sweet woodruff makes a good ground cover. but you may have confused walnuts with oaks.

you shoiuldn't have problems growing stuff under an oak other than dealling with dry soil issues.

Bill

You heard wrong, I bet. I have burr oak and grow any and every shade plant hardy to zone 3/4 I can find. Vines, hosta, fern, bleeding heart,LOV,astilbe, toad lilly, columbine,bulbs,Jacks,ginger,on and on my list goes. Black Walnuts can be tricky, maybe that was what you heard?

The term is 'allelopathy' and yes, oak foliage does have certain allelopathic properties that discourage some plants from growing in their immediate vicinity but it depends a lot on the oak species and the plant. It is nowhere near as strong or pronounced as it is with black walnuts. In most cases, it tends to be weedy grasses or turf that is discouraged. Most ornamental plantings will do fine underplanting oaks as long as you can deal with the root competition (dry soil, lack of nutrients and hard to dig and establish small plants).

I do a lot of shade gardening under Southern Live Oaks. The secret is to really pile on the compost under them before you start planting.

My trees had roots coming out of the ground that are a good eight or nine inches tall and I just piled in agricultural waste that I can get free here up to the root level and planted in that. As it has broken down, I keep adding shredded leaves to try to keep the organic content high.

As time goes by, the compost you put down is going to get totally choked with oak roots that will be competing for moisture so things that like wet feet won't be all that happy, but I've got a ton of hostas, bearded iris, ferns, lilies, day lilies, daffodils, ajuga, and this and that growing under my oaks.

I've not had any luck with astilbe or heucheras although I've tried them many times. I assume because they can't compete for water, but who knows.

I have the same problem with two Oak trees in my back yard. I planted Encore Azaleas around the base of each tree, but I had to dig them up they were dying. I lost 3 out of 15. I have added a link to my garden so you can see what I have.

This will be the third Summer that we have lived in this house. I started building my hardscape the first Summer. Hopefully I can finish the I can finish this Spring and early Summer. We planted about 60 Azaleas across the back the first summer and they seem to be doing pretty well. About half of them are in the shade of the two Oak trees and half are in full Sun till about 2:00PM. The root system of the two Oaks do not effect these Azaleas.

We planted the 15 Azaleas about 2 feet out, all around the tree trunks the second Spring. I did not build up the soil around the trees for fear of damaging the trees. The Azaleas just continued to get weaker and weaker till I dug them up and put them in the greenhouse. I will plant them someplace else this Spring.

Now my question is what will do well under the trees. As you can see they dominate the yard. I like Hostas and I just bout a bunch of Caladium bulbs, because they are so colorful. I am trying to get a lot of color into my garden this Summer. I am open to about anything that has a lot of color, will grow at the base of these trees and I prefer a perennial.

Here is a link that might be useful: The Garden

Have you tried a climbing hydrangea? I have one under my oak and it climbs up the trunk and spreads along the ground as a ground cover. Pretty white flowers and interesting red bark in the winter.

I will check that out, I have put it on my list.

I found a bunch of pictures of climbing hydrangea and really like the way that it looks. My question is how much will it damage the tree?

Try epimedium - gets about 1' tall with (mine are) beautiful yellow flowers in spring, spreads 3' or so. I have 3 of them planted under a huge oak and they thrive there.

Under a large oak, I have ferns, caladiums, native azaleas, Japanese azaleas, hosta, Japanese maple, nandina (clip the berries off so birds don't spread them), and wild violets.

The encore azaleas require full sun, so that's probably why rolacoy had problems with those under the shade of the oak.