Sugar kelp is a brown seaweed which can be found in the lower shore. It is common along the Irish coast on sheltered rocky shores and tends to grow in patches along the water’s edge. Just like other kelps, it is only visible during very low tides. Sugar kelp has a small, branching holdfast and a short stipe. It has a long, frilly frond and the centre is dimpled with no midrib. This species of kelp varies in colour from green/dark brown to yellowish brown and is slightly transparent. 

Traditionally, sugar kelp was used for fertiliser in Ireland. When dried, the sugars from the plant form a sweet-tasting white powder on the fronds. It is commercially grown, predominantly in Asia, as a food product and is commonly used as a sweetener in food and drinks. Also known as poor-man’s weather glass, when removed from water, the plant tends to go brittle when humidity decreases, soften when humidity increases and, as such, could be used to predict the weather.