Dancing in the Dark with Rhubarb
Or: The noisy secret to super sweetness

Q. Gene writes: What can you tell my friend David in central Indiana (Beech Grove/Indianapolis area) about growing rhubarb in the dark? Have you or anyone you know tried it in the USA? Thanks! I love listening to your show on Saturday afternoons on Indiana Public Radio. Say hi to Ducky for me!

A. I have a growing suspicion that Ducky is becoming more popular than me. He IS a heck of a lot cuter, but still...

Anyway, we were originally thinking about a tag team phone call from Gene and David. But if I had ever heard about this trick before, I had long ago forgotten it, so into the Research Rabbit Hole I went. What I learned was so cool I had to turn it into a Question of the Week so its wisdom and revelations will reside at the Gardens Alive website in perpetuity. Or at least a long time.

The technique comes to us from Great Britain, especially the 'Yorkshire Triangle' in the North of England, which is not a place where ships and planes disappear, but a nine square mile area where this type of 'forced rhubarb' is grown in sheds where no light is ever allowed to intrude. In fact, the crop is so light sensitive, it's harvested by candlelight, just as it was in the 1800s.

The website for America's Test Kitchen has one of the best articles on this, as well as a groovy photo of candlelight harvesting. (I hope the photog didn't use a flash!)

As Cook's Illustrated Senior Editor Alyssa Vaughn (the two websites seem to be intertwined) recounts: "Around 1817, a team of workers digging a ditch in London inadvertently sparked a horticultural revolution. The ditch was in the Chelsea Physic Garden, on the bank of the River Thames. The spark was the accidental burial of some dormant crowns of rhubarb, which...at the time, was primarily used as medicine. While field rhubarb is a warm weather crop, fresh, salmon colored stalks started poking out of the dirt mounds in the Physic Garden that winter--the first of many surprises in the unlikely life of cultivated rhubarb."

(Alyssa is such a good writer that I quoted that exactly, with a few edits, instead of my usual paraphrasing, which will now return.)

Note: I have been to that part of England, and sources are correct when they describe the region to be as cold and damp as the plant's original home of Siberia. (Leeds was one of the coldest and dampest places I have ever visited; I did not linger.) Anyway, this technique, like growing rhubarb the regular way outdoors, would not work in warm weather climates.

Ah, but if you are blessed with weather that is cold and damp, you're in luck! Not really, but you CAN grow rhubarb outdoors and force it. Pity the people in perfect climes.

It starts with two-year-old plants that have been grown outdoors. Rhubarb, a herbaceous perennial, dies back in the Fall, but in the right kind of climate will show above ground growth in December or January. Have your own personal 'growing shed' ready when the first growth appears. It has to be warm and pitch black inside. Experts agree that even using a flashlight could ruin things.

The roots you start with must be at least two years old; the only energy available for these forced plants to grow is stored in those roots. Once you force a root, don't force it again for at least two years. Replant the roots outside in the Fall so they can recharge in the bright sunshine for a few years.

This can also be attempted outdoors, the same way you blanch asparagus (to make it white instead of green). Simply cover the emerging plant with a light proof container (Washington and Jefferson were very fond of this ancient technique).

Then you have to keep things as warm as possible inside the container. Straw is the recommended 'mulch', but I think that soil, compost and/or well-shredded leaves would work just as well or better; but that's up to you. I'd bury the entire experiment to keep things even warmer and as lightproof as possible. Make sure your cover is tall enough to accommodate the final height of the rhubarb.

Whether indoors or outdoors, all sources agree that forced rhubarb grows FAST; much faster than regular rhubarb. In fact, many growers swear you can hear it growing, snap, crackle and pop. Eight weeks is the recommended growing time. This makes your warm, dark growing shed superior to outdoors. You can sneak inside at night--turn any outdoor lights out first--and check the growing plants by candlelight, which is way cool.

The point of all this? Forced rhubarb is much sweeter than when outdoor grown. The rhubarb grows fast because it's trying to find sunlight, but without that sun, the plant produces more sugars for growth. As a result, the stems are sweeter, as well as less tough and stringy. Sources agree that you can greatly reduce the amount of sugar that regular rhubarb requires in recipes.

A final note: You still have to trim off every bit of leaf and use only the stalks, just like regular rhubarb.

And now, for your dining and dancing pleasure, we bring you the sound of forced rhubarb growing, courtesy of the Gastro Obscura section of the Atlas Obscura. Be sure to tip the waitstaff.