Gardening season is in full swing – the time of year when flowers, shrubs and vegetables put on rapid growth and demand a little extra care to keep them thriving.
Though synthetic fertilisers can deliver quick results, they come with considerable environmental drawbacks. Their production and use contribute to water pollution, degrade soil health and increase greenhouse gas emissions, particularly nitrous oxide, which is linked to climate change.
For gardeners hoping to work more closely with nature, organic alternatives are becoming an increasingly appealing option – and few are as versatile or effective as seaweed.
How does seaweed work in the garden?
“Seaweed offers all kinds of natural advantages that can help you grow healthier, more resilient crops in your garden,” says Angharad James, product manager at Maxicrop.
“Its unique composition, rich in bioactive compounds and essential minerals, delivers measurable benefits to both plants and soil.”
Unlike many conventional feeds, seaweed works on several levels at once. Not only does it provide nutrients, it also contains naturally occurring plant hormones that support healthy growth and improve resilience.
The marine plant is rich in compounds known to help regulate key plant processes, including cell division, elongation and differentiation – helping plants establish stronger roots, healthier foliage and more vigorous growth overall.
“Cytokinins, for example, delay cell aging, which helps plants maintain their green, photosynthesising leaves for longer,” Angharad explains.
“Auxins promote root growth, ensuring better anchorage and nutrient uptake. These natural hormones provide a sustainable way to stimulate healthy and vigorous plant development.”
Seaweed also contains valuable trace elements including iron, manganese, zince, copper and boron. “While these elements are only required in small quantities, their impact on plant health is profound,” the expert says.
According to the RHS, these micronutrients are often lacking in common fertilisers, making seaweed a more than viable alternative. It also improve a plant's ability to cope with environmental stress, helping it withstand heat, frost and drought.
Fresh seaweed can improve soil structure in much the same way as manure, so for coastal gardeners, gathering washed-up seaweed from the beach can be an effective, natural and cost-effective way to enrich the soil naturally – although it's always wise to check local regulations before collecting.
For those further inland, dried and processed seaweed products are widely available in liquid, powder and pellet forms, offering a more standardised nutrient content and an easy way to incorporate seaweed into routine garden care.
Which plants benefit from seaweed?
One of seaweed's biggest strengths is its versatility. It can be used across almost every part of the garden, from lawn and flower beds to vegetable patches and containers.
Fresh seaweed can be dug directly into the soil as a conditioner. The RHS recommends burying it two or three spades deep at a rate of around one barrow load per square metre.
Dried seaweed meal can be added to borders and vegetable beds, while liquid seaweed feed is typically diluted with water and applied directly to plants or lawns.
Whether you’re growing flowers, tomatoes or simply trying to build healthier soil, seaweed offers a gentler, organic way to support the garden through the busiest months of the growing season.
And a garden that works with nature rather than against it can only be a good thing.
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Wanda Sachs is the Multiplatform Writer for Country Living and House Beautiful, exploring the latest in gardening, wildlife and sustainable living alongside interiors and property. She is particularly interested in human-interest stories, the intersection of design and pop culture, and the evolving relationship between urban and rural life. Previously, she served as Associate Editor at The Berliner in Berlin, where she reported on culture and fashion. Wanda studied English and German at the Goethe University Frankfurt and Exeter University.
