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Delphiniums are elegant perennials that produce spires of colorful flowers in shades of blue, purple, pink, white, red and yellow. They are popular in cottage-style and cutting gardens, as well as attracting butterflies and hummingbirds. However, delphiniums can be challenging to grow, as they are short-lived, picky about soil and climate conditions, and prone to pests and diseases. Here are some tips on how to plant, grow and care for delphiniums.
Choosing a Location
Delphiniums prefer a location that receives full sun for at least 6 to 8 hours a day, but also some shelter from strong winds that can break their tall flower stalks. They also need moist, well-drained soil that is rich in organic matter and slightly alkaline (pH 6.0 to 7.5). You can amend your soil with compost or aged manure before planting, and test the pH level with a kit or a meter. If your soil is too acidic, you can add lime or wood ashes to raise the pH.
Planting Delphiniums
The best time to plant delphiniums is in spring or early autumn, when the soil is not too hot or cold. You can start them from seeds indoors about 10 weeks before the last frost date, or buy transplants from a nursery. When planting, dig a hole twice the diameter of the root ball and set the plant so that the top of the root ball is level with the soil surface. Space the plants 2 to 3 feet apart, depending on the variety, and water them well.
Caring for Delphiniums
Delphiniums need regular watering, especially during dry spells. Do not let them dry out completely, but also avoid overwatering or soggy soil that can cause root rot. Mulch around the plants with organic material to conserve moisture and suppress weeds. Fertilize delphiniums once a month with a balanced fertilizer during the growing season, following the package directions.
One of the most important tasks for delphinium care is staking. Delphiniums have hollow stems that can easily snap under the weight of their heavy flower spikes. You can use bamboo stakes, metal rods or wooden dowels to support the plants. Tie the stems loosely to the stakes with soft twine or cloth strips as they grow.
Another way to keep your delphiniums healthy and blooming is deadheading. This means removing the spent flowers as soon as they fade, to prevent them from forming seeds and taking energy away from the plant. Some varieties of delphiniums will rebloom if you cut back the entire flower stalk after the first flush of flowers. Others will only bloom once in early to mid-summer.
Pests and Problems
Delphiniums are susceptible to several pests and diseases that can affect their growth and appearance. Some of the common ones are:
- Aphids: These are tiny insects that suck the sap from the leaves and stem, causing them to curl and distort. They can also spread viruses and fungal diseases. You can control aphids by spraying them with insecticidal soap or neem oil, or by releasing beneficial insects like ladybugs or lacewings that feed on them.
- Powdery mildew: This is a fungal disease that causes a white or gray coating on the leaves and stems, reducing photosynthesis and weakening the plant. It is more likely to occur in humid or crowded conditions. You can prevent powdery mildew by providing good air circulation around your plants, avoiding overhead watering, and applying fungicides if needed.
- Crown rot: This is a bacterial disease that causes the base of the plant to rot and collapse. It is often caused by poor drainage or overwatering. You can prevent crown rot by planting delphiniums in well-drained soil, watering carefully, and removing any infected plants as soon as possible.
- Slugs and snails: These are mollusks that feed on the leaves and flowers of delphiniums, leaving holes and slime trails behind. They are more active at night or during wet weather. You can control slugs and snails by hand-picking them off your plants, using traps or barriers, or applying baits or repellents.
Enjoying Delphiniums
Delphiniums are stunning plants that can add a vertical accent and a burst of color to your garden. They are also excellent cut flowers that can last for a week or more in a vase. To cut delphiniums for arrangements, choose stems that have at least two-thirds of the flowers open, and cut them early in the morning or evening. Place them in water immediately and change the water every few days.
Delphiniums are beautiful but demanding plants that require some extra care and attention. However, if you provide them with the right conditions and maintenance, they will reward you with their stunning blooms and fragrance. Delphiniums are worth the effort for any gardener who loves flowers.
