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Ask the Master Gardener: Delphiniums are beautiful but challenging

By: Trish Grenfell Placer County Master Gardener
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Question: I?ve failed with delphiniums in the past. Are there tricks to growing them well? And I am wondering if you can steer me to some colorful drought-tolerant annuals. Answer: Yes, delphiniums are majestic flowering, cottage garden plants. Their long, colorful flower spikes are an impressive sight, but they are a challenge to grow. They require average to moist watering, excellent drainage (subject to crown rot), good air flow without winds, full sun, supports to hold them erect, rich soil plus fertilizer and controls for spider mite, snails and slugs, powdery mildew and fungus diseases. And they do not like the summer heat in the Auburn area. Recommended hardiness growing zones for delphiniums are 3-7 and their AHS heat zones are 1-6. These ideal zones can be found in the higher elevations east of Auburn. Note: Auburn?s hardiness zone is 9b and heat zone is 7/8. If you like challenges and are determined to grow these plants anyway, try the Delphinium Belladonna hybrids, which can handle more heat. The Connecticut Yankee Series cultivar ?Blue Fountains? is a Belladonna whose growing zone is extended to hardiness zone 8 and heat zone 7. I suggest you thoroughly research and then allocate the time to nurture this wonderful flower. I will applaud your efforts and successes since I failed at growing delphiniums, pitifully more than once. Attractive drought tolerant annuals you might try: Blanket Flowers (Gaillardia pulchella), Nasturtiums, Marigolds, Rose Moss (Portulaca grandiflora), Sunflowers, Zinnias, African Daisies, Cosmos, Poppies, Morning Glory, Mountain Phlox, Sweet Alyssum, annual Salvias, and Verbenas. But don?t forget to plug in the attractive but not thirsty perennial herbs: oregano, sage, rosemary and thyme. Have gardening questions? Call the master gardener hotline at (530) 889-7388.