keep foliage dry. If your plant needs any supplemental watering, do it at the base so that the leaves stay dry. Because these plants are tall, they often need staking or support from neighboring plants. Delphiniums are known to attract slugs. How to Propagate Delphinium The best method for propagating delphiniums is to take a basal cutting in spring when the new shoots appear. Cut a small side shoot below the soil level, being careful to take some of the base. Dip the base in rooting hormone and pot it in a mixture of potting soil and sand or perlite. Types of Delphinium 'Blue Butterfly' Delphinium Mike Jensen Delphinium grandiflorum 'Blue Butterfly' grows to only 14 inches tall and has deep blue flowers with a hint of purple. It tolerates heat better than other delphiniums, blooming through most of the summer. Zones 4-7 'King Arthur' Delphinium Ed Gohlich Photography Inc Delphinium elatum 'King Arthur' is one of the Round Table Hybrids with 5- to 6-foot-tall flower spikes. It has reddish-purple flowers with a creamy white center called a bee. Zones 3-7 'Dasante Blue' Delphinium Graham Jimerson Delphinium elatum 'Dasante Blue' is a compact selection with rich blue flowers with light purple tones. It grows 34 inches tall and 12 inches wide. Zones 4-7 Pacific Giants Series Delphinium Greg Ryan Delphinium elatum Pacific Giants Series are towering plants with bloom stalks reaching up to 7 feet tall. Colors range from light blue to white, pink, and purple. Zones 3-7 'Summer Blues' Delphinium Justin Hancock Delphinium grandiflorum 'Summer Blues' offers soft blue flowers in summer. It grows 14 inches tall. Zones 4-7 'Summer Stars' Delphinium Marty Baldwin Delphinium grandiflorum 'Summer Stars' is a dwarf variety that produces pure-white flowers in summer. It grows 12-14 inches tall. Zones 4-7 'Summer Morning' Delphinium Courtesy of Benary Delphinium grandiflorum 'Summer Morning' is the first true pink variety of Chinese delphinium. It grows 12-14 inches tall, blooming all summer long on well-branched plants. Zones 4-7 Delphinium Companion Plants Joe Pye Weed Mike Jensen Joe Pye weed is a showstopper of a prairie native, producing huge, puffy flower heads in late summer. It prefers moist soils, but with its extensive root system, it also tolerates drought well. It's a large plant, growing 4 to 6 feet tall. Closely related, hardy ageratum is a spreading plant that grows to 2 feet tall. Another relative, white snakeroot, reaches 4 to 5 feet tall. All are great for naturalistic or cottage plantings and for attracting butterflies. Hyssops Marty Baldwin This hardworking group of perennials does so much. Hyssops bloom for a long time in wonderful colors atop tall, striking plants. They produce a nectar that is irresistible to hummingbirds and butterflies. Most are heat and drought-tolerant, and their foliage and flowers are fragrant, with scents ranging from licorice to bubblegum. Most require well-drained soil and prefer full sun, although they will tolerate light shade. Salvias Stephen Cridland There are hundreds of different types of salvias, commonly called sage. They all tend to share beautiful, tall flower spikes and attractive, often gray-green leaves. Countless sages (including the herb used in cooking) are available to decorate ornamental gardens, and new selections appear annually. They are valued for their very long blooming season, right up until frost. Not all are hardy in cold climates, but they are easy to grow as annuals. On square stems, clothed with often-aromatic leaves, sages carry dense or loose spires of tubular flowers in bright blues, violets, yellow, pinks, or reds that mix well with other perennials in beds and borders. Provide full sun or very light shade in well-drained average soil. Garden Plans for Delphinium Summer Cottage Garden Add interest and drama to your yard with this eye-catching, long-blooming garden plan. Garden size: 20 by 10 feet. Download this free garden plan Frequently Asked Questions How long do delphiniums live? After they have stopped blooming for the season, cut off the plants at ground level and sprinkle the area with fertilizer so the plant will be healthy the following year. Repeat this process each year, and these short-lived perennials will return for 3-5 years. How tall do delphiniums grow? Many delphiniums produce flower stalks up to 7 feet tall, but some varieties grow to less than 2 feet. It depends on the variety you select. The tallest of the delphiniums benefit from staking to protect them from wind damage. Was this page helpful? Thanks for your feedback! Tell us why! Other Submit Sources Better Homes & Gardens is committed to using high-quality, reputable sources—including peer-reviewed studies—to support the facts in our articles. Read about our editorial policies and standards to learn more about how we fact check our content for accuracy. Delphinium. North Carolina State University Extension.