Hydrangeas can produce more vibrant blooms and stronger stems in August if gardeners add seaweed to the soil, according to gardening experts. Seaweed is rich in nutrients that are not typically found in regular fertilisers, and it can enhance soil health, promote plant growth, and improve root systems.
Expert recommendation
Graham Smith MCIHort, a gardening expert from LBS Horticulture, said: “Seaweed is good for plants, as it contains many useful plant nutrients, such as nitrogen, potassium, phosphate and magnesium. It is also rich in trace elements that are not usually found in common fertilisers, such as copper, zinc and manganese.”
He added: “Flowering plants, particularly roses and hydrangeas, respond well to seaweed, producing more vibrant blooms and stronger stems.”
Gardening writer's tip
Gardening enthusiast and writer Mickey Gast also recommends seaweed for hydrangeas. On the Rural Sprout website, she said: “One ‘magic’ ingredient that hydrangeas in particular seem to love is seaweed.” She noted that it works well when applied during active growth, from March through September.
How to apply seaweed
Mickey prefers liquid seaweed for ease of use, but it is also available as a dry powder. While clumps of brown seaweed can be applied to plants, they should not replace fertiliser. A seaweed-based fertiliser is recommended, as gathering seaweed from beaches is illegal in the UK.
For liquid seaweed, the usual dilution is one part seaweed liquid to 100 parts water. For a two-and-a-half-gallon watering can, use about 100 millilitres of liquid. Add it to the can, stir, and use it instead of regular watering at the base of the hydrangea. It also works as a foliar feed, so it won't harm the plant if leaves are watered.
