Ageratum houstonianum
Blue Horizon

Ageratum houstonianum ‘Blue Horizon’ is an old-fashioned floss flower with extra height, long bloom, and fluffy lavender-blue flower clusters that are wonderfully pettable. Unlike short bedding types, this tall ageratum grows about 30" high on sturdy branching stems, making it useful for borders, cutting gardens, cottage plantings, and pollinator-friendly annual displays.

From late spring into winter in mild climates, ‘Blue Horizon’ produces rich, soft flower clusters up to 4" across above attractive emerald-green foliage. The airy blooms are excellent in fresh bouquets, where they add cool color and a soft, textural finish. In the garden, they pair beautifully with zinnias, cosmos, marigolds, calendula, salvias, and ornamental grasses.

Plant Ageratum houstonianum ‘Blue Horizon’ in full sun to light shade with rich, well-drained soil and regular water. Deadhead or cut for bouquets to encourage continued bloom. Easy, floriferous, and full of vintage charm, this tall blue floss flower is a lovely way to add soft color for months. Explore more seasonal favorites in our Annuals collection.

We guarantee that the plants we sell are healthy and viable at the time they leave our care.

If a plant arrives in substandard condition, please take clear photographs and contact us within 48 hours of delivery. To ensure eligibility under this guarantee, we strongly encourage you to open and unpack your shipment immediately upon delivery and inspect the plants thoroughly.

Read More

Standard live-plant shipping to eligible destinations is $16.99 for 1–6 plants, $22.99 for 7–12, $28.99 for 13–18, $34.99 for 19–24, and $40.99 for 25–30. For 31 or more plants, shipping is 20% of the order value. Expedited shipping is priced separately at checkout.

(AL, CT, DC, DE, FL, GA, IN, KY, ME, MD, MA, MI, NH, NJ, NY, NC, OH, PA, RI, SC, TN, VT, VA, WV)
(list of states subject to change seasonally due to extreme heat or cold conditions)

We cannot ship Annie's Annuals plants to P.O. boxes or outside the continental U.S.

Individual plants are shipped in 4" pots and we ship in boxes of 4, 6, 8, or 12 plants per box.

For more details, read our full Ordering and Shipping Policies

Get your plants off to a strong start with our care guide.

Download the Plant Care Guide (PDF)