Hmmm!! Somebody's been messin with Mother Nature, maybe?? If something cross-pollenated, you could get a sport. But it shouldn't look that different. Seriously, it doesn't look like you used sterile potting mix (soil) so there could have been some other kind of seed in there, and it just got happy and sprouted when you were watering the mango seed. The mango seed itself could have had twin embryos, which would account for the two mango sprouts.
If you really want to find out, you could very carefully dig up the mango seed you planted, pour water over, to wash off the soil and see if all the shoots are coming from it. Be gentle and disturb the roots as little as possible. I think the light green thing is just a visitor.
I would keep the one big healthy mango start and if you're curious as to what it is, transplant the light green plant into another pot, and see what it grows into. Post a picture for us when it blooms.
Um, not to throw cold water on you, but although growing a mango tree from seed is fun, you could be 5 to 8 years waiting for it to bear fruit. Then, the fruit you get from that tree will not necessarily be the same as the one you bought at the grocery store. If you want great fruit, and a tree that will bear sooner, go to a good nursery and buy a hybrid variety that is at least 3 or 4ft. tall. Don't know what varieties you can get down there in Oz, but the one I have is called 'Carrie' and has delicious golden fruits with very little fiber. It also doesn't grow into an 80ft tree, as some types of mango will.
We went to the local mango festival and tasted a whole bunch of different varieties before choosing the one we wanted to grow. Lots of fun!
I never knew you could get twin embryos from seeds! But I guess it makes sense, if we can have multiple babies than why can't Mother Nature! lol!
Yes, I am also definitely curious to see what the light green one is. I am going to dig it up and re-pot it. Jake did say it probably is a visitor.
This time round with the Mango growing, we were just doing it for fun to see if a store-bought fruit would actually grow from its seed. We had this theory that a lot of grocer's use retardants on their fruit so that they cannot reproduce.
We have another mango seed from a full grown tree that we are going to start. The fruit is super sweet and great texture. It's from an organic tree, so we will have to wait for the surprise fruit.
We are also going to get a great hybrid from a reputable nursery to have for the fruit. This will be our expected fruit bearing tree for eating. The others are just fun experiments.
Monoembryonic seeds produce one seedling via sexual reproduction and are not the same as either parent. Basically a cross between the two.
Polyembryonic seeds produce a number of seedlings, one of which is sexually reproduced and like neither of the parents. The other seedlings are clones of the mother, ie. identical to the mother plant.
I can't tell what it is but the "odd" plant isn't a mango, must have been introduced accidentally. The others are polyembryonic seedlings.
If you're interested in getting fruit you're better off buying a grafted tree. Seedlings take many years before fruiting, and that's under good conditions. A graft is as old as the tree it came off, usually well after fruiting age. So they will often fruit in their first year as a graft even though the plant can't support the weight of the fruit.
By the way, you can't be in zone 4a in Perth, unless you're living in a freezer, LOL. The coldest in Australia is about zone 7 or 8, and that's on top of Mt Kosciusko, the highest mountain in the country. I don't think even Tasmania is that cold.
OOppps! lol! I am DEFINITELY NOT in Zone 4a! Its HOT HOT summers here & The lowest temp in WA is probably about -1 and that's far away from me! I better fix that... Thanks heaps for your advice; I've learnt 2 new things today!
Jake and I just pulled up this double mango seed to separate them, and to our shock AGAIN, there is A THIRD mango shoot growing!!!! The seed still feels very full and has not yet started to decay at all! Jake had a look inside the little embryo sack thing and could see that there are other little shoots forming...
Is there such a thing as triplet or quadruplet embryos????