How to Grow Pacific Giant Delphinium

The Pacific Giant variety of delphinium produces large, semidouble flowers on tall stalks and is excellent for cutting. Most have white centers, except Blue Jay, Black Knight and Percival, which are black. Colors include lavender, pink, purple, light blue, dark blue and white. The plants grow up to 7 feet tall with large, palmate leaves and need staking to keep from toppling in rainy or windy weather.

Things You'll Need

• Spading fork
• Bone meal
• Organic fertilizer
• Compost
• Rake
• Pruner
• Aluminum foil

Instructions

1. Choose a planting area in full sun but protected from wind. Amend the soil with rich compost, digging it in to a depth of 1 foot. Pacific Giants need well-drained soil with plenty of organic matter.

2. Sow seed indoors under grow lights in February or March according to package directions, or buy plants at a nursery in spring. Plant into the garden in May, after all danger of frost has passed. Nursery transplants are likely to bloom lightly the first year and reach full bloom the second. Plants started from seed will bloom the second year.

3. Space the plants 2 feet apart. Add a handful of bone meal to the planting hole and mix it with the soil. Water well to settle the plant and eliminate air pockets. Water daily until the plants are established, then water weekly at the base. Avoid wetting the foliage.

4. Fertilize with an all-purpose organic fertilizer, 4-4-4 NPK or the like, after the plants are 2 inches tall. Mulch around the base with compost or manure to retain moisture and add nutrients.

5. When the plants are 10 inches tall, select one strong shoot and cut off all the rest at ground level. Stake the shoot with three or four bamboo canes about 4 feet tall, forming a square or triangle around the plant. Tie twine around the canes to make a cage. You can also use tall, strong tomato cages for delphiniums.

6. Cut off spent blooms but let the stems brown and die off, in order to spur a second flush of smaller flowers.

7. Cut all the stems to ground level in fall and rake up any fallen leaves. Cover the hollow stem stubs with a piece of aluminum foil to keep water out.

References

• Oregonlive: Growing Delphiniums
• Hume Seeds: Pacific Giant Delphinium
• Iowa State University Extension; Growing Delphiniums; Linda Naeve; June 13, 1997