For more info, google crape myrtle propagation (note correct/more-widely-accepted spelling is with an a instead of the e) or crape myrtle cuttings. Below is one google result that looks pretty informative. Here are a few things I would add to what the article says about softwood cutings:

I would definitely use a moisture dome/tent to conserve water evaporation from the leaves. Sometimes I use 2-liter soda bottles with the neck end removed and sometimes I use transparent/semi-transparent plastic storage containers, turned upside down, as covers.

Take the moisture dome/tent off every day or two and allow fresh air in.

Keep in a shady area to prevent the cuttings from being cooked in the hot sun. I often keep cuttings under my front porch until I know the cuttings have rooted well and I remove the moisture dome/tent. Then I gradually move them out into full sun over a period of a few weeks to give them a chance to adjust.

Carefully monitor soil moisture. You want to keep the soil at root level moist but not wet. Sometimes sticking a finger down into the soil may be necessary to check the moisture level. This is probably the most critical factor to success/failure.

Now is a good time to take cuttings.

Here is a link that might be useful: Crapemyrtle - Auburn University - College of Agriculture

I tried cuttings for the first time last fall. I stuck them in about October/November, put them under a soda bottle as described above in a shady area, and didn't touch them again until spring. I did yellow and red twig dogwood, a couple of roses, fothergilla and forsythia. Had great success with all. The dogwood was very late to leaf out and I thought they hadn't made it, but they finally did and are looking fantastic now! I will take them out of the "nursery" bed next spring and plant them in their permanent location.

The forums here have good information on propagation. I have asked them many questions.

Thanks for all of the info.

How large of cuttings do you normally use?

I have a small greenhouse but right now it does burn everything up if I'm not careful.
I like the plastic bottle idea. And we usually have plenty of those around here.

I have several rooted crape myrtle cuttings on the window sill right now. They will root easily in water if you give them enough time and reduce the majority of the leaves. Sticking them in a rooting medium probably results in quicker rooting than water but I haven't compared. I've found that a cutting about 6 inches long roots fairly reliably. What other plants are you looking at rooting?

The article I linked above recommends 4" to 6" cuttings. I'd say that's about right for crape myrtles.

BTW, rooting in water probably sounds "simpler", but I'd bet you'd have a better success rate with potting soil (or other similar medium like perlite, etc). Many woody plants don't root well in water. The ones that do, almost always develop roots less well suited for transplant. If you do use the water method, change the water frequently, consider adding an aquarium pump to increase oxygen in the water, and plant in soil as soon as roots start to significantly develop. The critical time for water-rooted cuttings is just after transplant into soil/potting mix.

Karen, I noticed you said that your greenhouse burn everything up. Do you have a shadecloth on it? If not, you should really consider that. Also, do you have vents? a fan?

Hi Brandon.
No shade cloth, which couldn't hurt, but it's not set where it gets full sun. I do keep the door and window open for better ventilation , but yeah, I could use a fan.

I was looking for a solar powered fan that wouldn't cost too much. I've got a very low budget to work with.

I've got a Wine and Roses Wigelia(sp?)shrub that I'd like to try rooting too.
Really just wanting to try my luck with everything in the yard. ;D

You can get shadecloth pretty inexpensive from Griffin Greenhouse & Nursery Supplies over on Old Rutledge Pike in Knoxville. I bet they even have a solar powered fan. I was going to look and see, but their website seems to be down at the moment.

Karen - it's really fun to try! :)

I'm trying to root Echinacea from stem cuttings right now. Potted them up last night. I don't know if I'll have any success...I think Echinacea are best propagated from root cuttings or by division of the small plantlets at the base. Of course, I read that after I'd already taken the cuttings. LOL But what the heck, might as well go for it.

I put mine in plastic cups with holes punched in the bottom, with a mixture of Miracle Gro potting soil and sand (only because that's what I had around). I coated the bottoms of the stems in rooting hormone, stuck them in the cups (making a hole with another stem first so I didn't knock off any rooting hormone). Then I put a plastic baggie over the whole top and taped it shut with duct tape. We will see!

Connie,

I've managed a few coneflowers by taking basal stem cuttings. I think as long as you get a little of the crown of the plant with your cutting you can get success. My purple coneflowers had many many babies this year so I didn't worry about cuttings!

Brandon, is Griffin's not a wholesaler only?
Also, does the greenhouse not need sun during the summer?
OR will the heat alone keep things warm?
I bet I've got something I could put on top for shade.
At one time I even had a very large shade cloth. Not sure where it got to.

Connie, yeah it sure is fun. I like seeing what I can grow or get growing. Seeds seem to take more time to get plants to a decent size and I've heard they may not bloom the same color as the parent plant.
In fact I got some crape myrtle seeds from a friend's shrub. It was a deep purple. The plants are now about 2 feet high and have a light lavender bloom.

Griffin concentrates on the wholesale side of their business but has no problem selling to individuals. They will sell shade cloth by the foot (cut to whatever you want). Buying pots, or something like that, can be a bit inconvenient to the retail customer, with limited needs, because they will only sell in case quantities.

Few plant actually require true full-sun. Most plants thought of as full-sun plants will do fine under something like 30% to 50% shadecloth during summer months. I'm not sure what percentage blocks Griffin keeps in stock. Just don't do a tarp or something like that that gives total block (I actually see those vegetable stand plant people try that sometimes).

Good luck with the crape myrtle, Karen. My whole family proudly has crape myrtles from Grandma's yard. Can't tell you how, though, Momma's memory is iffy on such things these days.

Dave, I don't think I got any crown...these were just straight stems. I'm hoping it might work...I dunno. I had GREAT luck with Salvia that way earlier this year. All of them took. But after I read about getting a bit of the base with Echinaceas, I went out last night and looked. Sure enough, there are several little mini-me's coming up at the base. If the cuttings don't work, that's my plan b! :)

Connie,

Salvias work very well like you said! One of my favorite plants in the garden - hard pick just one isn't it? Your mini-me's might be just the way to go! What kind of coneflower are you trying to propagate?

Dave, it's Green Jewel. I LOVE this coneflower. It blooms for such a long time (and even lasts a long time in a vase). It was one of the first to start blooming in spring, and last year it went on and on and on until frost finally got it (late October or November?).

And the color is just outstanding!

So far they still look OK. I wonder how long they'll take to root if they're going to?

Yes, it is hard to pick just one Salvia! I'm enjoying the black and blues right now (I kept two). :) Caradonna is pretty great too...I've gotten three rebloom so far from cutting back! Maybe just because they are young still, but even if they bloomed only once I'd still love them. I also got May Night at the swap (thanks Pat!), I have Snow Hill, and I got Transylvania in a mail swap. Definitely hard to pick just one! :D

Brandon, does Griffin's carry many different nursery pots?
I'm needing a short wide pot. Like 5x18inch

Oooops! Well I cut some viburnum branches and stuck them into decent dirt and watered. Due to a busy schedule I didn't keep up with the watering so they all died in the greenhouse. There were some that just dried up right away but you could tell others were doing ok.
Those didn't seem to take long to root.
I'll try again.

Yep, they have hundreds and hundreds of container types. BUT!!!, keep in mind that you are going to have to buy in full-case quantities. It's not unusually to have to buy in 50 to 100 pot increments.

For small lots, check out Knoxville Seed. They are more expensive and do a pitiful job and keeping any type of consistent inventory, but you can buy single pots of any type they have.

Here is a link that might be useful: Griffin's On-Line Catalog