Majskorn is ’grain of maize’, or, if you are an American ‘corn’. Majs and maize come via Spanish maiz from Arawakan, an indigenous language of the Caribbean.
Swedish korn means ‘grain’ but also the cereal species ‘barley’. (An older word for the species is bjugg.) English corn means ‘grain’ but also according to my dictionary a cereal species: in most of England ‘wheat’, in Scotland and Ireland ‘oats’ and in America ‘maize’. So the word is probably the name of the most commonly cultivated cereal in all these areas. The origin is Germanic *kurnam ‘small seed’ back to an Indoeuropean root *gre-no- from which also comes Latin granum ‘seed’, and hence, via French, English grain.
There is another English word corn, ‘hardeed skin on a foot’; that comes via French from Latin cornu ‘horn’. In Swedish it is called liktorn, literally ‘body thorn’.
These grains were sown two weeks ago. Now the surviving plants are about a decimeter in heigth.