Getting it to bloom

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

Also called Rosinweed, Entire-leaved rosinweed, Prairie rosinweed (Silphium integrifolium).

More about rosinweed

About Rosinweed

Silphium integrifolium · also called Rosinweed, Entire-leaved rosinweed · flowering

Silphium integrifolium is a robust native perennial of central and eastern US prairies, producing opposite or whorled rough-textured entire leaves along stout stems and a profusion of clear yellow daisy flowers from midsummer to early autumn. It is one of the more compact and garden-adaptable Silphium species, reaching a manageable 90-150 cm (3-5 ft), and has attracted research interest as a potential oilseed crop. Like other rosinweeds, it is deeply rooted and extremely drought-tolerant once established. Silphium integrifolium is not listed by the ASPCA as toxic to cats or dogs.

Plant type: flowering

The reasons rosinweed isn't blooming

Almost every non-blooming rosinweed 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 rosinweed 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 rosinweed to flower

Maximise sun. Give rosinweed 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 rosinweed and get the feeding right with the rosinweed 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

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

Rosinweed blooming — frequently asked questions

Why won't my rosinweed flower?

Rosinweed 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 rosinweed bloom?

Give rosinweed 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 rosinweed normally bloom?