Besides trials of Charentais, the Vegetable Experimentation Station has been conducting research on watermelon for several years. During the week of 12 August, the first watermelon was harvested from a plastic tunnel. These ripe watermelons, which are part of a variety trial, had been planted on 11 June. Melons planted 27 June in the same canopy will also soon give harvestable fruits.
Different varieties of mini watermelon
Five varieties are being compared in this variety trial. These varieties do not harvest very large pieces, which watermelon is known for, but just smaller fruits that are more suitable to consume in one go with a family or even alone. Between varieties, the fruit weight of the harvested pieces varies between one and three kg. The table below summarises the varieties adhering to in the trial.
| Variety | Seed house |
| Corellana RZ | Rich Swan |
| FWD 5550 | Sakata |
| Gatinho RZ | Rijk Zwaan |
| HVO 1582 | Uniseeds |
| Tigrimini | Uniseeds |
One plant per m² is planted and the crop requires little care. For now, no pests or diseases came in either, apart from a few spots of Verticillium, although spider mites are definitely a concern. Downy mildew can also cause problems in humid conditions.
Watermelons require a lot of heat
Even more than Charentais, watermelon needs a lot of heat. Although the plantings are planted more than two weeks apart, the harvest comes close together because the earliest crop grew very little in colder conditions. To give the crop enough warmth, the Trial Station leaves the tunnel walls down for as long as possible, with visible effects. Pollination is naturally via wild bumblebees and bees; when the plants flower, the tunnel walls are opened up a little so that pollinators can get to the flowers.
Despite all the heat required, it is still possible to grow tasty melons in Flanders. The varieties Tigrimini and Gatinho were also in trial last year and then achieved a production of 3.5 to 4 pieces per m², with the flavour always being very good.
Harvesting when ripe
Charentais melons easily show when they are ripe, watermelons do not. Therefore, it is more difficult to estimate ripeness and harvest watermelon. The best technique is to look at the attachment on the same node as the fruit, when this turns brown, the watermelon is harvestable. In many of these varieties, this is about five weeks after fruit set. Watermelon do not ripen further after harvest and are therefore more storable than Charentais, as long as you do not store them together.
These results came about with funding from BelOrta.