© Nick Shell
Once seen as a poor man’s food, only to be consumed at the end of a harsh winter, cultivation of the salt-tolerant plant Salicornia has multiplied in the past two decades.
Known variously as samphire, sea asparagus and glasswort, this growing interest has drivers both in supply and demand.
Excess sodium consumption is seen as a major contributor to high blood pressure, dubbed “a silent killer” by the WHO, prompting governments around the world to set sodium intake reduction targets. While Salicornia tastes very salty, its sodium content is much lower than rock or sea salt. More complex in flavour and with a range of bioactives, depending on the species, it has positioned itself as a healthier, tastier, plant-based version of traditional salt and fetches a premium price.
On the supply side, the growing threat of land degradation and salinisation that comes with rising seawater levels has seen salt-loving halophytes like Salicornia pushed forward as a solution by scientists and environmentalists.
With the main markets in South Korea, the UK and western Europe, the biggest growers are in Morocco, Spain, Israel, Netherlands and Mexico, where they are farming either in greenhouses or in fields.
But Salicornia can be an aquaculture crop too. Soilless saltwater cultivation was pioneered in Hawaii by Dr Wenhao Sun, who started Marine AgriFuture more than two decades ago. To encourage the spread of the technology, Dr Sun then founded Halophilic Marine Agriculture in 2023, together with Shell, who is now pioneering the practice in Vietnam.
The Fish Site recently spoke to Shell on what the model could bring to Vietnam.
What does Salicornia aquaculture look like? And how does it differ from traditional ways to grow these plants?
We have dubbed our approach “marine hydroponics”, meaning we grow plants with seawater as the primary cultivation medium, free of soil. While other farms grow Salicornia on soil – since it is a root plant with leaves – we grow them on platforms which float on the water. The roots are fully immersed in the seawater while the leaves and branches float on the surface.
For the time being, we operate in shallow saltwater ponds converted from shrimp production. This minimises exposure of the plants to wave action and makes it easy to work with the plants, while standing in waist deep water.
Our model farm consists of an earthen pond with consistent access to high salinity water which we keep at a depth between 0.8-1.2 m, with floating platforms with holes drilled into them at regular intervals to hold specially designed tubes where the Salicornia fits in. One platform will have around 1,200 individual plants. The typical pond size we work in is 3,000 m2, in which we will install 30 platforms.
What does a Salicornia production cycle involve?
At first, small tubes filled with cultivation media are seeded with a Salicornia seed. The tubes slide into a hole on a flat floating platform and are secured in place with the bottom of the tube poking through the bottom of the platform.
The seeds take a long time to germinate and are extremely vulnerable during the first 2 months of cultivation. So we often install shade material and rain protection during this cultivation phase.
After two months, the plant grows to approximately 6-10 cm height and the shoot is pruned at the tip. This prevents development of a woody stem at the centre and allows the plant to branch out as it grows.
After pruning, the plants take 2-3 weeks to grow back to a harvestable size before they are pruned again. These shoots are what sells, so we wash them, package, and bring them to market. If the plants are happy, they can go through 4-6 months of pruning cycles, but if they get stressed, they will mature, develop woody stems, and will no longer be marketable.
Salicornia are annual plants, so they will develop the woody stems eventually. Once this happens, the plants are pulled out from the floating platform and new seedlings are put in. The cycle repeats and you are looking at about 2-3 cycles per year.
© Nick Shell
What are the economics of Salicornia farming?
We supply two products. One is fresh Salicornia shoots, and the other is dried powdered Salicornia – often used as a healthy substitute for salt.
Fresh Salicornia shoots retail at prices between $21-$30 per kilogram in Europe, with some niche markets in South Korea and Japan. This can be eaten fresh with no processing, but a shelf life of between 2-3 weeks after harvest and the need to transport with a cold chain constrains the range of markets a farm in Vietnam can access.
Dried Salicornia salt is essentially dried shoots ground into powder which sell retail in Europe and the US for between $80-$120 per kilogram. Given it has a shelf life of over a year and doesn’t require cold chain transport, it is much less constrained by geography, but the loss of biomass when drying tightens margins. Making a profit off salt will need large scale production.
As a former shrimp farmer, I find Salicornia a much less volatile crop. There are no sudden crashes to worry about, and it provides a consistent trickle of cash, rather than the single harvest after a few months of cultivation.
A farm can typically produce between 15-20 tonnes of fresh Salicornia per hectare per year. Given the low-input nature of production and relatively consistent supply, this can be an attractive prospect for a landowner looking to generate revenue out of fallow land.
© Nick Shell
Why is Vietnam a good place to grow Salicornia?
Land use. Vietnam is densely populated and land is expensive. Combine that with the litter of disused shrimp ponds around the country and the fact that soil salinisation is making it harder to grow traditional crops in low-lying areas: if we can restore those lands and help landowners get a return on their asset, it would be a big win. A typical Vietnamese intensive shrimp farm will consist of 50-70 percent empty pond area used to disinfect inlet water. Our Salicornia growing platforms easily fit into these ponds.
Vietnam’s climate also allows us to cultivate year-round. Our customers often want Salicornia on their doorstep within 1-2 days of ordering; seasonality is not really an option for them. Looking at the competition, samphire growers using greenhouses have few constraints when it comes to the weather, but others are restricted by the seasons. They can grow at best for eight months per year. We harvest every day, so there is a possibility for us to supply fresh to markets abroad like South Korea.
Bringing an unknown food product into a new market is notoriously difficult. What’s your angle?
At the moment our customers are mainly local fine dining restaurants. Some of them were already importing samphire from abroad, so that was an easy sell. A bit below that we have our customer Grandma Lu, who are adding it to their gourmet banh mi.
That’s our segment now because of the price on the one hand; we’re just growing at a one-hectare pilot farm without economies of scale. But on the other hand, of course, to reach a mainstream audience we need to educate the market. We don’t have any illusions there – it’s a big mountain to climb.
We have a pretty good story, helping coastal communities adapt to sea level rises and soil salinisation. And some people see that. But, ultimately, we have to convince local consumers of the taste and the health benefits. For example, the vitamin B3 level of our samphire is off the charts. That’s great for vegans, who struggle to get that elsewhere.
© Nick Shell
How do you plan to scale?
We have a franchise model. Vietnam has a lot of independent landowners who you can implement tech on and then outsource the farming part to. Once we have the markets ready, we can bring our technology to them and save on land and labour costs.
That's what will bring the price down and make us really competitive in the global market. Ultimately, the vision is to make samphire a commodity product. As a powder, we could sell B2B in the multi-billion dollar low-sodium salt replacement market, currently dominated by potassium-based alternatives.
What is the biggest challenge when it comes to cultivating Salicornia in saltwater?
The nursery stage has been the hardest part. It took us a while to understand how to get seed germination rates up and keep young plants alive for the first few weeks. Once beyond that initial stage, Salicornia is a hardy, relatively low maintenance plant that can withstand a lot of adverse weather conditions.
You are currently growing in disused shrimp ponds. Is there potential to bring Salicornia together with shrimp into a polyculture system?
Yes! Our ponds are three-dimensional systems where the platforms occupy the water surface, with an additional 80 cm of water depth to grow something else. Seaweed is a good option; we found Gracilaria works very well. We’re also testing oysters, sea grapes and gastropods.
The really interesting piece is with the shrimp. Shrimp farms are already interested in testing out the technology, given it provides an opportunity to generate revenue from fallow land. For the time being, the water will flow in one direction: from inlet point, to Salicornia pond, on to the shrimp pond and then to discharge.
The dream is when we start recirculating wastewater from the shrimp as fertiliser for the plants. A kind of commercial scale saltwater aquaponics system. We already know the plants can survive in a closed recirculating system with shrimp – the challenge is controlling the microbial activity enough to meet food safety standards for human consumption. Once that piece gets figured out, we hope to bring significant changes in the way shrimp are farmed.
Finally, what advice would you give to farmers who are considering diversifying into Salicornia?
I think the hardy nature of Salicornia, together with the opportunity to integrate with another species is what makes Salicornia a really compelling value proposition. Salicornia farming isn’t very difficult once a few fundamental principles are understood and can be a consistent form of income. The plants do take a lot of attention, but changes are gradual, unlike shrimp which can die in a matter of hours. What’s important is to plan production cycles so that you can produce year-round.
