What does it mean that God created vegetation “whose seed is in itself” (Genesis 1:11And God said, Let the earth bring forth grass, the herb yielding seed, and the fruit tree yielding fruit after his kind, whose seed is in itself, upon the earth: and it was so.
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The passage reads as follows:

Genesis 1:11-12 [11] And God said, Let the earth bring forth grass, the herb yielding seed, and the fruit tree yielding fruit after his kind, whose seed is in itself, upon the earth: and it was so. [12] And the earth brought forth grass, and herb yielding seed after his kind, and the tree yielding fruit, whose seed was in itself, after his kind: and God saw that it was good.
See All...  And God said, Let the earth bring forth grass, the herb yielding seed, and the fruit tree yielding fruit after his kind, whose seed is in itself, upon the earth: and it was so. And the earth brought forth grass, and herb yielding seed after his kind, and the tree yielding fruit, whose seed was in itself, after his kind: and God saw that it was good.

God classifies according to size and use to the rest of creation. He does not classify according to structure as is done by modern scientists. The scientist has no right to declare God wrong because He does not use their system. That is the height of egotism. According to the Bible, vegetation is divided into the grasses (the food of animals), herbs (medicine and food for man and sometimes animals), and fruit trees (food for man). It may be that before the flood all herbs and trees had known value to man. We are still in the process of re-learning those benefits today. 

As to the fruit tree whose seed is in itself, this is quite a description. It means that God created these plants with the seed already in them to bring forth more of their kind. If the tree is compared to the chicken and the seed is compared to the egg, we can answer the question as to whether the chicken or the egg came first. It was the chicken. God created a chicken that had the ability in it to bring forth more chickens. 

Evolutionists still have a problem with the chicken or the egg; the plant or the seed. Which comes first when a major change occurs in the evolutionary development of the creature? They attempt to change the DNA by a beneficial mutation, but this does not fully solve the problem. It is an interesting question for evolutionists to ponder. But scripture cuts through the Gordian knot and solves the problem by direct creation. What simple beauty we see in Genesis, chapter one.