Getting it to bloom
Why won't my Sullivant's Milkweed bloom? (and how to make it flower)
Also called Sullivant's Milkweed, Prairie Milkweed, Sullivant's Prairie Milkweed (Asclepias sullivantii).
More about sullivant's milkweed
About Sullivant's Milkweed
Asclepias sullivantii · also called Sullivant's Milkweed, Prairie Milkweed · flowering
Sullivant's milkweed is a smooth, hairless native perennial of the tallgrass prairie of the central United States and southern Ontario, growing in rich, moist soils of undisturbed prairies, meadows, and floodplain edges. Unlike common milkweed it spreads much less aggressively via rhizomes and is better suited to garden settings. The single most important care fact is that it requires consistently moist, rich soil — it will not thrive in dry or sandy conditions. All Asclepias species contain cardiac glycosides and are toxic to cats and dogs.
Plant type: flowering
Watch for — Aphid colonies on stems and buds: Bright yellow oleander aphids (Aphis nerii) are a near-universal pest on milkweeds; tolerate modest colonies as they support predator populations, or remove by hand to protect flower buds.
The reasons sullivant's milkweed isn't blooming
Almost every non-blooming sullivant's milkweed traces back to one of these, roughly in order of how common they are:
- Too little sun — most of these need full sun (or very bright light) to flower well; shade gives leaves, not blooms.
- Too much nitrogen feed, driving lush foliage at the expense of flowers (very common with general or lawn feeds).
- The plant has not been deadheaded, so it stops flowering once it sets seed.
- Irregular watering — drought or waterlogging at the budding stage makes buds abort.
- It is still too young or was checked by a transplant and is rebuilding before flowering.
Feeding sullivant's milkweed a high-nitrogen general feed and growing it in too little sun — you get a big leafy plant and almost no flowers.
The fix — how to get sullivant's milkweed to flower
- Maximise sun. Give sullivant's milkweed the sunniest spot you have — for most bedding and fruiting plants, more direct light directly means more flowers.
- Switch the feed. Move off high-nitrogen feeds and use a higher-potassium "bloom" or tomato-type feed as it comes into flower.
- Deadhead regularly. Remove spent flowers often to keep it producing more rather than stopping to set seed.
- Water consistently. Keep moisture even through budding and flowering — drought-then-flood swings make buds drop.
Light and feeding do most of the heavy lifting here. Dial in the spot with the light guide for sullivant's milkweed and get the feeding right with the sullivant's milkweed fertilising schedule — the wrong feed (too much nitrogen) is one of the most common silent reasons a healthy plant makes leaves instead of flowers.
Bloom season and what to expect
Sullivant's Milkweed flowers across its growing season (mostly summer) and, kept fed and deadheaded, can bloom for many weeks or right up to frost.
Post-bloom care so it flowers again
Deadhead, keep feeding lightly, and many will rebloom; collect seed from the best plants at the end of the season if you want to grow them again.
For everything else this plant needs day to day, see the full sullivant's milkweed care brief and its watering schedule — a stressed, badly watered plant rarely has the energy to flower at all.
Sullivant's Milkweed blooming — frequently asked questions
Why won't my sullivant's milkweed flower?
Sullivant's Milkweed blooms on the season's growth given enough sun, warmth and the right feed — there is no cold or photoperiod trick, just good growing conditions and a bloom-leaning feed. The most common reason it is not happening: Too little sun — most of these need full sun (or very bright light) to flower well; shade gives leaves, not blooms.
How do I make sullivant's milkweed bloom?
Give sullivant's milkweed the sunniest spot you have — for most bedding and fruiting plants, more direct light directly means more flowers. Move off high-nitrogen feeds and use a higher-potassium "bloom" or tomato-type feed as it comes into flower.
When does sullivant's milkweed normally bloom?
Sullivant's Milkweed flowers across its growing season (mostly summer) and, kept fed and deadheaded, can bloom for many weeks or right up to frost.
What should I do with sullivant's milkweed after it flowers?
Deadhead, keep feeding lightly, and many will rebloom; collect seed from the best plants at the end of the season if you want to grow them again.
What is the single biggest mistake stopping sullivant's milkweed flowering?
Feeding sullivant's milkweed a high-nitrogen general feed and growing it in too little sun — you get a big leafy plant and almost no flowers.
Keep reading
- Sullivant's Milkweed care — the full brief (light, water, humidity, problems, pet safety)
- Sullivant's Milkweed light needs — usually the first thing to fix for flowers
- Sullivant's Milkweed fertilising — the right feed for buds, not just leaves
- Should I water my plant? The simple check
- Why is my plant wilting? Wet vs dry
- Underwatered plant — signs and rehydration
- Why won't my peace lily bloom?
- Why won't my jade plant bloom?
- Why won't my tomato bloom?
- All 4114 bloom guides in the Growli library