Leafy tops pesto: which greens you can eat, and which you must not

Carrot, radish, beetroot, turnip and fennel tops are edible and make a very good pesto. Rhubarb leaves, potato leaves and tomato leaves are not edible, ever, in any preparation. That is the first thing worth knowing before you tip a market bag into a blender, and it is exactly the thing most leafy-tops pesto recipes leave out.

Everything else comes down to a handful of practical points: wash the leaves properly, weigh your ingredients instead of guessing at handfuls, blend in short bursts, and keep the finished jar cold for a couple of days rather than a week. This article sets out those points with the sources behind them, and it is also honest about the cases where you should hold back, particularly if you take warfarin or have a history of kidney stones.

The short version

  • Edible and good in pesto: carrot tops, radish tops, beetroot leaves, turnip tops, fennel fronds, spring onion greens, tender leek leaves.
  • Never eat: rhubarb leaf blades, potato leaves and sprouts, tomato and aubergine leaves, pokeweed and unidentified garden plants.
  • Starting proportions: 80 g cleaned greens, 40 g seeds or nuts, 30 g hard cheese or 15 g nutritional yeast, 1 garlic clove, 80 to 100 ml oil, salt.
  • Storage: fridge at 0 to 5 °C, eaten within 48 hours in line with UK guidance for home-made leftovers, or frozen in portions.
  • Caveats: green leaves are rich in vitamin K, which matters on warfarin, and several green leafy vegetables sit among the higher oxalate foods, which matters if you have had calcium oxalate stones.

What leafy tops actually contribute to food waste

Switzerland’s Federal Office for the Environment puts food waste at 330 kilograms per person per year across the whole chain, from field to plate. Vegetable tops are a tiny slice of that: they weigh almost nothing, and a good share of them goes to compost rather than landfill. Turning your carrot tops into pesto is not a decisive climate action.

What it is: a way of paying for a bunch of carrots and eating all of it, getting a green sauce for the cost of some oil and seeds, and tasting things that are not sold in the chilled aisle. If you want the lever that genuinely moves household waste, it lies elsewhere, in planning what you buy and storing fresh produce properly. We have a dedicated guide on storing fruit, vegetables and pulses, and another on broths, pickles and peel crisps that covers the rest of your vegetable offcuts.

The edible tops, one by one

Carrot tops

The most used, and deservedly so. The foliage is fine and herbaceous, close to flat-leaf parsley with a sharper bitter edge. The thick stalks are fibrous: keep the leaves and thin stems, send the heavy stalks to the stockpot. Carrot tops take garlic well, and fatty nuts such as walnuts or almonds round off the bitterness.

One point worth settling, because the question comes up constantly: carrot leaves are commonly eaten and are studied as a food raw material. A team publishing in Molecules in 2023 isolated and quantified six flavone glycosides from Daucus carota leaves precisely because the leaves are treated as a recoverable by-product rather than waste. That work concerns laboratory extracts and says nothing about a health effect at the dose of a spoonful of pesto. It simply confirms that the leaf is food.

Radish tops

Sharper, peppery, with a texture close to young rocket. They wilt fast: after two days in the fridge the leaves are usually limp and yellowing already. Use them on the day you buy them. The slightly bristly fuzz disappears completely once blended.

Beetroot leaves

These are the leaves of the same plant as chard, and they behave the same way: fleshy, earthy, with coloured ribs. They are nutritionally dense. USDA FoodData Central gives, per 100 g of raw beet greens (SR Legacy record 170375), 3.7 g of fibre, 762 mg of potassium, 117 mg of calcium, 2.57 mg of iron, 30 mg of vitamin C and 400 µg of vitamin K. Those figures are for 100 g of raw leaves, which is far more than anyone eats in a spoonful of pesto: at the table, count on 10 to 20 g of greens per person.

Note the vitamin K figure. It comes back below, along with the fact that these leaves belong to the spinach and chard family, and both have practical consequences for some people.

Turnip tops

Mild, barely bitter, very close to spinach once wilted. They are also the richest in vitamin C of the group: 60 mg per 100 g raw according to USDA record 170061, alongside 190 mg of calcium, 3.2 g of fibre and 251 µg of vitamin K. Much of that vitamin C is lost if you heat the greens or let the pesto oxidise over several days, so do not build your vitamin C intake on a condiment.

Fennel fronds

The feathery growth on top of the bulb, strongly aniseed, effectively a herb in its own right. It is more delicate than the others: blended on its own, it takes over the jar. Cut it with parsley or turnip tops, and pair it with almonds rather than walnuts.

Other stems and leaves

Spring onion greens work very well, sweet and mild. The pale green leek leaves near the white, still supple, blend without trouble; the dark green upper leaves are tough and bitter and belong in stock. Spinach and chard stems can be added if they are tender. Celery leaves make a powerful pesto that needs cutting with something milder.

The leaves that must never go in a pesto

The prohibitions below correspond to poisonings documented by poison control centres, not to a general principle of caution.

Rhubarb leaves. The stalk is food, the leaf blade is not. MedlinePlus, the consumer database of the US National Library of Medicine, classes eating rhubarb leaves as a poisoning, with oxalic acid as the identified toxic component and anthraquinone glycosides as a possible one. The symptoms listed include burning of the mouth and throat, vomiting, diarrhoea and, in serious cases, seizures and kidney damage. Swelling in the mouth can become severe enough to prevent swallowing. Cut the leaves off and compost them.

Potato leaves, sprouts and green tubers. MedlinePlus describes solanine as very toxic even in small amounts, present throughout the plant but particularly in green potatoes and new sprouts. The effects are mainly gastrointestinal and are often delayed by 8 to 10 hours. The instruction is blunt: never eat a potato that is spoiled or green below the skin, always throw sprouts away, and never cook the foliage.

Tomato and aubergine leaves. Same botanical family as potato, the nightshades, and the same class of compounds. Steroidal glycoalkaloids such as tomatine and solanine are present in the aerial parts of these plants and are studied specifically for their antinutritional effects. You occasionally read that a tomato leaf perfumes a sauce; it is not a practice I will recommend here.

Pokeweed and garden foraging. MedlinePlus states that all parts of the pokeweed plant are toxic to humans, with the highest concentrations in the roots, leaves and stems. The general rule applies to anything picked outside the vegetable patch: if you are not completely certain of the identification, it does not go in the blender. Our piece on edible wild herbs covers the look-alikes worth knowing, including the wild garlic confusion.

Washing leafy tops properly

Tops arrive straight from soil and are dirtier than they look. They will not be cooked, so washing is the only step that removes what needs removing.

  1. Strip the leaves off the thick stalks before washing. Stalks trap grit at the base and you will spread it around if you wash the whole bunch as it comes.
  2. Drop the leaves into a large bowl of cold water and swirl by hand. Grit sinks. Lift the leaves out of the top rather than pouring the bowl through them.
  3. Repeat with clean water until the bottom of the bowl stays clear. Two passes are usually enough, three for beetroot leaves, which hold soil well.
  4. Spin them properly in a salad spinner, then pat with a tea towel. Residual water thins the pesto, dulls it and shortens how long it keeps.
  5. Discard anything yellow, slimy or brown-spotted. A leaf that has started to break down is not rescued by blending.

Sorting is also a decision point. If a third of the bunch has gone, make half a batch with what is still good rather than blending the lot out of principle.

The base recipe, weighed

A recipe built on “a handful of greens and a glug of oil” does not repeat from one week to the next. These proportions give roughly 200 g of pesto, enough for six to eight portions of pasta.

Ingredients

  • 80 g washed and dried greens, leaves and thin stems
  • 40 g sunflower seeds, or almonds, walnuts or cashews
  • 30 g grated hard cheese, or 15 g nutritional yeast for a plant-based version
  • 1 garlic clove, green germ removed
  • 80 to 100 ml olive oil
  • 1 tablespoon lemon juice
  • Salt

Method

  1. Toast the seeds. Three to four minutes in a dry pan over medium heat, stirring. They should colour and smell nutty, not smoke. This step changes the result more than anything else: raw sunflower seeds give a flat green note, toasted ones give body. Let them cool before blending.
  2. Grind the dry ingredients first. Seeds, garlic, cheese or yeast, a pinch of salt, blitzed to a coarse powder. Doing it in this order prevents hard nuggets in the finished sauce.
  3. Add the greens and lemon. Blend in short pulses, two seconds at a time, scraping the sides between pulses.
  4. Pour the oil in a thin stream with the motor running. The emulsion holds better and the sauce stays homogeneous longer. Stop at the texture you want: loose for pasta, firmer for toast.
  5. Taste and adjust. Salt last, because the cheese has already brought some. If it tastes too bitter, add lemon and fat, not sugar.

Why short pulses matter

A powerful blender running continuously heats the mixture. Heat accelerates oxidation of the leaves, which turns the colour khaki and hardens the bitterness. Short pulses keep it green. If you want a bright green that lasts, blanch the greens for thirty seconds in boiling water, refresh them immediately in iced water and squeeze them dry before blending: the colour holds for days, at the cost of some of the vitamin C.

Storage, the part most recipes get wrong

This is where leafy-tops pesto articles go astray most often, with their casual “keeps for up to a week”.

In the fridge. The UK Food Standards Agency advises setting your fridge between 0 and 5 °C and eating home-made leftovers within 48 hours, or freezing them. The US FDA sets the same temperature requirement at 40 °F, roughly 4 °C. A leafy-tops pesto is a raw, moist, unacidified preparation in which nothing has been heated: the 48-hour rule is the one that applies. The film of oil on top limits oxidation and therefore browning, but it sterilises nothing and does not extend shelf life.

In the freezer. This is the right answer for anything beyond two days’ eating. A domestic freezer at around -18 °C puts bacteria on pause. Freeze in an ice cube tray, then turn the cubes out into a bag: you take what you need without defrosting the batch. Cheese does not survive freezing well texturally, so if you plan to freeze, make the base without it and stir cheese in after thawing.

The garlic and oil question, worth understanding. Raw garlic under oil, left at room temperature, is a textbook botulism risk. Clostridium botulinum is a strict anaerobe, its spores are widespread in soil and are heat resistant, and the WHO notes that in the absence of oxygen they germinate, grow and produce toxin. The same fact sheet states that the bacterium will not grow in acidic conditions below pH 4.6. A study in Foodborne Pathogens and Disease in 2022 identified 37 cases of foodborne botulism in the United States between 1994 and 2021, including 4 deaths, linked to inadequate refrigeration of products that had not been processed to destroy spores; the authors explicitly recommend adding a secondary barrier such as an acidifier.

For your jar in practice: a pesto is not a garlic-infused oil. It contains leaves, salt, usually lemon, and it goes straight into the cold. The risk is low. But keep the three habits: refrigerate immediately, never leave a jar of garlic in oil sitting on the worktop, and do not treat “it is covered in oil” as a licence for long ambient storage. If flavoured oils interest you, our guide to home-made flavoured oils deals with the topic in detail.

Vitamin K, oxalate and nitrate: who this concerns

Green tops are not a neutral food for everyone. Three points deserve to be stated plainly, without alarmism and without being quietly skipped.

Vitamin K and anticoagulants. The NHS states that foods high in vitamin K, such as broccoli, spinach and other green leafy vegetables, can affect how warfarin works. Its advice is not to cut those foods out, but to avoid big sudden changes in diet and to talk to your warfarin clinic. The USDA figures give the order of magnitude: 400 µg of vitamin K per 100 g of raw beet greens, 251 µg for turnip tops. If you are on warfarin and you start eating leafy pesto daily, flag the change.

Oxalate and kidney stones. A review published in Nutrients in 2020 on dietary oxalate intake and kidney outcomes points out that oxalate has no known physiological function in humans, is cleared by the kidneys, and that a high dietary load has been linked to calcium oxalate stone disease and kidney injury. The table it reproduces gives 658 mg of oxalate per 100 g of spinach, 433 mg for rhubarb and 61 mg for beetroot, and it lists green leafy vegetables among the higher oxalate foods. Beet leaves belong to the same botanical group as spinach and chard. If you have had calcium oxalate stones, the point is not to exclude these vegetables but to discuss them with your doctor rather than doubling your intake on the strength of a cookery article.

Nitrate. Leafy vegetables accumulate nitrate in amounts that vary with light, temperature and fertilisation, as documented in a 2020 review in Foods. That variability is exactly why no composition table can tell you what is in your particular bunch. For a condiment eaten by the spoonful the question stays theoretical in adults; it is one more reason not to turn leafy pesto into a main dish for an infant.

None of this is a diagnosis or individual medical advice. If you are on treatment or a prescribed diet, the decision belongs to your doctor.

What leafy pesto really gives you

A pesto is a fatty, salty condiment. It does not compare with a portion of vegetables and nobody should read it that way.

What it does give you, at 25 to 30 g per plate: some fibre, a little plant potassium, calcium and iron, the unsaturated fats from the oil and nuts, and above all a reason to eat the steamed vegetables, wholegrains and pulses already in your fridge. The WHO recommends at least 400 g of fruit and vegetables a day and at least 25 g of fibre for anyone over ten; if a green sauce is what gets the ratatouille and the leftover quinoa eaten, that is where its value sits.

The thing to watch is salt. The WHO recommends limiting intake to less than 5 g of salt a day in adults, and condiments are an easy source to underestimate. Hard cheese already brings a lot: if you use it, salt lightly or not at all, and taste before correcting. Nutritional yeast brings savoury depth without the sodium, and we have a dedicated article on it.

On iron, a useful reminder: the iron in leaves is non-haem iron, absorbed considerably less well than animal iron and heavily dependent on what else is on the plate. The lemon juice in the recipe pushes in the right direction. Our piece on optimising plant iron absorption sets out what helps and what gets in the way.

Six ways to use it

Pasta. The classic, with one rule: never heat pesto in the pan. Drain the pasta, then stir the sauce through off the heat with two spoonfuls of cooking water. The starch in that water binds the sauce and stops the oil splitting.

On toast. Grilled bread rubbed with garlic, chopped tomato, a little salt. This is the use that shows off a radish-top pesto best, since the pepperiness comes through cold.

Pizza or tart base. In place of tomato sauce, spread thinly on raw dough before the toppings. Fennel-frond pesto works particularly well under courgette and ricotta.

Salad dressing. One spoon of pesto, one of vinegar, two of warm water, whisked. You get a thick dressing that clings to sturdy leaves or cold pulses.

Soup. A spoonful dropped on a squash or split pea soup at the last moment, left unstirred. The contrast between hot soup and cold pesto is enough to lift the bowl without further seasoning.

Roasted vegetables. After roasting, never before: at 200 °C the pesto would burn. It suits already caramelised roasted vegetables, whose sweetness answers the bitterness of the greens.

Five variations that work

  • Radish tops, chilli, cashew. The fat in the cashews tempers the radish heat. Good on tacos and corn tortillas.
  • Beetroot leaves, lemon, pumpkin seeds. The red ribs tint the pesto pink depending on how many you keep in. Lemon is mandatory here, not optional: the earthiness needs acid.
  • Fennel fronds, almond, orange zest. Aniseed and citrus belong together. Toast the almonds longer than you would other seeds.
  • Carrot tops, walnut, mustard. Half a teaspoon of mustard stabilises the emulsion and keeps the texture creamy a day or two longer.
  • End-of-week mix. Whatever edible greens are left, cut with parsley or basil to give the flavour a direction. Often the best jar, and never twice the same.

Common mistakes

  1. Blending a tired bunch. Limp leaves give a dull, bitter pesto. If the tops are more than two days old, throw out the soft ones and work with the rest.
  2. Keeping the thick stalks. They stay fibrous however long you blend and leave strands in the mouth. Leaves and thin stems only.
  3. Poor drying. Residual water blocks the emulsion, dilutes the flavour and shortens the fridge life.
  4. Blending too long. Heat oxidises, the colour turns, the bitterness climbs. Short pulses.
  5. Too much garlic. One clove per 80 g of greens is enough. Raw garlic grows stronger as it sits; a jar that tastes right on day one can be aggressive on day two.
  6. Salting before tasting. Hard cheese has already salted the mix.
  7. Believing oil preserves it. It limits surface browning and has no antibacterial effect. The 48 hours in the cold still stand.
  8. Heating the pesto. It loses its aroma and the oil separates. Stir it in off the heat.
  9. Cooking unidentified leaves. Rhubarb, potato, tomato, garden plants: check the list at the top of this article before blending a leaf whose origin you do not know.
  10. Treating it as a vegetable serving. It is a fatty, salty condiment. It accompanies vegetables, it does not replace them.

Frequently asked questions

Are carrot tops toxic? No. They are commonly eaten and are studied as a food material, including in recent scientific literature. The confusion usually comes from worry about photosensitising compounds in the carrot family, but that concerns prolonged skin contact with sap under strong sunlight, an occupational harvesting situation, not a spoonful of pesto.

Can I use beetroot leaves if I am watching my kidneys? That is a question for your doctor. Leaves from the spinach and chard family sit among the higher oxalate green leafy vegetables in the kidney stone literature. Occasional use is not the same question as a large daily intake.

Do the greens need to be organic? Not necessarily, but tops are thin leaves that you neither peel nor cook. Careful washing in several changes of water remains the main step, whatever the growing method. The broader question is covered in our article on whether you have to buy organic.

How long does leafy pesto keep? 48 hours in a fridge set between 0 and 5 °C, following the UK rule for home-made leftovers, or several months frozen in portions. Darkening at the surface is oxidation, not a safety indicator: it does not replace the calendar.

Can I skip the cheese? Yes. Nutritional yeast gives a cheesy note with far less sodium. A spoonful of white miso also works, provided you drop the added salt to zero.

Is a stick blender enough? Yes, in a tall narrow jug rather than a wide bowl, otherwise the leaves ride up instead of being drawn in. A mortar and pestle works too and avoids heating entirely, at the price of ten minutes of arm work.

What do I do with the thick stalks? Stock. They give body to a vegetable base alongside onion skins and celery tops. We set out the method in our umami-rich home-made broths.

Sources