what i have found to be, by far, the easiest way is to take an old tire, set it sideways on ground fill w/ sakrete and put a 3 inch pvc pipe 8 foot long standing straight up in middle of concrete. allow to set and then drill 1/2 inch or 1 inch hole straight thru pvc (evenly thru both sides), staggering your holes all the way up to top. Now take 5-7 foot foot pieces and push thru your holes. You can lock'em in w/ pvc liquid bondo but they really can't go anywhere. You now have a pvc tree that works great. And they are VERY hard to knock over. The centrivical force ( I think) makes them always want to stand upright. Rough up up w/ sandpaper before you drop them and algae will really take hold. Just my 2 cents worth.

How much does one of these weigh with the tire filled up with concrete?

it's fairly heavy but not as heavy as filling a 5 gallon bucket. don't use a real big tire. You can also build you a square w/ 2x4's and would would work same way.

i dont us tires cause when they get old and start brakeing down they pollute the water but good ideal i guess

spray the insides with Pam or silicone ... then cut the tire away from the concrete base. You could probably re-use the same tire, but may have to use duct tape to hold it together, while filling it with concrete.

... cp

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I did the board thing. Actually used an old landscape box i built for a tree. I gave may trees an angled branch design. Makes it nice to slide jigs off of.

Same principle with the main trunk and drilling holes. Then I cut my 1/2 PVC limbs to the length I want and grind one end at an angle. Pus it into the hole and lift up slightly. Hit the end with a rubber mallet and drive down until tight. As you add others they will tighten more. Throw a screw or two here and there just because.