How to Grow Cucamelon

If you are looking for a slightly more unusual plant to include in your vegetable garden, why not try a cucamelon? A reliable vining plant, the small fruits can, as the name suggests, resemble a small cucumber or watermelon. Also known as the mouse melon, sandita or Mexican sour gherkin, the cucamelon is increasingly popular for its crunchy texture and tart flavor.

If you want to learn more about these interesting little vegetables, including how to add them to your garden, our How to Grow Cucamelon guide is for you.

What is a Cucamelon?

Part of the cucurbitaceae or cucumber family the cucamelon (Melothria scabra) is a fast growing, vining plant. With a little care it is a pleasingly reliable addition to the garden.

The cucamelon is a unique heirloom plant. Native to Central America, no cultivars or hybrids have yet been developed.

The distinctive fruit of the Cucamelon. Cucamelon by poppet with a camera / CC 2.0

Melothria scabra can be grown as a frost tender perennial in tropical climates. Everywhere else it is commonly grown as a spring planted annual. These plants are considered hardy in USDA Zones 2 to 10.

Best planted in full sun and well draining soil the plants can reach up to 1 ft tall and spread over 10 ft wide.

Like the cucumber plant, small yellow flowers emerge in late spring or early summer. Following pollination these fade away to be replaced by small, striped green fruit. When mature the fruit is roughly the same size as a grape. The fruits of Melothria scabra often resemble small cucumbers. As well as being smaller than a cucumber the fruit is also more elongated.

Green on the outside, cutting the fruit open reveals white flesh. The fruit of the mouse melon is typically crunchy with a tangy lime-like tartness which compliments the usual cucumber-like flavor.

You can purchase young cucamelon plants from garden stores. After hardening off these are ready for transplanting into the garden. You can also grow mouse melon plants from seed. This is more affordable and not as complicated as you may think.

Starting Plants from Seed

You can either start your seeds undercover or, in USDA Zones 7 and warmer, directly into the garden.

If you are sowing directly, sow the seeds in a sunny spot, roughly half an inch deep. This can be done as soon as the last frost date has passed and the soil has started to warm up.

Space the seeds 1 ft apart. Following germination this can be thinned out to a spacing of 2 ft. Remember these are vining plants, they require some support from a trellis or bamboo stake to support their spread and keep fruit off the ground. During humid periods in particular, fruit that is allowed to contact the ground may rot.

You can also sow the seeds in individual biodegradable Coco Coir Nursery Pots undercover.

Like the cucumber, the cucamelon dislikes having its roots disturbed. This can cause the plant to fail. Starting seeds in biodegradable pots means that you can simply plant the seedling still in its pot in the ground without the need to remove the plant from the pot, potentially disturbing the root system.

Seeds can be started undercover around 3 weeks before the last predicted frost date. Fill the pots with moist, well draining potting soil or a sterile seed starting mix and sow one seed per pot.

Germination usually takes 7 to 14 days. Germination can be slow and erratic. Consequently you should always start more seeds than you need. This helps to protect against seedling failure.

Keep the soil moist. The temperature surrounding the seeds should average around 70 ℉. Seeds are unlikely to germinate if the soil temperature is below 60 ℉

Following germination, grow the seedlings on until they are at least 2 inches tall. Harden the seedlings off before transplanting out into the garden.

Before transplanting, work the soil over, removing any weeds and stones and breaking up large clumps of earth. This is also a good time to work in any necessary amendments such as compost.

Make a hole in the soil large enough to hold the biodegradable pot. When placed in the hole, the lip of the pot should sit level with the soil. Position the pot in the hole and cover with a light layer of soil or compost. Water well. As the plant grows and the roots develop the pot breaks down, allowing the roots to spread out.

If you are growing more than one mouse melon plant, space them 2 ft apart.

Don’t forget to install a Highland Garden Care Tomato Cage or other support. As well as keeping fruit off the floor, preventing rot, a support also helps to protect the vines from accidental damage.

Cucamelon vines are surprisingly tender and are easily injured when moving or harvesting. Training the developing vines enables you to easily access the ripe fruit without causing any damage. It also prevents them from becoming entwined, constricting or hampering fruit development.

Support the vining growth habit of the plants. Cucamelon by poppet with a camera / CC 2.0

Planting in Pots

You can also grow mouse melon plants in pots. A pot with inbuilt support, such as a GREEN MOUNT Raised Garden Bed Planter with Trellis, helps you to make the most of your vertical space.

Unlike other vining vegetables these are surprisingly light plants. This applies even when the vines are laden with fruit. Because the mouse melon is relatively lightweight, there is less risk of the plants becoming top heavy and falling over.

Plant one mouse melon plant per pot.

To encourage root development and healthy growth use a large pot, at least 5 gallons or 12 to 18 inches in size. Your chosen container should also have plenty of drainage holes in the bottom. An unglazed clay pot is a sturdy option which allows excess moisture to escape through its sides. Fill your pot with soil that is rich in organic matter. Plant as you would in the ground, the top of the cucamelons root system should sit level with, or slightly below soil level.

In favorable conditions plants mature in around 70 days.

Where to Plant

The cucamelon does best in a sunny spot and well draining soil. Do not plant the mouse melon close to a taller plant. As the taller plants develop and leaf out in late spring it may shade out the mouse melon causing it to fail.

As well as being frost sensitive the cucamelon is also sensitive to changes in temperature and humidity. The plants are best placed in a warm, temperate climate that replicates their native Central American conditions. In cooler, less temperate climates growing in a greenhouse enables you to maintain temperature and humidity levels around the plants.

Cucamelons require around 6 hours of direct full sun every day. In the hottest climates the plants may appreciate a little afternoon shade.

The soil should be light and well draining. Cucamelon plants prefer a slightly acidic soil but with the right care they tolerate most soil profiles. Work in compost before planting, this is particularly important if your soil isn’t very rich.

How to Care for a Cucamelon Plant

Following planting, there are a few little things that you can do to help your mouse melon plant thrive. Remember the happier it is the more productive your mouse melon plant will be.

Mulching the soil around the plant helps it to retain moisture and an even temperature. It also prevents weed growth. The cucamelon has a shallow root system. Weeding can disturb or damage the roots, causing the plant to fail. A layer of organic mulch not only suppresses weed growth but it also slowly breaks down, enriching the soil and further boosting your plants.

Keep the soil around the plant clear and tidy. Mexican Sour Gherkin Cucumbers by Jules Perry / CC 1.0

When to Water

Water your mouse melon plant regularly.

When caring for a mouse melon, you are aiming to keep the soil moist, not wet or overly saturated. If it doesn’t rain, a typical mouse melon plant requires around 1 inch of water a week. Plants growing in hot sunny conditions, as well as those growing in pots, may require more frequent watering.

Implementing a drip irrigation system, such as the one provided by the Bonviee Drip Irrigation System,  is an ideal way to slowly hydrate your growing fruit and vegetable plants, ensuring that you don’t over water them.

When watering, always water the soil, not the leaves. Wet leaves are a breeding ground for fungal diseases such as powdery mildew. If you do have to water from overhead, with a watering can or a garden hose, it is best done in the early morning. This gives the leaves the entire day to dry out before the cooler evening temperatures arrive.

How to Fertilize

Apply a starter solution when the seedlings are 3 to 4 weeks old. A starter solution can be made by diluting a balanced vegetable fertilizer to a quarter of the strength indicated on the label.

Fertilize the plants again in midsummer to promote fruiting. You can apply either a vegetable plant fertilizer or a high potassium liquid fertilizer for the second dose.

Do I Need to Prune Mouse Melon?

There is no need to prune growing mouse melon plants. Instead, lightly tying the vines to a trellis or tomato cage enables you to control the spread. Be careful when handling the vines, they are delicate and prone to damage.

Pinch back the tips of the vines in spring or early summer. Pinching out is best done when the vines reach 16 inches in length. Not only does pinching out encourage branching, it also leads to more flowering and fruit.

Pinching out vining plants encourages branching, flowering and more fruit to form.

Can I Overwinter a Cucamelon?

The cucamelon is typically grown as an annual plant. While you can try to overwinter the plants, it is not always successful.

To overwinter, in the fall, once fruiting has finished for the year, carefully lift the plant’s main radish-like root from the ground. Store in a pot filled with barely moist compost in a shed or garage over the winter months.

Water the stored plant occasionally. You are aiming to water just enough to prevent the soil from completely drying out.

The following spring, after the last frost has passed, replant the mouse melon in the garden.

If you are growing your cucamelon plant in a pot it can simply be moved inside in the fall.

With careful care, the underground tuber of the mouse melon can be encouraged to develop and last for several seasons.

Do I Need to Pollinate the Flowers?

There is no need for you to hand pollinate cucamelon flowers. Each mouse melon plant produces male and female flowers. This means that the plants are capable of  self-pollinating.

Most specimens growing outside naturally pollinate with help from the wind and visiting garden pollinators.

Growing marigolds and other pollinator friendly flowers close to your cucamelon plants helps to increase pollination and boost your yield.

Marigolds are great companion plants, drawing scores of pollinators to your vegetables.  

After pollination the male flower withers and dies away. The female flower, once pollinated, starts to develop a cucamelon fruit.

How to Harvest Mouse Melon Seeds

If you do not want to overwinter the plants, you can save seeds from some cucamelon fruit to sow on the following year.

To do this, allow a few fruit to remain on the vine at the end of the season. After a few wells the fruit becomes overripe and yellow.

Once the fruit has turned yellow it can be cut from the plant and sliced in half. Scrape out the seeds and pulp. Place the pulp and seeds in a jar of water for a few days, disposing of any debris and seeds that float to the top. The seeds which are at the bottom of the jar are viable and can be kept.

Rinse the viable seeds and dry in a single layer on a quiet windowsill. Once dried the seeds can be stored in a sealed paper envelope in a cool dry position until you are ready to use them.

Remember to label and date the envelope. Cucamelon seeds are best used within a year. They do not keep well.

How to Harvest Cucamelon Fruit

As the fruit develops, check it every day to see if it is ripe.Cucamelon fruit is ripe when it is ¾ of an inch to 1 inch long and firm to the touch.

Aim to harvest the ripe fruit before it exceeds 1 inch in diameter. Fruit that is allowed to sit on the vine for too long can become overly large and seedy. It also loses its flavor.

To harvest, use a garden scissors to cut the fruit from the plant. Do not pull the fruit away. This can damage the delicate vines.

Cucamelon fruit keeps well in a vegetable crisper for a few days. For longer term storage you can either pickle or can the fruit. Fresh mouse melon fruit has a variety of uses including a garnish for drinks or sliced into salads and salsas.

Common Cucamelon Problems

Despite being an unusual specimen the cucamelon is a pleasingly healthy and problem free plant, particularly when compared to other vining plants.

Sometimes aphids can infest the plants. Regularly inspect the foliage of your mouse melon plants for signs of infestation. If caught early enough aphid infestations are easy to treat. Wipe neem oil or citrus oil onto the affected leaves with a cotton wool ball. A homemade insecticidal soap can also be used.

The most common disease to affect the mouse melon plant is powdery mildew. Rarely serious, our guide to powdery mildew explains exactly what this issue is as well as outlining a range of preventative measures and treatments.

To prevent powdery mildew from developing on your plants correctly space them out when planting. This allows air to freely circulate around the plants. Training the vines to grow into space, so that they are not covering or becoming entangled with each other also helps to promote air flow, keeping the leaves problem free.

Another easy to adopt measure which helps to prevent powdery mildew is to only water the soil. Do not water from above, this dampens the leaves. Damp leaves are a breeding ground for fungal issues.

Finally, do not overwater your plants. Too much water can cause root rot to develop. A soil moisture sensor is a good investment if you struggle to work out how wet or dry your soil is.

The distinctive fruit of the mouse melon.

Ideal for a vegetable garden, thanks to its vining habit you can cultivate a cucamelon in vertical or even small container gardens. With just a little care and a lot of sun, these are pleasingly low maintenance, productive plants that provide you with a constant supply of freshy, zingy fruit throughout the summer months.