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Seaweed Tea
One name, two brews — the bucket that feeds your garden, and the cup that warms your hands.
Seaweed tea is a liquid feed made by steeping seaweed in water — and, confusingly, also a drink. The garden version is a week-long kelp brew rich in natural rooting hormones that seedlings love. The drinking version is a gentler thing: a small piece of dried dulse or sugar kelp steeped like any herbal tea. This page covers both, because people ask us for both on every workshop.
How do you make seaweed tea for the garden?
Take freshly cast kelp from the strandline, steep it in a covered bucket of water for a week or more, then strain and dilute. That’s the whole craft — the detail is below.
- Collect freshly washed-up kelp from the lower strandline — never pull living plants.
- Remove any plastic waste and foreign objects.
- Roughly chop the kelp with garden shears, place in a bucket and cover with water.
- Lid on — it will get lively, and the smell is honest — label with the date, and leave for at least a week.
- Strain, bottle, store somewhere cool and dark, and use within 3 months.
How do you dilute seaweed tea?
Add water equal to the number of weeks brewed — a 2-week brew takes 2 parts water to 1 part tea — up to about 1:10 for a long-steeped batch. Test on a single plant first, then water your seedlings and young plants with it, or spray it as a foliar feed.
Why does it work?
Kelps are high in rooting compounds — auxins, cytokinins and gibberellins — the same hormones produced in a plant’s root zone. Seaweed also carries magnesium, potassium and trace elements in a highly soluble, low-nitrogen package, which is why it has fed Scottish coastal gardens for centuries. There’s more on mulch and compost in Seaweed in the Garden.
Can you drink seaweed tea?
Yes — just not that bucket. Drinking seaweed tea is made fresh: steep a thumb-sized piece of dried dulse or sugar kelp in just-boiled water for five to ten minutes. Sugar kelp gives a smooth, faintly sweet, savoury cup — kombu tea by another name, drunk in Japan for centuries. Dulse brews darker and rounder, almost smoky. Add a slice of ginger if you like; on winter workshops we hand it round in enamel mugs on the beach.
A note of common sense: seaweed is naturally rich in iodine, so treat drinking seaweed tea as an occasional pleasure rather than a daily habit, and skip it if you have a thyroid condition — or ask your GP first.
Which seaweed makes the best tea?
- For the garden: any of the kelps — they carry the most growth hormone. Cast oarweed and sugar kelp are what our strandline offers most.
- For the cup: sugar kelp for sweetness, dulse for depth. Both dry well on a rack in a warm room and keep for months in a jar.
Collecting it the right way
Gather only washed-up seaweed for the garden bucket, work on the “take a third and move along” system, and never clear a beach — the strandline feeds whole ecosystems. For drinking-grade seaweed, harvest living plants with scissors, cutting, never pulling, from clean water on a falling tide — exactly what we teach on the shore.