Ageratum houstonianum
( aj - err - AH - tum hew - stone - ee - AN - um)
At-A-Glance Information
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Commonly referred to as Floss Flower, Mexican Painbrush, Pussy Foot, Blueweed or Bluemink, this annual enjoys full sun in cooler climates, partial shade to shade in warm ones. These flowers need regular water. These are native to Central America and the West Indies. They are easy to grow and dependable additions to the garden. Leaves are soft green and round, and dense flower clusters resemble powder puffs and will attract butterflies to your garden. All grow best in moist, rich soil.
This is a very cool plant that can be used as a natural insecticide in the garden. There is a part of this plant that produces a compound that interferes with insects' ability to procreate, leading to less garden pests. This plant is toxic to grazing animals, so take care when planting this puffy flower if you live near these creatures. |
Ageratum houstonianum Varietals
Floss Flower grows in zones 1-24, and is named for the Scottish physician who first collected and documented the plants, William Houston. The genus Ageratum gets its namesake from the Greek word 'ageras' which means non-aging, referring to the long-lasting blooms. There are many sub-species that vary in size, flower color, and habit. See the descriptions below for more information. To find your zone, click here: Zone Map.
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'Blue Surf'
4-6 inches tall. |
'Royal Delft'
4-6 inches tall. |
'Blue Mink'
9-12 inches tall. |
'North Sea'
9-12 inches tall. |
'Capri'
12 inches tall. |
'Southern Cross'
12 inches tall. |
'Blue Horizon'
2.5 feet tall, great as a mid-border plant and for cutting for arrangements. |
'Swing Pink'
Bright pink flowers, grows 6-8 inches tall. |
'Red Top'
Deep pink flowers, grows to 2.5 feet tall. |
'Summer Snow'
White blooms on a 9-inch tall plant. |
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Ageratum houstonianum Artist Series Compact, strong growing plants to 8-18 inches tall that bloom profusely in blue, violet, purple, and rose. |
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Caring for Ageratum houstonianum
These favorites of bees and other pollinators do best when planted in full sun to partial shade. If you live in a warmer climate, the more shade you can provide, the better. They are not picky about soil, as long as it is well-draining. Plants should be spaced 6-8 inches apart for best coverage and performance, and given a balanced fertilizer (such as a 10-10-10) once or twice a season. This is an annual plant, so it will need to be removed and replaced after it expires and replaced with another in the next growing season.
Propagation
Before trying this method, keep in mind that propagation of Ageratum houstonianum by seed does not ensure that you will end up with the exact same plant as you harvested the seed from. If you are looking for an exact clone, it is best to simply purchase another of the same species from a nursery. To complete this propagation method, you will need to allow your flowers to stay on the plant long enough to come to seed, so do not completely deadhead all of your flowers. Seeds will be mature and ready to harvest in late summer or early fall, when the flowers have dried and turn brownish. Cut the flower heads off of your plant at this time, and take the seeds out of their pods. For pictures of the dried flowers and seeds, see the images below. To grow Ageratum houstonianum from seed, follow these directions:
- Gather your materials. You will need a pot or seed tray, potting soil that is well-draining, and a spray bottle filled with water.
- Seeds can be sown in place or started indoors in the late wintertime and then transplanted outside. For best results, start indoors about 6-8 weeks before the last frost of the year, especially if you live in an area that is prone to frost. If you are growing just a few seeds, you can use a pot, though if you are growing more than just a few, use a growing tray. Prepare your pot or growing tray by filling it with potting medium.
- Place your seeds on top of the potting mix, spaced about 4- 6 inches apart. Sprinkle potting medium over the top until the seeds are covered. As the seeds are starting out, it is best to use a spray bottle to add moisture to avoid uncovering their soil topping. Keep the soil moist as the seeds develop, using a seed tray cover or plastic to cover your pot to keep moisture in and humidity high.
- Continue to monitor for moisture and adequate soil covering until the seeds start to sprout, which should take 7-21 days. Once the chance of frost has passed by, seedlings can be transplanted to a sunny area of the garden. Keep the soil moist as the plant develops.
Ageratum houstonianum seed pods.
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Ageratum houstonianum seeds are very small, and look like this.
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Problems and Pests
Ageratum houstonianum has few issues, but it is susceptible to:
- Spider Mites
Gallery
These flowers can make great additions to beds.
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The color of Ageratum houstonianum contrasts well with oranges and yellows.
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This species is one of the only true blue annual flowers, so it makes a great display in a multi-colored bed.
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Videos
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All about growing Ageratum houstonianum.
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Growing Ageratum houstonianum for cut flowers.
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Resources
The New Sunset Western Garden Book: The Ultimate Gardening Guide (2012) - Page 140, Ageratum houstonianum
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