Getting it to bloom

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

Also called Great Mullein, Common Mullein, Aaron's Rod, Flannel Plant (Verbascum thapsus).

More about great mullein

About Great Mullein

Verbascum thapsus · also called Great Mullein, Common Mullein · flowering

Verbascum thapsus is a biennial native to Europe and western Asia, now widely naturalised across North America. In its first year it forms a flat rosette of large, woolly, grey-green leaves; in its second year it throws up a stout, torch-like spike of yellow flowers reaching 1–2 m. Full sun and sharply drained, even poor soil are the two non-negotiable requirements — waterlogged conditions will kill it. Verbascum thapsus is not listed on the ASPCA toxic plant database and is generally regarded as non-toxic to cats and dogs, though the dense leaf hairs can cause mild skin or gastric irritation.

Plant type: flowering

The reasons great mullein isn't blooming

Almost every non-blooming great mullein 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 great mullein 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 great mullein to flower

Maximise sun. Give great mullein 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 great mullein and get the feeding right with the great mullein 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

Great Mullein 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 great mullein care brief and its watering schedule — a stressed, badly watered plant rarely has the energy to flower at all.

Great Mullein blooming — frequently asked questions

Why won't my great mullein flower?

Great Mullein 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 great mullein bloom?

Give great mullein 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 great mullein normally bloom?