Exotic crops call for exotic storage

Think of crop stores and your thoughts inevitably turn to grain silos, potato stores or even silage clamps. But for farmers who grow unusual crops – like blueberries, asparagus or globe artichokes, for instance – storage requirements can become pretty involved.

Clive Martin’s decision to convert 200ha (500 acres) of his 640ha (1580-acre) Fenland farm to organic production has led to rather more activity than merely growing organic cereals and other combinable crops.

A significant part of the newly-ordained organic area is given over to the production of “unusual” crops such as blueberries, butternut squashes, globe artichokes, asparagus and yellow and green French dwarf beans.

Trading as HolmSelect, at March, Cambridgeshire, Mr Martin says he has always had an interest in such crops but adds that deciding which ones to grow has not been easy.

“You have to be as sure as you can there are buyers out there for the crop when it is harvested and they are prepared to pay sufficiently to make the job worthwhile,” he explains.

But, important as marketing clearly is, it is only a part of the equation – there also needs to be grading, packaging and storage facilities to provide purchasers with the crop in a fresh, clean condition and presented in suitable packaging.

And on this score, last year Mr Martin invested in new grading and packaging lines along with refrigeration and humidity control areas.

“This is a new building which we need to get the best out of,” he says. “So the other important detail is that the crops we grow need to have a succession of harvesting dates to allow a sequence of processing operations, rather than everything happening in the same few weeks.”

At the entrance of the building, a scrub-up area allows staff to clean their hands and put on overalls and a hair net before entering the main processing area.

Within the main body of the building are generous numbers of stainless steel support conveyors, washing zones, automatic grading systems and packaging areas. Depending on the crop being processed, about 10 people work in this area.

The season kicks off in mid April with the asparagus – 24ha (60 acres) of it which needs to be picked over by hand every day during the season.

“For this, we hire in labour and create three separate teams which work behind field rigs holding pallets and baskets,” explains Mr Martin.

Taken to the new packhouse, the asparagus is immediately placed in the cooling room where a blast of cold, moist air reduces the temperature to 3C. The humidity level of about 90% prevents any drying out of the crop as it is cooled.

“It’s all about speed,” he says. “The reduction in temperature means the asparagus will stay fresh for a few days but ideally we like to wash, grade and package as soon as the crop departs the field so that it is ready for collection the next day.”

Clive Martin 

Clive Martin: Choosing a range of crops with different harvesting dates means the packhouse is used throughout the year, he says.

During the asparagus season, which ends in mid June, about 60t of produce is processed at a rate of more than 1t a day.

Next in line for the packhouse are the globe artichokes – a perennial crop that is planted in March and harvested in its first year during July/August and then, in its second year in late May. The globes are cut by hand and, in the packhouse are cooled down to about 3C before being packed in pairs.

“They will keep for up to a week but after that the outside leaves start to turn brown and they lose their initial attractiveness,” he says.

Despite this, Mr Martin believes the globe artichoke has a good (and untapped) potential in the UK and, properly marketed will produce a reasonable return.

Another fast-developing crop is blueberries, of which the farm now has 6ha (15 acres). Planted only three years ago, the crop has yet to yield its full potential but last year saw it yielding just over 3t. However demand far exceeded this amount.

Once again, it’s hand labour that brings the crop in over a period of about three weeks. A delicate crop, blueberries have to be handled and stored with care. To extend freshness, its temperature is reduced to 2C using one of the high humidity coolers.


One of the cooler-humidifiers. Crops are usually cooled to about 3C with the air humidity in the 90% range to prevent any drying out.

The future however, could see the blueberries being stored and packaged in a low oxygen/high nitrogen atmosphere – a system which would see the crop shrouded in plastic sheeting while in the store. A similar system has been used successfully to prolong the life of cherries when they are transported from the US to European markets.

“Combined with the low temperature, it should be possible to keep the blueberries fresh for a few weeks and extend their shelf life significantly,” points out Mr Martin.

Far from being cooled, butternut squash and other squashes need to be stored in a warm place to ensure they ripen properly. To achieve this, the freshly harvested squashes are placed in the insulated fridge areas with a heater.

“It’s a system that works very well and helps us to have complete control over the ripening process – when and how it happens,” he explains.

For the future, Mr Martin says he is not only aiming to increase the quality and yields from his organically grown crops but also to improve their marketing and presentation.

“Growing the crop is only half the job – it’s how you manage the storage and packaging that can make all the difference,” he concludes.