Summer · month 8 of 12
Milkweed and monarchs in August
The last generation, and the first pods
44species that can be in flower
12at peak bloom
41of them native
Summerseason
Where the monarchs are
The final breeding generation develops. Late in the month, in the north, the migratory generation begins to emerge: physically similar butterflies that will not breed, will live eight months instead of five weeks, and will fly to Mexico.
What to do this month
- Start the squeeze test on pods. Ripe when the seam splits under gentle pressure and the seed inside is brown.
- Leave tussock moth caterpillars alone. The plants have done their monarch work by now.
- Make sure something is flowering for fall. Goldenrod and asters matter more than milkweed from here on.
- Do not cut anything back yet.
What to look for
- Whorled milkweed flowering, often the last milkweed still in bloom.
- Pods swelling and changing from green to gray-green.
- Migratory-generation monarchs nectaring heavily and roosting communally at night.
North and south
The northern tier is already producing migratory butterflies. In Texas and the Gulf, breeding continues into fall.
In flower in August
44 species can be in flower somewhere in the country this month, 12 of them at peak. Natives are listed first.
| Species | J | F | M | A | M | J | J | A | S | O | N | D |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Swamp Milkweed | Not in bloom in January | Not in bloom in February | Not in bloom in March | Not in bloom in April | Not in bloom in May | In bloom in June | Peak bloom in July | Peak bloom in August | In bloom in September | Not in bloom in October | Not in bloom in November | Not in bloom in December |
| Narrowleaf Milkweed | Not in bloom in January | Not in bloom in February | Not in bloom in March | Not in bloom in April | In bloom in May | Peak bloom in June | Peak bloom in July | Peak bloom in August | In bloom in September | Not in bloom in October | Not in bloom in November | Not in bloom in December |
| Whorled Milkweed | Not in bloom in January | Not in bloom in February | Not in bloom in March | Not in bloom in April | Not in bloom in May | In bloom in June | Peak bloom in July | Peak bloom in August | In bloom in September | Not in bloom in October | Not in bloom in November | Not in bloom in December |
| Aquatic Milkweed | Not in bloom in January | Not in bloom in February | Not in bloom in March | Not in bloom in April | In bloom in May | Peak bloom in June | Peak bloom in July | Peak bloom in August | In bloom in September | Not in bloom in October | Not in bloom in November | Not in bloom in December |
| Poison Milkweed | Not in bloom in January | Not in bloom in February | Not in bloom in March | Not in bloom in April | Not in bloom in May | In bloom in June | Peak bloom in July | Peak bloom in August | In bloom in September | Not in bloom in October | Not in bloom in November | Not in bloom in December |
| Plains Milkweed | Not in bloom in January | Not in bloom in February | Not in bloom in March | Not in bloom in April | Not in bloom in May | In bloom in June | Peak bloom in July | Peak bloom in August | In bloom in September | Not in bloom in October | Not in bloom in November | Not in bloom in December |
| Mahogany Milkweed | Not in bloom in January | Not in bloom in February | Not in bloom in March | Not in bloom in April | Not in bloom in May | In bloom in June | Peak bloom in July | Peak bloom in August | In bloom in September | Not in bloom in October | Not in bloom in November | Not in bloom in December |
| Nodding Milkweed | Not in bloom in January | Not in bloom in February | Not in bloom in March | Not in bloom in April | Not in bloom in May | In bloom in June | Peak bloom in July | Peak bloom in August | In bloom in September | Not in bloom in October | Not in bloom in November | Not in bloom in December |
| Lemmon’s Milkweed | Not in bloom in January | Not in bloom in February | Not in bloom in March | Not in bloom in April | Not in bloom in May | Not in bloom in June | In bloom in July | Peak bloom in August | In bloom in September | Not in bloom in October | Not in bloom in November | Not in bloom in December |
| Slimpod Milkweed | Not in bloom in January | Not in bloom in February | Not in bloom in March | Not in bloom in April | Not in bloom in May | Not in bloom in June | In bloom in July | Peak bloom in August | In bloom in September | Not in bloom in October | Not in bloom in November | Not in bloom in December |
| Common Milkweed | Not in bloom in January | Not in bloom in February | Not in bloom in March | Not in bloom in April | Not in bloom in May | Peak bloom in June | Peak bloom in July | In bloom in August | Not in bloom in September | Not in bloom in October | Not in bloom in November | Not in bloom in December |
| Showy Milkweed | Not in bloom in January | Not in bloom in February | Not in bloom in March | Not in bloom in April | In bloom in May | Peak bloom in June | Peak bloom in July | In bloom in August | Not in bloom in September | Not in bloom in October | Not in bloom in November | Not in bloom in December |
| Zizotes Milkweed | Not in bloom in January | Not in bloom in February | In bloom in March | Peak bloom in April | Peak bloom in May | In bloom in June | In bloom in July | In bloom in August | Peak bloom in September | In bloom in October | Not in bloom in November | Not in bloom in December |
| Butterfly Weed | Not in bloom in January | Not in bloom in February | Not in bloom in March | Not in bloom in April | In bloom in May | Peak bloom in June | Peak bloom in July | In bloom in August | In bloom in September | Not in bloom in October | Not in bloom in November | Not in bloom in December |
| Broadleaf Milkweed | Not in bloom in January | Not in bloom in February | Not in bloom in March | Not in bloom in April | In bloom in May | Peak bloom in June | Peak bloom in July | In bloom in August | Not in bloom in September | Not in bloom in October | Not in bloom in November | Not in bloom in December |
| Hall’s Milkweed | Not in bloom in January | Not in bloom in February | Not in bloom in March | Not in bloom in April | Not in bloom in May | In bloom in June | Peak bloom in July | In bloom in August | Not in bloom in September | Not in bloom in October | Not in bloom in November | Not in bloom in December |
| Sand Milkweed | Not in bloom in January | Not in bloom in February | Not in bloom in March | Not in bloom in April | Not in bloom in May | In bloom in June | Peak bloom in July | In bloom in August | Not in bloom in September | Not in bloom in October | Not in bloom in November | Not in bloom in December |
| Woollypod Milkweed | Not in bloom in January | Not in bloom in February | Not in bloom in March | Not in bloom in April | In bloom in May | Peak bloom in June | Peak bloom in July | In bloom in August | Not in bloom in September | Not in bloom in October | Not in bloom in November | Not in bloom in December |
| Desert Milkweed | Not in bloom in January | Not in bloom in February | Not in bloom in March | In bloom in April | Peak bloom in May | Peak bloom in June | In bloom in July | In bloom in August | In bloom in September | Not in bloom in October | Not in bloom in November | Not in bloom in December |
| Rush Milkweed | In bloom in January | In bloom in February | In bloom in March | Peak bloom in April | Peak bloom in May | In bloom in June | In bloom in July | In bloom in August | Peak bloom in September | Peak bloom in October | In bloom in November | In bloom in December |
| Green Comet Milkweed | Not in bloom in January | Not in bloom in February | Not in bloom in March | Not in bloom in April | In bloom in May | Peak bloom in June | Peak bloom in July | In bloom in August | Not in bloom in September | Not in bloom in October | Not in bloom in November | Not in bloom in December |
| Engelmann’s Milkweed | Not in bloom in January | Not in bloom in February | Not in bloom in March | Not in bloom in April | Not in bloom in May | In bloom in June | Peak bloom in July | In bloom in August | Not in bloom in September | Not in bloom in October | Not in bloom in November | Not in bloom in December |
| Slimleaf Milkweed | Not in bloom in January | Not in bloom in February | Not in bloom in March | Not in bloom in April | Not in bloom in May | In bloom in June | Peak bloom in July | In bloom in August | Not in bloom in September | Not in bloom in October | Not in bloom in November | Not in bloom in December |
| Pineland Milkweed | Not in bloom in January | Not in bloom in February | Not in bloom in March | Not in bloom in April | Not in bloom in May | In bloom in June | Peak bloom in July | In bloom in August | Not in bloom in September | Not in bloom in October | Not in bloom in November | Not in bloom in December |
| Fewflower Milkweed | Not in bloom in January | Not in bloom in February | Not in bloom in March | Not in bloom in April | In bloom in May | Peak bloom in June | Peak bloom in July | In bloom in August | Not in bloom in September | Not in bloom in October | Not in bloom in November | Not in bloom in December |
| Tall Green Milkweed | Not in bloom in January | Not in bloom in February | Not in bloom in March | Not in bloom in April | Not in bloom in May | In bloom in June | Peak bloom in July | In bloom in August | Not in bloom in September | Not in bloom in October | Not in bloom in November | Not in bloom in December |
| Pineneedle Milkweed | Not in bloom in January | Not in bloom in February | In bloom in March | Peak bloom in April | Peak bloom in May | In bloom in June | In bloom in July | In bloom in August | Peak bloom in September | In bloom in October | Not in bloom in November | Not in bloom in December |
| Bract Milkweed | Not in bloom in January | Not in bloom in February | Not in bloom in March | In bloom in April | Peak bloom in May | Peak bloom in June | In bloom in July | In bloom in August | Not in bloom in September | Not in bloom in October | Not in bloom in November | Not in bloom in December |
| Texas Milkweed | Not in bloom in January | Not in bloom in February | Not in bloom in March | Not in bloom in April | In bloom in May | Peak bloom in June | Peak bloom in July | In bloom in August | In bloom in September | Not in bloom in October | Not in bloom in November | Not in bloom in December |
| Rusby’s Milkweed | Not in bloom in January | Not in bloom in February | Not in bloom in March | Not in bloom in April | In bloom in May | Peak bloom in June | Peak bloom in July | In bloom in August | Not in bloom in September | Not in bloom in October | Not in bloom in November | Not in bloom in December |
in bloom peak bloom
See the full bloom chart for all 72 species.
August questions
What milkweed blooms in August?
44 milkweed species can be in flower somewhere in the United States during August, with Swamp Milkweed, Narrowleaf Milkweed, Whorled Milkweed, Aquatic Milkweed at peak. Bloom times shift several weeks later as you move north.
What are monarch butterflies doing in August?
The final breeding generation develops. Late in the month, in the north, the migratory generation begins to emerge: physically similar butterflies that will not breed, will live eight months instead of five weeks, and will fly to Mexico.
What should I do in the milkweed garden in August?
Start the squeeze test on pods. Ripe when the seam splits under gentle pressure and the seed inside is brown. Leave tussock moth caterpillars alone. The plants have done their monarch work by now. Make sure something is flowering for fall. Goldenrod and asters matter more than milkweed from here on.
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Milkweed USA. (2026). Milkweed and monarchs in August. Retrieved DATE, from https://milkweedusa.com/calendar/august/
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"Milkweed and monarchs in August." Milkweed USA, 2026, https://milkweedusa.com/calendar/august/. Accessed DATE.
Chicago
Milkweed USA. "Milkweed and monarchs in August." Last modified 2026-08-01. Accessed DATE. https://milkweedusa.com/calendar/august/.
BibTeX
@misc{milkweedusa_calendaraugust,
title = {Milkweed and monarchs in August},
author = {{Milkweed USA}},
year = {2026},
url = {https://milkweedusa.com/calendar/august/},
note = {Accessed DATE}
}