Rock Melons – a sweet tunnel house treat!
Identifying different varieties of melons can be a minefield! But, but for the purposes of our December tunnel house growing guide, we’ll stick with rock melons, those gorgeous orange centred, fragrant-fleshed, green net-skinned melons that we can never get enough of. A member of the Cucurbitaceae family, rock melons (Cucumis melo var. Cantalupensis) grow outdoors in sheltered spots in regions with a reliably hot summer climate. But for those with a tunnel house, it’s also possible to produce a harvest from melon vines even when you live in a cooler part of the country. And early to mid summer is by no means too late to get the plants them in the ground. Rock melons mature in 80-120 days, and with summer weather often lingering well into autumn, a December planting can get seedlings off to a strong start rather than their languishing earlier in cold soil.
Source
Rock melons are heat-lovers, tolerating temperatures of 12-15°C but preferring a daytime temperature range of 25–35°C and night-time temperatures of between 15–20°C. Seedlings won’t perform well until conditions in your tunnel reflect this (generally speaking, cooler regions will be gathering sufficient tunnel house heat for melon growing by early summer). Fortunately, rock melons seedlings are usually still available in garden centres in late November-early December.
If you want to grow your own plants from seed, raise them undercover in coir seedling pots on a germinating pad or a similarly warm situation. Choose a sterilised commercial seed raising mix to avoid fungal disease attacking the plants. Seed takes from 1-2 weeks to germinate, and seedlings are usually ready to transplant into the tunnel house 2-3 weeks later. That’s a total of 4-5 weeks from sowing, so check past soil temperature records, and count backwards to find out the best time to sow seed.
Ground work
Rock melon grow best in moderately loose, free-draining ground that is rich in organic material. While they will grow in containers, the fruit tends to be smaller, so where possible, give the seedlings a space in your tunnel house bed. To prepare the growing space, loosen the ground to the depth of a garden fork’s tines. Avoid actually digging up the ground as you will only be turning under good top soil. Instead, push the fork deep into the ground, and rock it back and forth to loosen the subsoil. Next, use the back of the fork’s tines to break up any clumps of soil to a depth of half the fork’s tines. Mix in sterilised compost (a bucket per seedling) and sterilised manure pellets (a cup per seedling). Rock melon will tolerate a slightly acid soil so rather than add lime (which will not benefit the likes of tomatoes which may occupy the same space next season), skip any sweetening of the soil. Stir some mycorrhizal fungi into the soil to promote nutrient acquisition. Water the ground deeply each day for 2 days prior to transplanting.
While the bed absorbs the moisture, prepare a liquid manure feed of chopped kelp, sterilised compost, and comfrey leaves. Soak a bucket each of these ingredients in a covered barrel of fresh rain water.
Support
Rock melons are a vining plant, and left to their own devices, will sprawl over the floor of the tunnel house, occupying more space than you may have available for them (sprawling plants that hug the ground also invite attack from slugs and snails that hide in the dampness beneath foliage). To avoid sprawling, provide support before you transplant the seedlings into the ground. Twine will not be strong enough to hold up the plants once they begin fruiting. Instead, use a horizontal or leaning frame work for the plants to climb up into.
Transplanting
Rock melon are ready to go into your tunnel house when soil temperatures are reliably warm (see above). Use a garden thermometer to test for this before you transplant. When planting your seedlings, use a trowel to create pockets 60-80cm apart. If you are planting more than one row, keep the distance between rows at 90cm. Water each planting hole well, and plant the seedling, still in its compostable coir pot, to limit root disturbance. If the seedlings are in non-compostable containers, take great care with easing them out, and ensure as much soil as possible remains around the roots. When planting, ensure that the soil around the stem doesn’t come up any higher than it was in the seedling container. Gently firm the soil around the base of each plant, and mulch with a light material (such as un-treated pea straw).
Maintenance
As your rock melon seedlings grow, water them deeply once or twice a week, using your liquid fertilizer to provide one of these doses of moisture. Cease the liquid feeding once flowering commences. Encourage pollinators to take an interest in the plants by growing flowering plants in and around the entrance to the tunnel house If temperatures drop, or if pollinators are scarce in the tunnel house, gently hand pollinate with an artist’s soft-bristled paintbrush.
It’s important that the seedling grow as quickly as possible and without check. For this reason, be vigilant with pest control, squashing sap suckers with your fingers in the first instance. If the pests persist, apply a spray made from 1/4 tsp hard bathroom soap dissolved in half a litre of boiling water that has been left to go completely cold. Repeat every 3-4 days. Note: if you are growing organically, there is no need to completely rid the plants of pests – a healthy balance is what you are aiming for because the general strength of the plants means they can hold their own against a degree of pest attack. Melons enjoy humidity but you must strike a balance between providing this and keeping fungal disease at bay. Keeping the tunnel house well ventilated day and night can help.
Harvesting
In good conditions, your melons will be ready to pick in 12-16 weeks. Aim to remove them from the vine as soon as they are mature as this reduces stress on the plants. Give the melons a tap (a hollow sound indicates ripeness). Ripeness is also indicated by a yellow tinge along the ribs of the skin, and by a sweet smell around the stem end of the fruit. If fruit detaches easily from the vine with a gentle pull, it is usually ripe.
Tips
Pinch out the growing tips of the vine at the fifth leaf point. This encourages the side shoots to grow, and it is these shoots that produce flowers. Once flowers have set fruit, pinch out growth beyond them (apart from one or two leaves) to help the fruit develop.
Keep the ground beneath the vines well weeded to allow air to flow freely around the plants
If growing rock melons in pots, choose a container that is at least 40cm in diameter.
Once flowering commences, water with a liquid feed made from kelp only.
Water the plants at the base of their stems, avoiding wetting foliage or fruit.