Pressure Canning: How to Make One Harvest Last All Year

When you’ve had a bumper harvest and don’t want to waste what you’ve taken months to grow, there is one fantastic method that will help you to preserve as much of this bounty as possible. There’s no freezer space needed, no complicated recipes, and it’ll mean you can store almost anything from the garden at room temperature for a year or more.

I’m going to share two effortlessly adaptable variations, and making the case for why a pressure canner might just be the best investment you could make for your garden…

Pick Perfect Produce

Anything you preserve is only ever as good as what you pick, so timing your harvests just right is of the essence. For instance, beans should be young, firm and snappy, and picked before the pods turn stringy or the seeds inside start to swell too much, while carrots are best pulled while they’re still tender, before summer’s heat makes them woody at the core.

Whatever you’re picking, always go for produce that’s clean and blemish-free – nothing bruised, split, or the least bit past its prime. Preserving won’t improve on what we start with, so only the best makes the cut.

Under Pressure

Pressure canning is just as it sounds – canning or bottling produce under pressure, which is fantastic because the alternative, water bath canning, only ever brings the produce up to boiling point. That’s fine for foods with a higher acid content (for instance most fruits), but low-acid foods like most vegetables may harbour the spores that cause botulism, a rare but genuinely serious form of food poisoning.

Pressure canning uses pressure to trap steam and push the temperature up way beyond boiling point to around 240ºF (around 116ºC), which is more than high enough to destroy those spores. It’s the only method proven safe for canning vegetables on their own, without added acid. I like pickles, but I don’t want everything to taste tart and sharp, and pressure canning enables that.

Pressure Canner Equipment List

Let’s take a moment to talk money, because a decent pressure canner isn’t exactly pocket change – you’re typically looking at anywhere between £70 to £200 ($100 to $300), depending on its size and features.

But consider that a single quart or litre jar of canned beans holds roughly two pounds or a kilo of fresh produce. If beans cost, say, £2.50 or $3 per pound in the shops, that makes a jar of them worth around £5 or $6 – and that’s before you even factor in the freshness or the flavour of your own home-grown organic goodness.

Can just 20 jars across a season, and you’ve matched the cost of the canner – and it doesn’t stop there because, of course, that canner will go on to pay for itself time and again, season after season, for years to come.

But the bit I especially love is that, unlike freezing, once you’ve canned your produce, no more power is needed. No precious freezer space, no worrying about a power cut spoiling months of hard work. Just a cool, dark shelf, and food that’s ready whenever you need it. For anyone serious about growing their own, I really do think that this is one of the best investments you can make in your kitchen.

So let’s get canning! Alongside the pressure canner itself, we’ll need much the same kit as for water bath canning: canning jars with two-piece lids, a rack for them to sit on, a jar lifter, a wide-mouthed funnel, a ladle, and something non-metallic like a rubber spatula to release any air bubbles. A useful thing worth having is a magnetic lid wand, just to lift those hot lids out of their warming water without fishing around, but tongs will do the job too.

Do check your canner’s manual for its exact capacity and settings before you start – there are a few different types out there, and yours might vary slightly from mine.

Before you start, bring your canning jars up to temperature so they don’t crack when you add hot water. There are a couple of ways to do that. You can pop the jars into the canner on a rack to lift the off the bottom, add around 4in (10cm) of cold water, and turn on the heat to gradually bring the water up to a gentle simmer. The jars can stay in there till they’re needed.

Alternatively, simply lay them onto a baking sheet and pop them into the oven. Turn on the oven to around 200ºF (around 95ºC) and keep them in there till everything’s up to heat and the glass has warmed right through.

Pressure Canner Basics: Plain Packing Vegetables

The simplest thing you can possibly do with a pressure canner is to preserve vegetables just as they are, with nothing more than a little water and, if you like, a pinch of salt. This is blissfully brilliant because once you’ve got this method nailed, it will work for any low-acid veggies you’re likely to be harvesting, whether that’s beans, carrots, peas, sweet corn, beetroot – you name it!

Start by washing your vegetables well, then trim and cut them to the size you want. You can then either raw pack, where the raw vegetables are simply packed straight into the jar, or hot pack, where they’re briefly boiled first to preserve their colour a bit better.

Pack the prepped produce fairly snugly, but don’t crush anything down in the process. Leave an inch, (2-3 cm) of headspace at the top of the jar.

If you fancy it, for added flavour now’s the time to add a pinch of salt – about half a teaspoon for a pint jar, or a full teaspoon for a quart. Use purpose-sold canning and pickling salt to avoid the water going cloudy, but if you can’t find that, any salt is fine. Cover the produce with boiling water, keeping that one inch of headspace.

Slide a bubble remover or spatula down the inside of the jar to release any trapped air, and top up with a little more water if the level drops. Wipe the rims clean with a cloth, then twist on lids fingertip-tight so they’re snug, but not overly forced.

Return the jars to the rack inside the canner so they’re not touching, making sure there’s still around 3cm (7 cm) of boiling water in the bottom. Lock on the lid securely and turn the heat up to medium-high.

The next step is venting to clear out any trapped air. Let a steady plume of steam escape from the vent for a full ten minutes before adding the weight or pressure limiting valve.

Once vented, add the weight and let the pressure build to 10 pounds for a weighted gauge, or 11 for a dial gauge – and then start a timer, depending on what you're canning:

Once the time’s up, turn off the heat and - this bit’s important - just leave it be. Don’t force-cool it or rush to release the pressure, just let it drop back to zero on its own, which can take anywhere from 20 minutes to an hour.

Pressure Canner Vegetable Stock

You can use the very same principles to make something indispensable for all manner of recipes: a homemade vegetable stock. It’s the perfect way to use up all those slightly wonky bits and pieces such as carrot tops, celery ends, onion skins, herb stalks – alongside whatever’s cropping well of course.

Really, there’s no fixed recipe here: a rough mix of carrots, celery, onions, and a few herb sprigs is a good base, but you can swap in whatever you’ve got a glut of. Roughly chop everything up. There’s no need for neatness, because it’s all getting strained out later. Then pop it all into a big stockpot and cover generously with water.

Bring it up to the boil, then drop it down to a gentle simmer for around an hour, letting all that flavour work its way into the water. And once it’s ready, strain out the vegetables through a sieve, cheesecloth or muslin, and ladle the hot stock straight into warmed jars, leaving that same inch (2cm) of headspace. This is what’s called a hot pack, because the food’s already piping hot when it goes in, so it’s an especially quick and easy jar to fill.

Again, remove any air bubbles, wipe the rims clean, and then seal them exactly as before. Pop the jars into the canner with the same process as before: vent for ten minutes then bring them up to pressure. Stock takes about 30 minutes for a pint or half-litre-sized pot, or 35 for quarts or full litres.

And that’s genuinely it. Come the depths of winter, you’ll have a shelf of at-their-prime vegetables and stocks, perfect for transforming into instant soups, stews and risottos.

The Final Steps

To safely remove jars from the canner, wait until it’s fully depressurised, then wait another ten minutes. Carefully remove the lid, tilting it away from your face to dodge any escaping steam. Lift the jars out onto a folded towel using jar tongs, and leave them completely undisturbed for at least 12 hours.

After that, all that’s left to do is to check that each lid has sealed properly by removing the band and pressing the centre – there should be no give or popping up and down. Anything that hasn’t sealed should go straight into the fridge to be used within a few days. Everything else gets a label, a date, and a spot on a cool, dark shelf, where it’ll happily keep for at least a year.

And that’s pressure canning demystified – a fantastic way to make sure nothing you’ve grown ever goes to waste again. Let me know in the comments what you’re most looking forward to canning this year!