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Ageratum
Ageratum houstonianum
Ageratum blooms from June through October.
Months here are Northern Hemisphere months; in the Southern Hemisphere, shift them by six months.
Growing Ageratum
Plant it in full sun. It prefers moderate water. It is hardy in USDA zones 10–11. Expect it to reach about 12 in tall and 12 in wide at maturity, in roughly 1 year (checked).
What was checked
Fifteen fields were checked against named botanical sources, each recorded beside the sources that carried it, with every unsettled point written down and decided: mature height and spread, hardiness zones, sun, water, bloom months and color, the trait tags, soil, diseases, pests, toxicity, the plant's own names, and years to mature size, which rests on a recorded house rule where no publisher states one and is marked so. Each fact above carries its own mark. The planting, spacing and size sections are derived from these checked facts by a fixed rule, not checked separately, and the plant type is the library's own classification.
When to plant Ageratum
Wait until all danger of frost has passed, then plant out Ageratum into warm soil; in most zones that means late spring. Planted then, it flowers from June to October.
Month-by-month timing for your zone is on the planting calendar; if you garden near zone 10, the middle of this plant's hardy range, start with zone 10 in January. Derived from the plant's category, zones and bloom months plus typical zone frost dates, not checked separately.
How big does Ageratum get?
12 intall5 ft 7 inan adult12 inwideSee Ageratum in a garden plan: the planner shows it in 3D beside everything else you add, growing toward this size over the years.
How far apart to plant Ageratum
Derived from the mature spread above by a fixed rule, not checked separately: spacing is the spread, center to center.
Space Ageratum about 12 in apart, center to center, so each plant has room to reach its full width.
Add Ageratum to a garden plan and the planner draws it at its full width, so you see the spacing before you buy.
Where these facts come from
Ageratum's height, spread, hardiness zones, sun, water, bloom months and color, years to mature size, trait tags, soil, diseases, pests and toxicity were checked against 13 published sources on August 21, 2026. Each one is linked below with every fact it carried, which can include a fact this page still marks as not yet checked, because a source carrying a value is not the same as the value being held to the standard. Facts not in that list, and the planting, spacing and size sections, are not covered by these sources.
- Missouri Botanical GardenPlant Finderheight, spread, hardiness zones, sun, water, bloom months and color, years to mature size, trait tags, soil, diseases and pests
- NC State ExtensionPlant Toolboxheight, spread, hardiness zones, sun, water, bloom months and color, years to mature size, trait tags, soil, diseases and pests
- University of Illinois Extensionheight, hardiness zones, sun, bloom months and color, trait tags and soil
- University of Wisconsin HorticultureUniversity of Wisconsin-Madison Division of Extension, Wisconsin Horti...height, sun, water, years to mature size, trait tags, diseases and pests
- seedman.comSeedman.comhardiness zones, sun, water, bloom months and color and soil
- Purdue ArboretumExplorerheight, sun, water and soil
- Swallowtail Garden Seedssun, trait tags, soil and pests
- plantura.gardenPlantura Magazineheight, sun and trait tags
- hort.cornell.eduCornell University Department of Horticulture, NYS Horticulture Study...height and sun
- mrec.ifas.ufl.eduUniversity of Florida IFAS Mid-Florida Research and Education Centersoil and toxicity
- Purdue ArboretumExplorerheight and sun
- University of Georgia ExtensionCAESheight and hardiness zones
- grow.edenbrothers.comEden Brothers planting guidesun
How the checking works, and what each standard covers, is on the verified plants page.
Comes in 4 varieties across 3 colors
Same plant, same care - pick the color you are growing.
Compare every variety in the Ageratum group
Every figure is the variety's own page fact. Tap a name to open it.
| Variety | Color | Blooms | Hardiness | Sun | Size (H × W) |
|---|---|---|---|---|---|
| Ageratumthis page | Blue | Jun–Oct | Zones 10–11 | Full sun | 12 in × 12 in |
| Blue Horizon | Blue | Jun–Oct | Zones 10–11 | Full sun | 24 in × 12 in |
| Pink | Pink | Jun–Oct | Zones 10–11 | Full sun | 12 in × 12 in |
| Purple | Purple | Jun–Oct | Zones 10–11 | Full sun | 12 in × 12 in |
| White | White | Jun–Oct | Zones 10–11 | Full sun | 12 in × 12 in |
Good to know about Ageratum
Curated from university extensions, botanic gardens and other primary sources, with the source named on every note. A note reports what its source says; where that differs from a fact above, the fact above is this entry's stored value, and its mark says whether it has been checked.
Safety
Chronically toxic to grazing livestock: eaten over weeks it causes fatal liver damage. Low risk to pets and people, but never use any part as food. per Veterinary and Human Toxicology
Worth knowing
The fuzzy powder-puff look comes from dense heads of tiny tubular florets with no petals; it is in the daisy family despite looking nothing like one. per NC State
Size depends on cultivar
Dwarf bedding types stay about 0.15 to 0.3 m tall; the species and tall cut-flower cultivars reach 0.6 to 0.9 m, two to three times bigger. Check the label. per Wisconsin
Deer and rabbit resistant
Deer and rabbits rarely browse it, so it is a good pick where they are a problem. Resistant, not fully deer-proof: hungry deer may still sample it. per NC State and UGA
Feeds butterflies until frost
It flowers from early summer until the first frost, giving butterflies a steady nectar supply. A common, moderate (not top-tier) choice for butterfly plantings. per NC State and University of Illinois
Deadheading depends on cultivar
Older seed strains turn brown and ragged unless you deadhead; many modern hybrids are self-cleaning and need little. Deadheading also prolongs bloom and cuts disease. per Wisconsin and University of Illinois
Head off mildew and mites
Powdery mildew loves shade, crowding and humidity; spider mites flare in hot, dry spells. Space for airflow, water at the base in the morning, and keep soil evenly moist. per University of Illinois
What pairs well with Ageratum
Good companions share its growing conditions and add something it lacks: an earlier or later bloom, a lower carpet in front, or structure through winter.
Rock Cress
Shares full sun and low to moderate water; blooms in mid spring, before this one opens; evergreen, so the bed keeps its shape through winter; lower at 4 in, for the front of the border.
Rosemary
Shares full sun and low to moderate water; blooms in early spring, before this one opens; both offer pollinator forage, in different months; evergreen, so the bed keeps its shape through winter.
False Indigo
Shares full sun and low to moderate water; opens in late spring and overlaps into this one's season; its seed heads stand through winter, for structure and the birds; both offer pollinator forage.
Sneezeweed
Shares full sun and moderate water; its seed heads stand through winter, for structure and the birds; both offer pollinator forage; taller at 3.5 ft, for the layer behind it.
Freesia
Shares full sun and moderate water; blooms in mid spring, before this one opens; both offer pollinator forage, in different months; yellow against blue, for contrast.
Viburnum
Shares full sun and moderate water; blooms in mid spring, before this one opens; stands well above at 6.5 ft, a canopy to plant beneath; both offer pollinator forage, in different months.
Ninebark
Shares full sun and moderate water; opens in late spring and overlaps into this one's season; both offer pollinator forage; stands well above at 6.5 ft, a canopy to plant beneath.
Lilac
Shares full sun and moderate water; blooms in mid spring, before this one opens; stands well above at 10 ft, a canopy to plant beneath; both offer pollinator forage, in different months.
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Design a garden with this
Drop this plant onto a 3D plan, see how it fills in, and watch your whole garden bloom across the year.