We already had a post covering a similar topic last year, but there are many different kinds of plants in the greenhouse, each with its own attributes that make them unique. There will likely be more of these posts to show off the large variety that we have in the greenhouse.
One of them that's actually been mentioned before is Sedum nussbaumerianum. It is a succulent that has been in the greenhouse for almost two years now, and it's grown significantly ever since. It was formally known as Mexican sedum until recently; the scientific name is Sedum nussbaumerianum, and another common name is "Coppertone Sedum". I posted a picture of it on GardenWeb Forums to see if anyone could properly ID it and got a response within an hour.
Notice that some parts of the 'stem' look unusually barren; I plucked leaves off of those places in an attempt to propagate the succulent. This sedum can be propagated via cuttings, but it's a very slow process, and so far I've only gotten two out of ten or so cuttings to root. Naturally, sedum grow slowly, and many of the cuttings I took rotted before they could root. Sedum nussbaumerianum would be great for plant sales or for the green roof, if we had more plantlets, but for now, the few clones I have will remain in the greenhouse.
The other interesting plant is the snow pea. It is a fast-growing plant that utilizes tendrils to wrap around anything nearby to provide support. Without a trellis or some support system, snow peas don't do very well since their stems (vines) are rather thin and weak. One of our members used chicken wire to provide an initial trellis (there are at least 3-4 plants in the pot), and once they had outgrown the wire, he trained the tendrils towards the PVC pipes used in the greenhouse watering system.
However, even after that, the snow pea continued to grow, eventually reaching the top of the greenhouse (the glass panes). Normally, snow peas can grow up to six feet (two meters) tall, so this one still has a long way to go before it reaches its full potential height. Also, we have yet to see it flower, but snow peas are known for their beautiful displays of color when they flower, so we're all looking forward to it.