how companies make good quality watermelon seeds? can I do it by myself? why we can't plant seeds from normal watermelon in the grocery store
Sure, you can grow your own watermelon seeds—good quality ones, too.
Please, don't use seeds from fruit you buy in the grocery store. You run the risk of growing plants illegally if you do that (they could have utility patents or they might be plant protected varieties, have plant patents, etc.) Utility patents are a lot more restrictive than plant patents, by the way. Grocery store fruits are also more likely to be genetically modified (and GMOs are more likely to have utility patents covering their genes). However, if you contact the producer of the watermelons and find out if that plants are not restricted by intellectual property laws, then they're perfectly fine to grow—except they might be hybrids (but I wouldn't recommend letting the hybrid-thing stop you, personally). Or, they might be tetraploids (and if you grow those mixed in with diploid watermelons, then they might cross and produce triploid plants that produce seedless watermelons, which might frustrate a breeding project a little).
All you need to do is the following:
- Obtain some watermelon seeds. You can buy them (usually for less than the cost of a watermelon fruit), trade for them, or find someone who will give them to you for free. Get a good kind. This is rather subjective. I like Verona, Congo, Santo Domingo Winter, Weeks NC Giant, and Black Diamond, personally. However, Tom Watson and Ledmon are some of the best-tasting I've had. Red-seeded Citron is very prolific and easy to grow (but it's not sweet).
- Grow the seeds.
- Harvest your fruits.
- Ferment the seeds (you can look up the process online). Fermenting the seeds is a way to help improve germination rates of the seeds you end up getting; it also is supposed to help remove some diseases from the seeds (but I don't know that it removes anthracnose). Alternatively, you can do something else to protect your seeds. I personally don't ferment them, since it's a smelly process that takes a lot of time and space; instead, I got a Z4EX from zapperguy.net, I put the seeds in water, and I zap them with it, with each of the frequencies. It's not a proven process, but it's what I do. A lot of the time, I'll put seeds in labeled herbal tea bags (the bags are empty at time of purchase) when I zap them (so I can do lots of kinds of seeds at once). However, watermelons tend to have more seeds than will fit in one bag (so, yeah; that helps me most with tomatoes).
- Dry the seeds. I usually dry them on brown paper bags in a room with a fan. The fan helps them dry faster without molding (and the brown paper bags do, too). Drying them inside the empty herbal tea bags works just fine, by the way. When they're dry, to save time, I just leave them in the bags, and maybe put the whole herbal tea bag in a plastic bead bag (which is like a miniature Ziplock bag). They dry faster in a warm room. When they're dry, I like to store them in a foam cooler (but there are lots of other ways to store them that might be better).
- Freeze the dry seeds. There are a few benefits to this. 1. Some diseases (and pests) don't survive freezing very well. You can use a very cold freezer as long as the seeds are dry. If they're not dry, it'll likely kill them. 2. This also isn't a proven thing, but it seems to me like seeds that have been frozen (after they've been dried) tend to be more vigorous when you grow them. There's no hurry to freeze them, though (you don't need to freeze them right away). In fact, you don't need to freeze them at all; I just tend to think it makes the plants more vigorous, personally (I need to experiment with this more). Some people store their seeds in the freezer the whole time. You might like to do that, but I don't personally (we have power outages sometimes, but also I just like to store my seeds without the need for electricity; when I freeze them it's just a temporary thing, as an experiment in increasing vigor).
- Grow the seeds. If you have a short season, you may want to either put a bunch of seeds in the spot where you'll want them to sprout the next year (so they'll overwinter and volunteer there), or else start them indoors or in a greenhouse early and transplant them. People say you shouldn't grow them too big before the transplant, but in my experience, it doesn't matter so long as you prune them back before or after the transplant (the pre-transplant leaves can hold the plant back if they're old). If you have a long season, just direct-seed them unless pests have a habit of destroying your seedlings or something.
- Make sure the plants you grow have a good supply of nutrients.
- Acclimatize your seed stock. What I mean is, keep saving your seeds every year and growing them (the more generations you grow them, the better they should do in those conditions, although in my experience that works better with some varieties than others).
Anyway, it's easy to grow loads of your own watermelon seeds. It's pretty fun. I personally like the small black seeds that you usually find in winter watermelons (such as King Winter). They're easy to eat raw. White ones tend to be very difficult to eat raw. Other kinds are moderately easy to eat raw (but usually not as easy as the black ones). It's harder to find large watermelons with this seed type, but they do seem to exist (if I'm visually interpreting that picture correctly); Desert King also seems to have black seeds by the look of the pictures. It's hard to tell if that link has the seed type that I mean, although it looks like it in the picture. I had a cross between Tom Watson and what I think was King Winter last year, and it was pretty close to the best of both worlds, with small black seeds, larger fruit and flesh that tasted almost like Tom Watson. I'm growing the F2 this year—which will likely be different (but hopefully I like it!)
I understand that Sangria F1 is a common variety that grocery stores have been known to use (at least in the past). So, if you grow that, you might get results similar to what you find in the grocery store. However, the next generation from saved seed may be different (but it might still be good); each seed will produce a unique kind of seed (and the same for their offspring).
Many watermelons sold in grocery stores are so called hybrids. These melons are grown from F1 hybrid seeds. There was recently a question about what a F1 hybrid means, see here for my explanation.
As a consequence of the hybrid technique, the seeds that develop in your watermelons, do not all produce the same kind of melon. So you can get new varieties, but also you can get the same watermelon back. One thing you can be sure about is that not all melons will be the same. That is if your watermelon from the store is really a F1 hybrid. I can imagine that some small local farmers don't use F1 hybrid technique, but we do not know where your store bought these melons. See here for a nice explanation about the situation of watermelons grown from seeds.
You may use the seed of grocery store, but there are few problems:
we get usually not optimal fruits: these fruits are harvested early (because time of transport, storage, and selling/use).
Ripen fruits do no mean ripen seeds.
selection and hybridization: that make a lot less good seeds.
How to make seeds? Try to find a old watermelon (better of local production, so it is hopefully harvested later then others), keep the seeds and seed them. A lot. Few could growth. Then next years: keep one, so that fruits full ripen.
Note: it is much easier to buy (cheap) seeds of watermelon, of a variety adapt for your climate.