The best logs for growing mushrooms in the UK are freshly cut hardwoods: oak, beech, birch, alder, ash and elm. Fruit woods such as apple, pear and cherry also work. Softwoods and conifers do not, so leave the pine, spruce, larch and leylandii for the fire. The wood must be freshly cut, with its bark intact and its moisture still in it.

Once you know what is in the woodpile, the rest is simple. Each Outdoor Mushroom Log Growing Kit comes with 30 inoculated wooden spawn plugs, beeswax for sealing the holes and log ends, and full instructions. You supply the log, a drill, an 8mm bit and a way to melt the wax. Kits start at £10.00, or £8.00 each when you order more than 2 of the same variety, and the plugs keep in the fridge for two to three months while you wait for the right log.

Can you grow mushrooms on any log?

No. A log is food, and the fungi we grow are fussy eaters.

Wood-loving mushrooms live on lignin and cellulose, the two things that make timber stiff. Hardwoods hold plenty of both in a dense structure that takes years to break down. That slow meal is what gives you three to five years of cropping from one log rather than a single flush.

Softwoods are different. Pine, spruce, fir, larch, cedar and leylandii carry resins and phenolic compounds the tree makes to defend itself. Those sit in the wood long after felling and stall the mycelium of the species we grow. Conifers are sappy too, and often reach you already colonised by blue stain fungi.

If all you have is conifer, do not force it. Grow indoors instead and come back to logs when hardwood turns up. The range of ready growing mushroom kits arrives already colonised and crops in weeks rather than seasons.

What does "freshly cut" actually mean?

It means the log came off a living tree, and it means weeks since the saw went through, not months. Aim to inoculate between two and eight weeks after felling.

A living tree defends itself. Its sapwood carries anti-fungal compounds and its cells are still active, and those defences are strongest straight after felling. Drill within the first two weeks and those residual compounds can hold your spawn plugs back, which is why you rest the log rather than drilling it the same afternoon.

Leave it longer than eight weeks and you lose the other way. The log dries from the ends inwards, mycelium cannot advance through wood gone hard and light, and every airborne spore in the hedgerow has had time to move in ahead of your plugs. So: fell, rest two to eight weeks, inoculate.

The full method, from drilling pattern to where to stack the finished log, is in our guide on how to grow mushrooms on outdoor logs.

What size should a mushroom log be?

Thick enough to hold water, short enough to lift.

Diameter drives longevity. A thin branch holds little food, colonises fast and is spent in a season or two. A stout trunk section takes longer to colonise but crops for years. Forearm through to thigh thickness is the sweet spot most growers settle on, because that is the size that holds moisture through a dry spell without needing two people to move it.

Length is about handling. You want a log you can lift on your own, roughly the length of your arm. Too short and it dries from both ends at once. Too long and 30 plugs are spread too thinly to colonise it before something else does. If your log is oversized, cut it down or use two kits.

Why does the bark matter?

Bark is the log's skin. It holds moisture in and keeps competitors out.

A log with tight, unbroken bark sits in a shady corner for years and stays damp inside. Strip it, or use a log whose bark is already sloughing off, and the wood dries fast while every passing spore has a way in. Loose bark is also a reliable sign the tree has been dead a while. Scuffs from felling are nothing to worry about. What you avoid is a log gone grey and shaggy.

How do you judge moisture without a meter?

Use your hands and your ears. Three tests, no equipment.

Weight. Pick it up. A fresh hardwood log is heavy for its size because it is full of water. If it feels light, it has dried out.

The cut ends. Fresh end grain is pale, damp and often slightly sticky. Deep splits running from the centre outwards mean months of drying.

The knock. Rap it with a piece of the same wood. Damp wood thuds. Dry wood rings.

Fail all three and it is firewood. If it is borderline and a species you want, stand it in a water butt for a day before inoculating. That works better on birch and alder than on oak.

Which wood suits which mushroom?

Every suitable hardwood works with every variety we supply. What changes is the pace and how long the log keeps going.

Oak. Dense, tannin rich and slow. It takes its time to colonise, then gives the longest cropping life of any wood here. The traditional choice for Shiitake.

Beech. Dense like oak but quicker to take. What growers reach for when they want oak's longevity without oak's patience. Good with Shiitake and Lion's Mane.

Birch. Fast. Softer, thinner barked and full of moisture, so mycelium runs through it quickly and fruiting comes sooner. The trade off is a shorter working life. Oysters love it.

Alder. Much like birch: quick to colonise, generous early on, less durable long term. Often free from clearance work on damp ground.

Ash. Medium density, reliable. With ash dieback there is a lot coming down. Take it from a living tree, not a standing dead one, because the dead ones are colonised already.

Elm. Dense, tough, slow, long lasting once colonised. Harder to come by, but if it turns up, take it.

Fruit woods. Apple, pear, cherry and plum all work. Gnarled and short in the trunk, so expect awkward lengths, but they colonise well and are often free after an orchard prune.

Matching wood to the seven log kit varieties

The log kit range runs to seven varieties, and each has a wood it gets on with best.

Shiitake (Lentinula edodes) is the classic log mushroom, the most widely cultivated log species in the world. Oak and beech first, then ash. To taste it before committing to a log that fruits in 12 to 18 months, the Shiitake ready growing kit at £19.95 crops indoors in weeks.

White Oyster (Pleurotus ostreatus var. florida) is the fastest and most forgiving. Birch, alder, beech, poplar and willow all suit it. More in our piece on growing White Oyster mushrooms outdoors in the UK.

Summer Oyster (Native) and Tarragon Oyster (Native) are UK natives, already suited to our climate and trees. Beech, birch and ash.

Lion's Mane (Hericium erinaceus) prefers dense wood. Beech and oak give the best results, and the log wants deeper shade than the oysters.

Golden Enoki (Flammulina velutipes) does well on softer hardwoods: birch, alder and the fruit woods. It fruits in autumn, later than most, as the weather turns cool.

Turkey Tail (UK Native) is Trametes versicolor, the newest addition. A native bracket fungus found on dead and dying hardwood across Britain, fan shaped with concentric bands of colour. Tough and leathery rather than tender, so it is used for teas and decoctions rather than cooked as a vegetable, with a long history of traditional use, particularly in East Asia. Oak, beech and birch all suit it.

Worked example one: a silver birch has just come down

A homeowner in Sussex has a silver birch taken out by a tree surgeon on a Saturday in March. The crew leaves the trunk and limbs stacked by the shed. Here is the run of it.

Saturday. Ask the crew to leave the straight sections rather than chipping everything. Keep the trunk and the thicker limbs, forearm thickness and up.

Sunday. Cut to length with a bow saw, roughly arm's length per log. Four logs from the trunk, two from the limbs. Stack them off the ground on a pallet, shaded, on the north side of the shed, covered loosely with hessian, not plastic, because plastic sweats.

The wait. Two weeks or so, comfortably inside the two to eight week window. Long enough for the tree's defences to drop away, short enough that the wood is still heavy and the cut ends still pale.

Meanwhile. Birch is quick and soft, which suits oysters, so White Oyster and Golden Enoki are the sensible picks. Three kits of one variety works out at £8.00 each. Plugs go in the fridge on arrival.

Inoculation day, late March. Drill 8mm holes round each log, tap in the plugs, then seal every hole and both cut ends with melted beeswax. Thirty plugs covers a log this size.

After. Stack the logs in the shadiest corner, standing on soil or half buried in leaf litter, and leave them. Water in a long dry spell. Birch being quick, first fruiting may come early in the 12 to 18 month window rather than at the far end.

Worked example two: sorting a mixed load of firewood

A neighbour offers a trailer load of "logs". Here is how to sort it.

Out: anything with needles, a resin smell or orange-brown sappy end grain. Pine, spruce, larch, leylandii.

Out: anything grey, light, shaggy barked or with fungi already fruiting on it. That log has an owner.

Out: anything split for the fire. Splitting destroys the bark and lets the moisture go.

Keep: whole rounds of oak, beech, birch, ash or fruit wood with tight bark, pale damp end grain and real weight. Knock two together. Thud, not ring.

Maybe: rounds that look right but feel light. Stand them in a water butt overnight and reassess.

From a typical trailer load, expect three or four usable logs, enough for one or two kits. The rest is firewood, which is what it was always going to be.

Where can you get logs in the UK, legally?

Four reliable routes, and one rule.

Your own garden. Any hardwood you fell or prune yourself is yours, subject to Tree Preservation Orders and conservation area rules. Check with your council before a saw comes out.

Tree surgeons. The best source in the country. They pay to dispose of arisings, so a request for a few lengths of hardwood is often welcomed. Ask for whole rounds, unsplit, and name the species.

Woodland thinnings. Estates, community woodlands and conservation groups thin regularly and the wood often goes for chip. Ask the woodland manager.

Firewood merchants. Useful, with one caveat: most sell seasoned, split wood, which is no good. Ask for green, unsplit rounds.

The rule: never take wood from land you do not own without permission. That includes commons, council woods, National Trust land and the roadside. Removing timber without consent is theft, and there is nothing to gain by it when tree surgeons give the stuff away for free.

Common mistakes and what to do about them

The log turns out to be the wrong wood. If you have already drilled a softwood log, you have lost those plugs. Do not chase it. If you have not drilled yet, the log becomes firewood and you find a hardwood replacement. If you inoculated a hardwood but picked a mismatch, say Lion's Mane on birch rather than beech, carry on. It will work, just not for as long.

The log was already dead when you found it. The most common failure of all. A log lying in a wood for a year is not empty, it is full. Native fungi, bacteria and insects moved in within weeks of it hitting the ground, so your 30 plugs arrive into an occupied house and lose.

Storing logs before inoculation. Off the ground, in shade, out of the wind, loosely covered with something breathable. Never plastic, never full sun. Stack cut ends inwards where you can, since that is where moisture escapes.

Stumps and branches. A fresh hardwood stump can be inoculated in place by drilling the cut face and the sides. Good use for a stump you cannot remove, though results are less predictable because it is still joined to a root system. Branches under wrist thickness colonise fast and give one or two small flushes: worth doing with leftover plugs, not worth buying a kit for.

Frequently asked questions

Find a hardwood log, rest it two to eight weeks, then put spawn in it. That is the whole job, and the log does the rest for years. Six generations of growing at Merryhill Mushrooms says the same thing every time: the log you choose on day one decides how good the next five years are.