Every variety has its own specific characteristics. Because we are broadly represented in the chain and grow 2nd year onion sets and process them industrially, we know exactly what varieties are most suitable for every specific application. Our years of experience in the field allows us to provide tailored advice, based on the cultivation goal.


Because we have our own fleet at our disposal, we are very flexible when it comes to delivery. We know how important it is to you to have your order delivered right on time. Delivery straight to the plot, urgent orders and backorder are no problem for us. Of course we will pick up any remainders and empty crates after planting.


Preparing (heat treatment)
The onion is a biennial plant. In the first year, the bulb is formed and top growth occurs. In the second year, they flower.

In the cultivation of 2nd year onion sets, there is maximum focus on the development of the bulb. During growth, flower stalks may form. This is undesirable, since it leads to less yield. In addition, it adversely affects the storage-life of the onion.

In our preparation cells, we can carry out an accurate heat and humidity treatment, killing the sprout stalk of the onion sets. Because of this the growing power is concentrated in the bulb, preventing the onion from forming flower stalks after planting the onion. To achieve the desired effect, this process, which is under supervision of Naktuinbouw, must meet specific requirements. Every variety is subject to different requirements with regard to the duration of the treatment.

Preparation is not required for all varieties, because in many varieties, the percentage of flower stalks in 2nd year onion sets is minimal. However, white and red varieties are very sensitive to flower stalk formation in general. Therefore, we recommend the prepared variants for professional growers.

Disinfecting prior to planting is the foundation for healthy onion growth. Disinfection takes place by means of a dipping treatment using substances developed to that end. They make sure that the onion sets are protected against certain diseases. We strongly recommend having the onion sets disinfected by us. This to prevent contamination and failure, for instance due to the soil disease fusarium.


We can sort in every desired size. The most common sorting for the professional cultivation in the Netherlands and Belgium is 10/21 mm. Depending on the cultivation goal, we can deliver in different sorting.

For the industry for instance, a uniform size is desirable. This, to achieve the highest return possible. Therefore, the industrial processor is likely to choose the size 14/21.

Because, in England, there is almost only demand for course consumption onions (60+) growers in that country usually choose sorting in 3 dimensions (10/14, 14/17 and 17/21). Because of that, we are able to steer very accurately on plant density, and as a result of that, on earliness and the coarseness of the batch.

The even more course size sorting (21/24) are earlier and result in more yield than the finer sorting, but ultimately, they are not interesting for professional growers in the Netherlands and Belgium. This, because more starting material is required, making its cost higher. In Norway and Finland the more course dimensions are popular, but this is mainly due to the shorter growing season.


The amount of required plant material per hectare depends on several factors, including the desired plant density, the number of rows per bed and the number of pieces per kilo. With the help of the graph below, the amount of plant material necessary can be determined by approximation. If desired, we can issue a "set count" for every batch to be delivered. With this, we can determined the exact number of pieces per kilo. We recommend ordering a little more, because returning an excess is easier than supplementing shortage. Especially when the planter is already on the plot.


It is important for the onion sets to be stored as dry as possible after receipt. The best is to store in crates with an open (mesh) bottom in a well-ventilated area. Where possible, ventilation should take place on a drywall. Of course, low humidity is beneficial. Moisture makes the onion sets grow roots, and when they dry out, they will not grow back.

The temperature is less important, but usually, onion sets are stored at temperatures between 8-10 ˚C.

We can provide you with a high-quality mobile drywall, suitable for pallets and crates.