If you can do 12" deep; do it! The roots won't go deep enough to become invasive that way. Raspberry roots are strong enough to break thru weed-block so going deeper would avoid that problem.

From what I know of raspberries, they can have very invasive root systems (several feet down and over) and are definitely strong enough to break through weed barrier. I agree with the previous thread. I would not put them near my septic. They spread like crazy and septic water would be very tempting to them. I had some raspberries in a pot in early Spring because I didn't have the bed ready yet (they were dug out and gifted by grandma).... They had about 12 inches of root growth in a month. I don't think they are shallow rooted... (blueberries are, though!)

Your clay will definitely present a barrier for their roots, but I'd encourage you to do some more research on this. You might want to find someone in your area with raspberries and ask them how they do in that soil...

My brother grows raspberries in a 2 1/2 foot deep raised bed with a thick landscape fabric lining. He's had them for at least 5 years with no escapes. So I would recommend a raised bed higher than you think you would need, just to be safe.

my raspberry bed was made using lasagna method 3x6 feet cardboard over the lawn and three plants down the center. They have spread well into the bed over the past few years. I mulch up the edges of the bed in spring and fall and mow the grass up to the edge every week with the regular lawn mowing, so spreading has not been a problem. The mower must shear any new shoots and that seems to keep them at bay.

Yes they love the sun!

Alright, I've got an updated plan. At the moment, I'm thinking of getting a BIG rubbermaid tub and drilling some holes in it for drainage. Cover these up with some kind of permeable cover (screen, landscape fabric, etc.) and then bury the whole thing in the ground. Then I'll build a raised bed (1-2' sound good?) on top of this and plant my raspberries in it.

Gives good depth I figure. Any more thoughts?

I'm wondering why you are worried about the spread so much, Assuming you are planting them in your yard, Once you get an established hedge, your lawnmower will take care of them spreading out of control.

I planted 10 plants 2 years ago in a 30 ft row and now have a nice 8x35 hedge of them with about 60 primocanes this year. I just picked a width and then mow over anything outside of my desired hedge.

I don't think they will spread if you are constantly mowing the new growth. I mean they will likley always try to spread but once you mow a cane once or twice with your early spring moving, they should die back down and not get the energy they need to spread further. I would personally just go with a 6 or 12 inch raised bed and no weedblock on the bottom. Just a waste of money IMO.

i have raspberries in raised beds. I like this for a couple reasons. first they dont spread as much. I actually dont mind them spreading into the lawn as much as i mind them spreading into the vegetable gardens and flower gardens :/

mostly i like the beds because I LOVE the different varieties of raspberries and dont want them to mix. I love knowing the differences in my poka, brittons, carolines, heritage, canby, annes etc. I have noticed that the raised beds are not nearly as effective. They are not as well insulated against heat and cold in summer/ winter. This spring Im going to try to bury some huge black plastic pots that the large trees come in. The roots may run 2 feet down and out the drainage holes but they could never join another pot. I will keep the rims about 2-4" above the ground. I'll drill many very small holes in the middle for better drainage. ..... thoughts?

follow up. container planting raspberries is working fine. not quite as well as in other garden spots but this could be the hot location of the raised beds. im trying one more box in the eastern corner of my yard this spring. any one else have experience planting raspberries in containers/ raised beds?