Vegetable leaves and stems – edible or toxic? (by Robin Gale-Baker)

Robin Gale-Baker, from Sustainable Macleod, is a major contributor to this website, covering all aspects of food growing and eating.

With the advent of artisan butchers and fishmongers featuring using the animal or fish top to toe, there’s a temptation to also do this with vegetables. Beware, however, that not all vegetable leaves or stems are edible and some are quite toxic.

Let’s start with a few edible ones:

• Carrot tops are edible and can be used as a substitute for basil in pesto.
• Turnip tops likewise make good pesto. Also, the young leaves can be added to salads.
• Radish leaves can be used in the same way as turnip tops.
• Sweet potato leaves can be eaten raw or cooked, like spinach.
• Beetroot leaves can be used as a substitute for spinach or silverbeet. They also make good pies (e.g. spanakopita) and soups.

Non-edible vegetable tops include:

• Parsnips. Parsnip leaves emit a compound called furocoumarin from their stems. This is a white, liquid that, when exposed to the sun, becomes caustic and can cause anything from blistering to burning of the skin, mouth or throat.
• Anything in the Solanaceae family, including potatoes, tomatoes, peppers, chillis and eggplants. Whilst the fruits of all these can obviously be consumed, the leaves are dangerous when ingested because they contain high concentrations of a compound called solanine.
• Potato leaves are highly toxic and should never be ingested. As most people are aware, green potatoes are an absolute no-no too. Potatoes exposed to light or cold (as in the fridge) develop solanine in sufficient quantity to potentially cause stomach problems.
• Tomato stems and leaves are now served in some restaurants as part of roasted tomatoes on the vine. Perhaps chefs get away with the very small quantities on the plate but they are toxic, containing a compound called tomatine.
• Peppers, chillis and eggplants likewise have toxic leaves from solanine concentration.

When we think about the solanaceae family, it should perhaps be no surprise that the leaves are not edible. This is the deadly nightshade family after all.

Just because one plant in a family is edible does not mean that similar looking plants are. In the carrot family (Apiaceae), for example, Queen Anne’s lace (Daucus carota) is edible whilst hemlock (Conium maculatum) is highly poisonous.

Bitterness is often an indication of poisonous alkaloids so the more bitter tasting a leaf is the more suspicious you should be.

Some final points:

• Both sweet peas (Lathyrus odoratus) and everlasting peas (Lathyrus latifolius) are toxic.
• Rhubarb leaves contain oxalic acid in sufficient quantities to cause a range of serious symptoms, often requiring a trip to hospital.
• Fig roots and stems, like parsnip stems, contain furocoumarins and, particularly when weeding, gloves and safety glasses should be worn to avoid burning of skin and eyes.