'Black Knight' delphiniums are part of the Pacific Series of cultivars, which are optimized for areas with cool to moderately warm summer climates. Andy Mabbett / Wikimedia Commons / CC By 3.0. Caring for Delphinium Delphiniums require regular watering, specifically during the dry summer months. Most delphiniums lose some of their toxicity as they mature. In hot, humid climates, these perennials may live only two or three years. Grow 'Black Knight' when a mousy little wallflower of a plant just won't do. Delphiniums need more fertilizer than you may be used to giving your perennials. Along with hollyhocks (Alcea rosea) and foxgloves (Digitalis spp. Delphinium 'Black Knight' (Delphinium 'Black Knight') will reach a height of 1.7m and a spread of 0.75m after 2-5 years. Suggested uses. Cut plants back after initial flowering for a possible second showing in fall. Delphinium blooms make excellent cut flowers, and many gardeners plant them to enjoy their striking flowers indoors (after cutting, that is). Used by themselves and planted in a mass, they can form a border or soften the look of a fence. Delphinium is a good option for container planting, partly because it doesn't live a long time, and most gardeners' pots tend to see a lot of turnover anyway. The flowers are excellent for cutting. Horses are also affected by the plant but are less likely to eat it than cows. During the bloom, deadhead the primary flowering stalks, leaving the smaller side-blooming flowers that are thriving. If unsupported, the stalks of this plant snap easily in strong winds. Removing faded spikes at the base will encourage repeat blooming in fall. It performs much better where summertime heat waves are more the exception than the norm. Care should be taken to protect young plants from snails and slugs, as they can cause considerable damage. Stake with bamboo canes in mid-spring. Delphiniums like neutral soil; if yours is acidic, amend with wood ash or lime to add alkalinity. By using The Spruce, you accept our, Landscape Uses for 'Black Knight' Delphinium, Black Knight' delphinium, 'Black Knight' larkspur, 14 Best Landscape Plants With Purple Flowers, How to Grow and Care for Red Hot Poker Plants, How to Grow and Care for Purple Wood Spurge (Euphorbia Purpurea), Perennial Cornflower (Perennial Bachelor's Button) Plant Profile. Plant 'Black Knight' delphinium in an area that receives a daily dose of six hours or more of direct sunlight. In hot, humid summer regions, plants do not usually last more than 2 to 3 years. Copyright © 2000 - 2020 Valleybrook International Ventures Inc. Delphinium NEW MILLENNIUM™ ‘Blushing Bride... Delphinium NEW MILLENNIUM™ ‘Double Stars&r... Delphinium NEW MILLENNIUM™ ‘Sunny Skies&rs... Delphinium NEW MILLENNIUM™ ‘Super Stars&rs... Delphinium NEW MILLENNIUM™ ‘Dusky Maidens&... Delphinium ‘Magic Fountains Cherry Blossom/White... Alphabetical list of all 4,000+ perennials here. Grow delphiniums in a humusy soil that drains well. Growing 4 to 6 ft in height and 1 ft wide, ‘Black Knight’ often requires staking for support. Plant in a fertile, well-drained soil in full sun. CAUTION: Harmful if eaten. Delphinium seeds and young plants are moderately toxic to dogs and cats, causing gastrointestinal upset and other symptoms. Plants are often attacked by mildew in mid summer; simply cut back hard to encourage fresh foliage. delphinium Black Knight Group RHS Plants for Pollinators plants This plant will provide nectar and pollen for bees and the many other types of pollinating insects. Delphinium care includes applying a balanced liquid fertilizer every month as the plants are heavy feeders. Use a high phosphorous fertilizer each year, in early spring. Used by themselves and planted in a mass, they can form a border or soften the look of a fence. For this reason, it's helpful to plant them next to a fence or wall, where they get some protection from the wind. Plants should be replaced every 3 to 4 years as they will become woody and begin to decline with age. The Spruce uses cookies to provide you with a great user experience. Delphiniums are hard not to notice in the landscape. Introducing "One Thing": A New Video Series, The Spruce Gardening & Plant Care Review Board, The Spruce Renovations and Repair Review Board. If unsupported, their stalks snap easily in high winds. For young plants, leave about two to four of the best stalks; for older plants, leave five to seven. Soil should stay just barely moist and never dry out, nor become soggy. 'Black Knight' delphinium has average water needs. This selection has … Landscape Uses for 'Black Knight' Delphinium Along with hollyhocks (Alcea rosea) and foxgloves (Digitalis spp. Blooming for weeks from early to midsummer, this Pacific hybrid adds a wonderful architectural presence in the garden and draws the attention from quite a distance. In warmer climates, they may be treated as annuals. Apply a … Apply a fortnightly balanced liquid feed during the growing season. In view of the "thriller, filler, spiller" planting strategy, delphinium is clearly a thriller: its flower stalk shoots straight up for several feet, making it not only a vertical feature but also a dramatic centerpiece for the pot. So it is better to focus on giving them optimal drainage in winter rather than mulching them. As tall, floppy plants, Black Knight delphiniums require staking. Plants form a low mound of deeply-cut green leaves, bearing tall spikes of satiny flowers. Learn tips for creating your most beautiful (and bountiful) garden ever. After the bloom, cut the flower stalks (not the whole plant) to the ground; in most areas, this will produce a second, smaller bloom late in the season. The ‘Black Knight’ delphinium displays semi-double dark purple flowers with dark eyes forming tall spikes and deeply-cut green leaves. If you do apply mulch, keep it away from the crown. But it is the impressive height and tightly packed spikes of oddly shaped flowers that gain delphiniums so much attention. If your delphiniums are performing poorly, the book Essential Perennials offers these tips: Black spotted foliage can mean cyclamen mites. ), delphiniums are classic cottage garden plants for use in the back row of a mixed flower bed. The risk of losing them in winter from poor drainage is greater than the risk posed by the cold. Some gardeners mulch delphinium for winter protection, but be aware that crown rot can be a problem for these plants. ), delphiniums are classic cottage garden plants for use in the back row of a mixed flower bed. Keep the soil moist but not wet. Unfortunately, no matter how much care you give them, delphiniums are not long-lived perennials.