Getting it to bloom

Why won't my Purple Milkweed bloom? (and how to make it flower)

Also called purple milkweed (Asclepias purpurascens).

More about purple milkweed

About Purple Milkweed

Asclepias purpurascens · also called purple milkweed · flowering

An uncommon North American native milkweed bearing rounded clusters of deep rose-purple flowers that are richly scented and highly attractive to monarchs and bees. It tolerates part shade better than most milkweeds and favours moist, well-drained ground. As an Asclepias it has milky sap and is toxic to cats, dogs and horses if eaten.

Plant type: flowering

Watch for — Slow to establish: Purple milkweed can be slow and finicky to settle in and may take a couple of seasons to bloom well. Be patient and avoid disturbing the roots once sited.

The reasons purple milkweed isn't blooming

Almost every non-blooming purple 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 purple 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 purple milkweed to flower

Maximise sun. Give purple 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 purple milkweed and get the feeding right with the purple 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

Purple 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 purple milkweed care brief and its watering schedule — a stressed, badly watered plant rarely has the energy to flower at all.

Purple Milkweed blooming — frequently asked questions

Why won't my purple milkweed flower?

Purple 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 purple milkweed bloom?

Give purple 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 purple milkweed normally bloom?