Native throughout the northern hemisphere and the high mountains of tropical Africa, delphinium, which is also commonly called larkspur, is a genus of approximately 300 species of perennial flowering plants in the buttercup family.
Admired for its flowers that vary in color from purple and blue to red, white or yellow, the delphinium plants produce spikes that can reach two to six feet in height. Their size makes them a good choice for planting in the back of borders.
Larkspur gets its name from the fact that its flowers have five petal-like sepals that grow together to form a hollow pocket with a spur at the end.
Its seeds are small and shiny black. Please note that delphinium seeds, as well as the rest of the plant, are poisonous. Great care should be taken to insure that delphinium is not grown in pastures where cattle graze. If eaten, the plant will cause vomiting. Consumption of larger amounts can lead to death within hours of ingestion.
The plants, which are pollinated by bumble bees and butterflies, produce beautiful blooms from late spring through late summer. Many species are grown for use in flower arrangements.
Delphiniums grow best in well-drained soil. The plants prefer full sun and require fertilization in early spring and again later in the growing season. Plants that have yellow foliage or appear to be stunted need additional fertilizing.
Fresh seeds are best for planting. The best temperature range for germination is 50 to 60 degrees Fahrenheit.
Refrigerate delphinium seeds for 24 hours and then soak them in room-temperature water for three to four hours before planting. Keep the soil moist, not wet. Do not allow the soil to dry out. Delphiniums usually germinate in 15 to 21 days.
Delphiniums do take a bit of extra work. Because of their height, the hollow and brittle flower spikes are easily damaged by wind and rain. The weight of the flower spikes can cause the stems to snap and break. One way to avoid this problem is to install support stakes in the ground early in the growing season so that you do not damage the root system.
Most species of delphiniums bloom from early to mid-summer. They work well as cut flowers and tend to last in a vase for approximately a week.
Once the plants have flowered, cut off the old stalks to promote additional flowering later in the summer or early in the fall. Don’t expect the second round of flowers to be as nice as the first.
Unfortunately, delphiniums often tend to be short-lived perennials. The average lifespan is two to three years in the garden. Plan on replanting frequently.
Crown rot is a disease that often plagues delphinium growers. A progressive wilting of the stems is a sure sign of crown rot. Plants that have crown rot need to be removed and destroyed. The soil needs to be sterilized before replanting. Spacing delphinium plants at least three feet apart in the garden can minimize the disease.
Red spider mites are also common pests, especially if junipers are planted near the delphiniums. Plants suffering from an infestation of spider mites have a brownish discoloration on the leaves. A forceful spray of water may cure the problem. If not, apply malathion or Neem oil according to directions.
Interested in learning more about delphiniums? Visit Plant Care dot com for all sorts of info.
For further information about poisonous plants can be found on the University of Missouri Extension.
Visit UC Davis to learn more about keeping cut delphinium flowers fresh.