Blue Planet Ageratum is a frost-tender annual flower that brings reliable, long-lasting color to gardens in warm climates and containers everywhere. This cultivar of Ageratum houstonianum grows 24 to 30 inches tall with a compact spread of 8 to 12 inches, making it a striking vertical accent in borders and mixed plantings. Hardy in zones 10 and 11, it thrives in full sun to partial shade and adapts well to moderate watering, flowering prolifically through the season when given the right start.
Partial Sun
Moderate
10-11
30in H x 12in W
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Moderate
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Blue Planet stands out for its tall, columnar growth habit that towers above typical ageratums, delivering bold vertical interest rather than the squat mounding forms most gardeners expect from this genus. The deep blue flowers create an intensely saturated color statement in the garden, and this cultivar's vigor means you get weeks of continuous bloom without the constant deadheading some shorter varieties demand. Starting seeds indoors at 70 degrees Fahrenheit is straightforward, and the plant rewards patient growers with flowers that persist well into fall.
Blue Planet Ageratum is grown as an ornamental flowering plant, valued for its blue blooms in garden borders, containers, and mixed plantings. Its height makes it particularly useful as a backdrop flower or focal point rather than an edging plant, adding vertical dimension to annual displays.
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Start seeds indoors 6 to 8 weeks before your average last frost date. Germination occurs at 70 degrees Fahrenheit. Press seed into the soil surface without covering, as light aids germination. Maintain consistent moisture and warmth until seedlings emerge, then provide bright light to prevent legginess.
Transplant outdoors only after all frost danger has passed and soil has warmed, since Blue Planet Ageratum is frost-tender. Harden off seedlings gradually by exposing them to outdoor conditions over 7 to 10 days before final planting. Space plants 12 inches apart to allow adequate air circulation around the mature 8 to 12-inch width.
Direct sowing outdoors is not recommended except in very mild climates. If attempting direct sow, wait 2 to 4 weeks after your average last frost date and sow seeds on the soil surface in a consistently warm spot.
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