Gadenin日本語Get the appSlugs and snails on the first spring growth
The main damage sorrel takes all year happens in a fortnight. The new leaves emerge in cold, damp, early-spring weather at exactly the moment slugs become active and there is almost nothing else green for them to eat. A crown can be reduced to chewed stumps in a couple of nights, and because the growing points are at soil level the damage sets the plant back badly.
The damage is unmistakable: ragged holes in the middle of leaves rather than at the edges, slime trails across the crown, and worst damage after mild wet nights. Check by torchlight an hour after dark if you want to confirm it.
Clear the ground around each crown at the end of winter. Old dead sorrel leaves lying over the crown are the perfect daytime shelter, so raking them off removes the population before the new growth appears. Beyond that, a ring of grit or wool pellets round each crown, or hand-picking after dark for the first two weeks of growth, gets the plant past the vulnerable stage. Once the leaves are up and the plant is growing fast, slug damage stops mattering.
| Symptom | Likely cause | What to do |
|---|---|---|
| Ragged holes mid-leaf, slime trails | Slugs or snails | Clear debris from the crown, hand-pick after dark, ring with grit |
| Pale winding tunnels or blotches inside the leaf | Leaf miner larvae | Pick off and bin affected leaves; do not compost |
| Small orange or brown pustules on the underside | Rust | Remove affected leaves, thin the clump, improve airflow |
| Clusters of small insects on the flower stem | Aphids | Cut the flower stem out at the crown, which removes them |
| Whole plant limp in heat, leaves leathery | Drought stress | Water deeply, mulch, cut back hard and let it reflush |
Leaf miners make blotches you cannot wash off
Sorrel belongs to the dock family and is attacked by the same leaf-mining flies that mine docks. The adult lays eggs on the leaf and the larvae feed between the upper and lower surfaces, leaving pale winding tunnels or, more often on sorrel, irregular translucent blotches that later go brown and papery. The leaf is not poisoned, but it looks unpleasant and the mined tissue is not worth eating.
Nothing sprayed onto the leaf reaches a larva living inside it, so the only effective response is physical. Pick off mined leaves as you see them and bin them rather than composting them, which breaks the cycle by removing the larvae before they pupate. Sorrel produces leaves fast enough that removing a dozen costs you nothing.
If the infestation is heavy across a whole clump, cut every leaf off an inch above the crown, remove all the material, and feed and water. The regrowth comes clean, and you have effectively skipped a generation of the pest.
Docks growing nearby are a reservoir for the same leaf miner. Clearing docks from the edges of the plot reduces the pressure on sorrel more than anything you can do to the sorrel itself.
Rust in still, damp conditions
Rust shows as small orange to reddish-brown pustules on the underside of the leaf, with yellow spotting visible from above. It appears in humid weather with poor air movement, and it is far more common in a crowded, congested clump than in a well-spaced one. It rarely kills sorrel but it spoils the crop and weakens the plant over a season.
Management is cultural. Remove affected leaves promptly and bin them. Thin out a congested clump so air moves through the center, and if the clump is more than three or four years old, take the chance to lift and divide it. Water at the base rather than over the leaves, and water in the morning so any splash has dried by evening. Avoid heavy nitrogen feeding, which produces the soft crowded growth rust likes best.
In a bad year the reliable reset is the same as for leaf miner: cut the whole plant down to an inch above the crown, remove and bin all the material, and let it regrow clean.
Aphids arrive with the flower stems
Aphids on sorrel almost always cluster on the flower stem rather than the leaves. The stem is soft, sappy and upright, and it is precisely the part of the plant you should be removing anyway. Cutting the stem out at the crown as soon as it appears removes the aphid colony with it, which is why a plant kept properly deflowered rarely has an aphid problem at all.
If aphids do get onto the leaves, a firm jet of water knocks them off and the leaves are tough enough to take it. Sorrel is picked and eaten fresh, often raw, so it is not a plant to spray; physical removal and cutting out the affected growth handles it completely.
Problems that are not pests
Two common complaints about sorrel have nothing to do with pests or disease. The first is leaves going tough, small and unpleasantly harsh: that is a plant running to flower, or one that has dried out at the root, and the fix is cutting the flower stems and watering deeply rather than reaching for a spray. The second is the crop turning khaki in the pan, which is simply what the leaf acid does to chlorophyll under heat and is not a fault at all.
The third thing worth naming is winter dieback. Sorrel is hardy to around minus 20F (minus 29C) and dies back to nothing above ground in cold winters. A bed that looks empty in late winter is not a bed of dead plants. Mark the crowns before the leaves go, and leave them alone until growth restarts.
Keep a short note of the first date you see slug damage and the first date you see leaf mines each year. Those two dates repeat closely from season to season and let you clear debris and start checking a week before trouble starts, rather than a fortnight after.