Introduction to Watermelon Plants
Watermelon plants, part of the cucurbit family, are similar in appearance to courgette and squash plants, featuring flat, green, and slightly furry leaves. These plants are known for their yellow flowers and fruit. They can either be left to scramble across the ground or trained to climb a frame, allowing for space optimization. To produce ripe fruit, watermelons require up to three months of sun and heat, necessitating a long, hot summer for success.
How to Grow Watermelons
Growing watermelons involves selecting a moist but well-drained soil in a sheltered, sunny spot. For optimal results, it’s recommended to grow them in a greenhouse or polytunnel. Regular watering and weekly feeding with a high potash fertilizer are essential. To create a bushy and productive plant, pinch out the growing tip once five to six true leaves have formed, then thin subsequent side shoots to allow four to develop. Pinch out the tips of these four shoots once six leaves have formed. Harvest the fruit with a sharp knife when tapping it produces a hollow sound.
Where to Grow Watermelons
For the best chance of success, grow watermelons under cover in a greenhouse or polytunnel. If opting to grow them outside, choose a sheltered spot in full sun. Growing watermelons in pots is also possible, but they will require more frequent watering and feeding than those planted in the ground. Consistent watering is crucial for a good crop. For pots, select a compact-growing variety like ‘Little Darling F1’ and plant it in a large container at least 35cm high and wide, using high-quality, peat-free potting compost combined with organic matter such as well-rotted manure.
How to Plant Watermelons
Sow watermelon seeds into peat-free seed compost from mid-April to early May, keeping them in a heated propagator set between 18ºC and 21ºC. Transplant seedlings into individual pots when they are large enough to handle, or purchase ready-grown young watermelon plants. Transplant them into larger pots and grow them in a warm spot such as a conservatory or greenhouse. If growing watermelons outside, wait until the last frosts have passed (typically early June) before planting out. Harden off the plants over a couple of weeks by gradually exposing them to the outdoors. Plant in deep, fertile soil enriched with well-rotted manure or garden compost. If growing in a greenhouse or polytunnel, there’s no need to harden off plants, just plant them into the greenhouse border with plenty of well-rotted manure or homemade compost.
How to Care for Watermelons
If training your watermelon plants to grow vertically, tie their stems to the support frame as they grow since they are not self-clinging. As fruits develop and become large, support them individually to prevent the stem from collapsing under the weight. Old bras and t-shirts can be used to create ‘hammocks’ for the developing fruit. Consistent watering is especially important for ensuring good fruit quality, size, and flavor. Pay particular attention to watering once the fruits have started to form. Feed the plants with a liquid fertilizer high in potash, such as tomato fertilizer, diluted as directed, and apply it weekly from when the first fruits start to develop.
When to Harvest Watermelons
Harvesting watermelons at full ripeness is crucial for enjoying their sweetest flavor. A good indicator of ripeness is the toughness of the skin; if pressing it with a fingernail leaves a mark, the fruit isn’t yet ripe. Alternatively, tap the fruit; it will produce a hollow sound when ripe. Cut the fruit from the plant using a sharp knife.
