Among American native pine species, Ponderosa is perhaps the most popular species to collect and train as bonsai. I can think of numerous other species that seem more suitable to bonsai based on needle characteristics, but the relative ease of availability of good, collectible Ponderosa specimens make them more popular than other pines (e.g. Lodgepole, Western White, or Shore).
Ponderosa can have a wonderful ruggedness to them, exhibiting bark as flaky or crusty as any tree. The sometimes twisting trunks and branching can be a wonderful starting point for a powerful bonsai composition.
The natural variability in needle characteristics in Ponderosa is such that you might assume that there are different species. In fact, there are numerous varieties and even variation within the recognized varieties. In hiking in the central Sierra Nevada I find trees with large, straight, and slightly yellow-green needles, while trees collected in Oregon and in the Rockies seem to have shorter and greener needles. In some cases the needles are much less straight and the trees look very unkempt in their natural state. Is it important for needles to be straight for bonsai purposes? The answer to that may be an opinion rather than a fact, but having straight needles certainly contributes more to a look of cleanliness and order.
The rate at which Ponderosa grow in containers is also something of a puzzle. These are trees that can reach 200 hundred feet high in the wild; you would expect them to be able to grow quickly. Yet, across all the specimens that I have had, even the strongest typically will only make branch extensions up to about 1″ per year while in a bonsai container. The mixed curse and blessing of this is that if you have all the branching you need at the time of collection you can, in a few years, create a tree that will be very low maintenance. The opposite is true of a tree where a large amount of foliage is needed to complete the composition – it will take many years for the tree to create this in a bonsai container.
Whether or not enough foliage is present on a collected tree and the specifics of the needle characteristics are not typically among the most important factors in selecting a good specimen in bonsai. Typically you should be more concerned with the shape and movement of the trunk. But, collected Ponderosa can have an enormously-long timeline before they become show-ready if you don’t think of a way to overcome these issues.
Grafting Japanese Black Pine (JBP) or Red Pine (JRP) onto Ponderosa is one solution to both the slow-growing foliage and the sometimes undesirable needle characteristics.
Since Ponderosa cannot be decandled like JBP or JRP to manage needle size, the foliage is more difficult to use as the scale of the composition gets smaller. Trees that are under 15-18″ as a finished bonsai will often be challenging to style with good detail. While grafting has its own challenges, it is certainly a good option for smaller Ponderosa trunks.