Believed to have originated in southern Africa in the region around Namibia, watermelons have made their way across the globe and have become a beloved snack and symbol of summer in the US. Watermelons love heat, and their weak vines make them highly susceptible to the cold, so it’s vital to only plant seeds in areas with long growing seasons and warm nights. While most types of watermelons found in grocery stores have the classic striped rind and pinkish-red edible flesh, more unique varieties exist that possess a yellow or light green rind and orange, green, yellow, or even purple insides! These more “exotic” varieties will surely make a statement at your next BBQ.
The Amarillo F1 watermelon is a fairly early, hybrid, seedless variety with sweet, yellow fruit that generally weigh around 15 lbs. Seedless watermelons are a little more finicky than those with seeds and may be less productive overall. Interestingly, they require a pollinator watermelon in order to set fruits. These seeds are usually included when you buy seedless watermelon seeds, or you can pick any seeded watermelon with a similar maturity time. Amarillo is a great variety due to its resistance to developing hollow heart disorder.
Seed Depth: 1″
Space Between Plants: 2–5′
Space Between Rows: 6′
Germination Soil Temperature: 70–80°F
Days for Germination: 7–10
Sow Indoors: 4–6 weeks before average last frost.
Sow Outdoors: Transplant 3–4 weeks after the average last frost or when soil temperatures reach at least 70°F
Vegetative: As watermelon vines are relatively weak, grafting watermelon to pumpkin or gourd stock can improve your yields. For more information, check out our Helpful Links section below.
This plant requires warm climates and moderate humidity to really thrive, so plant in the winter for tropical regions and early summer for temperate zones. While watermelons don’t care for extreme heat, they are more tolerant of heat than cold, so err on the side of growing in higher temperatures (i.e., above 80°F) rather than below 70°F if temperatures do not stay between this range for long in your region.
Natural: Full sun but will tolerate partial shade in extreme heat.
Artificial: As watermelons prefer heat and lots of sun, an HID lighting system is best for starting your plant indoors. For best results, expose seedlings for at least 10 hours a day, although more will probably be required. Make sure to keep lights at least 6″ from the tops of your plants to prevent burning.
Soil: Prefers loamy soils that will hold moisture but not become boggy. A soil pH between 5.0 and 7.0 will keep plants happy and healthy with an ideal range falling between 6.0 and 6.8.
Soilless: Seeds will germinate in most soilless mixes but prefer those that contain coco coir or well-rotted manure which hold moisture well.
Hydroponics: Will thrive in hydroponic systems such as an ebb and flow system.
Aeroponics: Will thrive in an aeroponic system.
Water: Requires high levels of water, so aim for 1–2″ per week and decrease as the fruit begins to form, ceasing watering altogether a week or so before harvest. Avoid wetting leaves by watering at soil level when irrigating as moisture on leaves can encourage disease.
Nutrients: A relatively heavy feeder, plants will do best if soil is amended with a rich compost or manure prior to planting. Prior to flowering, give plants a nitrogen rich fertilizer and switch to fertilizers heavier in potassium once they flower.
Foliar: An Epsom Salt foliar will help plants uptake nutrients from the soil and composts, while a weekly application of fish emulsion in the earlier stages of growth will help your plants produce large fruits later on.
Mulching: Using a dark colored cloth around your plants can help the soil retain heat and keep down weeds.
Deficiency(s): Stunted fruit growth is a common indicator of nutrient deficiency, so increase fertilization if your fruits are not growing well. A boron deficiency can lead to hollow heart disorder, which results in hollow cavities in the center of fruits. This can also be a pollination issue.
Rotation: To help keep soil healthy and disease free, avoid planting cucurbit family plants after one another in the same plot for at least three years.
Companions: Grows well with corn, peas, beans, sunflowers, nasturtiums, oregano, radishes, and beets. Avoid planting with potatoes.
Harvest: Figuring out when to harvest watermelons can be quite tricky as size and firmness don’t always indicate ripeness. We recommend keeping an eye on the curly vine which is located where the watermelon stem meets the main vine. When this tendril starts to turn brown, stop watering your plants. After a few days to a week, the tendril should be completely dried out and slightly brittle to the touch. Check the bottom of your watermelon where it is resting on the ground; if the white spot has turned to yellow, it’s ready to harvest! To pick, clip the stem a half inch to an inch above the melon. That’s it!
Storage: Can keep for up to a week in the refrigerator.
Fun Fact: Seedless watermelons can sometimes develop empty, white seed coats in place of fully developed seeds. Because they’re not ‘true’ seeds, they’re totally OK to eat (no worries about having a watermelon vine growing in your stomach!).
Preserve: While watermelons are most commonly consumed raw, there are certainly some less-known (but not less delicious) ways to preserve melons for future eating. Watermelon rinds may be pickled while the fleshy fruit can actually be dried in the oven. Set oven to its lowest temperature and place a sheet of .5″ thick slices on the top rack. Leave the oven door slightly ajar and allow pieces to sit for a few hours. Turn when they start to dry. Remove from the oven and store in a container.
Prepare: Cut open and enjoy! Can also be used in juices, but be sure to remove seeds first.
Nutritional: As watermelons are mostly water, they are not as jam-packed with nutrients as some other fruits, but that doesn’t mean they are without nutritional value. Watermelons contain significant amounts of vitamin(s) C and A as well as the antioxidant compound, lycopene.
Medicinal: Some studies have suggested that lycopene may reduce the risk of certain cancers such as prostate, stomach, and lung. It’s furthermore been tentatively linked with reducing blood pressure and improving bone health.
Make this Yellow Watermelon and Berry Salad with your sweet and succulent homegrown yellow watermelons.