Fall · month 9 of 12
Milkweed and monarchs in September
The migration, and the best month for seed
24species that can be in flower
5at peak bloom
21of them native
Fallseason
Where the monarchs are
Peak fall migration through the central flyway. Monarchs stream south in numbers, roosting in trees overnight and feeding constantly. In the West they head for the California coast.
What to do this month
- Collect seed. Bag near-ripe pods with a rubber band so they cannot burst and scatter.
- Separate seed from floss with the coin-in-a-paper-bag method.
- Plant plugs in the South so roots settle before winter.
- Leave stems standing. They hold seed and shelter overwintering insects.
What to look for
- Overnight monarch roosts, sometimes hundreds of butterflies in one tree.
- Pods opening and floss lifting on the wind.
- Goldenrod and asters covered in migrating monarchs.
North and south
Peak migration passes through the northern plains in early September and Texas in October. Cape May, Peninsula Point and the Texas coast are all good places to see it.
In flower in September
24 species can be in flower somewhere in the country this month, 5 of them at peak. Natives are listed first.
| Species | J | F | M | A | M | J | J | A | S | O | N | D |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 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 |
| 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 |
| 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 |
| Emory’s Milkweed | Not in bloom in January | Not in bloom in February | Not in bloom in March | In bloom in April | Peak bloom in May | In bloom in June | In bloom in July | In bloom in August | Peak bloom in September | Not in bloom in October | Not in bloom in November | Not in bloom in December |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| Curtiss’ 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 |
| Feay’s 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 |
| 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 |
| Prostrate 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 | In bloom in September | Not in bloom in October | Not in bloom in November | Not in bloom in December |
| Savannah 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 |
| Tropical Milkweed introduced | In bloom in January | In bloom in February | In bloom in March | In bloom in April | In bloom in May | Peak bloom in June | Peak bloom in July | Peak bloom in August | Peak bloom in September | In bloom in October | In bloom in November | In bloom in December |
| Balloon Plant introduced | Not in bloom in January | Not in bloom in February | Not in bloom in March | Not in bloom in April | In bloom in May | In bloom in June | Peak bloom in July | Peak bloom in August | In bloom in September | In bloom in October | Not in bloom in November | Not in bloom in December |
| Giant Milkweed introduced | In bloom in January | In bloom in February | Peak bloom in March | Peak bloom in April | In bloom in May | In bloom in June | In bloom in July | In bloom in August | In bloom in September | Peak bloom in October | In bloom in November | In bloom in December |
in bloom peak bloom
September questions
What milkweed blooms in September?
24 milkweed species can be in flower somewhere in the United States during September, with Zizotes Milkweed, Rush Milkweed, Pineneedle Milkweed, Emory’s Milkweed at peak. Bloom times shift several weeks later as you move north.
What are monarch butterflies doing in September?
Peak fall migration through the central flyway. Monarchs stream south in numbers, roosting in trees overnight and feeding constantly. In the West they head for the California coast.
What should I do in the milkweed garden in September?
Collect seed. Bag near-ripe pods with a rubber band so they cannot burst and scatter. Separate seed from floss with the coin-in-a-paper-bag method. Plant plugs in the South so roots settle before winter.
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APA
Milkweed USA. (2026). Milkweed and monarchs in September. Retrieved DATE, from https://milkweedusa.com/calendar/september/
MLA
"Milkweed and monarchs in September." Milkweed USA, 2026, https://milkweedusa.com/calendar/september/. Accessed DATE.
Chicago
Milkweed USA. "Milkweed and monarchs in September." Last modified 2026-08-01. Accessed DATE. https://milkweedusa.com/calendar/september/.
BibTeX
@misc{milkweedusa_calendarseptember,
title = {Milkweed and monarchs in September},
author = {{Milkweed USA}},
year = {2026},
url = {https://milkweedusa.com/calendar/september/},
note = {Accessed DATE}
}