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Common gardening claims about mint, checked against the evidence. Sourced, and written for Scottish gardens. Every verdict links to the research or authority behind it.
16 claims we could check for Mint: 10 busted0 disputed1 untested5 hold up
Mint is one of the most shade-tolerant herbs, growing well in partial shade and preferring moist but well-drained conditions. In full sun it needs more water.
What to do: Give mint partial shade if you have it, particularly in the afternoon. Full sun works but demands more watering. The one thing mint genuinely dislikes is dry soil.
RHS lists a genuinely wide spread of species and varieties with distinct flavours, not shades of the same taste: spearmint and peppermint alongside apple mint, chocolate mint (described as tasting like an after-dinner mint), pineapple mint, Moroccan mint and lime mint, plus real differences in leaf size, texture and plant habit between them.
What to do: Choose by use rather than grabbing whatever's on the shelf: spearmint for general cooking, apple or pineapple mint for a milder fruity note, chocolate mint for desserts. Grow more than one in separate containers if you cook with mint often — they're different enough to be worth it.
The quantities involved make this hopeless at garden scale. Meaningfully diluting a soil that is 40 per cent clay takes around 250kg of grit or gravel per square metre. A barrowload does nothing, and adding modest amounts can destabilise the structure and leave the ground harder to work than before you started.
What to do: Add bulky organic matter instead: manure or composted bark, dug in generously. Raise beds to lift roots above the wet, and consider not digging at all. Those three do what the sand was supposed to do, and they compound each year rather than needing repeating.
In Scotland: Heavy clay runs right through the Central Belt, so this is one of the most expensive mistakes a Scottish grower can make. Two tonnes of grit for a small bed is not a purchase anyone makes twice.
This does the opposite of what it promises. A free-draining pocket surrounded by clay has nowhere to drain to, so it fills and holds water like a bucket sunk in the ground: the hole becomes a sump and the roots sit in it and rot.
What to do: Plant at the same level as the surrounding soil and improve the whole bed rather than one hole. Where drainage is genuinely bad, raise the bed so the roots sit above the wet instead of in a pocket of it.
In Scotland: Worth knowing here because our rainfall keeps that pocket topped up. In a dry climate a sump might drain between downpours; through a Scottish autumn it simply stays full.
Digging works against fertility rather than for it. Turning the ground releases soil nitrogen and damages the soil's biology. The structure that fungi, worms and roots build up over a season is undone every time the spade goes through it.
What to do: Leave the ground alone and feed it from the top. Spread compost or well-rotted manure on the surface and let the soil life pull it down. Dig only where you actually need to, such as lifting root crops or clearing perennial weeds.
In Scotland: There is a practical bonus here: undug ground carries weight better and warms marginally earlier in spring than freshly turned wet soil, which matters when the season is already short.
This was a fair complaint a decade ago and it has not aged well. Peat-free quality has greatly improved in recent years, and dedicated research has found some carnivorous plants grow better in peat-free mixes than in peat. What is true is that peat-free behaves differently: the watering and feeding requirements are not the same, because the ingredients have different physical and chemical properties from peat.
Our read Most bad experiences with peat-free are a watering problem rather than a compost problem. It dries differently, so the habits you built on peat will let you down for a season until you adjust.
What to do: Read the bag rather than assuming, since feeding and watering advice genuinely varies between mixes. Buy fresh: old stock breaks down and performs worse regardless of what it is made of. If one brand disappoints, try another rather than writing off the category.
In Scotland: This matters more here than almost anywhere in Britain. Scotland holds a great deal of the UK's peat, those peatlands are major carbon stores, and peat-based compost comes out of them. The performance excuse for buying peat no longer holds up.
A container limits how far roots can spread and cuts the plant off from the reservoir of moisture and nutrients that open ground provides, increasing the need for both watering and feeding. You are taking on work the soil would have done for free.
Our read Pots are a solution to a problem, not an upgrade: no ground, bad drainage, a crop that needs containing, or somewhere warm against a wall. Chosen for those reasons they are excellent. Chosen by default they make the job harder.
What to do: Use the ground where you have it. Where you do use pots, go bigger than feels necessary, expect to water far more often, and feed through the season because there is no soil reserve to draw on.
This is the theory underneath half of every companion planting chart, and it is the wrong mechanism. Research at Wellesbourne, Britain's long-standing centre for brassica and carrot pest work, found that insects hunting a host land on green and avoid bare brown soil. Colour, size and shape decide where they settle. Artificial green plants, and even green paper releasing nothing at all, disrupt them as well as living companions do, and aromatic plants perform no better than bland ones.
What to do: Stop choosing companions by scent. If ground cover is what disrupts the pest, the useful question is whether something low and green grows between your rows, not whether it smells of anything.
Water droplets do not focus sunlight enough to burn foliage. Scorch on new plants comes from insufficient hardening off far more often.
What to do: Water whenever the plant needs it. Watering at ground level rather than over the leaves is still worth doing, but for disease and evaporation reasons, not for scorch.
In Scotland: Rarely the limiting factor here anyway, though it matters under cover, where watering habits drive humidity and therefore disease.
Grounds do contain nitrogen, phosphorus, potassium and magnesium, so the feeding half is not baseless. The acidifying half is not: their effect on pH is very minor and temporary. Spread thick they cap the soil and block water and air, and residual caffeine can suppress root and shoot growth.
What to do: Put them in the compost bin rather than straight on the bed. If you actually need to change pH, that is a job for lime or sulphur guided by a soil test, not for coffee.
In Scotland: Most Scottish soils are naturally acidic already, so the acidifying claim solves a problem you probably do not have and may worsen one you do.
No trial exists comparing the flavour of shade-grown and sun-grown mint. The claim circulates among herb gardeners but appears to be based on the observation that shade-grown leaves are softer and more tender, which is a texture point rather than a flavour one.
Our read Mint in partial shade does produce softer, larger leaves because the plant is reaching for light. Whether that translates to better flavour is unmeasured and probably subjective. Grow it where it thrives and pick it young, which matters more than sun or shade.
What to do: Pick leaves before the plant flowers, when the oils are strongest. Harvest regularly even if you do not need it, because cutting back encourages fresh growth and delays flowering.
Mint spreads aggressively by underground runners, so the advice is to plant it in a container or a bottomless bucket sunk into the ground to contain the roots. Left unchecked, it will colonise a bed in a single season.
What to do: Sink a large pot or bottomless bucket into the ground and plant mint inside it, leaving the rim above soil level so runners cannot climb over. Lift and divide every few years as the container fills with roots.
In Scotland: Scottish rainfall and cool summers make mint more vigorous here than in the south, which is saying something. The container is not optional.
Mint roots easily from stem cuttings in water. Softwood cuttings are a standard propagation method for mint, and a healthy supermarket sprig treated the same way will usually root within a week.
What to do: Strip the lower leaves from a 10cm stem, place in water on a windowsill, and pot it up once roots are a few centimetres long. Choose organic or unsprayed mint if possible.
In Scotland: A windowsill-propagated mint plant started in spring will be ready to go outside by June and will establish fast in Scottish summer conditions.
Mint spreads aggressively by underground runners, and once established in open ground it is genuinely difficult to remove. The advice is to plant in a container or a bottomless bucket sunk into the soil to contain the roots.
What to do: Plant mint in a large pot or a container sunk into the ground with the rim above soil level. If you want a mint bed, use a barrier at least 30cm deep. Tug out runners that escape each spring.
In Scotland: Mint's vigour is amplified here by moisture and mild temperatures. A single plant in open ground can colonise a square metre in a single Scottish growing season.
This one earns its reputation. A layer of organic mulch conserves moisture, keeps the surface from cracking, suppresses weed germination by keeping light off the soil, and feeds the ground as it breaks down. It is worth doing directly for heavy soils, where it does more good than the grit people usually reach for.
What to do: Mulch onto ground that is already moist, not baked dry, or you seal the dryness in. Keep it clear of stems, and use compost, well-rotted manure or composted bark rather than anything that has not broken down.
In Scotland: Our rainfall means moisture retention matters less here than it does south, so the weed suppression and the slow feeding are the real prizes. On heavy ground a surface mulch also spares you digging wet soil, which does more harm than the weeds would.
Hoverflies and lacewings eat aphids as larvae but live on nectar and pollen as adults, so a plot with nothing in flower starves the insects doing your pest control. UC IPM is clear that this works and equally clear about its limits: the benefit falls away with distance from the flowers, and it will not always show up as fewer pests.
Our read This is the one piece of companion-planting folklore that survives, and it survives because it works by feeding predators rather than by confusing pests with smells. Note what it is not: a guarantee, or a replacement for mesh where a pest is serious.
What to do: Put the flowers close among the crop rather than in a border at the far end of the plot, since the effect is local. Aim for something in flower across the whole season rather than one big flush.
Tested and false means somebody ran the experiment and the practice did not work.Sources disagree means reputable authorities contradict each other.Never tested means the claim circulates but we found no study either way — our reasoning is openly labelled as ours.Evidence supports it is the plain case, though it often carries a condition worth reading.
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