Milkweed in Colorado
Colorado is one of the most milkweed-diverse states in the West, with roughly twenty species spanning shortgrass plains, foothills, mesas and the Western Slope. Showy milkweed along the South Platte and Arkansas river corridors does most of the monarch work, while the eastern plains hold rarities such as wheel milkweed found almost nowhere else.
The best milkweed to plant in Colorado
Native to the state, garden-worthy and useful to monarchs. Start here if you are planting rather than identifying.
All milkweed species in Colorado
| Species | Height | Flower | Bloom | Soil | Monarch |
|---|---|---|---|---|---|
| Swamp Milkweed Asclepias incarnata |
3 ft–5 ft | pink, rose, white | June to September | Wet / Average | |
| Butterfly Weed Asclepias tuberosa |
1 ft–3 ft | orange, yellow, red | May to September | Dry / Average | |
| Showy Milkweed Asclepias speciosa |
2 ft–5 ft | pink, rose | May to August | Average / Dry | |
| Antelope Horns Asclepias asperula |
1 ft–2 ft | green, cream, maroon | March to July | Dry | |
| Green Antelopehorn Asclepias viridis |
1 ft–2.5 ft | green, purple | April to July | Dry / Average | |
| Common Milkweed Asclepias syriaca |
3 ft–6 ft | pink, mauve, white | June to August | Dry / Average | |
| Whorled Milkweed Asclepias verticillata |
1 ft–2.5 ft | white, green | June to September | Dry / Average | |
| Hall’s Milkweed Asclepias hallii |
1.5 ft–3 ft | pink, mauve | June to August | Dry | |
| Green Comet Milkweed Asclepias viridiflora |
1 ft–3 ft | green | May to August | Dry | |
| Broadleaf Milkweed Asclepias latifolia |
1 ft–3 ft | green, cream | May to August | Dry | |
| Sand Milkweed Asclepias arenaria |
1 ft–2.5 ft | cream, green | June to August | Dry | |
| Plains Milkweed Asclepias pumila |
4 in–1 ft | white, cream | June to September | Dry | |
| Engelmann’s Milkweed Asclepias engelmanniana |
2 ft–5 ft | green, yellow | June to August | Dry | |
| Slimleaf Milkweed Asclepias stenophylla |
1.5 ft–3.3 ft | cream, green | June to August | Dry | |
| Poison Milkweed Asclepias subverticillata |
1 ft–3 ft | white, green | June to September | Dry | |
| Pallid Milkweed Asclepias cryptoceras |
4 in–1 ft | cream, pink | April to June | Dry | |
| Dwarf Milkweed Asclepias involucrata |
4 in–10 in | green, cream | April to June | Dry | |
| Longhood Milkweed Asclepias macrotis |
8 in–1.7 ft | green, cream | April to August | Dry | |
| Wheel Milkweed Asclepias uncialis |
2 in–6 in | maroon, green | April to June | Dry |
Rare or protected in part of this range: Wheel Milkweed. Do not collect seed or plants from wild populations of these species.
Planting milkweed in Colorado
Sow seed outdoors in September to November, before the ground freezes. Winter then supplies the cold-moist stratification most milkweed seed needs, and germination happens naturally as the soil warms. If you have missed that window, chill seed in the refrigerator for 30 days and sow after your last frost. The full method is here.
Colorado spans USDA zones 3a–7a, so check the zone range on each species page before committing. Match the species to your site rather than the other way round: dry, sunny and poor suits butterfly weed and the whorled species; a damp spot suits swamp milkweed; shade suits very few milkweeds at all.
Plant at least ten stems in one group rather than scattering them, because female monarchs find dense patches far more readily. Add late-season nectar such as goldenrod and asters so the fall migratory generation has fuel as well as host plants. How to lay out a monarch garden.
Where to buy milkweed in Colorado
Start with Colorado Native Plant Society. State native plant societies run the plant sales worth going to: locally grown, untreated stock, at a few dollars a plant, sold by people who can tell you where to put it.
In Colorado
Non-profit running a native plant nursery and demonstration gardens on the Colorado Front Range.
Elsewhere in the mountain west
Independent Intermountain West native plant nursery.
Ships to you
One of the widest milkweed seed and bare-root ranges anywhere, with germination codes listed for every species.
Long-established independent nursery specializing in Midwestern natives.
Independent seed producer supplying restoration-scale native seed by the pound.
Family-run native seed producer for the eastern and central states.
Family-run Texas seed house focused on regional ecotypes.
These favor independent nurseries and non-profits over chain garden centers, which mostly stock unlabeled tropical milkweed and often cannot tell you whether it has been treated with neonicotinoids. Search the full directory by ZIP code.
Milkweed in Colorado: common questions
What milkweed is native to Colorado?
19 milkweed species are recorded in Colorado, including Swamp Milkweed (Asclepias incarnata), Butterfly Weed (Asclepias tuberosa), Showy Milkweed (Asclepias speciosa), Antelope Horns (Asclepias asperula). The full list is on this page.
What is the best milkweed to plant in Colorado?
Swamp Milkweed, Butterfly Weed, Showy Milkweed are the best combination of native, available and garden-worthy for Colorado. Swamp Milkweed is the easiest to start with.
When should I plant milkweed seed in Colorado?
Sow outdoors in September to November, before the ground freezes, so winter provides the cold stratification the seed needs. If you have missed that window, stratify seed in the refrigerator for 30 days and sow in spring after the last frost.
Does milkweed grow wild in Colorado?
Yes. 19 species occur in Colorado, typically on roadsides, field margins, prairie remnants and along watercourses. Colorado is one of the most milkweed-diverse states in the West, with roughly twenty species spanning shortgrass plains, foothills, mesas and the Western Slope.
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Milkweed USA. (2026). Milkweed in Colorado. Retrieved DATE, from https://milkweedusa.com/states/colorado/
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Milkweed USA. "Milkweed in Colorado." Last modified 2026-08-01. Accessed DATE. https://milkweedusa.com/states/colorado/.
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url = {https://milkweedusa.com/states/colorado/},
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}