I've been wondering this myself, and you inspired me to do a Google search. Here's the first link I found: from Plant Delight's Nursery.

A couple of key passage:

"Most baptisias root easy in spring when the growth is soft, the success rate drops off to zero as the plants harden. Cuttings should be dipped in a rooting hormone, and then kept in high humidity until they root...usually about 8 weeks.

Another problem with cutting propagated baptisias is one of overwintering. If the cutting grown plants do not develop enough starches after they root, they will not form new growth buds for the following spring. In spring, a mass of roots will simply fail to send up any foliage. We have found that after rooting, plants that are placed directly into the ground seem to develop growth buds faster than container grown plants. The other option is to keep newly rooted containerized plants in a warm greenhouse or on a windowsill until the new buds develop at the base, and they can be allowed to go dormant. New advances such as tissue culture propagation of baptisias has done wonders to increase numbers more rapidly and overcome some of the overwintering issues that we have faced with conventional cuttings."

I wonder if I'm too late already?

I'm glad you found that article -- I reading it in a magazine a few years ago but couldn't remember the particulars.

Hmmm, trouble with overwintering.... I might give it a try but not expect too much. I think I'll e-mail PD about how late you can try to root cuttings, see if I get a response.

Adrienne at Plant Delights e-mailed me back today. Here is her response:

We've actually steered away from cuttings and are working with tissue culture and seeds. Though, when we did do cuttings, it was very early before the flowers emerged. So, it may be too late this year. Usually, March and April is better. If you want to try the seed method, collect them and store them in room temperature for about a month. The pods need some time to dry and dehisce. Basically, you are waiting for the pods to turn brown. Cut them as soon as they turn brown and let them continue to ripen on their own. Once the are ripe, the pods will split and expose the seeds. The seeds are fairly small and light brown to grey in color. When you are ready to pot them, place them in a cup and pour boiling water over them. Let them sit for a night and place them in a pot the next day. Keep the potted material in a well lit area and mist once in a while until germination. The seeds need a scarification in order to germinate. The hot water will do this.
Good Luck.
Adrienne R. Roethling
Garden Curator of Juniper Level Botanic Gardens
at Plant Delights Nursery Inc.

Well, that ain't good news (as per my attempted rescues mentioned in earlier post). So far (after a whopping 3 days!), the B. lanceolata (not B. cinerea as I first typed) cuttings look okay, two transplants look fine, but three are in various stages of blackening...