Cucamelon seeds and how to plant them

I love planting cucamelons in our vegetable garden. In fact, I love them so much, they’re featured in my award-winning book, Veggie Garden Remix! Cucamelon plants are easy to grow and prolific, with each producing hundreds of small oval fruits that look like tiny watermelons but taste a lot like cucumbers. With more gardeners wanting to grow cucamelons, many nurseries are now offering seedlings. Yet savvy gardeners can easily grow their own plants by starting cucamelon seeds indoors in mid-spring.

You may also know cucamelons as Mexican sour gherkin, mouse melon, or sandita. They’re a vegetable that originates in Mexico and Central America. Cucamelons have been a part of my vegetable garden for many years. When I wrote my award-winning book, Veggie Garden Remix, the first section I tackled was cucamelons because it’s such a fun crop to write about. However, it’s not just me that loves this quirky vegetable. My entire family enjoys the crunchy fruits of cucamelons, especially my children, nieces, and nephews who are all happy to help me harvest baskets of the grape-sized fruits.

When to plant cucamelon seeds 

Timing is everything when it comes to starting cucamelons seeds indoors. In zones 3 to 6, cucamelon seeds should be sowed under grow lights or in a sunny window about six weeks before the last expected spring frost. Impatient gardeners (like me!) might want to sow them earlier to get a head-start on the growing season. This may sound like a good idea, but once cucamelon seeds have sprouted, they quickly turn into vigorous vines and can become a tangled mess beneath a grow light.  

Gardeners in warmer climates – zone 7 and above – don’t need to start their seeds indoors. Their season is long enough to direct seed in garden beds once the risk of frost has passed.

Planting cucamelon seeds

When you’re ready to sow the seeds, fill seeding trays or pots with a pre-moistened high quality soilless potting mix. Sow the seeds a quarter inch deep. I like to cover my trays with a sheet of plastic wrap to hold soil moisture. Once the seeds have germinated, I remove the plastic to allow good air flow.

After planting the cucamelon seeds, place the pots or trays in a sunny window or beneath grow lights. I prefer grow lights as they produce stronger, stockier seedlings. My set-up is simple: fluorescent fixtures fitted with one warm and one cool bulb. I have the fixtures hung on chains so that I can move them up as the plants grow. Ideally, the fluorescent bulbs should only be a few inches away from the seedlings so they receive maximum light.

How to germinate cucamelon seeds

Cucamelon seeds can be slow to germinate, taking several weeks to sprout. To speed up the process, place the trays or pots on a heating mat. Most heating mats increase the soil temperature by 10 to 20 F above the temperature of the room. It’s also important to provide consistent moisture to promote good germination. Never allow the potting mix to dry out! Use a hand mister or water the trays from the bottom to maintain soil moisture.

How to care for cucamelon seedlings

Once cucamelon seeds sprout, the plants are relatively low care. If using grow lights, keep them turned on for sixteen hours a day. Also pay attention to soil moisture. Cucamelon plants appreciate even moisture but don’t want to be sitting in water. Too much moisture may encourage root rot. I also fertilize the young plants with a half strength dose of fish emulsion fertilizer every two weeks.

Once the seedlings are a few inches tall, they can be moved to larger pots. I usually upsize my cucamelon plants to four inch pots. I also insert a small bamboo post in the pot to provide something for the plants to climb. It helps prevent the vines from tangling. This is mainly an issue for plants started too early. The first year I started cucamelons indoors, I sowed the seeds about ten weeks before the last spring frost. By the time I could move them to the garden, each plant was about three feet long and it took me an hour to untangle the plants. I quickly learned to start them at the right time.

How and when to harden off cucamelon plants

Begin to harden off cucamelon seedlings around your last expected spring frost date. I don’t rush my plants into the garden as cucamelons are cold sensitive and can sustain damage if the temperature drops or there is a frost. Instead, I begin the process around the last frost date and plant them in my garden beds or containers seven to ten days later when the weather is more settled. 

To harden off:

• Day 1 – Take the plants outside on a mild day and place them in a shady spot. Bring them in that night. 
• Day 2 – Put them outside again but introduce them to an hour or two of early morning or late afternoon sun. Bring them indoors at night if the temperature is forecast to fall below 50 F (10 C).
• Day 3 – Give them a half day of sun, but bring them indoors at night if the temperature is forecast to fall below 50 F (10 C). 
• Day 4 – Give them a full day of sun. Leave them out if the temperatures are mild.
• Day 5 – Give them a full day of sun. Leave them out if the temperatures are mild. 
• Day 6 – They can be moved to the garden anytime. If the night temperatures are still chilly, wait another few days to transplant, or cover the plants with a cloche or mini hoop tunnel. 

How to plant cucamelons in a garden

Cucamelons love heat so find a spot in your garden that offers full sun and shelter from strong winds. I plant cucamelons at the base of trellises, tunnels, or other strong supports. The vines look delicate but they can climb eight feet or more and produce many side-shoots. A strong structure is essential. If you have plenty of space, you can let the plants sprawl along the ground. I find it more difficult to find the small fruits when the plants are not grown vertically.

Before transplanting, dig a few inches of compost or aged manure into the soil. Carefully pop the plant out of its pot, handling the roots carefully as they don’t like to be disturbed. Plant the seedling into the prepared spot, firming the soil gently around the roots. Water well after planting.

Trellises and tunnels for cucamelons

As noted above, cucamelon plants are vigorous vines that love to climb. I usually plant a cucamelon vine on either side of my bean tunnels to mix with the various pole bean varieties, but I also plant them at the base of wire A-frame trellises or cucumber trellises. They are natural climbers and you don’t have to worry about helping the plants attach to their supports. Their tendrils latch on securely and propel the plants UP!

Cucamelon plants that are grown in containers on a deck or patio should also have supports to climb. You can attach pea and bean netting to stakes or a wall, or move the container to the base of a trellis.  

Growing cucamelons

Once cucamelon plants are established in the garden and growing well, they are pretty low maintenance. I keep an eye on soil moisture, watering when there has been no rain. I also mulch around each plant with straw or shredded leaves to help the soil retain moisture. To promote healthy growth and plenty of fruits, I fertilize every few weeks with an all purpose liquid organic fertilizer. Watch out for pests like cucumber beetle and diseases like powdery mildew. 

Cucamelons have separate male and female flowers and for pollination to occur, pollen must be transferred from the male to the female flowers. Bees typically do this job, but if you don’t find your plants are forming fruits, you may wish to hand pollinate using a small, dry paintbrush. Carefully touch the bristles to the male flower and then to the female flower. Quick and easy!

When and how to harvest cucamelons

Harvest cucamelons, or as we like to call them, little watermelons, often – usually about seven to ten days after flowering – for the highest quality fruits. Those that are left to mature on the vine will have a more sour flavor. We enjoy them fresh from the vines but also dipped in hummus, added to salad and salsa, and pickled. Towards the end of the season, I let some fruits mature on the vine so they can be gathered for seed saving. Did you know that cucamelon plants form tubers and they can be dug and overwintered in a sheltered spot like a basement? The tubers can then be planted the following spring. 

For more information on growing cucamelons and cucumbers, be sure to check out these articles:

• Check out this excerpt on cucamelons from Niki’s best-selling book, Veggie Garden Remix
• Our friends at Garden Therapy have written an excellent post on growing cucamelons
• How to overwinter cucamelon tubers
• Cucumber plant problems: common issues and how to deal with them organically
• How to grow cucumbers in containers

Are you going to start cucamelon seeds this spring?