Gardening: Seaside bounty for soil

By Meg Liptrot

Meg Liptrot praises Neptune's great gift for gardeners - seaweed.

Richard Dale takes advantage of seaweed thrown up on Milford Beach after a storm. Photo / Meg Liptrot
Richard Dale takes advantage of seaweed thrown up on Milford Beach after a storm. Photo / Meg Liptrot

I love wild weather, and growing up beside Manukau Harbour we had our fair share of king tides and fierce winds buffeting our family home. Happily, my Dad and I are beachcombers at heart and you can spot us a long way off, heads down, scanning the beach for special shells, stones or sandblasted glass.

Dad's finds include a large collection of pegs now gracing the washing line and a Russian watch that still works.

A favourite film of mine growing up in the 70s was Storm Boy, about a child who lived on a beach in Australia and spent his time with his beachcomber father, building a life with flotsam and jetsam washed up on the beach. He had an Aboriginal friend, Fingerbone Bill, and a pelican named Mr Percival to keep him company.

After a storm, I often head to the beach to take in the washed, clear air and blow the cobwebs away, although these days, I'm more interested in the copious quantities of seaweed left on the high-tide mark after wild weather. This nutrient-rich gift from the sea is an easy way to improve soil fertility in the garden. My mother makes use of eelgrass, a dominant seaweed which grows in the Manukau.

We have used a few loads of another species of harbour seaweed in the environment centre gardens. The greyish-white seaweed looks like a lot like a balding man's toupee. A friend who worked for the Auckland Council parks department had a job which involved clearing truckloads of this spongy seaweed from Blockhouse Bay beach.

We have used it in the gardens, and the mix of seaweed and sand has improved the quality of our New Lynn clay soil. Hopefully, it doesn't contain contaminants from the Manukau Harbour sewage treatment plant. Seaweed is known to take up excess nutrients such as nitrogen in polluted areas, helping to clean the sea.

At home in Grey Lynn, our best source of seaweed is from the rocky East Coast beaches. Milford Beach often has a mother lode wash up after stormy weather. Brown seaweed species such as Neptune's necklace, flapjack, strap kelp and paddleweed can be found here.

The Seaweed Association says we have more than 1000 species of seaweed on our coastlines and more than 300 species have been discovered in the past two decades. If you are interested in identifying seaweed, go to algaebase.org. A simple search for "seaweed" turned up about 3000 images. I'm still searching for the "grey toupee" seaweed's proper name.

Health-food for soil

Seaweed is rich in micro-nutrients and alginates, which make soil nice and crumbly and better to work with. It also gives beneficial soil bacteria a boost, which is good news for plants. Making seaweed liquid fertiliser is easy. Half fill a barrel with seaweed then top up with rainwater and leave it to break down. A new method I discovered for making seaweed concentrate is to leave seaweed in a bag or closed bucket and let it break down for a couple of months. Dilute the resulting paste in water then use a watering can to apply the solution. You can also use seaweed fertiliser as a foliar feed which also helps plants resist fungal disease.

Giving Back

Sandhoppers and other beach invertebrates eat decomposing seaweed and birds rely on these tasty critters. Removing some seaweed for use in the garden when plenty has washed up after a storm is not going to ruin the beach ecosystem. But refrain from collecting seaweed if there's not much lying around to ensure beach life-cycles will keep running as they should. Marine reserves are no-go for any sort of beachcombing, including taking seaweed - but picking up rubbish is always going to be appreciated.

I noticed a fair bit of plastic tangled up in the seaweed we collected. Plastic rubbish is floating around in every ocean on the planet, causing havoc with marine life. If you think this is no big deal, check out the North Pacific Gyre online. The vortex of plastic rubbish is estimated to be least the size of Texas, possibly much larger.

Plastic hangs around a very long time, eventually breaking into small pieces which fish, turtles and seabirds confuse with food. Last year a "South Pacific Gyre" was discovered, directly implicating this country and our Pacific neighbours.

Say no to plastic

It's easy to cut down on our use of plastic.

• Say "no'' to plastic shopping bags.

• Re-use containers where possible.

• Buy products packaged in cardboard or glass. Even better, shop from bulk bins. Always recycle.

• To find out more about the ocean gyres up in the ocean, go to 5gyres.org

• If you've noticed too much rubbish on your local beach and are keen to organise a clean-up, visit sustainablecoastlines.org

• In 2012, the Herald on Sunday held a very successful "Beach Busters'' clean-up campaign in conjunction with Sustainable Coastlines, removing a total of 6.8 tonnes of rubbish over 10 weeks.

For information on issues affecting the Manukau Harbour, such as future plans on the sewage treatment plants, visit the Manukau Harbour Protection Society at mhrs.org.nz

- Herald on Sunday

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