These seeds fell on rocky places, where there is not much soil. They grow quickly as a result of shallow soil, which may seem like a good thing in the moment. However, once the sun comes up, the plants scorch and wither because they have no root.
The seeds fallen on rocky ground represents someone who hears the Word and at once receives it with joy. But because they have no root, they only last a short while. As soon as trouble or persecution comes, they quickly fall away.