I have been charged with filling a donated Teddy-bear topiary form for placement in a community children's rose garden. The form is 24" high by 32" across at its widest point. What can I grow that is tall enough, hardy enough (we also have very hot and dry summers, but an automatic watering system at the park), but friendly to children? I've considered boxwood, but some varieties are too short while others are poisonous(!!!) so not a good choice for children! Help!