Looking for cover, part 2

Those who have been reading this blog for a while may recall my consternation last June on the subject of ground covers. I was trying to find a suitable ground cover for our small front yard, which is a real nuisance to mow because of its placement (up a flight of stairs from the back yard, where the mower is stored). The problem was that every plant I could find was in some way ill-suited to our yard, which has a western exposure (meaning full sun in the afternoon) and rich but heavy clay soil. The few I found that were capable of tolerating these conditions (such as creeping jenny and blue-star creeper) were all described as invasive by at least one source.

Well, I've done some further research on the subject, and I've come up with a few alternatives that look like they might be workable. None of the choices is perfect, but they look like the best of a bad lot. The candidates are:

1. Herniaria glabra (commonly known as green carpet or rupturewort). This plant is native to Europe, but it's described as a fairly "sedate" plant that's easy to keep under control and unlikely to become invasive. Although it's slow-growing, sources indicate that it will eventually form a nice, dense, low-growing mat that will do a good job keeping out unwanted intruders. It can grow in just about any soil, is drought-tolerant, and, according to some sources, can handle foot traffic nearly as well as grass. And, as a bonus, it provides "winter interest" by turning a nice reddish hue in the fall. Its only drawbacks are that (1) it's not a native plant, (2) its "sedate" growth means that it will probably take quite a while to become fully established in the yard, and (3) despite its many advantages, it's not that common as a landscape plant, which could make it hard to find. I might have to order it online and hope the plants don't suffer too much in transit.

2. Barren strawberry (Waldsteinia fragarioides). Like the rupturewort, this plant forms a dense, low-growing carpet that can stand up to foot traffic. It can tolerate clay soil and grows in full sun or part shade. Some sources describe it as drought-tolerant, while others say it requires consistently moist soil. It's evergreen and produces yellow flowers from spring through early summer, which is a nice feature, although not quite as nice as adding winter interest (since blossoms aren't in short supply at that time of year). This plant actually is native to the northeastern U.S. and thus can't literally be described as "invasive," but one of my garden guides, The Philadelphia Garden Book, describes it as a "relentlessly overbearing" plant that shouldn't be grown outside a container. On the other hand, that aggressiveness could be a benefit in some ways, since I'll be trying to grow it in such unfavorable conditions. Like the rupturewort, this plant doesn't seem to be widely available, and the sources I've found online charge $5 or more for a single plant, so planting the whole yard with it could get rather expensive.

3. Lastly, we have the humble Dutch white clover (Trifolium repens). Many gardeners view this plant as a troublesome lawn weed, but others love having it in the lawn because it grows easily and is a nitrogen-fixing plant that serves as a natural lawn fertilizer. I do have some clover in my yard already, so this is the one plant of the three that I know for a fact will grow in my soil. It does indeed produce nice, lush, green growth, and it doesn't get too tall to walk on. Like the barren strawberry, it flowers in the spring, although I don't consider its blossoms very attractive. Some sources say it can't take a lot of foot traffic, but I'm not planning to ride a horse across it; I just need to be able to step on it occasionally while pruning the cherry tree or weeding the flower beds, and it seems to be able to handle that much. It's also the cheapest option of the three, since it's fairly easy to grow from seed. White clover is native to Europe (although it has naturalized throughout the entire continental U.S.), and the USDA warns that it "can be weedy or invasive." However, the Center for Invasive Species and Ecosystem Health describes clover as being a "troublesome weed" only in certain southeastern states.

So, ecofrugal readers, I put it to you: which of these is the best choice? Is an aggressive native plant a better choice than a non-aggressive, non-native plant? Is the inexpensive, easy-growing clover an ecofrugal choice, or is it an invasive weed? Which one will make the best carpet for my yard? Or is my best option to buy some of each, plant them all together, and let them try to cover all the ground among the three of them?