Crimson sweet watermelon growing

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No one can tell you exactly how to pick a good watermelon, because so much of the flavor depends on growing and storage conditions. What I can give you are tips to teach you how to tell if a watermelon is ripe – PLUS – I’ll tell you how to store a watermelon for best flavor and nutrition.

How to Tell if a Watermelon is Ripe – 4 Tips to Help You Pick a Good Watermelon

Good watermelon or bad watermelon? Growing conditions and storage make a huge difference in watermelon flavor and texture, but these tips will help you choose the best available watermelon. Some of these tips will help you tell when a watermelon is ripe on the vine, others apply to both garden watermelons and watermelons at the grocery store or farmers market.

Ripe watermelons are a little trickier to identify than muskmelons. Muskmelons slip right off the vine (i.e. come loose on their own) when ripe. Watermelons don’t fall off the vine when ripe.

#1 – Check the Field Spot on the Underside of the Watermelon

The underside of the watermelon where it touched the ground should be buttery yellow to dark yellow in color. This is called the field patch or field spot. If the field spot as pasty white as a bald guy’s head in the middle of a Wisconsin winter, it probably hasn’t reach peak ripeness.

Different growing conditions and different types of melons will produce a range of colors (inside and out). Warmer weather usually yields a darker field spot.

#2 – Check the Sound to See if a Watermelon is Ripe

This is a classic way to pick a good watermelon, and the internet is filled with descriptions of how a ripe watermelon should sound. Most say “flat” or “dull”. I think that’s a poor description. For my part, “flat and dull” is the sound you get when you rap on something like a giant zucchini – or an underripe watermelon.

A ripe watermelon should have a nice, deep hollow sound, more like a drum or knocking on a door. I did a quick video (below). My Powershot D10 doesn’t quite do it justice, but you get the general idea.

#3 – If you want a ripe watermelon, make sure your watermelon is at full growth

This is for those trying to figure out how to tell if a watermelon is ripe in the garden. If you’re watching the patch, you can tell when a particular watermelon is large, well filled out, and hasn’t changed significantly in size for some time. Days to maturity will give you a rough estimate of expected watermelon ripening time. For first time growers, you can check the expected size on the package and weigh them if you want, but the best way to tell is to observe the growth habits of the watermelon.

#4 – Check the Little Curling Tendril Located Where the Watermelon Stem Joins the Main Vine

This is another tip for checking ripe watermelons in the garden. Right where the stem to your melon joins the main vine, there should be a little curling tendril of vine. If the tendril is still green and springy, the melon is still growing.

If this little tendril is brown and dried, odds are your melon is as ripe as it’s going to get. Sometimes all your vines may start dying back before you’ve harvested, not just a tendril. Ready or not, your watermelons are done growing. Also, if it’s been dry, sometimes the tendrils will dry back prematurely, so check the other signs first.

Jerry shares:

I mostly agree with the methods mentioned in this article.

My dad grew watermelons for many years in Florida so he had the advantage of following the fruit’s development to complete ripeness. I have passed his knowledge on to many friends who confirm his method of ripeness selection.

Because so much depends on soil fertility and irrigation/rainfall sweetness is hard to determine. However, determining RIPENESS is a fairly full proof method. Thumping a melon doesn’t mean much at all regarding sugar content.

In fact, the only indicator a consumer has in the market for determining the melon’s RIPENESS is by pressing on the blossom end of the water melon to see how much “give” it has. The blossom end is opposite the stem end. If it is ripe there will be some give when pressed with the thumb. If it’s not ripe it will be hard as a rock. A watermelon that’s TOO ripe it will give little resistance, and likely be “mealy” inside.

It’s always worked for me, for what it’s worth.

Thanks, Jerry. I still find the “thump” helpful, and will give blossom end poking a try next time we pick a watermelon out at the store.

How to Store Watermelon

Before our melons were ready, I picked one up at the grocery store that I really shouldn’t have bought. It was during our brief hot spell this summer, and the melons had obviously been stored too cold because they were chilled and sweating in the bins. Sure enough, I got it home and the flavor was bland and the texture was mushy. Melons like it warm! Storing watermelons at room temperature also makes them more nutritious.

From the article “Watermelon Fruit nutritional value health benefit” by Ray Sahelian, M.D.:

Watermelons stored at room temperature deliver more nutrients than refrigerated or freshly picked melons. Researchers tested several popular varieties of watermelon stored for 14 days at 70 °F, 55 °F and 41 °F. Whole watermelons stored at 70 °F, which is about room temperature in air-conditioned buildings, had substantially more nutrients. Compared with freshly picked fruit, watermelon stored at 70 °F gained up to 40 percent more lycopene and 50 percent to 139 percent extra beta-carotene, which the body converts to vitamin A. Watermelons continue to produce these nutrients after they are picked and that chilling slows this process.

The usual shelf life for watermelons is 14 to 21 days at 13 °C (55 °F) after harvest. At refrigerated temperatures, such as 41 °F, watermelon starts to decay and develop lesions after a week.

So don’t store your melon in the fridge until it’s cut (or chill only briefly right before serving). Once it’s cut and refrigerated, eat it up ASAP.

Tips from “An Experienced Farmer” on How to Pick a Good Watermelon

There are numerous web pages, photos and videos circulating on the internet right now (2018) claiming that they are “tips from an experienced farmer” on how to pick a good watermelon. Some of these are valid ways to check if a watermelon is ripe, some of them are flat out wrong. I suspect that the information was made up as a way to sell round watermelons with marks on them. I’ll review these “tips” (listed in italics) to let you know what’s right and what’s wrong.

#1 – Look for the Field Spot

The yellow spot, known as the field spot, is the place where the watermelon rested on the ground. Ripe watermelons always have creamy yellow or even orange-yellow spots, not white. – CORRECT, as noted above

#2 – Look for ‘webbing’

These weblike brown spots on the watermelon mean that bees touched the pollinating parts of the flower many times. The more pollination, the sweeter the fruit is. – WRONG

As noted by Texas A&M Agrilife Extension Plant Disease Handbook:

“Cracks, scarring, and pitting can be caused by mechanical damage when vegetables are young, Insects can also cause such injury. Animals, such as wild hogs and racoons, can cause more substantial damage.”

In my experience, heavy exterior scarring often leads to tough or woody areas inside the fruit. (Mild scarring is not a problem.) More scars does not mean a sweeter watermelon.

#3 – ‘Boy’ and ‘Girl’ Watermelons

Many people do not know that farmers differentiate watermelons by gender. For example, ’boys’ are bigger, have an elongated shape, and a watery taste. The ’girls’ have a rounded shape and are very sweet. – WRONG

All watermelons come from female flowers, which have a small swelling at the base of the flower. There are no male watermelons. The shape of the watermelon is determined by the variety of watermelon. A round watermelon is not necessarily a good watermelon. For the melons pictured below, both were good, but the so-called “male watermelon” (the longer one) was sweeter then the round one.

#4 – Pay Attention to the Size

It is better to choose neither the largest nor the smallest watermelon. Select an average-sized fruit. And note, please: large or small, the watermelon should feel heavy for its size. – SIZE DOESN’T MATTER

Check out a bin of watermelons at the grocery store, and you’ll typically find that they are all similar in size. Other than selecting a ripe watermelon in the garden (that has reached full growth), size doesn’t matter. If you start lifting watermelons, I bet in most cases you’ll find that their weights are similar as well. Odds are that a given batch of grocery store melons all came from the same area and ripened under the same conditions, so this isn’t a particularly useful tip.

#5 – Inspect the Tail

A dried tail indicates that the watermelon is ripe. However, if the tail is green, it probably means that the watermelon was picked too soon and will not be ripe. – MAYBE

As noted above, it’s the tendril next to the watermelon on the vine that acts as a ripeness indicator. The vine itself may or may not indicate ripeness. A brown stem could mean that the watermelon was harvested some time ago, and it had time to dry, or it could mean that the plant was dying when the watermelon was harvested. You have no way to know for sure.

Good Watermelons for Northern Growers

Growing watermelons with a fairly short growing season can be a challenge, but with a little extra TLC we manage a good harvest. Some of our favorite watermelon varieties include:

  • Orangeglo
  • Blacktail Mountain
  • Chelsea
  • Yellow Petite

Even though Orangeglo and Yellow Petite don’t get red, the same rules still apply for determining if they are ripe. Here’s one of my favorite watermelon photos from a few years ago.

Picking the Perfect Watermelon

Back in my late teens and early 20’s, my jobs at the family catering business included picking out the watermelons and carving the watermelon boats for parties. I was known as the resident watermelon expert, almost guaranteed to be able to pick out a good watermelon, if there was a good watermelon to be found. The last time I carved up a watermelon was for a Green Bay Packer party that we hosted for family and friends.

Unlike some fruits, watermelons do not ripen further once they are off the vine. Choose carefully, and store watermelons the right way to keep them flavorful.

Can you tell if a watermelon is ripe by smell? Nope. Uncut watermelons are less fragrant than muskmelons, because they don’t have that open end where the vine was formerly attached. You will never find me sniffing watermelons in the grocery store, but you may find me sniffing cantaloupes. (I do my own stunts. 😉 )

Thanks for reading! We love your shares and comments. Did I miss any tips that you use to pick a good watermelon? Leave a comment and share your thoughts.

You may also enjoy:

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Originally posted in 2014, updated in 2017, 2018.

The watermelon is a tender, warm-weather annual. Watermelons along with muskmelons and cantaloupes are sometimes called summer melons. Grow watermelons in the warmest, frost-free time of the year.

  • Sow watermelon seed in the garden or set out transplants 3 to 4 weeks after the last average frost date in spring.
  • Start watermelon seed indoors about 6 weeks before transplanting seedlings into the garden. Start seed indoors in 4-inch or larger biodegradable peat or paper pots that can be set wholly into the garden so as not to disturb the roots.
  • Watermelons require 65 to 90 frost-free days to reach harvest.

Where to Plant Watermelons

  • Plant watermelons in full sun.
  • Watermelons grow best in loose, well-drained, but moisture-retentive soil rich in organic matter.
  • Add aged compost and aged manure or a commercial organic planting mix to the planting bed before planting. Turn the soil to 12 inches deep.
  • Melons prefer a soil pH of 6.0 to 6.8.
  • Plant watermelons on hills or mounds or on raised rows. Solar heat hitting the soil on a mound or raised row will keep plants and roots warm.
  • Create a mound 6 to 12 inches high and 5 feet across.
  • If planting in ground-level beds, warm the soil in advance of planting by laying black plastic sheeting on the bed two weeks before planting.

Watermelon seed will germinate in about 10 days at 65°F, sooner in warmer soil.

Watermelon Planting Time

  • Sow watermelon seed in the garden or set out transplants 2 to 3 weeks after the last average frost date in spring.
  • Garden soil temperature should be at least 70°F at planting time. Pre-warm the soil by placing black plastic sheeting over the planting bed for two weeks prior to planting.
  • To get a head start on the season and in short growing season regions, start watermelon seed indoors about 6 weeks before transplanting seedlings into the garden; start seed in biodegradable peat or paper pots at least 4 inches in diameter that can be set wholly into the garden so as not to disturb roots.
  • Watermelon seed will germinate in about 10 days at 65°F, sooner in warmer soil.
  • Watermelons grow best in air temperatures ranging from 70° to 90°F.
  • Avoid growing watermelon where night temperatures dip below 50°F; this will cause the fruit to lose flavor.
  • If temperatures exceed 90°F for several days, flowers will drop without setting fruit.
  • Watermelons require 65 to 90 frost-free days to reach harvest depending on the variety.
  • Watermelons will tolerate no frost. In cool or short-season regions, grow smaller varieties that come to harvest quickly.

Sow watermelon seed in the garden or set out transplants 3 to 4 weeks after the last average frost date in spring. Start watermelon seed indoors about 6 weeks before transplanting

Planting and Spacing Watermelons

  • Sow watermelon seed 1 inch deep.
  • Sow 4 to 6 melon seeds on a mound or hill.
  • Germination will occur in about 10 days when the soil is 70°F
  • Thin to 2 or 3 strong seedlings on each hill when seedlings have developed three or four true leaves. Cut the thinned seedlings at soil level with scissors so as not to disturb the roots of the remaining seedlings.
  • Space mounds or hills 5 to 6 feet apart.
  • Mounds can range in height from a few inches to more than 12 inches tall; mounds will allow vines to run away down the slope. You can train vines to circle the mound.
  • If you are growing watermelon in rows space plants 4 to 5 feet apart and space rows 6 feet apart.
  • Grow 2 watermelon plants for each household member.

More tips: Watermelon Seed Starting Tips.

Support melons growing on a trellis with netting.

Growing Watermelons Vertically

  • Watermelons can be grown up a trellis.
  • Use a trellis at least 8 x 8 feet wide or wider. Make sure the trellis is well-anchored.
  • Space plant at the base of the trellis 3 to 4 feet apart.
  • Train vines up the trellis; secure the vines to the trellis with elastic garden tape.
  • Support melons growing the trellis with netting.
  • You can also grow watermelons on an A-frame trellis. Lean two trellises together, tie them at the top and anchor the base of each trellis.

Container Growing Watermelons

  • Watermelons are usually too large to grow in a container.
  • Select a bush, dwarf- or mini-cultivar to grow in a container.
  • Chose a container that is at least 18 inches wide and deep to grow one watermelon.
  • In short growing season, regions extend the season by starting melons in containers indoors; move them outdoors when the weather has warmed but be careful not to pinch or break the vines.

Watering Watermelons

  • Watermelons are 95 percent water. They require plentiful regular, even watering for quick growing.
  • Give watermelons 1 to 2 inches of water every week (1 inch equals 16 gallons.)
  • Keep the soil moist until fruit reaches full size then stop watering while the fruit ripens.
  • Mulch to retain soil moisture. Spread straw or dried chopped leaves around watermelon plants after the soil has warmed. You can also lay black plastic sheeting or garden fabric across the planting bed. Cut an x-slot in the fabric to plant.
  • Water at the base of plants with a soaker hose or drip irrigation. Wetting the foliage will leave plants susceptible to fungal diseases such as powdery or downy mildew.
  • Keep the soil evenly moist during flowering and fruit development. A week or so before harvest cut back on water; dry soil will help plants concentrate sugars in the fruit.
  • If leaves are wilted in the morning, the plants need water. Wilting leaves at the end of the day is not uncommon.

Feeding Watermelons

  • Prepare planting beds with aged compost and aged manure or a commercial organic planting mix. Turn the soil to 12 inches deep.
  • Add several inches of aged manure across planting beds the autumn before planting.
  • Side dress watermelons with compost or manure tea or a dilute solution of fish emulsion every 2 to 3 weeks during the growing season.
  • Watermelons can be side dressed with an even organic fertilizer such as 10-10-10 early in the season but once flowers and fruit appear, reduce nitrogen and increase phosphorus and potassium; use a 5-10-10 fertilizer.

Companion Plants for Watermelons

  • Plant watermelons with corn, radish, beans, and nasturtiums.

Watermelon Pollination

  • Watermelon plants produce both male and female flowers.
  • Male flowers appear a week or two in advance of the female flowers. Male flowers attract bees that are needed for pollination once female flowers appear.
  • Female flowers will have a small bulge at the stem end of the flower. This bulge is an embryonic fruit.
  • Some male flowers will die and drop before female flowers set fruit.
  • You can hand pollinate watermelon flowers using an artist’s bristle brush. Rub the brush in the male flower to collect pollen then rub the brush in the center of the female flower to transfer the pollen.
  • You can attract bees to your garden by planting flowering herbs such as dill, borage, and lavender nearby.

Set the growing watermelon on a tile or wood. This will keep the melon off the ground and help it stay warm,

Caring for Watermelons

  • Early in the season cover plants with a floating row cover. This will keep insects away and hold warm air around plants. Once plants begin to flower, remove the row cover during the day so that bees can get to the flowers.
  • Encourage watermelon plants to set three or four fruits at the same time; if a plant sets one fruit early, pinch it out to encourage the plant to develop several fruits at the same time. One fruit off to a head start can suppress all further fruiting on the vine until that fruit matures.
  • Cultivate carefully around vines until they cover the ground and smother out competing weeds.
  • Mulch around watermelons with straw, dry chopped leaves or set down black plastic or garden fabric. Mulch will keep down weeds and conserve soil moisture.
  • For sprawling watermelons, place a tile, wooden shingle, or a piece of plastic under each melon to keep the fruit clean and dry and to store solar heat which will help ripen fruit.
  • About 50 days before the first expected autumn frost, remove all new blossoms from a plant; this will allow the plant to concentrate its energy into the development and ripening of fruit already on the plant.

More tips: How to Grow Watermelon for Best Flavor.

Watermelon Pests

  • Aphids and spotted and striped cucumber beetles will attack melons.
  • Hose away aphids with a blast of water or pinch out infested foliage.
  • Hand-pick and destroy cucumber beetles promptly; they can transmit cucumber bacterial wilt to melons. You can also control cucumber beetles by spraying insecticidal soap, neem oil, or dusting with kaolin.

More tips: Melon Growing Problems: Troubleshooting.

Watermelon Diseases

  • Watermelons are susceptible to anthracnose, altenaria leaf spot, bacterial wilt, and powdery and downy mildew.
  • Planting disease-resistant varieties when they are available and maintaining the general cleanliness and health of your garden will help cut down the incidence of disease.
  • Do not handle the vines when they are wet; this can spread fungal diseases.
  • If a plant does become infected remove it before it can spread the disease to healthy plants.
  • Bacterial wilt which is spread by cucumber beetles can cause watermelon plants to suddenly wilt and die just as they begin to produce fruit. Control cucumber beetles as soon as they appear.
  • Anthracnose is a soil-borne fungal disease that can cause leaf spots, leaf drop, wilting and sometimes death. Keep the garden clean and plant disease-resistant varieties. Remove diseased plants from the garden immediately.
  • Powdery mildew and other fungal diseases can be prevented and slowed by spray-misting plants with compost tea or a solution of 1 part skim milk and 9 parts water.

Limit water for a week in advance of the harvest to concentrate sweetness.

Harvesting Watermelons

  • Watermelons will be ready for harvest 65 to 90 days after sowing depending on the variety.
  • When watermelons are ready to harvest vine tendrils will begin to turn brown and die off. If the tendrils are green the melon is not ripe.
  • A ripe watermelon will make a dull hollow sound when thumped.
  • The soil-side of a watermelon will turn from white to pale yellow when the fruit is ready for harvest.
  • Ripe melons will have a sweet aroma at the stem end.
  • Limit water for a week in advance of the harvest to concentrate sweetness.
  • Watermelons on a single plant will all be ready for harvest over a two week period.
  • Use a sharp knife or garden pruner to cut the watermelon away from the vine.
  • Watermelons do not continue to ripen off the vine.

Storing and Preserving Watermelons

  • Watermelons will keep in the refrigerator for up to a week if not cut or sliced, but sweetness and flavor may diminish.
  • A cut watermelon will keep in the refrigerator for about 4 days. Wrap the melon tightly in plastic to prevent cold burn or dehydration.
  • It takes about 12 hours to chill a large watermelon.
  • Watermelons can be kept in a cool, moderately moist place for 2 to 3 weeks without refrigeration.
  • Melon flesh can be frozen and rinds can be pickled.

More tips: How to Harvest and Store Watermelon.

Watermelon Varieties to Grow

More varieties to grow: Watermelons for Home Gardens: Top 12 Varieties.

About Watermelons

  • The watermelon is a long-trailing annual plant.
  • Watermelons can be solid green or striped green and white.
  • Watermelons can be oval, oblong, and round.
  • Fruits can weigh from 10 or 15 pounds to more than 100 pounds. Fruits are commonly 30 pounds or more.
  • The watermelon has a thick, solid rind with sweet, succulent flesh that can be pink, red, yellow, orange, or grayish-white.
  • Male and female flowers appear on the same vine.
  • Botanical name: Citrullus vulgaris
  • Origin: Tropical Africa

Watermelon Seeds – Crimson Sweet HEIRLOOM – OPEN POLLINATED

When to plant:

If you live in a climate with a short growing season, consider starting your watermelon seeds indoors 4 to 6 weeks before transplanting seedlings into the garden. Sow watermelon seed directly, or set out your transplants 3 to 4 weeks after the last average frost date in spring. Watermelon demands warm temperatures – both soil and air. Transplant or direct sow watermelon seeds only when the average soil and daytime air temps are at least 70F. Watermelons are heavy feeders and need soil rich in nutrients. They grow best in loose, well-drained, but moisture-retentive soil rich in organic matter. Amend your soil with aged manure, seaweed, and/or compost before planting.

How to plant:

Dig a hole 12” deep and 24” wide, fill with compost, manure and several handfuls of sand – this will create an area that is both moisture retentive and well-draining. Use the soil that was removed from the hole to create the mound and then sow your seed or transplant there.
Sow Watermelon seeds 1” deep, planting 4-6 seeds (or transplanting 2-3 of your strongest seedlings) in mounds that stretch 24” across. Planting on hills or mounds ensures that roots stay warm and the soil is well-drained. If direct sowing, wait until your young seedlings have developed three to four true leaves and choose to keep your strongest 2-3 plants by cutting the thinned out seedlings at soil level with scissors. If you pull out your weakest seedlings, you may disturb the tender roots of your remaining plants, so use of scissors or clippers is advised. Build mounds 5-10 feet apart.
We advise using a nitrogen fertilizer on your watermelon plants until flowers form. Then, switch to a high phosphorus and potassium fertilizer like liquid seaweed. Keep area well weeded, we don’t want our watermelons fighting for nutrients and water. Because this is a warm-season crop, it is helpful to mulch around the base – this will help with weed control and moisture retention.
Watermelons are 95% water and require plentiful, even watering for quick growing. Keep the soil moist until fruit reaches full size then stop watering while the fruit ripens.

When to harvest:

Stop watering your watermelons about 10-14 days before the fruits are ready to harvest, this will concentrate the plant’s sugars and your watermelon will be sweeter. You may want to place a board under each melon to keep the fruit clean and dry. Watermelons will be ready to harvest after 70-90 days from sowing. Most people tap their watermelons and listen for a dull thump to know when the fruit is ripe. Other maturation signs include the ceasing of growth, the yellowing of the underside and the drying of the stem near the fruit’s base.

Other tips (if any): Companion plants are corn, radish, beans, nasturtiums, marigolds and oregano. Bad companions are potatoes as they attract many of the same insects that feed on watermelon plants.

Avoid growing watermelon where night temperatures dip below 50 F; this will cause fruit to lose flavor. If temperatures exceed 90F for several days, flowers will drop without setting fruit. Watermelons require 70-90 frost-free days to reach harvest and will tolerate no frost. In cool or short-season regions, plan ahead by starting indoors or choose smaller varieties that come to harvest early.
Watermelon leaves commonly wilt in the afternoon sun, this is ok. If you see the leaves wilting before noon, immediately water as it is a sign of stress due to the heat and drought. Never allow the vine itself to become dry. A soaker hose or drip irrigation is the best way to water.
If you live in an area where the weather and soil are dry, try planting your watermelon in inverted hills rather than mounds. Make an inverted hill by removing two inches of soil from a circle 24” across, and use this soil to make a rim around the circle. This way, irrigation water or rainfall can be captured. We know lots of gardeners in Zones 9 and above use this technique for their watermelon, squash, beans, and many other summer vegetables.
Regular, even watering will help fruits avoid blossom-end rot which is caused by fluctuation of soil moisture.

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