Select Seed. Select Produce. From our Garden to yours!
Sweet, juicy, homegrown watermelons-- the essence of summer magic with run-down-your-chin refreshment and explosive taste!! The perfect dessert or afternoon refreshment to quench that hot summer thirst and sweet cravings. No guilt here… these abundant fruits satisfy your sweet tooth with health boosting vitamin A and C, flavonoids, and anti-oxidants, such as beta-cartotene and lycopene, in every slurpy bite. No cholesterol and fat. Perfect!
Growing NotesWatermelons (Citrullus lanatus) are warm season tender annuals in the Cucurbitiacea family, which includes cucumbers, melons, summer squash and winter squash, and gourds. Like their cantaloupe cousins and the cucurbit family, watermelons like heat.
Growing watermelons requires warm soil, above 70 degree F. We typically direct seed our watermelon the end of May; we are on the 46th parallel in what used to be Zone 3 but is now rated Zone 4. Our last frost date averages around May 10th. We have found no advantage to starting watermelon ahead of time, due to transplant shock, which erases any growth gained by starting them ahead of time. We usually have ripe melons by about August 20th. That varies by the number of heat units during the growing season but we have never had to go to any extra lengths to ensure a good harvest. We plant at a ¼ to ½ inch depth, 9 inches apart, in rows 5-6 feet apart. Germination is 6-10 days and days-to-maturity is 80-90 days.
If you are further north, or if you would like to go the extra mile to ensure a good harvest, you can utilize black plastic, which will speed soil warming for earlier planting. Floating row covers can help by trapping warm air near plants, providing more heat units early on. Floating row covers can also protect young seedlings from insect pressure. However, you have to be sure to remove the covers prior to flowering so that your pollinators can do their job of ensuring a good fruit set.
The plants need loose, fertile, well-drained soil with sufficient organic matter, a good supply of nitrogen and a pH 5.8-6.8. Watermelon is heat tolerant and should be planted in full sun. Good drainage is key! You can kill a watermelon with too much water. These plants originate in Africa; they are storing water, much like a cactus. They like it hot and relatively dry. Watermelon plants have moderately deep roots and watering is seldom necessary unless the weather turns dry for a prolonged period. Remember this is a desert plant. You can kill watermelon by overwatering!
All of our varieties are bred and selected for dry-land farming; we do not irrigate our watermelon or any of our other seed crops. Our annual rainfall is 18-20 inches. However, there have been many years that our rainfall has been far short of that. Even in our worst droughts, we have never seen Sweet Dakota Rose watermelon wilt.
If you find it necessary to water, do so early in the day so that leaves can fully dry, quelling the growth of disease organisms. Avoid overhead watering. Soaker hoses or drip irrigation deliver water directly to soil, helping prevent possible spread of fungal diseases among wet foliage. Watering during ripening is said to dilute the sugar content of your fruit.
Diseases in WatermelonCarefully inspect any wilt you see in your watermelon patch; make sure you do not dismiss wilting as a water or drought related issue without ensuring that it is not disease related. Fusarium Wilt in watermelon is caused by fungi (Fusarium oxysporum) and can be seed and/or soil borne. Other possible diseases are Powdery mildew (Sphaerotheca fuliginea and Erysiphe cichoracearum), Root rot (Pythium and Phytophthora spp.), Verticillium wilt (Verticillium dahliae), Bacterial Fruit Blotch (BFB) (Acidovorax avenae subsp. citrulli) and Cucumber mosaic virus; remove, identify, and destroy any infected plants.
Wet conditions encourage diseases. Prevention strategies are to provide plants with space to avoid a dense, airless canopy, and avoid wetting the foliage. As stated above, if the vines and leaves do not fully recover from drought or heat stress overnight and you find it necessary to water, do so early in the day so that leaves can fully dry, quelling the growth of these disease organisms. Powdery mildew can also be reduced by avoiding overhead watering and providing good air circulation. Give plants plenty of space and keep weeds in check to maintain air circulation in the canopy.
PestsStriped Cucumber beetle feeding can damage young leaves so extensively that plants either die or are stunted in growth. In our experience these insects often appear in our cucurbits after a strong south wind. If the plants are in the two to four leaf stage, they are particularly vulnerable. The insects target weakened plants first and can literally suck the plant dry, destroying all of its leaf area. In addition to the feeding damage, these insects can transport diseases. Prevention strategies include crop rotation and removal of crop debris to discourage overwintering of these pests. Tents can be constructed of fine netting, cheesecloth, or floating row cover to protect young plants. (Remove before flowering to allow pollinators to do their job.)
If the cucumber beetles are detected, hand picking is one strategy, if the bugs are few and far between. Trap crops or companion crops, such as tansy, may be planted to lure pests away from the production areas long enough for your watermelon to get established. Another strategy is the use of sticky traps and pheromones to lure beetles away from main crop and to the trap them, impeding mating, which will breed a more serious invasion as the season progresses. Sticky traps are also a good pest monitoring strategy, helping you ascertain their numbers.
If pest numbers climb, another strategy is to dip or spray seedlings with kaolin clay to deter the insects from feeding on young plants. You can also combine clay with insecticidal soap, such as Safer BrandTM, or neem oil, such as Ahimsa Neem Oil.
If pest numbers become a serious threat for crop loss, PyGanic can be used as a last resort to provide immediate knockdown. PyGanic contains botanical pyrethrum (derived from chrysanthemum) and is OMRI listed for use in organic production. These interventions should only be used if absolutely necessary.
For more information on control strategies, see the ATTRA publication, Cucumber Beetles:
Organic and Biorational Integrated Pest Management, available for download here.) at: https://attra.ncat.org/attra-pub/summaries/summary.php?pub=133
Squash vine borer is another potential pest in watermelon. As the borer boroughs its way inside the vine, it will cause plants to look wilted, even when moisture is plentiful. If you see wilting, check for signs of disease and look for signs of damage along the vine. If it appears to be vine borer damage, slice open the stem, remove the borers and destroy them, being careful to do as little damage to the vine as possible to aid in healing.
Flowering and Fruit SetWatermelon vines bear male and female flowers. (Remember, when vines start to bear flowers, remove any row cover.) You can tell the female flowers by the small swelling at the base of the flower; when pollinated this small swelling starts to grow into your fruit. Don’t be alarmed when some of the male flowers, which appear first, fall off shortly after they open. The female blossoms will begin to appear about a week later. If later fruiting flowers drop in large numbers, it is probably due to insufficient pollination, an increasing problem due to the loss of many of our pollinators, both wild and domestic. Frequent bee visits are needed for adequate pollination and good fruit set. Look for bees between 7 and 8 a.m. If bees are not visiting your plants and there is an insufficient fruit set, hand pollination is possible using an artist's paint brush.
WeedsTackle weeds before vines start to run. It will be difficult to move among vines at a later stage without crushing them. Upright weeds are easy to spot; just bend low to the level of the plant canopy and scan for anything above the canopy—likely a weed. Keep a sharp eye out for the ground hugging weeds like purslane and prostate pigweed, as well as vining weeds, like wild buckwheat or bindweed. These love to “hide” in amongst your watermelon vines. If you find it necessary to pull a weed in the watermelon patch, take off your shoes and tip-toe through the vines, avoiding crushing the vines. If the weeds are already setting seed, put them in a pail and remove the whole plant from the field.
Harvest and StorageHow do you know when the watermelon is ripe? Where the vine attaches to the melon, there is a little tendril. When that tendril is completely dried down, the melon is likely ripe. Look on the underside, the spot where the melon rests on the ground; when a watermelon is ripe, its belly will go from near white to creamy yellow. You can also thump or rap on the rind of the watermelon; experienced gardeners can judge ripeness by listening for a low-pitched thud. Rap on some fruits that show signs of ripeness and ones that don’t to tune your ear.
Seed Saving InstructionsWatermelon is cross-pollinated AND insect pollinated. Unless hand pollinating, take caution if you are planning to save seed, especially if you or your neighbors are growing different varieties that will cross with each other. If different varieties cross-pollinate, the watermelon itself will still look and taste like Sweet Dakota Rose watermelon; you won’t even know it crossed with anything. If you save and plant that seed back the next year, you will get completely different watermelon throughout your patch, rather than good production of predictable quality.
Different varieties of watermelon must be isolated by at least 1 mile to keep the seed true to type. In addition to the isolation by distance, physical barriers such as shelter belts, orchards, woods and buildings between the fields can further reduce risks of cross-pollination.
To save seed, harvest the best watermelons from the best plants, free of any disease. Remove and crush the pulp with the seeds and make a juicy slurry. A light fermentation will help in the cleaning process. Simply let the slurry sit in a warm place for 1-2 days, stirring twice daily. Then add water, let the heavy seeds sink to the bottom, decant the water and pulp being careful not to pour off the heavy seeds, and repeat until water runs clean. Screen seeds; put a fan on them and allow them to dry thoroughly on the screen, stirring occasionally to prevent them from sticking together. Melon seed will remain viable for 4-6 years under cool and dry storage conditions.