A Gardening Journal

Popcorn Bush

cassia-didymobotrya-spike-640

 

There's never enough black in the garden—especially when combined with a joyfully unsophisticated color like butter yellow.  Each takes the curse off the other.  Popcorn bush brings black in through the back door, so to speak, via the scales that cover its fingertip-sized buds. 

 

As they open, the bright and cheery flowers quickly shed their black overcoats—but not all of their sophistication.  Look at those pistils and stamens!

 

cassia-didymobotrya-flower-b-640

 

The pollen-producing stamens are the least of the show: They're the small frilly bits right at the center of the flower.  But the pistils—which are what receives the pollen—are almost blushingly genital.  Despite its frankly penile profile, the long green pistil is the real deal, maturing to long and green pea-podity.  The dark-brown horns at either side look just as frank—but in seeming mimicry of Fallopian tubes.

 

cassia-didymobotrya-podsa-640

 

But they're just for bluff and show, withering away while the pea-pod itself burgeons. 

 

Of course, you could just as well enjoy popcorn bush's flowers just for their aesthetics.  The horns are a deep and dark note of contrast with the vivid petals just like the sensational black bud-covers, while the bright-green pistil echoes the green of the foliage.

 

Even the veins of the petals are high-style: their brown is a first cousin to the brown of the horns.

 

cassia-didymobotrya-flower-640

 

Popcorn bush looks so simple at a glance—but so sophisticated in close-up.

 

 

Here's how to grow this disarmingly-charming flowering shrub:

 

Latin Name

Cassia didymobotrya, Senna didymobotrya

Common Name

Popcorn Bush; Peanut Butter Senna

Family

Fabaceae, the Pea family.

What kind of plant is it?

Shrub.

Hardiness

Zones 8 - 10.

Habit

Upright and single-trunked.

Rate of Growth

Fast.

Size in ten years

A shrub six to eight feet.  Can reach full height in one season, even when grown as annual.

Texture

Delicate and detailed—but on a large scale—with bold pinnate foliage punctuated by profuse vertical spikes of complex yellow flowers.

Grown for

its butter yellow flowers, which are in vertical spikes to about a foot tall, arising from surprising and dramatically-contrasting near-black buds. 

 

its foliage fragrance, which is released when the foliage is brushed or stroked.  To some noses, it's warm buttered popcorn; to others, peanut butter.  Either way, the odor makes the foliage unpalatable to deer.

 

its quick growth and precocious flowering—plants can be in bloom in 4" pots at the nursery—which make it useful as an annual.

Flowering season

In the hottest climates with the longest growing season, Spring through Fall.  Otherwise, Summer and Fall.  

Culture

Full sun, heat, and any well-drained soil.  Faster in rich soil. 

How to handle it

Where growing popcorn bush as an annual, handle it just like you would a dahlia or a tomato:  Don't set out young plants until the weather and the soil are both fully settled into their Summer warmth.  Drought-tolerant when established.

 

As with most Pea Family species, popcorn bush is easy from seed, which you can save from plants of the previous season and sow, shallowly and in warmth, in February or March. 


Although even a single flower spike is a show, this is a plant where More is More.  As an annual, then, try not to slow it down.  In my experience, younger plants transplant much better than older, so it's better to buy them as soon as you see them at the nursery, even if this means potting them up interimly in a gallon pot for a few weeks before transplanting into a garden bed or in a really large container for the Summer. 

 

On the other hand, there are also things you can do to help first-year popcorn bushes along, too.  Plant in full sun and in rich soil, water when the the soil feels dry, and fertilize once a month with fish emulsion.  Don't pinch or prune, which will only delay the flowering.  If you want a broader volume of popcorn bush than you can get from a single plant, plant them in groups, two feet apart.

 

 

Where hardy, this plant will perform for years, so there's much less of a rush.  Get the plant established and then just let it do its thing.  The plant is drought-tolerant when established.  Older plants can get rangy, but can be pruned back heavily as growth is starting up in early Spring. 

Downsides

As long as your weather is hot and you've launched your plant with care, popcorn bush is easy and fun.  Self-seeding could be an issue in the subtropics and tropics, where the seeds would be hardy.

Variants

There are many cassias, typically with yellow flowers, and habits from annuals and perennials to shrubs and trees.  Few are hardy outside the subtropics, but some are so fast growing they're exciting even as annuals.  Cassia hebecarpa is one of the few hardy species, best grown by cutting to the ground each Spring like you would a bush clover, and dead-heading promptly when the flowers are through to prevent lavish self-seeding. 

Availability

Seeds are available on-line; plants are available at destination retailers.

Propagation

By seed.

Native habitat

Africa.

Add comment


Security code
Refresh

 
 
FacebookTwitterRSS Feed

Subscribe to Email

join our mailing list
* indicates required