Sorrel Garden Myths: What Holds Up

“Sorrel leaves are just a salad green, so there's no limit on how much you should eat”

Common sorrel is harmful if eaten in large amounts, and gloves are recommended when handling it. Its sharp, citrusy tang comes from oxalic acid, which is why it's normally eaten in smaller quantities than a typical salad leaf.

What to do: Use sorrel as a flavouring or accent leaf, the way it's traditionally treated in soups, sauces and small salad portions, rather than as a bulk salad green eaten in the quantities you'd use for lettuce or spinach.

“Sorrel is drought-tolerant once established, like thyme or rosemary”

Dry weather is itself a bolting trigger for sorrel, and it prefers fertile, moisture-retentive soil rather than free-draining ground.

What to do: Keep sorrel well watered, particularly in dry spells, rather than treating it like thyme or rosemary and leaving it to fend for itself once established.

In Scotland: Sorrel's moisture preference is a genuine match for damp Scottish ground, the same pattern already found for lovage.

“Sorrel needs winter protection outdoors, like some more tender herbs”

All three sorrel types are hardy throughout the UK, and common sorrel specifically carries an H7 hardiness rating on its individual plant page, hardy in the severest European continental winters below -20C.

What to do: Skip winter protection for ground-grown sorrel entirely. Only container plants need moving somewhere sheltered, and even then the concern is winter waterlogging causing root rot, not cold.

In Scotland: H7 is among the hardiest ratings a crop can carry, a genuinely low-risk pick for an exposed Scottish garden.

“Sorrel self-seeds so aggressively that once you plant it, it will spread out of control through the bed”

Sorrel does self-sow readily once it's allowed to flower and set seed, but it only spreads by seed, not by running roots or rhizomes the way mint or ground elder do. A single pass with secateurs to snip off the flower spikes before they set seed stops the spread completely for that season.

What to do: Cut back flower stalks as soon as they appear if you don't want volunteer seedlings; leave a few if you're happy to let it fill in a patch for free.

In Scotland: In a short Scottish growing season, a bit of self-seeding is a cheap way to keep a patch going since sorrel seed doesn't stay viable in soil for long, so there's little risk of it building up into a persistent seed bank the way some weeds do.

“If sorrel is growing wild and thriving in a patch of your garden, that tells you the soil there is acidic”

Wild sorrel does have a strong tolerance for acid soils, which is where the idea comes from, but tolerance isn't the same as a requirement. It thrives just as well in neutral or even slightly alkaline soil, especially where fertility is low and there's little competition from other plants. Poor drainage and low nutrients, not pH, are often the real reason it's dominating a patch.

What to do: Don't skip a proper soil pH test just because sorrel is doing well somewhere; use it at most as a hint that fertility or drainage might be poor there.

In Scotland: Plenty of Scottish soils genuinely run acidic, especially on peaty or moorland-derived ground, so it's tempting to use sorrel as a shortcut, but that same acidity is common enough here that it isn't a distinguishing sign of anything.

“Sorrel is pest-prone and needs regular spraying to keep slugs and aphids off it”

Sorrel's main vulnerability is slugs and snails going after seedlings and young leaves, and it can pick up aphids on soft new growth, but treatment for aphids is rarely needed. There's no case for a routine spray programme.

What to do: Focus effort on slug protection while plants are young and small; once established, leave aphids alone unless an infestation is visibly heavy.

In Scotland: Scotland's damp summers do mean slug pressure on young seedlings is genuinely higher than in drier parts of the UK, so it's worth protecting new sorrel plants specifically from slugs here, even though spraying for aphids is still pointless.

“Like most productive perennial herbs, sorrel clumps need dividing every year or two to stay productive”

Established sorrel clumps only need dividing roughly every four to five years, far less often than the annual or biennial split some perennial herbs need.

What to do: Leave clumps undisturbed for several years and only lift and split when the centre starts to look tired or production visibly drops.

In Scotland: With a shorter growing season, dividing sorrel too often sets it back before it's had time to build up the root reserves it needs to bounce back quickly the following spring.

“"French sorrel" is just another name for ordinary garden/common sorrel — it's the same plant”

RHS treats French sorrel (Rumex scutatus) and common sorrel (R. acetosa) as two distinct species with different growth habits and flavour: French sorrel is a low, mat-forming plant to 15-45cm with grey-green, juicy, citrus-flavoured leaves, while common sorrel is an upright UK-native perennial to about 50cm with a sour, slightly astringent, lemony flavour. Confusingly, RHS's own plant record for Rumex scutatus lists "garden sorrel" as one of its alternative common names, which is exactly why the two get muddled in seed catalogues and recipes.

What to do: Check the Latin name on seed packets if the distinction matters to you: Rumex scutatus for the milder, low-growing French type, Rumex acetosa for the sharper, upright common type. Either is fine to grow, but don't expect one to behave or taste like the other.

“Dig sand or grit into heavy clay to break it up”

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.

“On clay, dig a big hole and fill it with grit so the roots drain”

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.

“You have to dig the ground over each year to keep the soil fertile”

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.

“Peat-free compost doesn't grow plants as well as the peat stuff”

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.

“Plants do better in pots than in the ground”

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.

“Strong-smelling plants confuse pests and hide your crop”

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.

“Crushed eggshells, bark mulch or wool pellets stop slugs”

Testing the most popular home slug barriers found no reduction in damage from crushed eggshells, bark mulch or wool pellets. This is Britain's most repeated slug advice and it does not work.

What to do: Skip the barrier. Nematodes, evening hand-collection, and raising plants to a decent size in modules before planting out all do more.

In Scotland: This one costs us more than most. A wet, mild climate is close to ideal for slugs, so a barrier that does nothing is a bigger loss here than in a dry southern garden where the pressure is lighter anyway.

“Watering in sunshine scorches the leaves”

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.

“Coffee grounds acidify your soil and feed your plants”

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.