Tart Greens

The greens in this chapter have a pleasant and sometimes striking sour or acidic flavor. They are suitable for occasions where you want to add some mouthwatering character to a dish. Tart greens are often added to milder greens (foundational greens) or complex dishes to add interest and nuance. Like foundational greens, they can also cut the power of pungent and bitter greens but are in no way neutral like foundational greens. They are edible raw and cooked, but their best uses depend on what you are preparing. Tart greens have the potential to greatly improve a dish by using just a little or to dramatically change the character of a dish by adding a lot. People will enjoy them as a flavor enhancer for other foods or eaten on their own.

Each of the greens in this section has its own characteristic flavors and textures. Fresh, they are excellent in combination salads, added to sandwiches, used as garnishes, and made into pestos and other green-based sauces. If you are like me, you will enjoy salads with nothing but sour greens. Cooked, their flavors mellow, often giving the impression of foundational greens when a hefty squirt of lemon juice is added. They go well with other vegetables and any kind of meat, especially fish.

The plants covered in this section include curly dock, broad-leaved dock, sheep sorrel, and wood sorrel. Most of these plants happen to be either in the buckwheat (Polygonaceae) or the oxalis family (Oxalidaceae). The only sour vegetable you will typically find in the supermarket is rhubarb (Rheum spp.). French sorrel (Rumex acetosa), eaten as a green, is sold in nurseries for planting in your garden. It is as close to the plants in this chapter as you will get from a non-wild perspective. Both rhubarb and French sorrel are in the buckwheat family.

Oxalates and Sour Flavor

Oxalates, also known as oxalic acids, are well known to be in the plants in this section. Because of that, people assume that it is the oxalates that are the source of the tart flavor they are sensing. Any acid will probably have a sour taste. But the sour of oxalates in the greens we eat may not be strong enough for us to taste. I say this because both spinach and wild spinach have just as much if not more oxalates than the plants in this section, but neither spinach tastes sour. So how can spinach be so high in oxalates and not be sour? Because plants have more than one acid. Other acids found in plants include ascorbic acid, citric acid, malic acid, formic acid, and many others. Every plant covered in this section has enough combined acid that it will taste sour and turn a dull olive-green when boiled. Wild spinach stays bright green when cooked, even though it has gobs of oxalates. So either wild spinach has chemical components that neutralize oxalate’s acidity, or there are other acids in the plants in this section to make them sour to the taste.

Nutritionally, sour greens tend to be high in iron, zinc, vitamin C, and soluble oxalates. Nutrient values, unfortunately, are often listed under the label “docks” rather than the specific dock that they are. So, in truth, the values given in the wild greens nutrient chart listed as Rumex spp. could be any of four species: Rumex crispus (curly dock), Rumex obtucifolius (broad-leaved dock), Rumex acetosella (sheep sorrel), or Rumex acetosa (French sorrel). The assumed species is curly dock, but we just don’t know. Much more nutrient analysis needs to be done.

Phytochemical data is preliminary, but Rumex crispus and Rumex obtucifolius appear to be high in total phenols, have more myricetin than red wine and black tea, and have more quercetin than onions and black tea. Myricetin and quercetin are flavonoids.

Some books will give warnings about plants with oxalates poisoning sheep, cattle, or chickens. These accounts are real but do not apply to humans. First, these animals have different physiology and digestive processes than humans; they are less able to manage oxalate intake. Second, all animals poisoned were restricted to eating the mass of their total diet from days to weeks of very high oxalate plants. Imagine trying to eat about eight pounds of spinach every day for a week as over 50 percent of your diet. Oxalates are relatively harmless in the context of a normally diverse human diet. (See Oxalates and Nitrates for more information on oxalates.)

Flavors offered by sour greens are an excellent addition to the gourmet’s arsenal of tastes. Some of the sour greens grow all year long; others are more seasonal. Growing conditions and season greatly affect their quality and availability.