Wakame and Cucumber Sunomono: The Five-Minute Seaweed Salad

Sunomono is the salad that shows up unannounced: a small, cold dish of vinegared cucumber and seaweed set down before anything else arrives, sharp enough to wake your palate up and light enough that you forget it happened until you start craving it again the next day. The version most people fall for first is wakame kyuri-su — rehydrated wakame and paper-thin cucumber in sweetened rice vinegar — and it is genuinely a ten-minute dish if you have dried wakame in the cupboard.

This is the complete method: the salting step that keeps the cucumber crisp, the dressing ratio that balances instead of puckers, and the small variations that turn one recipe into a season of salads. If you are new to cooking seaweed at all, this is one of the two or three dishes I'd start with.

What sunomono actually is

Sunomono (酢の物) means simply "vinegared things." It is a category, not a single recipe — a family of small, cold, vinegar-dressed dishes served as a starter or a palate-clearing side in Japanese meals. Octopus sunomono, crab sunomono, cucumber-only sunomono: the constants are a sweet-sour dressing (usually built on rice vinegar), cold ingredients sliced thin or cut small, and a serving size closer to a couple of forkfuls than a bowlful.

Wakame and cucumber is the archetype because the two textures argue perfectly. Wakame rehydrates silky and slightly chewy with a mild marine sweetness; salted cucumber stays glassy and crisp. The dressing — vinegar, sugar, a little soy — is bright but gentle, nothing like the aggressive vinaigrettes of Western salad culture.

Wakame itself deserves a note. Undaria pinnatifida is the same species I profiled in our wakame species guide — native to the cold northwest Pacific, now farmed on every continent and, frankly, invasive in several. Buying farmed wakame from managed waters is one of the easier ethical choices in seafood. If you want the whole picture of how it differs from kombu and nori in the kitchen, our wakame vs kombu vs nori guide covers it.

Ingredients: what you need and what you can swap

For two generous side servings (or four small starter portions):

• 10 g dried wakame (about a loose handful of the fanned-cut kind)
• 1 large cucumber (300 g-ish), or 3–4 small Lebanese/Persian cucumbers
• ½ tsp fine sea salt for salting the cucumber
• 3 tbsp rice vinegar (unseasoned — seasoned rice vinegar has sugar and salt already in it)
• 1–1½ tbsp sugar
• 1 tsp soy sauce
• 1 tsp toasted sesame seeds, plus a few extra to finish

The vinegar matters more than anything else on the list. Rice vinegar is soft and slightly sweet at around 4–5% acidity; distilled white vinegar at the same volume will taste harsh and one-note. If rice vinegar is impossible to find, dilute apple cider vinegar with a third water and expect a fruitier, less classic result.

Choosing the wakame

Dried wakame comes in two main cuts. Cut wakame (small fanned pieces, already removed from the tough central rib) is what you want here: it rehydrates in five minutes and needs no trimming. Whole dried wakame with the stem attached is cheaper per gram but you'll need to soak longer and cut away the rib. Avoid the salted, wet-packed wakame for this dish unless you rinse it very thoroughly — it can swamp the dressing with salt. Our guide to buying seaweed sustainably has label-reading notes if you're choosing between brands.

Choosing the cucumber

Thin-skinned cucumbers — Japanese, Lebanese, Persian, or a good continental/telegraph — are ideal because you can skip peeling and their seeds are tender. A thick-skinned slicing cucumber with big watery seeds will dilute the dressing and go floppy; if that's what you have, peel it in stripes and scrape out the seed core.

The method

1. Rehydrate the wakame

Cover the dried wakame with plenty of cold water and leave it for 5–8 minutes. It will expand dramatically — ten grams becomes a small heap. Drain, gather it into a ball, and squeeze firmly. Taste a strand: it should be clean, oceanic and mild. If it tastes aggressively salty or fishy, give it another quick rinse and squeeze. Cut into bite-size lengths if the pieces are large.

Cold water, not hot. Hot water rehydrates wakame fast but dulls the colour and softens the texture toward flabby.

2. Salt the cucumber

Slice the cucumber into rounds about 2 mm thick — as thin as you can manage with confidence, no mandoline required. Toss with the half teaspoon of salt in a bowl and leave for five minutes. The salt pulls water out of the slices, which is the entire trick: the cucumber crisps, seasons, and — crucially — stops watering down your dressing on the plate.

Squeeze the slices gently in your hands, in two or three batches, and let the liquid drain away. Don't rinse unless you wildly over-salted; a light squeeze leaves the seasoning where you want it.

3. Build the dressing

Stir the rice vinegar, sugar and soy sauce until the sugar dissolves completely. Taste it. The target is a soft sweet-sour where you notice the sugar and vinegar in the same instant; adjust with a pinch more sugar or a splash more vinegar until it lands there. Different rice vinegars vary enough that no ratio should be treated as law.

4. Combine and dress

Toss the squeezed cucumber and wakame with the sesame seeds and the dressing. You can serve it immediately, or rest it in the fridge for 15–30 minutes so the vegetables absorb the dressing. Both are correct; the rested version is slightly more seasoned and slightly less crisp, and I genuinely prefer it in summer.

Divide between small bowls, spoon a little of the pooled dressing over each, and scatter the extra sesame seeds on top.

Technique notes: what separates good sunomono from great

Squeeze harder than feels polite. Both the wakame and the cucumber carry water that will leak into the dressing and dilute it within minutes. The dressing should cling, not pool into soup.

Serve it cold, in small portions. Sunomono loses charm fast in a big warm bowl. Chilled small bowls, a few forkfuls each — the dish is a punctuation mark, not a paragraph.

Dress close to serving time. Thirty minutes of marination is lovely; six hours is not. The cucumber softens and the wakame starts to stain it green. If you're prepping ahead, keep the components separate and combine at the table.

Sesame is not optional in spirit. Toasted sesame seeds add the one warm, nutty note in an otherwise cool dish. If you enjoy this flavour pairing, our homemade furikake takes the sesame-seaweed idea in a dry, sprinkleable direction.

Variations worth your time

With ginger: a teaspoon of very finely grated fresh ginger in the dressing — the single best variation, and my default.

With crab or prawns: flaked cooked crab meat or a few poached prawns turns side dish into first course. This is close to what izakayas serve at triple the portion price.

With octopus (tako su): blanched octopus sliced thin, dressed the same way. Firmer, chewier, more substantial.

With wakame stems: if you can get salted wakame stems (kuki wakame), rinse and blanch them for crunch; they're like sea green beans.

A dried-chilli thread or two for those who like heat against acid. Restraint required.

Serving, storing and what to eat it with

Sunomono sits happily beside anything grilled, fried or rich — it is the classic counterweight to tempura, karaage, and oily fish like mackerel. It's also a natural first course before miso soup with wakame and rice for a light meal, or alongside onigiri for a packed lunch that won't stink up the train.

Leftovers keep a day in the fridge in a sealed container, though the cucumber texture declines. The dressing alone keeps a week and doubles as a quick pickle base — pour it hot over sliced radish or turnip and you have overnight pickles. Dried wakame, for its part, keeps for a year or more in an airtight jar away from light; see our seaweed storage guide for the details. Tidewright's own Harvest line works with exactly this model — shelf-stable dried kelp products that make coastal farming practical at small scale.

Key takeaways

• Sunomono means "vinegared things" — a category of small cold Japanese salads; wakame-cucumber is the archetype.
• Use cut dried wakame rehydrated in cold water (5–8 minutes), squeezed very dry.
• Salt thin-sliced cucumber for five minutes and squeeze: this crisps it and protects the dressing.
• The dressing is roughly 3 parts rice vinegar to 1–1½ parts sugar plus a teaspoon of soy — always taste and adjust.
• Dress within half an hour of serving, serve cold in small bowls, and finish with toasted sesame.

FAQ

Can I make sunomono ahead of time?

Partially. The wakame can be rehydrated and squeezed a day ahead; the cucumber can be salted and squeezed a few hours ahead. Keep both refrigerated and separate from the dressing, then toss together up to 30 minutes before serving. Fully dressed sunomono keeps about a day but loses crispness progressively.

Is wakame raw in this dish?

Effectively, yes — and that's normal. Commercial dried wakame is blanched before drying, so the deep green colour you see on rehydration is the sign that it's already been heat-treated. It is safe and standard to eat without further cooking.

What can I use instead of rice vinegar?

Diluted apple cider vinegar (two parts vinegar to one part water) is the best substitute, though fruitier. White wine vinegar works in a pinch diluted the same way. Avoid distilled white vinegar at full strength — its acidity is harsher and flattens the sugar balance.

My wakame tastes too strong or fishy. What went wrong?

Usually one of two things: it needed a second rinse after soaking (cheap wakame sometimes carries more surface salt and sediment), or it soaked too long in hot water and developed stewed, muddy flavours. Cold water, short soak, firm squeeze.

Can I use other seaweeds in sunomono?

Yes — but texture-changed ones. Rehydrated tosakanori or agar-like reds bring crunch; blanched sea spaghetti works well. Kombu is too tough raw for this cut, though very thin shavings of tsukudani-style cooked kombu can be dressed as a richer relative of the same dish.