Cucamelon Plant: Mighty Mouse Melons

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In the summer of 2021, I went into the back portion of my yard covered in bamboo and discovered vigorous vines that had cropped up over the canes. The leaves tipped me off, giving me a sense that this plant was a member of the cucurbit family. After some confusion, I learned it was the cucamelon plant.

Cucamelon plants have a long history in the global south, from Venezuela up to Mexico. It was first cultivated by indigenous peoples and has relatives all over the world. This melon is so easy to grow, and it attracts virtually no pests. There’s no reason why your summer prep shouldn’t involve cucamelon seeds.

So how does one care for cucamelon vines? If you’d like to incorporate it into your own garden, read on. Follow these instructions and you’ll have ripe cucamelons in the heat of the summer, and a huge harvest to keep growing many summers in the future.

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Quick Care Guide

Harvest your cucamelons when they’re roughly the size of an olive or grape. Source: Lorin Nielsen

Common Name(s)	Cucamelon, Mexican mini watermelon, Mexican cucumber, sour gherkin, mouse melon, pepquinos
Scientific Name	Melothria scabra
Days to Harvest	60 to 75 days
Light	Full sun
Water	1 inch per week
Soil	Rich, well-draining
Fertilizer	Fish emulsion only in the poorest soils
Pests	None
Diseases	Downey mildew, powdery mildew, cucumber mosaic virus

All About The Cucamelon Plant

Cucamelon plants (Melothria scabra) are commonly referred to as mouse melons, Mexican mini watermelon, Mexican sour gherkin, or pepquinos. The common name for this vine is largely determined by the culture discussing it. Because the origins of these plants are indigenous, many of the indigenous words used to describe them translate in English to ‘mouse melons’.

Cucamelon plants have been used for food and medicine among indigenous people in South and Central America since before colonial times. They made their way to North America via colonization. In 1866 it was scientifically classified by a French botanist. Today there’s still controversy around this classification, as cucamelons resemble a great many cucurbits across the world.

The cucamelon vine is voracious at 8 to 9 feet, and seeds germinate within 10 days of sowing in early spring. The 1 to 3 inch-wide leaves resemble a typical domesticated cucumber, with three or five lobes each. They are rough with small hairs covering their surface. The vine produces both male and female flowers that look essentially the same: yellow with five petals. Female flowers receive male flowers’ pollen from insects or the wind.

After successful pollination in early summer, female flowers drop, and in their place, grape-sized fruits form that look just like tiny watermelons. They mature and ripen in 60 to 75 days. As cucamelon matures, tuberous roots form. They remain in the soil to return if conditions allow in warm areas. They are a lovely annual in colder regions.

The only edible portion from a cucamelon harvest is the tiny fruit. Cucamelons taste like cucumbers with an extra tang. Catch these Mexican sour gherkins while they are light to rich green. When they turn purple, they are no longer edible and become a powerful laxative. If these adorable fruits are too dark, they are best used for medicine by indigenous people in their native region.

Planting Cucamelons

Start cucamelon seeds 9 to 12 inches apart 4 to 6 weeks before the last frost date in spring. Cucamelons can be grown indoors, in a warm area, or you may start seeds indoors and transplant them outdoors after the last spring frost. Another appropriate method for starting Mexican miniature watermelon is to direct seed in your garden bed, raised bed, or container. Give the plants plenty of space, and provide a trellis. Growing cucamelons vertically helps you save space. Otherwise, the vine will sprawl out and take over. The area in which you plant should have well-draining soil and lots of direct sunlight. If you’re container-growing, provide a large deep plastic, terra cotta, or clay pot. Several gallons is best.

Care

Cucamelon forming — A cucamelon forming on the vine. Source: poppet with a camera

Mexican sour cucumber spreads rapidly once it is established in a garden space. Let’s discuss how to help your plants grow.

Sun and Temperature

Grow cucamelon in an area with full sun. Some afternoon shade is acceptable. Cucamelon thrives in warm weather and even hot weather where water is readily available. Planting should not occur until the last frost has passed in spring. The cucamelon growing season is much shorter in colder climates. Optimal temperature ranges for these plants occur in the 65 to 75 degree Fahrenheit range during the day.

Despite the tendency for these plants to produce more in warmer weather, their USDA hardiness range is wide, from zone 2 to 10. They are hardy in zone 7, where you’ll find them growing wild. Do not grow this plant before frost has passed because freezing weather will kill it. In very hot climates, provide some partial shade in the late afternoon, and water thoroughly to prevent slowed pollination. Provide frost cloth in a snap freeze.

Water and Humidity

Give your cucamelon at least 1 inch of water per week. Since these plants are prone to mildews, always water at the base of the plant so cucamelon tubers receive moisture, rather than the leaves. Soaker hoses and drip irrigation provide the best irrigation. Cucamelon is drought tolerant, producing gorgeous green leaves and tiny flowers even in dry seasons. Lack of water affects fruit size, so provide water regularly. There’s no need to water in rainy seasons.

Soil

The key to cucamelon nutrient content is well-drained soil. They grow in poor, nutrient-deficient soil. Amending garden beds or containers with some potting soil, or even rich soil amended with aged manure provides enough for underground tubers. The optimal pH in which to grow cucamelons is 6.0 to 6.8.

Fertilizing

When you grow cucamelons, there is no need to provide fertilizer. Especially if you plant cucamelons in rich soil, too much fertilizer burns the plant. The tubers are sensitive to high nutrient content and will rot in too much fertilizer.

Pruning/Training

When growing cucamelons, prune them back a bit to prevent them from overtaking your garden. If you notice any powdery mildew, remove those tendrils as soon as possible to prevent spread to the same plant or even multiple plants nearby.

Train the plant on a trellis. Young cucamelon seedlings should be planted in an area where they can be guided up a trellis. Whether that’s an arched, staked, or tee-peed trellis doesn’t matter. Growing cucamelons means they’ll grow a lot, and easily. During the growing season prevent the cucamelons from attaching to other plants, like your nearby tomato plant. Either snip the tendril from the plant and remove it or untwine the tendril from the nearby plant and twine it to the trellis again.

Propagation

When you’re growing cucamelons, collect cucamelon seeds from your first harvest. Then plant cucamelon seeds next spring. Within each of the melons, there are several tiny seeds that all have the potential to grow into a new plant. When you harvest cucamelons sort out those melons you’ll eat from seed cucamelons. Carefully slice each seed melon in half and scoop out the seeds. Place them in a jar and cover them with water for 1 to 2 days, stirring daily. Then lay them all out on a paper towel, and move them around so they don’t adhere to the towel. Store fermented seeds in a paper envelope. This is how you save seeds to grow cucamelons in the seasons to come.

Planting cucamelon seeds is simple, and more information about that is in the planting section of this piece. As you grow cucamelons, you may find your harvests yield so many seeds you don’t know what to do with them. Give them to friends who want to learn to grow cucamelons, or alternately, plant cucamelons in multiple parts of your garden. Seed saving is the best way to propagate these plants.

Harvesting and Storing

We’ve discussed how to grow cucamelons. Now let’s talk about how to harvest cucamelons and store them to use later on.

Harvesting

Grow cucamelons and harvest them when they are the size of grapes, and firm to the touch. If you pick them later while they’re still green they may be slightly bitter and seedy. Do not eat them when they are purple. At that point, it’s too late to enjoy. Simply pick off cucamelons with your hands, or from the ground. Wash them gently in water and they’re ready to go!

At the end of the season, overwinter cucamelon tubers to plant again in the following spring when the soil temperature allows it. Simply snip the plant at the base, and dig up the tuber. Then plant it in a small pot and bring it into an area where the temperature doesn’t get too cold. The tuber will produce one plant again in spring. For those who grow cucamelons in colder regions, overwintering tubers is a great way to keep the plant going in future seasons.

Storing

Before you save seeds, sort out those cucamelons that you’d like to eat. Fresh cucamelons should be eaten within a few days and stored in a paper bag in the crisper of your refrigerator. Grow cucamelons to make olive-sized pickles as well! These will keep in an airtight jar for six months. Unfortunately, this is the only long-term storage available when you grow cucamelons. Freezers and dehydrators deteriorate the flesh of the fruit and make them inedible.

Troubleshooting

The tuberous root structure of the cucamelon is quite unique. Source: UnconventionalEmma

When you learn how to grow cucamelons for the first time, you might run into a few issues. Let’s discuss those and what to do about them.

Growing Problems

If you underwater the cucamelon, it could produce much smaller fruit than normal, making it hard for you to get a good harvest. You can still save the smaller fruit and extract seeds to grow them again in the following spring. However, you might not have a harvest that sells at a farmers’ market or even enough to eat. Try, try again.

Another issue that can arise is a lack of pollination. Because cucamelons are open-pollinated, they’ll need assistance in places where other pollinating plants aren’t present. Try hand-pollinating them just like you would cucumbers indoors, or in greenhouses where bees, flies, and beetles can’t access them.

Nutrient surpluses and deficiencies can cause disproportionate production of leaves versus fruits, or maybe even no flower production. Don’t over-fertilize your plants. If you notice discoloration on leaves related to nutrient deficiencies, consult a guide to determine which nutrients are lacking, then add them lightly to the soil.

Pests

No significant pests infest the cucamelon. That’s pretty cool, huh?

Root knot nematodes have been known to attack the tuberous root zone if they’re already present and feeding on other plants. An application of beneficial nematodes can help to reduce the pest-nematode numbers.

Diseases

The mold pathogen Pseudoperonospora cubensis is a fungal pathogen that can cause downy mildew on cucamelon. It produces angular lesions that yellow the leaf cells of your vine. It causes reduced yields, misshappen fruit, and sometimes sunscald on the tiny melons. Often this disease occurs when conditions are too wet and warm for extended periods of time. First, remove all damaged parts of the plant and dispose of them in the trash. Neem oil sprayed on the plant every 7 to 10 days outside the flowering and fruiting period can control the disease. In larger infections, spray copper fungicide every 7 to 10 days until the infection is under control.

Podosphaera fuliginea is a pathogen associated with powdery mildew on cucamelon. It presents as a powdery film on leaves and vines. In infestations, the fungus grows into mycelial mounds that reproduce to spread elsewhere. Remove all affected parts of the plant and dispose of them. Then use neem oil or copper fungicides in the mode described in the last paragraph.

If you notice dark green mottling on the leaves of your cucamelon, you might have cucumber mosaic virus. There is no known control for this disease. The only way to prevent its spread is to remove all parts of the plant and dispose of them in a sealed plastic bag.