As a turner, I use many species of hardwood trees. On this website at any one time you are likely to find pieces made of oak, ash, beech, yew, walnut, boxwood, sycamore, acacia, plane, holly, cherry, chestnut, plum, apple and others. You can find examples by using the search box at the top of the page.
I rarely use softwoods such as pine or fir. This is not just because hardwoods are more durable, though it is an important factor. The reason that I don't use most softwoods is that often the grain is not homogeneous enough. It has alternating hard and soft bands that may show too clearly in the finished item.
The classification of hard and softwood comes from botany; softwood trees are conifers, and hardwoods are mainly deciduous. Yew is technically a softwood but is physically harder than many species classified as hardwood. It turns very well and all turners like yew wood.
The banding in softwood has to do with climate. In temperate latitudes, trees grow most quickly in spring and early summer and that wood is softer and more porous than the slower growth at other times. The annual variation makes the visible rings in the log, and counting them gives you the age of the tree. Slow-growing trees have their rings closer together and their timber is more valuable. In contrast, tropical species grow all year round and are much more uniform in density.
Hardwood trees from temperate zones also show their growth rings clearly, but there is less difference in hardness between different seasons.
As a maker of bowls, I like timber from large trees. But small ones have their uses too. My wooden mushrooms are made of small branches from large trees, or sometimes from the main 'trunk' of a small shrub. These shrubs can sometimes reach large sizes - privet, for example, can grow tall if not controlled. And holly can become a substantial tree in time. Some shrubs have fine, compact grain and finish well, though others such as elder or buddleia (and some larger species) have a tube of soft pith down the centre that limits their use.
All hardwood is porous. But some species have much more visible pores than others. Some oak varieties have large pores like pin pricks, big enough to see through in a thin section. They show in the finished item, unless filled. In past times, cabinet makers went to some pains to fill the pores, enabling a glass-smooth finish. Now, many woodworkers are happy to show the natural appearance of the wood. But the pores do affect the function of a bowl. An oak salad bowl, with its exposed porous end grain, might leak oil.
Some wood species have characteristic medullary 'rays'. These are radial sheets of cells that play a part in sap distribution. The rays are visible as small flecks or as wider patches or streaks, depending on the angle at which they intersect the surface of the wood. This means that the same piece of wood can have markedly different appearance, depending on how it is cut. Quarter-sawn oak, cut parallel to the rays, looks quite different from plain-sawn oak. Wood from a plane tree, when cut in the right direction, is known as lacewood for its complicated ray structure that resemble lace.
Turned work does not show these rays so clearly as cabinet work, as the surface is only parallel to them at one point on the curve. But they can often be seen as a band on the side or rim of a bowl.
A log can be sawn in different ways. If simply cut into parallel slices, the growth rings will be aligned differently in each plank. The first and last slices, closest to the surface of the log, have the rings more or less parallel to the faces of the plank. These planks are 'plain sawn' or 'slab' cut, and although attractive in turned work, are more likely to warp than quarter sawn timber.
Quarter sawn planks are sawn directly through the middle of the log and may include its centre. The growth rings are more or less parallel with the edges of the plank. This wood is much more stable, and preferred for cabinet work.
Plain sawn and quarter sawn wood look different in turnings because the angle of the growth rings forms a major part of the figure. Often a bowl contains both, the 'slab' part usually in the bottom of the bowl, the 'quarter' at the rim.