I've grown tomatoes in hay bales.

I also had a huge Miss Huff Lantana that lived in a bale and rooted into the soil. That one did not come up the next year, but most Miss Huffs are peeping out around here right now.

Zinnias might be fun, or Marigolds. Common but hardy and thrive on neglect. Seeds are cheap. Throw in a little soil and 10-10-10 with them just to see what you get.

Nancy the nancedar

I've seen where you hollow out a gallon pot sized hole in the bale and fill it with potting soil and plant your decorative sweet potato. It does take a lot of water but in warm weather the vine will cover the bale in a short amount of time.

trailing nastursiumns, morning glories, moonflower vine - like others have said - hollow out a space and put in some potting soil first. If you are coming to the Raleigh Swap - I can bring you a moonflower shrub (datura) that will trail however it will get a couple feet tall also but will spread out and has heavenly evening scent....

Lynne

Thanks for all the suggestions, I may try some of them in other bales sometime. Plus I started a file after googling on growing in bales. Lots of neat ideas out there! Meanwhile I finally decided what I'm going to do and thought I'd share. I love thunbergia, especially the white ones. I had an extra trellis which I wasn't using and decided to put it right in the center/front of the bales. Then sowed thunbergia seeds along the front of the bale in the ground. Some will climb the trellis and the others should scramble around on the bales. If they do happen to keep going they can climb over and around the gingers behind it with no harm.

Tapping toes impatiently now. Can't wait to see how it turns out. Last year they covered everything in site when I grew them up a wire rack.