Parts of a plant: we did this in Playschool a few weeks ago with kids ages 1-5 and took our time talking about the various things a plant needs to grow as we added each one and then our labels. We added a label for the stem, one for the leaf, and the petals. For the flower petals we used cupcake liners, a great activity for kids especially preschool age that's interactive, educational, and fun! A great precursor to planting real flowers or plants in the classroom or home as we did yesterday!
Amazing Pumpkin unit ideas...it has EVERYTHING pumpkin (science, literacy, music, art, dramatic play, math, etc). Check it out if you're in a theme based centre or if the children are interested in pumpkins in High/Scope. If you're in Montessori, well, I'm sorry but I have no idea if you could ever incorporate these. Like I said, sorry.