A bunch of chives left on the worktop at 20 °C burns through its reserves 24 times faster than the same bunch at 0 °C: 540 milligrams of CO2 per kilogram per hour against 22, according to the tables in the United States Department of Agriculture’s Handbook 66. Almost everything else on this page follows from that single figure. Cold does not preserve herbs by magic. It slows a respiration that keeps consuming sugars and aroma compounds until the last leaf gives up.

Two caveats belong right here. Your fridge is not at 0 °C. And basil is the one herb that breaks the rule, by a margin of ten degrees. Those two qualifications explain why the shelf lives quoted in professional handling guides are almost never achieved in a home kitchen.

What actually kills a bunch of herbs

Three processes run in parallel, and they call for different countermeasures.

Respiration first. A cut leaf is still living tissue, oxidising its own sugars. Handbook 66, the reference work for North American cold chain practice, publishes these measured rates in milligrams of CO2 per kilogram per hour:

Herb	0 °C	10 °C	20 °C	Ratio 20/0
Chives	22	110	540	24.5
Dill	22	103	324	14.7
Mint	20	76	252	12.6
Thyme	38	82	203	5.3
Sage	36	103	157	4.4
Basil	36	71	176	4.9
Parsley	22 to 38	78 to 150	176 to 221	5.8 to 8.0

Water loss second. Parsley is the best documented case. At 0 °C with 95 to 100 per cent relative humidity, its commercial storage life reaches one to two months, and the end point corresponds to roughly 20 per cent weight loss. At 18 to 20 °C with 85 to 90 per cent humidity, the same source gives three days. A factor of ten to twenty, achieved by changing nothing but the surrounding air.

Ethylene third. Fresh herbs produce very little of it but are extremely sensitive to it. Parsley releases 0.08, 0.44 and 0.80 microlitres per kilogram per hour at 0, 10 and 20 °C, and as little as 0.4 microlitres per litre in the surrounding atmosphere is enough to accelerate yellowing once it is stored above 0 °C. That is the technical reason a bunch of herbs stored next to ripe apples or tomatoes yellows faster than one kept on its own.

The number that shifts every storage time: your fridge

The published figures for distribution assume 0 °C. A domestic refrigerator is nowhere near it. A citizen science study in the Journal of Food Protection fitted 361 Scottish households with data loggers on the top and bottom shelves. The mean temperature was 5.17 °C, with household averages running from -0.39 °C to 10.94 °C. More than half the appliances, 55.4 per cent, ran above the recommended 0 to 5 °C range, and 27 of the 361, or 7.5 per cent, never reached that range at any point during the trial. Top shelves averaged 5.89 °C, bottom shelves 4.45 °C.

Map that 5 °C onto the respiration table and the arithmetic becomes concrete. Parsley goes from 22 to 38 milligrams of CO2 per kilogram per hour at 0 °C to 49 to 70 at 5 °C, roughly a doubling. The one to two months of the professional guide become a matter of weeks in an average appliance, and a matter of days in one running at 8 or 9 °C. None of which makes domestic refrigeration pointless. It means you should stop reasoning in absolute shelf lives and start with the one action that has a measurable effect: find the coldest spot in your appliance and keep herbs there. That spot is almost always at the bottom.

Basil is the only herb that cold damages

Handbook 66 splits culinary herbs into two entries, annual and perennial, and exactly one species gets the opposite instruction to all the others. Basil suffers chilling injury below 12 °C. The symptom is browning and then blackening of the leaves, and chilling also increases its susceptibility to decay. The professional instruction is explicit: do not cool it below 12 °C after harvest, store it at 12 °C with 95 to 100 per cent relative humidity, where it holds for two weeks, and do not display it in refrigerated units below that threshold.

Set that threshold against the 5.17 °C average of domestic refrigerators and the verdict is plain. A normal fridge sits seven degrees below basil’s chilling injury threshold. Leaves that blacken within two days in the cold are not badly packaged. They are cold injured.

The logical answer is neither the fridge nor the worktop. At 20 °C basil respires at 176 milligrams of CO2 per kilogram per hour against 36 at 0 °C, nearly five times as fast, and it loses water accordingly. The 12 °C target corresponds to a cellar, a larder, an unheated pantry, the door shelf of an appliance set warm, or a wine fridge. If you have none of those, the honest call is to treat basil as a two or three day product and process the surplus straight away, as pesto or frozen cubes, rather than hunting for a storage spot your kitchen does not contain.

How long each herb really keeps

The figures below come from the two Handbook 66 entries and describe professional storage at the stated temperature and relative humidity. Treat them as a ceiling rather than a promise, and discount them generously for a home appliance running at 5 °C.

Herb	Target temperature	Relative humidity	Life under optimal conditions
Parsley	0 °C	95 to 100 %	1 to 2 months
Chives	0 °C	95 to 100 %	2 to 3 weeks
Mint	0 °C	95 to 100 %	2 to 3 weeks
Rosemary, sage, thyme	0 °C	90 to 95 %	2 to 3 weeks
Savory	0 °C	95 to 100 %	up to 3 weeks
Coriander, dill	0 °C	95 to 100 %	2 weeks
Marjoram, oregano, tarragon	0 °C	90 to 95 %	1 to 2 weeks
Chervil	0 °C	95 to 100 %	1 week
Basil	12 °C	95 to 100 %	2 weeks

Two practical lessons come out of this. Parsley is by a wide margin the most robust herb on the list, which justifies buying it in a large bunch while treating chervil or coriander as purchases for the week ahead. And rosemary, sage and thyme want slightly lower humidity than the tender leaves, which is why a perfectly airtight bag rots them while the same bag would suit parsley.

The fridge method, rebuilt around the right mechanism

The goal is not to wet the leaves. It is to hold nearly saturated air around them while letting CO2 and ethylene escape. The professional cold chain achieves that compromise with perforated polyethylene liners, which prevent dehydration without trapping gases. At home the equivalent comes down to five steps.

Take the herbs out of their retail packaging as soon as you get home, especially films pressed directly against the leaves, where condensation collects. Pull out any crushed, stained or yellowed leaves without hesitation: those are the ones carrying moulds and bacteria, and they contaminate the rest of the bunch. Pat the leaves dry if they are wet, because free surface water feeds decay while humid air protects. Put the bunch in a box or a perforated bag with a sheet of kitchen paper to buffer excess moisture. Store the lot in the lower part of the appliance, away from ripe fruit.

One often ignored detail matters as much: cut herbs with a knife rather than tearing them by hand, and cut them at the last moment. Every mechanical injury is an entry point for moulds and decay bacteria, which Handbook 66 explicitly notes as developing first on damaged leaves and cut stem ends.

The glass of water: what it does and what it does not

Standing the stems in a few centimetres of water works, but not for the reason usually given. Water does not genuinely rehydrate cut foliage through its vascular system the way it sustains cut flowers. What it does is hold high humidity around the stems and delay the wilting from dehydration that is parsley’s normal mode of failure.

That defines its limits. The method does not slow respiration, which depends only on temperature. It offers no protection against ethylene. It does not suit woody herbs such as rosemary and thyme, which prefer 90 to 95 per cent humidity and rot with their feet in water. And it requires changing the water, without which the glass becomes a culture broth in direct contact with cut stems. So the glass of water is a sound reflex for parsley, coriander and mint, a poor idea for hard-leaved herbs, and never a substitute for cold.

Freezing: the only method that stops the clock

Freezing is the only technique on this page that halts respiration rather than slowing it. It wrecks the texture, since ice crystals rupture cell walls, and thawed leaves will be limp. For anything that goes into cooking, a sauce or a soup, that loss of texture is irrelevant.

Three formats cover most uses. Whole leaves, washed and then genuinely dried, frozen flat on a tray before transfer to a bag, let you take exactly what you need. Chopped herbs drowned in a little water or oil in ice cube trays give portions ready for the base of a pan. Pesto and blended sauces freeze the same way, in cubes.

That last form deserves a safety note, because it is the only herb-in-oil variant that extension services endorse for long storage. Oregon State University Extension Service states explicitly that crushed vegetables and herbs in oil can be frozen in ice cube trays and then packaged in airtight containers, and that pesto must be refrigerated and used within four days or frozen for long-term storage. Here the freezer is not a convenience, it is the condition of preservation.

On duration, sub-zero storage sets no safety limit as long as the cold chain holds. The limit is quality. Aroma fades, oxidation continues slowly and odours migrate between foods, which the same guidance advises avoiding with genuinely airtight containers. Label with the freezing date and judge by smell rather than by the calendar.

Drying: quickly and warm, not slowly

Drying is the oldest method, and it is also where domestic advice diverges most from technical guidance. The National Center for Home Food Preservation gives precise parameters: preheat the dehydrator to between 35 and 46 °C, go up to 52 °C in humid regions, lay the leaves in a single layer, and expect one to four hours. Sun drying is not recommended, because it costs aroma and colour.

The decisive distinction is not between noble and ordinary herbs but between tender and tough leaves. Sturdy herbs, rosemary, sage, thyme, savory and parsley, air dry very well in small hanging bundles with no equipment at all. Tender high-moisture herbs, basil, oregano, tarragon, lemon balm and the mints, will mould if they do not dry quickly. For those, the same source suggests drying in a perforated paper bag, in very small quantities at a time, or leaf by leaf between sheets of kitchen paper in a very cool oven, a method it recommends specifically for humid climates.

That is the exact opposite of the common advice to air dry a big bunch of basil slowly. For this family of herbs, slowness is the problem, not the solution.

A few harvest and storage markers complete the picture. The best time to cut most herbs is just before the first flowers open, at the bursting bud stage, early in the morning once the dew has evaporated. Leaves are dry when they crumble and stems snap when bent. Storage goes into airtight containers, kept cool, dry and dark.

What drying costs in aroma, and what it does not

A study published in 2024 in the Journal of Food Science compared, on purple basil, freeze drying, sun drying, convective drying at 45, 50 and 55 °C, and microwave drying at 350, 460 and 600 watts. It documents a more nuanced trade-off than a flat “drying destroys everything”.

Raising the drying temperature improved retention of total phenolic content by an average of 16.28 per cent, and raising microwave power by 27.98 per cent. In the other direction, higher temperature lowered anthocyanin content and antioxidant activity. The drying methods significantly changed the composition of volatile compounds, with microwave drying producing a distinctly different aroma profile. The dominant volatiles measured in the leaf were linalool, 81 to 1176 micrograms per gram of dry weight, 1,8-cineole, 45 to 816, and methyl cinnamate, 13 to 638. The authors single out freeze drying, sun drying, convective drying at 45 °C and microwave drying at 600 watts as favourable.

Two limits belong alongside those numbers. This was one purple basil cultivar, and extrapolation to thyme or sage is not established. And the very wide ranges for the volatiles show how much variation there is between samples: the direction of the effects is more solid than their magnitude. The transferable lesson is that a dried herb’s aroma is not a weakened version of the fresh herb but a different profile, which is why dried basil disappoints on a raw tomato and performs perfectly well in a simmered sauce.

The practical counterpart is blunt: dried herbs are three to four times more concentrated than fresh ones. To substitute for a fresh herb in a recipe, use a quarter to a third of the stated amount. Most disappointment blamed on the quality of dried herbs comes down to that ratio.

Herb oils: the one real hazard on this page

A homemade flavoured oil is not a harmless preserve, and this is the point to be clearest about. Oil creates an oxygen-free environment, exactly the condition Clostridium botulinum needs. The bacterium is anaerobic, its spores resist heat and are widespread in soil, river water and sea water, and therefore on plants. The World Health Organization notes that botulinum toxin acts on the nervous system, that symptoms usually appear 12 to 36 hours after exposure within a range of 4 hours to 8 days, and that the disease is fatal in 5 to 10 per cent of cases. The same fact sheet gives the parameter that governs everything downstream: the bacterium does not grow in acidic conditions, below pH 4.6.

The precedent exists and it is documented. In 1985, thirty-seven people were diagnosed after eating a chopped garlic in soybean oil product served in a restaurant.

The current recommendation from Oregon State University Extension Service, in its entry revised in January 2025, is therefore stricter than what you usually read. Fresh herbs or vegetables in oil must be refrigerated and used within four days, or frozen. Mixtures based on dried garlic or dried herbs in oil fall under the same four day instruction. Pesto follows the same rule, and no research supports canning it. The guidance asks you to label the container with the preparation date and the use-by date four days later.

Two routes lead out of that four day window. The first is the freezer, in airtight cubes. The second is acidification, and it has been studied. Work published in 2014 in Food Protection Trends measured the effect of a 24 hour soak at 21 °C in a 3 per cent citric acid solution. For chopped garlic, a ratio of one part garlic to three parts solution brings the pH below the 4.2 target the authors adopted as a safety margin under the regulatory threshold of 4.6. For herbs, a ratio of one part herb to ten parts solution took basil from a pH of 6.28 to 6.50 down to 2.77 to 3.18, oregano from 6.48 to 6.67 down to 3.13 to 3.38, and rosemary from 6.28 to 6.74 down to 3.71 to 4.11. These are not protocols to improvise: the ratios, times and temperatures have to be followed exactly, and the extension service points to its dedicated publication rather than to a loose adaptation.

The short version, for anyone unwilling to weigh out citric acid: infuse the oil hot, strain it carefully so no plant solids remain in suspension, and treat any oil that still contains leaves, stems or garlic as a short-life refrigerated product rather than a pantry bottle.

Vinegar does not raise this problem

The contrast between oil and vinegar is instructive, because it isolates the real variable. Cider or wine vinegar sits far below the pH 4.6 threshold that blocks Clostridium botulinum. That is why the same Oregon State University entry notes that raw garlic may be stored in vinegar at room temperature, while it must be refrigerated in oil.

A herb vinegar therefore comes without the four day constraint: a few sprigs of tarragon, basil, sage or mint in a clean bottle, three to four weeks of infusion away from light, and a strain. The two precautions that remain are to use perfectly clean, thoroughly dry herbs, and not to dilute the vinegar with water, which would raise the pH and remove exactly the protection you are relying on.

What herbs genuinely bring to a plate

This is where the usual nutrition talk gets the scale wrong. Fresh herbs are extremely nutrient dense per kilogram. The Swiss Food Composition Database gives, per 100 grams of raw parsley: 58 kilocalories, 3.9 grams of protein, 4.3 grams of fibre, 850 milligrams of potassium, 210 milligrams of calcium, 5.9 milligrams of iron, 132 micrograms of folate and only 38 milligrams of sodium. Raw basil shows 250 milligrams of calcium and 5.5 milligrams of iron, chives 130 micrograms of folate, peppermint 9.5 milligrams of iron.

The problem is that nobody eats 100 grams of parsley. A generous tablespoon of chopped parsley weighs around 5 grams, one twenty-fourth of the 120 gram vegetable portion used in the Swiss dietary recommendations. Those 5 grams supply roughly 43 milligrams of potassium, 11 milligrams of calcium, 0.3 milligrams of iron and 7 micrograms of folate. At that scale, calling parsley a source of iron or calcium makes no sense.

Their real contribution runs through a different route, and that one is better supported. Global mean sodium intake in adults was 4278 milligrams per day in 2021, about 11 grams of salt, more than double the World Health Organization recommendation of less than 2000 milligrams of sodium, or under 5 grams of salt. Herbs, meanwhile, bring almost no sodium: 38 milligrams per 100 grams of parsley, 9 for basil, 3 for chives.

A review published in 2026 in Nutrition Reviews gathered seven studies described in four publications, all randomised within-subject crossover designs in older adults. Adding culinary spices restored liking of reduced-fat foods to levels comparable with the full-fat versions for most items tested. The strategy was less effective where fat carries the texture, a creamy pasta dish being the type case. For sugar reduction, it worked mainly in foods with complex flavour profiles where sweetness is not the dominant character. In protein-rich meals, adding spices increased flavour intensity and improved acceptance.

The reach of those results deserves stating precisely: they concern spices, an older population, and sensory liking rather than a clinical benefit. What they support is that a properly aromatised dish tolerates a cut in salt, fat or sugar without losing its appeal. That is the main nutritional reason to keep herbs available all year, and it has nothing to do with their vitamin content. If that lever interests you, our page on seasoning without salt using herbs, spices and citrus sets out the combinations that work, and our salt-free flavourful cooking plan turns it into a week of meals.

A word on dried herbs and safety, since the subject rarely comes up. A review published in 2026 in Comprehensive Reviews in Food Science and Food Safety notes that the low water activity of dried ingredients, fruits, vegetables, herbs and spices, limits microbial growth but does not eliminate bacterial pathogens, which can survive in them for extended periods. The practical consequence: a dried herb stirred into a simmering sauce raises no question, while the same herb sprinkled over a ready-to-eat dish with no further cooking follows a different logic, which is one more argument for freezing when the herb has to stay raw.

Five mistakes that keep coming back

Storing basil in the fridge with everything else. An average domestic appliance runs at 5.17 °C, seven degrees below basil’s chilling injury threshold. The blackening is not a packaging failure.

Washing herbs and then storing them wet. Humid air protects, free surface water feeds decay. Handbook 66 notes that moulds and bacteria develop first on damaged leaves and cut stem ends.

Slowly air drying a big bunch of basil. Basil, oregano, tarragon, lemon balm and the mints mould unless drying is fast. Small quantities, a perforated paper bag, or a dehydrator at 35 to 46 °C.

Leaving fresh herbs to infuse in oil at room temperature. This is the only practice on this page that carries a serious risk. Refrigeration and four days, or freezing, or complete straining of all solids.

Dosing dried herbs like fresh ones. They are three to four times more concentrated: a quarter to a third of the amount you would use fresh.

Adapting to your situation

You buy a big bunch at the Saturday market. Sort and dry it on arrival, keep three days’ worth of parsley or coriander in a perforated box at the bottom of the fridge, and freeze the rest in cubes straight away rather than betting on a week of shelf life.

Your fridge is an old appliance. In the Scottish study, 7.5 per cent of appliances never reached the 0 to 5 °C range. A cheap thermometer left for a week on the bottom shelf will tell you whether your problem is your herbs or your fridge.

You grow your own. This is the only setup that removes the problem, since harvest happens at the moment of use. Our pages on growing herbs on a balcony and on an indoor aromatic garden all year round cover the growing side, and cutting just before flowering remains the quality marker.

You mostly cook simmered dishes. Freeze everything in cubes and stop worrying about texture. The loss of firmness after thawing does not show in a soup or a tomato sauce.

You want raw herbs in salads all year. No preservation method delivers that. Seasonal fresh herbs, possibly topped up by an indoor crop, is the only honest answer.

You have a surplus of tops and stems. Treat them as herbs and turn them into pesto or stock, as set out in our anti-waste practices and our page on turning greens into pesto.

The limits of this page

The storage times quoted come from a commercial cold chain handbook, established at controlled temperature and humidity: they are a theoretical ceiling, not a forecast for a kitchen fridge. The domestic temperature data come from a Scottish sample of 361 households, useful as an order of magnitude but not as a measurement of your appliance. The drying study covers one purple basil cultivar and does not transfer mechanically to other species. The review on spices and food liking concerns older adults and sensory measures, not health outcomes. The oil safety guidance comes from a United States university extension service, but it rests on the microbiology of Clostridium botulinum, which does not change from one country to another. Nothing on this page replaces medical advice, and the composition figures are table averages rather than measurements of your own bunch.

Frequently asked questions

Should herbs be washed before storing? Washing removes soil but leaves free water on the surface. If you wash, dry them properly, in a salad spinner or a cloth. Otherwise wash them just before use.

Airtight bag or perforated bag? Perforated, or a box left slightly open. The point is to keep humidity in while letting CO2 and ethylene out. Woody herbs, rosemary, sage and thyme, tolerate lower humidity than tender leaves.

Why do my herbs yellow next to fruit? They are highly sensitive to ethylene while producing very little. For parsley, 0.4 microlitres per litre is enough to accelerate yellowing once it is stored above 0 °C.

Is blackened basil still edible? Cold-induced blackening is physiological damage rather than a sign of spoilage, but it increases susceptibility to decay. Discard soft or mouldy parts and use the rest quickly in cooking.

How long should frozen herbs be kept? Freezing sets no safety limit as long as the cold chain holds; the limit is aroma. Date them, wrap them airtight to avoid odour transfer, and judge by smell.

My homemade basil oil has been on the shelf for two weeks. Now what? Oregon State University Extension Service limits refrigerated herb-in-oil mixtures to four days and does not endorse room temperature storage while plant solids remain. A bottle like that goes out, and the strained or frozen version gets made instead.

Is sun drying a good idea? Not for herbs. The National Center for Home Food Preservation advises against it explicitly, because of the loss of aroma and colour.

Can several herbs share one container? For freezing and drying, yes, and that is the basis of homemade blends. For fresh storage, keep basil apart from the rest at a minimum, since it does not belong at the same temperature.

Sources

• USDA, The Commercial Storage of Fruits, Vegetables, and Florist and Nursery Stocks, Handbook 66, entries for Annual Culinary Herbs, Perennial Culinary Herbs and Parsley
• Temperature Profiling of Household Refrigerators in Scotland Using a Citizen Science Approach, Journal of Food Protection, 2026
• Oregon State University Extension Service, Herbs and vegetables in oil, SP 50-701, revised January 2025
• World Health Organization, Botulism fact sheet
• Acidification of Garlic and Herbs for Consumer Preparation of Infused Oils, Food Protection Trends, 2014
• National Center for Home Food Preservation, Drying Herbs
• Effects of different drying processes on the quality changes in purple basil leaves, Journal of Food Science, 2024
• The Use of Herbs and Spices to Improve Food Liking and Diet Quality, Nutrition Reviews, 2026
• A Risk-Based Framework for Ranking Microbiological Hazards for Dried Fruits, Vegetables, Herbs, and Spices, Comprehensive Reviews in Food Science and Food Safety, 2026
• World Health Organization, Salt reduction fact sheet
• Swiss Food Composition Database, FSVO
• FSVO, Swiss dietary recommendations for adults

To go further: preserving herbs by freezing, salt and oil, recycling dried herbs into infusions, salts and oils, the essential spices and herbs of a flavourful vegetarian kitchen, local medicinal herbs worth cooking with, edible wild herbs such as nettle and wild garlic, homemade gourmet gifts built on herb salt and a guide to homemade flavoured oils with garlic, herbs and citrus.