Great incremental game, especially for your first full game and only done in a week. Personally I like the slow start since it made every upgrade feel satisfying to buy. I agree with some of the others that the holding down a button is tedious, in my humble opinion it would be better if you just had to hover the cursor on a button and then maybe have to do something else too (like water the plants) so you just can't leave the cursor hovered on the button all day.
Another suggestion is to add more plants and let the player place them out where they want so you can have your own unique little plant farm :)