Best ground cover between/among trees

We have a row of different trees along one fence, and weeds seem to grow like crazy between them. Is there a ground cover plant that would work to keep the weeds down? The area doesn't get a lot of sun. Anything that stays fairly low and doesn't look weedy would be great!
One of the main weeds that keeps cropping up is, I think, creeping buttercup.

We could probably put mulch down to take care of the weeds, too. Would that be a better idea? For some reason, I'm more drawn toward planting some ground cover plant, if that would do the job.

It's generally really wet here (lower BC), and the temps are fairly mild (rarely below freezing, rarely very hot).

This message was edited May 28, 2013 12:23 PM

Mulch would really help a lot.
Choosing the right ground cover plants would depend on what zone you are in. I know you said lower BC, so I would assume a similar zone to the northern part of Washington.
So whatever zone that is...

A low growing shrub could work. Something that spreads widely, but does not get too tall. There are some low growing forms of Ilex crenata, if that is OK in your zone. Paxistema is another possibility. Find out which ones are available, and if they would work in your area. There are some low growing forms of Mahonia. This is not such a great ground cover by itself, but in combination with others it will add texture and color (yellow flowers) and attract birds (they eat the fruit)
A somewhat more vine-like plant would keep on creeping and running. Euonymus fortunei radicans is one such.
A more herbacious plant, no woody stems that will keep on rooting, and creeping underground is another possibility. Lamium maculatum is not very aggressive, but grows in shade, and has bright colored leaves. There are several species and varieties of Knotweed (New name Persicaria, old name Polygonum). Most are pretty tough, even aggressive. Some are OK in colder zones, some are not, so do some research. These are not for dense shade. Dappled light under the trees is probably OK. No sun at all is not.

I think your best best is to get the weeds under control before planting anything. I've had success in smothering out weeds with laying down cardboard or a thick layer of newspaper, then compost and mulch. In the beds I've been a little too ambitious in planting before getting weeds taken care of, I regret that choice every time I have to trample something in order to pull a weed or am afraid to spray them because of possible overspray. In one bed that I was losing a battle with bindweed, I eventually just ripped everything out so I could start fresh.

Euonymus fortunei is a bit more aggressive than I like, but if you don't have other garden beds near these trees it would certainly work well.

Another groundcover that does well under trees and in a lot of shade here in Zone 5 is Pachysandra. It's an old standby here, but I like how it looks very neat and tidy. There are even some varieties with variegation.

I just planted some Lamium Orchid Frost and Purple Dragon underneath a maple in our yard and am looking forward to seeing how it does. It is nice to have the silvery leaves shining in the shade and it has nice pink, purple or white flowers. However, I think Lamium may need more sun than the others.

Vinca minor is another vining groundcover with nice purple flowers, which is also an old standby here. But I just love the flowers so I plan on putting some in under a crabapple tree.

For a more experienced gardener, these choices probably aren't very exciting but they get the job done and, except for the Lamium, they are also evergreen which should be good for keeping the weeds under control.

This message was edited Jun 12, 2013 9:51 AM

My go to ground cover is galium odoratum. Loves shady, moist sites, spreads very nicely, deer resistant, and evergreen in some places. Ultimately, though, I agree with wickedelph in that you should get control of the weeds before planting anything. You could just spray the whole lot of them and then go back two weeks later planting whatever it is you decide. Good luck!

Some other interesting ground covers: barren strawberry, Canadian ginger, gro-low sumac or shrubby sumac. I regret allowing any euonymus vines around my yard since the climb and choke the trees. They are very hard to remove. Otherwise they are evergreen in winter so that is a good feature.