Picking a watermelon at the peak of ripeness is really tough. I’ve tried looking for color change on the bottom, condition of the tendril nearest the melon, and the thump test. All of these techniques are pretty tough to master.
However, I have one method that has never let me down and if you don’t have too many vines, it is fairly easy. Watch your female flowers and when the fruit sets, stick a pop-sicle stick in the ground next to it with the date written on it. If you find one that has been set for a few days, just back date your marker. Pick your ripe melon 33 days later. It should be pretty close to perfect. If it is a little green for your tastes, pick the next melon at 35 or 36 days. If it is a little over ripe for your tastes, pick the next melon at 30 or 31 days. Once you dial in the number of days that you like, it is pretty much fool proof. 33 days works pretty good for varieties that grow to 8 to 20 lbs. I have not grown the big melons, they may take a little longer.
Newbie watermelon grower question, how do you know the fruit is set?
Also, i got a ton of tiny black bugs crawling inside the watermelon/melon flowers is this something that needs to be sprayed?
Once pollinated, the small melon at the base of the female flower will either start to grow or start to shrivel. If successful, it should start to grow the day after it flowers, that is your set date. (Actually, it is more important that you are consistent with what you call the set date each time rather than being perfectly accurate.)
Hard to say if the bugs are a problem without a picture. No-See-Ums were always attracted to my flowers. They are super small and pose no threat.
Unfortunately, I dont have a camera with good enough macro to take a pic the are that small. They hang out inside of cucumber melons and watermelon flowers. About 10 per flower but its hard to tell since the are small and are pretty fast.
Edit: if the female flower shrivels but the melon at the base looks healthy does that mean it is set or can it still shrivel and fall off?
The flower will always shrivel. The fruit will start growing if it is set. Early in the season many fail to set. Later in the season, as the vine gets larger, very few fail to set. In fact, it is not unusual for the vine to set more than it can grow to proper size. I would usually let one set and pick off others that set after that until 10 days had passed, then let another one set, wait 10 more days and let another one set. Most of the varieties I grew could reliably support 3 fruits continuously at top quality and I liked having the harvest spread out evenly.
Im very surprised at how fast the melons grow. Im talking about a noticeable difference in size from one day to the next. A week ago it was the size of a marble today its the size of small avocado.
God yes…Mine are on my farm that i can only be at on the weekends. They easily Double in size every week. Unfortunately so do my weeds!!! 
Any luck with the watermelon harvest?
As a matter of fact. My Sangria did just OK. I had a few really good ones but we had soooooooooo much rain a bunch exploded in the field from to much water and I had to get most of them to soon since they were all going that way. I had 4 or 5 that were ripe and good. Now the WhiteWonder/Oraneglo I got seeds from mountain donkey have been very good. Nice a ripe and very tasty
I would say its a partial success. The container seemed to dwarf the melons. 3 Alibaba watermelons that were like 3-5 lbs. they are supposed to be between 15-40lbs. They were perfectly ripe. The sugar baby plants had like 6 melons around 3lbs. Some were sunburned, not as tasty as alibaba. Maybe next year ill try to grow some in ground to see if i can get bigger melons.
A word on alibaba watermelon. They seem to be extremely heat tolerant. We had a day were we hit 120f. The plants were in a fabric container. I watered it twice but it didnt even wilt.
Sorry to hear that they didn’t size up well. Interesting note on Alibaba. It has a reputation for being very sweet and your experience confirms that.
Do you need to thin the fruit for them to mature? I have maybe 6 on one vine all around the same size. Some have 10+ fruits.
I’ve also noticed a lot of leaf die back starts no from the trunk. New growth looks good though.
I was really late to get started. Here is 1 of 2 Blacktail Mountain. Bottom is yellow but tendril is still green. I’m sure it’s been (33 days) / a month since it began developing.
Dax
NiceGuy, It is a bit challenging to grow watermelons in Spokane, WA. The season is rather short and watermelons need time and heat. I found that my vines could usually support 3 melons each. More than that and melon growth would stall out and quality would be poor. I suppose a longer growing season would allow the vine to get bigger and possibly support more fruit, but that was never an option for me. Also, my vines would try to set all of the fruit at one time which resulted in them all ripening at the same time. Then I would pick them and a new crop would set and I would have to wait another 33 or so days for my next melons and by the time the second crop was close to ripe, it was getting pretty cold in Spokane.
So…, I started letting one fruit set, then wait 10 days and let a second fruit set, wait another 10 days and let a third fruit set, 10 more days let a fourth fruit set, pick fruit number one at approx 33 days and keep going on that schedule until frost killed my vines. Fruit quality was always top notch and I got to enjoy melons all season long.
It is not uncommon for leaves at the base to die later in the season. I found I could keep them alive the longest by not getting them wet and not over watering. Hope this helps!
Ok thanks Spokanepeach. We get a decent season here, very hot and wet. I’m surprised more people don’t grow them locally, as they are quite expensive in stores. The quality seems very good to me.
I remember the cold of the PNW. Very short summer to enjoy. Fewer pest problems though I would imagine?
My plants put out a lot of vines, theyre probably over 30 feet long now. I was ready for them this year, a lot of landscape fabric and blue tarp. Moles are causing the most issues this year.
Sounds like great watermelon weather! Are you able to get Densuke seeds? Have you tried to grow them?
Hello Fruitnut! We have chatted on the fig forum a few years back. This is a very old thread but find watermelon growing to be my favorite crop along with tomatoes. You said your soil acts more like sandy loam? I deal with sandy soil here in Florida, and sandy loam will never be able to wait 7 days for water. The best you will get out of it normally would be 2-4 days and that is with luck. I know climatically that could change by maybe a day, or possibly not.
I was watering about every 4-5 days this year. My soil is much better than what I think of as typical FL sand.
Ok, gotcha! Good to hear from you. I just put out my watermelon seeds about 2 1/2 weeks ago on virgin watermelon soil and have been checking on other peoples grow outs for their thoughts on favorite melons. I have about 9 varieties planted for some new trials!