The Gartneriet PKM nursery was founded by Poul and Marie Madsen north of Odense, Denmark, in 1948. Since then, their son Kristian and their grandson Poul have become the second and third generations of the family to join the company. PKM currently employs a workforce of 165 people plus temporary staff at peak times. It produces 20 million pot plants a year and exports 90% to the European market, primarily to the retail channel. Niels Erik Andersson has been Production Advisor at PKM since 2011.

PKM channels 5% of its annual revenue back into product development to ensure that the company maintains its strong reputation as a supplier of healthy plants. “Product innovation is very important, of course,” comments Andersson. “But we need to compete with the rest of the EU and we can’t do that on quality and reputation alone. Price is an increasingly important factor for our customers, which means we also need to continuously improve our efficiency. Denmark is a high-wage country, so automation is a key way of reducing our costs. Not only that, but it’s hard work in a nursery. Especially in view of the ageing workforce, it makes sense to reduce the physical burden on our employees and let the robots do the heavy stuff.”

That is one reason why the grower’s high-tech greenhouses are highly automated. For example, in the planting department, robots are used to place the individual seedlings of Schlumbergera and Rhipsalidopsis in the sales pot with millimetre accuracy.


Therefore, when CEO Jack Møller was looking for further ways to improve efficiency around three years ago, it made sense to consider automating – and even robotising – other stages of production. “Packing is a particularly labour-intensive process, involving 70-80 employees at peak times, so when Møller saw a WPS automated packing system in action on a trip to the Netherlands, he was keen to explore the possibilities. Development work started in autumn 2016 and the system was then implemented in stages from early 2017 onwards,” recalls Andersson.

The result is a large, automated system combining internal transport, robotised sorting and packing on three of the four packing lines. “The first implementation stage was for picking, sorting and sleeving,” he explains. “We run a just-in-time operation based on agreements with our retail customers to supply the right quantity of plants with the right amount of flowers on the right date. So all our plants have to be sorted and graded based on their developmental stage before packing.”


In the system, the robot first picks the plants from the bench, eight pots at a time, and places them in small carriers for fast and easy transport during the packing process. Then the plants are graded by a vision system and matched with the orders. If the plant fits into an order, it continues in the packing system. Otherwise it is returned to the greenhouse.

The grading system has another important function, according to Andersson. Retail buyers place their orders – including details of quantity, size, flower-grade quality, labelling, sleeving/wrapping and delivery date – in the central order handling system called ‘DANPOT’. This interfaces directly with the new system, which uses the information in the packing process.

“Each carrier contains a passive RFID tag and, during grading, the tag number is linked with information in the order system. When a plant passes a tag reader at an action point, the system combines the tag number and order information to determine what has to happen next in the process, such as adding a label showing price information or plant-care details.” In that case, the relevant label is printed and automatically attached to the pot. “Next, each plant is sleeved if necessary – either in the own sleeve or a customer-specific one,” he adds. The sleeving system was supplied by Terra International, but WPS – with Bart van Meurs as team lead – arranged for it to be specially modified for the grower. “The final step in the process is to put the plants in the marketing tray. This is done by three robots, and each robot can cope with four different tray types: 6, 8, 10 and 12-hole trays.”


Once the system is at full speed, the two picking robots will be sending a total of 4,000 plants/hour through to the next stage of the dispatch process. In comparison, the average employee is able to sort and pack 250 plants/hour manually. “Besides the manpower saving, this system has made it easier to introduce shifts so we can benefit from 24-hour efficiency. It has also reduced the amount of overtime and eliminated long days for our employees,” states Andersson.

Another benefit of this integral solution is that it is based on electronic data transfer. Eliminating manual data entry has reduced the chance of mistakes as well as saving time and money.


What makes this project so innovative is its complexity. “We’ve set the bar high – we are trying to merge all the activities into a single packing system,” admits Andersson. “Something like sleeving is relatively simple, for example, but robotising the foil-wrapping of the trays has proven to be more challenging because it involves lots of steps: the tray is placed on a platform then a funnel covers the plants, the foil is attached to the tray, the turntable rotates the tray and the funnel, and then the foil is cut before the tray is ejected.”

Flowering plants are very delicate and easily damaged. Plus there are slight differences in the sizes of trays from different suppliers – only at millimetre level, but a couple of millimetres can make a big difference for a robot. “This is being tackled by adjusting the distance parameters in the system. We’re around 95% of the way to full implementation now, so I’m sure it will be resolved soon.” And once it is, the next step could be to automate the quality control stage of the process after sleeving, he adds.

LED pilot

Alongside this project, PKM is working on a pilot to improve energy efficiency through the use of LED lighting. “Our greenhouses are already fitted with double screens, and they are heated based on district heating using residual heat from power plants. So the only way to further reduce our energy bill is to save on electricity costs,” says the production advisor.

“We tried a 100%-LED system seven years ago and achieved around 25% energy savings, but in the winter period the plants produced under LED needed a 3 to 5-day-longer production time compared to high-pressure sodium (HPS) lamps. We are now trialling a hybrid system – 50% HPS and 50% LED – on 3,000 sqm. This combination gives us the full spectrum so we are hoping that we will be able to save energy without affecting the production time or plant quality.”


Founded in Denmark in 1948, the Gartneriet PKM nursery’s production area today covers 165,000 sqm of 20 m wide-span glass greenhouses (Venlo blocks) and an outdoor area of 40,000 sqm. The nursery has year-round production of crops including Campanula, Schlumbergera, Rhipsalidopsis, Gentian and Helleborus, depending on the season. The high-tech greenhouses include robotic solutions in the planting and packing areas.

Text: Lynn Radford.