How do I teach her which flowers are ok?

ok so the little field behind our house has wild violets%26amp; nasturtiums all over %26amp; a rosebush on the side I frequently let my daughter eat the violets %26amp; nasturtiums if she wants them because they are edible %26amp; good in salads. She sees me making rosehip tea from time to time so I know she knows about that too.I know theyre safe, noone has access to them but us, but the thing is,we're going to be visiting a friend of mine from high school in a few weeks who lives in the suburbs. I asked her if theres any edible plants in her area. She said she didnt know but she'd check into it. So what I'm wondering is, once we get there, whatever plants there are there, edible or not, will probably have pesticides/herbicides, etc. on them,and if there are any of the same flowers my daughter is used to munching on...how do I explain to a 1 1/2 year old that the ones there are bad but the ones at home are good? Please no funny business about eating flowers, it sounds funny but they are edible(%26amp; good!)......

How do I teach her which flowers are ok?
Maybe you can explain that she shouldn't eat any flowers in nature unless Mommy is there and says it's okay. Explain that some flowers use the rain and the sunlight to grow but some flowers need chemicals or "medicine" to grow. Tell her that little girls can't eat flower "medicine". Maybe she can relate the pesticides to something she knows.
Reply:Make sure that you are out there with her trying the plants. Do your own reserch in the area. Your friend would be truly upset if she was wrong and something awful happened.
Reply:Keep it simple. Tell her the flowers in the city are pretty to look at but these ones are dirty, so she can't eat them. The flowers where you live are clean and yummy. As young as she is, I'm sure she'll have adult supervision the whole time she's outside so someone will be around to make sure she doesn't eat the flowers!
Reply:You have to be very vigilant with an 18 month old anyway. Keep a close eye on her. She's too young to understand.