The large woody roots are anchor roots. The smaller soft roots are the feeder roots. Disturbing lots of feeder roots can affect the health of the tree.
Planting any shrubs under a tree can cause problems, both to the shrubs and the tree. Because roses are heavy feeders and use lots of water, using lots of fertilizers can cause growth spurts in the tree. Tree roots will take much of this fertilizer from the roses and the tree roots will mingle with the rose roots.
A successful way to grow roses under a tree is to use potted roses. Even then, unless placed on flat stones, the roots will grow into the soil thrugh the drainage holes.
This is not all that bad until you want to move the pots.

Thanks Karl.

I have a rooted cutting of Traviata under a large Oak about 10 feet from the trunk and about 3' inside the drip line. Oak roots are everywhere. The Traviata is about half the size of a sibling (also a rooted cutting) that is growing in near optimal conditions. They were both planted in 2003. The shaded one is about 6 x 2.5, very healthy (lots of dark green leaves, I spray for BS) and has blooms through out the season, but not as many as its sibling. The sibling is about 6 x 4 (but it gets more pruning).

I have a rooted cutting of Queen Elizabeth (planted 2004) just inside the drip line and did well all summer, too. Lately, itÂs looking a little drought stressed, but thatÂs understandable since itÂs only rained here 3 times all summer.

As a matter of fact theyÂre healthier than most annuals, perennials, and a Hydrangea planted nearby. I have a Karen Blixen between the two, that IÂm planning to SP in favor of Souvenir du Dr Jamain(sp?) that is supposed be more shade tolerant.

I heard if you plant a very vigorous variety under a tree it will be a scaled-down version of itself.

My grafted Traviata is turning into a monster (about 10x5, planted in 2002) with pruning, and my grafted QE is no slouch either.

It is possible that the oak will take over eventually but IÂve enough results from these 2 to make it worth it. I think you have to experiment.

Dennis

Thanks Dennis.

I'll probably go ahead and experiment with planting near the tree next spring, but I'll make sure to research the types of plants that would be most compatible with the tree.

Or then again, maybe I'll just go with pots.

we've had a very difficult time trying to grow plants/flowers/veggies under a mature mountain ash tree - full sun, plenty of water, soil tested. and everything dies. I would not recommend growing any plants under a mountain ash tree. Even the rhodies next to the darn mountain ash have shrivelled up and died. time to cut the darn tree down I'm afraid