The cowl took just under 50g of yarn, leaving enough for a hat.
Keeping with the garden theme (the cowl had a trellis stitch) the hat has seed stitch ribbing.
Decreases are worked at four points around the hat.
The hat is worked from the brim up, I am going to work on a top down version at some point to make use of every last yard of yarn. This came comfortably out of the 50g left over, with just 2g remaining.
So from 100g of aran yarn you can make a cowl and a hat.