After eating a grapefruit a few days ago I took 4 of the big seeds and planted them in an unused window planter box whose dimensions are 22 by 7 inches. I know this is small and grapefruit trees are usually planted in the ground but these seeds have produced immediate plants that are growing higher and higher daily. My question is: Will any fruit appear at any time? Will it survive? There is a lot of sun where the box is located and I water it as soon as I feel that the earth is drying up.
Thank you for your help
Certified GKH Gardening Expert
They will grow, and they may or may not produce fruit. It will take around 6 years or more before you will be able to find out. It will not be a grapefruit, however. It will revert back to one of the parents, or even further back. This can often be edible, but much more often it is not.
That does not mean that you can't grow it and appreciate it for what it is, but you can't have any expectations of the tree. It is going to be a total mystery.
Also, there will likely be thorns... Lots of them and far too many to count. As long as you can cope with that, then there is not any reason not to keep them alive.
Their care will be similar to any citrus, so I will include our articles on citrus here: https://www.gardeningknowhow.com/edible/fruits/citrus