Your Kholodok are showing some stress and are not sizing up like normal. You can use the suggestions I’ve previously posted to tell when they are ripe. Keep in mind Kholodok is a storage watermelon which has to be stored indoors cool and dry for a month or two to reach best flavor.
- A ripe watermelon will change from glossy appearance to a dull matte. This varies a bit but color change occurs on all watermelons. It may not be very obvious on yellow skin varieties.
- A ripe watermelon develops a lumpy/bumpy feel which you can feel with your hand but can’t usually see. Feel a few and you should get an idea how much change occurs between unripe and ripe. Caution that some commercial varieties like Dixielee stay smooth even when ripe.
- The tendril that grows from the node where a watermelon is attached will turn brown to dark brown when ripe. I don’t know of any exceptions to this rule.
- A ripe watermelon will feel heavier. Heft a few both ripe and unripe to train your ability to detect which are ripe.
- A ripe watermelon will give a distinctly muffled sound compared to unripe when thumped. Thump a few and you should be able to tell the difference in sound.
- A ripe watermelon develops a “ground spot” which may be white, yellow, or pale green depending on variety. Color is unimportant, size is. A larger ground spot indicates ripeness.
- Malformed watermelons are often poorly pollinated and may have areas that are unripe. Normal shapes include round and oblong. Size of a ripe watermelon is determined by genetics and can range from 1 pound up to a bit over 200 pounds.
- Some varieties of watermelon have been selected for very thick rind. Bradford is an example. People used to make watermelon rind pickles from these varieties. Bradford is a delicious watermelon and well worth growing, but be aware of the thick rind.