How do I make a cement tree limb for a flower bed?

I'd start with PVC pipe -- add joints, etc. to make the shape you want, then wrap with reinforcing wire, chicken wire, etc. to 'form' the shape you want; then collect strips of burlap or other heavy material and wrap the 'form' to the shape you want; then apply the thin set/skim coat concrete to cover

https://www.pinterest.com/leankcreations/fake-concrete-trees-branches-and-more/?lp=true I've never done this .. but it's doable!

You will have to first make a Mold. There are kits but they can be really expensive. You can diy a mold with silicone caulking. Check these out

https://www.amazon.com/Cast-Mold-Silicone-Rubber-Gallon/dp/B008UW4OPC

http://makeitatyourlibrary.org/living-play/worlds-easiest-silicone-mold#.W4R7-Z9lA0M

After you make your mold you just fill it up with concrete (Not just cement, cement is basically a glue) you mix cement with sand and gravel and water to make a paste and then fill your mold. Let it sit a few hours. After you remove it from the mold put in a shady spot and cover with plastic. You need to keep it moist for several days to "cure" the concrete. The longer you can keep it moist the stronger it will be

Hi D, Before you go out and spend all kinds of money do a little research:) One mix which is much lighter in weight than Portland cement (which is what is used) is called Hypertufa. The mix which you make has been around for a long time. I have Googled some links for you to start your research with. Good luck and have fun making your limbs :)

how to make Hypertufa tree limbs - Google Search