Ok I've read alot but nowhere does it say how many per plot because when I try thats the first thing they ask also in the green house for those rectangle beds how many per?

This is what im trying to do:

Plant canis root-imp stool-glowing mushroom-blisterwart -wheat in equal quanities if possible.

I was thinking in the outside garden 6 wheat and 5 cannis root is this 1 wheat and 1 cannis root per spot for 5 cannis root and 6 wheat growing at 1 time? Because it asks how many I want to plant per little spot it give 15 possible and there is 11 spots, I don't think that I can plant 15 per spot correct?

In the greenhouse(3 beds 6 planters) I want to plant plant imp stool, glowing mushroom, and blisterwart so how many do I plant per bed and per planter?

Lastly after I pick these do I have to replant with more of the same like the first time because that would diminish the harvest significantly wouldn't it?

Thanks for the help

Honestly, I don't remember how many ingredients you're getting per plant type.

What you can do, however, is plant one of each ingredient you've had in mind, head out for 2-3 ingame days, get back, harvest them and write down how many you've gotten per type. Then, you'll be able to distribute them the way you want.

According to http://www.uesp.net/wiki/Skyrim:Greenhouse you can't actually plant multiple samples in one patch ("(if you choose more, it will display a message and remove only one from your inventory)"). I really suggest you experiment with these things - obviously it's fine to come here with questions, but a lot of stuff can be figured out with trial and error - if you're really worried just make a save before you do things you're not sure about. If you'd tried clicking to plant multiple samples you'd not have needed to wait for answers as the game would have gone "actually, you can't do that" (I dunno why it gives the option, something about how the menus are set up, I guess.) The link also gives the number of samples you can harvest for each plantable ingredient. You do not need to re-plant.