Melon & Watermelon

History

Cantaloupe and watermelon are members of the Cucurbitaceae family, also known as the cucurbits or gourd family (see Figure 1). This family includes crops such as cucumber, summer and winter squash, and gourd.

Melon is a general term for fruit produced by various members of this plant family and refers to netted and non-netted fruits, including cantaloupe, muskmelon, honeydew, and Asian melon. Cantaloupes are often referred to as muskmelons. Musk is a Persian word meaning “perfume” which refers to the fruit’s musky, sweet fragrance. Most Americans use the word cantaloupe rather than muskmelon to describe this fruit. “Cantaloupe” is believed to derive from the Italian “cantaluppi”, which pays homage to the location where the first cantaloupe was introduced to Rome. Cantaloupe likely originated in the Middle East, specifically Persia (modern day Iran) or Africa. The earliest cultivation recorded is around 2,400 BC in Egypt. Seed was reportedly brought to the Americas by Columbus in 1494. By 1535, cantaloupe was grown by Native Americans near Montreal.

Watermelon likely originated in tropical Africa, with production described in ancient Egyptian records more than 4,000 years ago. Watermelons were also cultivated in China as early as the end of the 9^th century. Watermelon was largely unknown in the Mediterranean countries until introduced by the Moors in the 13^th century. Native Americans were growing this crop in the Mississippi and Illinois River Valleys during the French exploration of the U.S in the 1600s.  Both cantaloupes and watermelons were widely spread throughout the world by colonists and explorers (see Figure 2).

Based on the origin areas for cantaloupe and watermelon, these crops prefer hot, dry climates and can grow well in Louisiana if planted in well-drained soil. Watermelon is more tolerant of the humid climate than cantaloupe. Both crops are annuals (with a life cycle of one year) that require a long, warm growing season.

Varieties

Cantaloupe and watermelon have many varieties producing fruit that vary in color, shape, and size. This guide covers cantaloupe and three types of watermelon (diploid/seeded, icebox, and triploid/seedless). Note: Honeydew and Asian melons are different types of melons in the same species but are not covered here.

Most cantaloupes are round with a hard, corky, beige-colored rind with sweet orange flesh. Can­taloupes are typically separated into two categories: (1) Eastern and (2) Western (see Figure 3). Eastern types are ribbed or grooved, larger, and generally have a shorter shelf life than Western types (only a few days). Western types are found frequently in grocery stores and are typically smooth with a corky beige netting, round, and usually have a two-week shelf life. Both cantaloupe and watermelon produce sweet fruit and have a vining habit, but cantaloupes have a seed cavity and watermelons do not.

Watermelons are larger, oblong blocky fruits, generally with a solid green or green-striped rind and bright red flesh (although they can also be orange or yellow fleshed). Watermelon varieties can also be without mature seeds. The three types of watermelon differ by size and seeds: (1) diploid – medium to large with seeds, (2) icebox – small and round with seeds, and (3) triploid – large and “seedless” or having only small, immature seeds (see Figure 4). Triploid watermelons are hybrids that lack growth hormones for normal fruit development and therefore are seedless. Triploid watermelons require insect pollination from diploid flowers (diploid varieties are planted with the triploids and are often included in seed packets) for successful triploid fruit development.

Cantaloupe and watermelon have either open-pollinated (including heirloom) or hybrid varieties. Seeds from heirloom varieties like Hale’s Best (cantaloupe), Charleston Gray (diploid watermelon), and Sugar Baby (icebox watermelon) have been saved for at least 50 years, can be saved each season and replanted, and are open-pollinated.

Cucurbit plants have separate male and female flowers on the same plant (termed monoecious), requiring pollen to be transferred from male to female flowers for proper fruit development to occur (see Figure 5). All cantaloupe and watermelon varieties are insect-pollinated, so if saving seed, different varieties must be separated by 800 feet-1/2 mile for cantaloupe, and 800 feet for watermelon, to avoid easy cross-pollination. Generally, it is not recommended to save seed for future planting with hybrid varieties, as they are usually not expressed properly in the next generation.

It is recommended to select disease-resistant varieties whenever possible. See the recommended cantaloupe and watermelon varieties for Louisiana in Table 1.

Table. 1 Recommended Cantaloupe and Watermelon Varieties for Louisiana

When and How to Plant

Cantaloupe and watermelon seeds should be direct seeded outside or transplanted during the recommended planting dates (see Table 2). As warm season crops, plant outside when the soil temperature has warmed to at least 60-65 degrees F (there should be no danger of frost), although cantaloupes prefer 65-75 degrees F and watermelon does best at 70-85 degrees F. Seedlings are susceptible to cold-shock and may be stunted if soil and air temperatures are too low. The use of a soil temperature map can help guide planting decisions.

Refer to the Cantaloupe and Watermelon Planting Guide (Table 2) for the recommended spacing when direct seeding or transplanting and allow plenty of space for vines to sprawl. Plant 6-8 seeds about 1-2 inches deep in a hill. Cover with soil and water in; seedlings should emerge in 10-12 days. When they emerge, thin to 3-4 plants per hill. When a few true leaves develop, thin to 2 plants per hill (if necessary). Early plantings may require a row cover for protection. The optimum growing conditions are hot, dry days (80-95 degrees F) and warm nights (65-70 degrees F).

In general, growing triploid watermelon takes more care and management than diploid watermelon. Triploid seeds germinate poorly, especially at low temperatures, and the seeds are more expensive and less vigorous. The seed coat of these seedless watermelons tends to stick to the seedling as it emerges, at times slowing/distorting seedling growth. For these reasons, they should be established as indoor transplants 2-4 weeks before the desired transplant date (see Table 2 for recommendations). Use large seed germination trays that are at least 1.5 inches in diameter to allow space for root growth. Soilless potting mix should be pre-watered and allowed to drain before seeding, and no additional moisture applied for at least 48 hours after seeding. Use good-quality seed with high ger­mination; only one seed per cell is sufficient. Seeds should be positioned with the pointed end (radicle) up to reduce the chance of the seed coat sticking to cotyledons. Seeds will germinate best in a well-lit area (such as a greenhouse or windowsill) with a temperature between 85-90 degrees F for 48 hours. A seedling heat mat and plastic dome lid are helpful in maintaining ideal germination conditions. After germination, seedlings grow well in temperatures between 70-80 degrees F during the day and between 65-70 degrees F at night. Keep soil moist, which usually requires daily light watering. Cantaloupes and diploid watermelons may also be started as transplants using the same process. Seed trays can be kept in 65-80 degrees F after emergence (usually 5-10 days).

A few days before planting transplants outside, it is recommended to follow a hardening-off process to transition seedlings to outdoor conditions. Cantaloupe and watermelon transplants should have 2-3 true leaves when planted outside. Transplant 1-2 melon seedlings per hill.

Table 2. CANTALOUPE AND WATERMELON PLANTING GUIDE

Where to Plant

Cantaloupe and watermelon prefer well-drained, sandy loam soil; they don’t tolerate heavy clay soil. Full sun (6 hours/day) is required. Cantaloupe and watermelon plants prefer a soil pH between 6.0 and 7.5, but watermelon can tolerate more acidic soils with a pH as low as 5.5. It is recommended to plant in box beds or traditional raised garden rows that are about 4-8 inches tall and 12-14 inches wide, or hills, to ensure good drainage and prevent disease. In all types of gardens, it is recommended to add a 2-3-inch layer of compost, peat moss, rotted hay, or other organic matter and mix into the soil to optimize plant health. If growing melons in soil with poor fertility or in cool temperatures, the fruit may not be flavorful or sweet. Due to their vining habit, cantaloupe and watermelon plants require a lot of space.

Black, white, or reflective plastic mulch — or a plastic fabric/film — is recommended to increase soil temperature, yield, fruit size and quality, while controlling weeds and preventing insect pests and disease. Mulching will also help to deter common melon insect pests like cucumber beetles. Drip irrigation is also recommended when using plastic mulch to maintain ideal soil moisture and to encourage productive plants.

Floating fabric row covers are also recommended for this crop, especially when planting early, to improve growth and deter pests during the seedling stage. Row covers should be removed when plants begin to bloom in order to optimize pollination.

Each season, rotate plant families — avoid planting crops from the same plant family in the same area of the garden — to reduce disease and pests. A longer crop rotation of 3-4 years is recommended for Cucurbitaceae crops to reduce insect pest pressure and risk of disease.

Plant Care

Watering

Take care not to overwater melons as this will result in less sweet fruit and increase the risk of cracking. Cantaloupe planted in sandy soils will require about 1 inch of water twice a week. Watermelons have fairly deep roots and are more drought tolerant, but adequate water is essential after seeding/transplanting outside for blooming, fruit set, and growth. Watermelons require about 1-2 inches of water every 10-14 days until fruit are close to harvest size. At this point, stop watering to maximize fruit quality and to avoid diluting sugars in the fruit.

Fertilization

Cantaloupe and watermelon require adequate but not excessive nutrients for good development. Overfertilization with nitrogen may cause plants to remain in a juvenile, vining stage and delay flowering and fruiting. Deficiency in calcium may result in blossom-end rot of watermelon. A physiological disorder, calcium deficiency is more often a problem with uneven watering, which causes calcium to remain undissolved in the soil and unavailable for uptake by plant roots. If the problem persists with consistent watering, soil testing is recommended. The soil test results and interpretation may be discussed with the local county extension agent. Uneven watering (cycling between very wet and very dry) can also contribute to hollow heart in watermelon.

Organic fertilizer such as compost, fish emulsion, composted poultry litter or manure, worm castings, and blood or bone meal originate from living organisms. They are far more environmentally sustainable and safe than traditional synthetic fertilizers. They naturally release nutrients more slowly and over a longer period of time. When applying organic fertilizer, it is important to use in unison with compost, cover crops, and crop rotation, which all work together to build soil health. Learn how to convert inorganic fertilizer recommendations to organic fertilizers here.

Alternatively, a synthetic fertilizer may be used at a rate of about 1.25 pounds (2.5 cups) of 13-13-13 for every 25 feet of row or 75 square feet. Broadcast, or sprinkle evenly, over the soil and then mix in about 3-6 inches deep using a rake. Supplemental sidedressing, or reapplication of synthetic fertilizer, is recommended when plants start vining. Sidedressing is the addition of a small amount of fertilizer to the soil around already established plants when the plant begins to fruit or vine, primarily to provide nitrogen. Sprinkle 2 tablespoons around each plant, keeping it about 6 inches away from the plant stem; water into the soil. Additional sidedressing may be applied every 3-4 weeks. Because of their slow, steady release of nitrogen, crops fertilized with organic fertilizer do not need to be sidedressed. Fish emulsion may be used as a quick-release form of organic fertilizer if needed.

Support

Trellising cantaloupe and watermelon is not necessary, but this vining crop requires lots of soil surface to sprawl in the garden or field. If grown vertically they will require much less room and can even be planted in box beds. Due to the large fruit weight, growing cantaloupe and watermelon vertically will require strong trellis such as wire cattle fencing and an innovative sling for individual fruit. See this video on how to create an easy melon sling.

Weeds

Plastic mulch will control most of the weeds; hand-pull weeds close to the plant, especially in the planting holes. It is important not to allow weeds to shade plants, since they have a low, sprawling habit. These crops have a deep taproot, up to 36 inches for cantaloupe and 60 inches for watermelon.

Insect Pests and Diseases

Aphids are a common insect pest for cantaloupe and watermelon plants and can transmit harmful viruses like cucumber, watermelon, and zucchini yellow mosaic viruses. Other common insect pests include cucumber beetles, spider mites, squash vine borer, and squash bugs. Regular monitoring can help identify symptoms of these insect pests and allow for early treatment and management. These crops are also susceptible to viruses (e.g., cucumber, watermelon, and zucchini yellow mosaic viruses), fungal diseases (e.g., anthracnose, downy and powdery mildew), and physiological disorders (e.g., blossom-end rot). Some varieties are resistant to specific diseases and these should be selected and planted. Generally recommended tools for prevention are using reflective mulches, avoiding overhead irrigation, improving air circulation, and crop rotation (at least 3-4 years). See Table 3 to aid in diagnosis and management of some common melon insect pests and diseases.

Table 3. Organic and Natural Management for Common Cantaloupe and Watermelon Insect Pests and Diseases

Harvest and Storage

When ripe, the exterior of the cantaloupe will turn beige and the fruit should easily slip from the vine when harvested. If the fruit has a “full slip” from the stem (naturally slips off with no stem attached to the fruit), it is fully ripe and should be consumed within 3-4 days. Cantaloupes are often harvested at a “half-slip” (partially slips, leaving half of the stem/pedicel attached to the fruit) so they will store for 2 weeks. During peak production, cantaloupes may be harvested every 3 days. Cantaloupes should be stored between 36-41 degrees F (95% humidity).

Watermelons do not slip from the vine like cantaloupes when they are fully ripe. Varieties differ in their times to maturity; there are several signs that are used to determine maturity. Watermelons should be harvested when the underside touching the ground (ground spot) turns from white to yellow and the tendrils near the fruit are brown and dry; this normally is around 45 days after fruit set. The skin should not be easily penetrated by a fingernail and should feel rough to the touch. A dull thud when tapping the fruit may also indicate ripeness. It is recommended to cut watermelons from the vine in order to leave a small stem (1-2 inches). Fruit should be stored between 50-60 degrees F (90% humidity) for 2-3 weeks.

One cantaloupe or watermelon plant will produce 1-2 fruits for large varieties or 4-6 fruits for small varieties. Cantaloupes and watermelons are generally eaten fresh; watermelon rinds may be preserved by pickling and canning.

Cantaloupes and Watermelons are Nutritious and Good for You

Good source of Vitamin A

Important for eye health, a strong immune system, and cell growth

Rich in Vitamin C

Important for bones, skin, blood vessels

High in Potassium

Essential for body function, especially the heart, kidney, nerves, bones, and muscles

Watermelon contains the carotenoid Lycopene

Antioxidant that may prevent cancer and improve heart health

Recipes

Common methods of preparing cantaloupe and watermelon

Video on how to cut cantaloupe and watermelon

Taste-testing ideas: melon cooler (blended melon “juice”), melon salsa, cold melon soup, fruit salad, fruit popsicles, watermelon and feta salad, melon smoothie bowls

Other websites with many cantaloupe and watermelon recipes:

USDA MyPlate Kitchen: Cantaloupe, Watermelon

Produce for Better Health Foundation: Cantaloupe, Watermelon

SNAP-Ed San Francisco: Cantaloupe, Watermelon

SNAP-Ed Arizona: Cantaloupe, Watermelon

Sources

• Southeastern Vegetable Extension Workers, 2020 Southeastern U.S. Vegetable Crop Handbook
• LSU AgCenter, Louisiana Vegetable Planting Guide
• LSU AgCenter, Louisiana Commercial Vegetable Production Recommendations
• LSU AgCenter, Vegetable Gardening Tips: Watermelon
• UF Extension, Planting Guide
• UF Extension, Vegetable Production Handbook of Florida
• Texas A&M AgriLife Extension, Vegetable Varieties for Central Texas
• Texas A&M AgriLife Extension, Easy Gardening: Melons
• Texas A&M AgriLife Extension, Vegetable Resources: Watermelons
• Texas A&M AgriLife Extension, Commercial Crop Guides: Watermelon
• Texas A&M AgriLife Extension, Commercial Crop Guides: Cantaloupe/Muskmelon
• Maynard, Donald N & Hochmuth, George J (2007). Knott’s Handbook for Vegetable Growers (5th edition). John Wiley & Sons, Inc.
• Decoteau, Dennis R (2000). Vegetable Crops. Prentice-Hall, Inc.
• Swiader, John M & Ware, George W (2002). Producing Vegetable Crops (5th edition). Interstate Publishers, Inc.
• UMass Extension Vegetable Program: Disease, Insect, and Mites Fact Sheets
• University of Minnesota Extension, Viruses of cucurbits
• Purdue Extension FoodLink: Cantaloupe
• Purdue Extension FoodLink: Watermelon
• Sukprakarn, S, Juntakool, S, Huang, R, and Kalb, T (2005). Saving your own vegetable seeds—a guide for farmers. AVRDC publication number 05-647. AVRDC—The World Vegetable Center, Shanhua, Taiwan. 25 pp.
• Seed Savers Exchange, Seed Saving: A Guide to Isolation Distances
• University of Georgia Extension, How to Convert an Inorganic Fertilizer Recommendation to an Organic One, Circular 853