Most are accustomed to the standard red radishes, some have delved into white radishes but black radishes are another path in the radish realm that you may want to explore.
Black Radish Characteristics and Uses
Black radishes (Raphanus sativus niger) are more full flavored, peppery and pungent than most radish varieties, they also tend to be a tad larger. Standard radishes can go from seed to supper in as little as 3 weeks, Black radish takes longer, 2 - 3 times longer.
There are several varieties. Black Spanish Round Radish aka Noir Gros de Paris, Spanish radish, Gros Noir d'Hiver or Black Mooli resembles a turnip in size and shape but not coloration or flavor. It is charcoal black on the exterior, sometimes with just a smidgen of purplish black. The interior flesh is crispy, moist and a pristine white. Some 'Black' radishes aren't all that black but are more of a deep brown, somewhat like a meld of black radishes and standard red - pink radishes. Other varieties are elongated, something like a carrot as oppossed to the customary globe shape.
Most Black Radishes grown commercially are used to make dietary and medicinal supplements, but a few find their way into the specialty produce stores and culinary wonderland of Bistro's and Gourmet Retautrants.
When eating these radishes raw some people peel the outer skin as they find it too peppery and spicy, personally I like to keep it on - but that's just a personal preference.
In addition to being bigger, darker more pungent and stronger Black radishes also last longer. They can keep all winter long if properly stored. Don't freeze them, you'll ruin them, simple refrigeration in a carton that allows for some air circulation is all you need. Storing them in a cool dry location packed into a box of moist sand is another method sometimes used, but not too many people want a box of sand in their house.
Planting Black Radish
Growing Black Radish isn't all that different from growing standard radishes, with the big exception being that they will take longer to mature and occupy slightly more space. Start from seed in early to mid summer follow the spacing requirements as per the seed pack for your particular cultivar and get growing.
Choose a site that gets at least six hours of sunlight daily. Loosen the soil to a depth of roughly 1.5 to 2 feet, which is the depth of the average garden spade.
Black radishes are slightly more tolerant of heat better than the short rounder red radishes, but should still be kept well watered in the dog days of summer. Water regularly and gently, not excessively.
Avoid excess organic materials and manure or fertilizers high in nitrogen. Excess nitrogen will encourage lush foliage at the expense of the radish roots.
Light mulch enriched with wood ashes will help suppress weeds and root maggots. Radishes tend to bolt to seed and become too pungent to eat if grown in dry soil. With excessive watering the roots sometimes split and rot. You have to hit the Goldilocks level so far as water is concerned - not too much or too little but just right.