Posted: 18/04/2016 at 12:04
Lots of good ideas above. I recently bought a pot of creeping red-flowered saxifrage and have split it into three smaller plants, which are all growing fast, so this and similar rockery plants are also a possibility. You or your friends may have this kind of thing going spare, and if you pot them up now that shoild be grand by July.
You could buy petunias as plugs and pot them on. The trailing ones (e.g. surfinia) are very impressive in a pot.
If you have a bay tree, you can trim this and sell small branches of it. Or rosemary, or sage - a friend of mine asked me for some sage to treat a horse with toothache (no, honestly!) and remarked that it's very hard to buy fresh sage.