I'm looking for a fast growing tree with a thick trunk.

[biwa]

I'm looking for a cold-hardy (~20 degrees F) tree that grows quickly and has a thick trunk. Can anybody recommend something to me? How about oak, poplar, maple, or cherry? Or pussy willow?

Thanks in advance for your recommendations!

[MaineDesigner]

We're going to need more information to give you an informed answer. Where are you? Is the site moist or dry? Full sun or part shade? What is the soil like? Do you specifically want a deciduous tree?
Speaking very generally faster growing trees tend to have weaker wood and may be more prone to drop branches if this is an issue.

[biwa]

I am in Virginia, zone 7. The ground is dry on top and moist underneath. The soil is clay, and slightly acidic. Part shade. I don't care what kind of tree it is, it doesn't have to be deciduous.

I don't mind if the tree has weaker wood as long as the trunk is strong. If the branches fall off, the tree will just grow new ones, so that's no big deal.

[MaineDesigner]

As long as the part shade isn't too dense you can probably get good results from one of the maple species. Acer rubrum the Red or Swamp Maple, Acer saccharinum the Silver Maple, and hybrids of these two Acer x freeemanii are all relatively fast growing. Hedge Maple Acer campestre isn't as fast growing but it is a little more shade tolerant if you have more than light shade. Thuja occidentalis, the American Arborvitae and some Picea, Spruce species might be worth a try too.

[biwa]

Those all sound like good ideas. I like red maples, so maybe I'll plant one of those. They grow well around here. I think a local tree would be a good choice because then I could root the saplings from cuttings rather than spending hundreds of dollars at a nursery just to get trees that might not do well because they're not native.

An evergreen might be a good idea too. Is there a reason why you chose those species over other ones? My brother has a real pretty long-needle pine tree (you know, the ones that drop their needles a lot and make a huge mess on your lawn). If I got some cuttings from it, would the resulting saplings grow as well as the Spruce or American Arborvitae that you mentioned?

[MaineDesigner]

I'm not sure which pines you are referring to but in broad brush pines tend to like sandy, well drained soils and full sun. Up here I do see some White Pine, Pinus strobus succeeding in less than ideal conditions. Pinus nigra is also somewhat tolerant of difficult soils but not very tolerant of shade. I have no personal experience with Pinus virginiana but is reported to be quite tolerant of clay soils and fast growing. I think your biggest obstacle with any of the pines is that they all really want full sun. Hemlocks, arbs, some spruce and some fir tend to better tolerate light to moderate shade.

You are right about local genetic strains of any tree being more likely to succeed. I've never tried to root maple cuttings but if all else fails you could start them from seed. I'm rather doubtful that you could get pine cuttings to root but again you could start them from seed.