Take a plant species description book with you, do not rely on what the sales help tell you unless you have dealt with this nursery before and you know for a fact that they have honest knowlegeable help. In the west any nursery worth its salt will have a copy of Sunset's Western Garden Book right on the counter for you to use, but it is better to take you own so you have it when you are actually looking at the plant.
If you live in the west you can use the maps in the front to find out what zone you live in to make proper plant choices according to cold hardiness and other factors. This is far to superior to USDA zones and they do not correspond. Sunset's maps are much more detailed and consider far more information than the blanket USDA zones. If you don't live in the west take some time to read through the section to find the zone that most closely matches your area and use this number to aid in plant selection. Since the book includes zones from San Diego to the mountains of Washington almost the entire country should be able to find a comparable zone except the deep south and the upper midwest.
Armed with kind of information about plant material you can make intelligent choices about the cold hardiness, watering requirements, and growth habits of any particular plant that strikes your fancy.
Since this is mostly for beginners, I suggest that you look for deciduous material, or hardier evergreens such as juniper. Stay away from Pines unless you have several years of experience under your belt. Some may disagree with me, but I don't consider pines other than Pinus mugo to be beginner plants. Most pines in nurseries are already wrecked anyhow for bonsai.
For the most part stay with one gallon material since this will be inexpensive and no big deal if it succumbs to overambitiousness. Also stay away from grafted material unless you know what to look for in grafts and the pitfalls of high grafts, ugly grafts, mismatches, etc. Go for seedling material and cuttings. This will also be the least expensive material.
Bargain basement areas are often a great resource for bonsai shoppers. Here you will find the large trunked root bound material at good prices already dwarfed for you. However, pass up stuff that looks like it is on its last legs unless you have some experience. Take rootbound material home and immediately pot it up to the next larger size regardless of what size the final bonsai will be. This will insure the survival of the plant and invigorate the top so you can do some work on it the following season. Do not overwork root bound material because it has no reserves, you must re-invigorate the plant first.
Look for plants with small leaves and twiggy branching, they will make the best bonsai candidates. In general stay away from plants with compound leaves. These are plants that have leaves that are usually large with many small leaflets. These plants will usually not ramify (create small twiggy branches).
If you want evergreens stay with tough plants like juniper and cedar if you are in an appropriate area. Broadleaf evergreens may or may not be easy, you will have to consult your text.
Deciduous material such as maples, hornbeam, hackberry, elm, hawthorn, linden, malus (apple), Prunus (plum, peach, apricot), and liquidambar are fairly easy to work with.
Remember that the strong impulse to have that little tree in the pot will become a very boring experience if that is your only interest in bonsai. Most people have much more fun with their collections of pre-bonsai and bringing the trees along, watching them grow, planning their future, and finally potting them up as bonsai. These trees born of love are much more valuable than mall bonsai.
© 1996, Brent Walston
About the Author
Brent Walston
Evergreen Gardenworks
Evergreen Gardenworks is a mail order nursery. To receive their catalog just send your name and snail address to PO Box 1357 Ukiah CA 95482 or request it via email bonsai@pacific.net.