Rows should be spaced about 2m apart; this distance can vary slightly according to the cultivar and the equipment used for cultivation and weed control.
In-row spacing should be between 50cm and 80cm. With cheap, open pollinated varieties, closer spacing to increase yield will do no harm.
If you are starting planting early in the season, it’s a good idea to use pre-germinated seeds. In this case, plant the seeds in moist soil so as not to damage the emerging root. The seed is usually placed about 2cm deep.
Seedless watermelons (triploids) must be planted with normal diploid watermelons to ensure enough pollen, as seedless varieties produce little or no pollen.
Plant a pollinator variety at each end of the land, then alternate two rows of the seedless variety with one row of normal diploids.
The pollinator variety must flower just before the seedless variety to ensure sufficient and timely pollination. Some pollinators are better than others, and may produce more male flowers.
Ask for guidance when buying your seed. Make sure, too, that there is a market for the pollinator. Finally, ensure that the pollinator variety has a distinctly different appearance to the other watermelons to avoid confusion during harvesting, as they’re harvested separately.
Seedless watermelons are more difficult to germinate and have lower seedling vigour than normal diploid watermelons, so it’s far better to plant their seed in seed trays. Here, they can receive optimal germinating conditions.
Excessive moisture during germination or less than-ideal temperatures can lead to losses, which can prove costly with this expensive seed.
Secure a market beforehand
You get fewer plants from seedless watermelon seed. At the same time, the seed is substantially more expensive. So before planting them, make sure that your customers are willing to pay the much higher price that these watermelons command.
It’s also important to arrange for ‘seedless’ stickers to be placed on the fruit. Without this, customers won’t understand why it’s selling for a premium.
Incidentally, seedless varieties do contain ‘pips’, but they are small, white, underdeveloped, and perfectly edible.
Triploids have become popular in many countries, and will probably become increasingly important in South Africa as more consumers try them. Switching to them might be a viable option, despite the extra care required during cultivation.
Control Cutworm timeously
All the foregoing will be wasted, though, if your watermelons are attacked by cutworm. Fortunately, control these days is easy, cheap and effective, so it’s not worth taking a chance. Apply a pyrethroid over the area before planting or emergence.
Pollination is also an important factor, and you should ensure that there are sufficient pollinator insects in the area. Watermelon nectar is not a favourite of honey bees and they may seek another source of nectar if one is available close to the watermelon lands.
Generally, one hive per hectare is sufficient. In some areas, solitary bees, which are much smaller than honey bees, are better pollinators.
Their numbers will depend on the type of flora in the area.