My idea is to use two links of sturdy chain. Most of one link would be embedded and the other one would be left loose so it could be put over, perhaps a piece of rebar bent so that the tip would point up, then a right angle for an inch or two, then another right angle going down (into the ground). I suppose the loose link could also be considered to be a hanger of sorts. Depending on the length of the rebar, the leaf could float above plants in the garden or sit on the ground.

So my question is, would the chain react badly with the concrete?

Hope I didn't confuse too many people with my description.

Aluminum (Al)

Embedded aluminum roof flashing, aluminum water stops, aluminum electrical conduit, introduced aluminum powder (sometimes used to foam concrete), or embedded structural aluminum shapes may all corrode in concrete or mortar. In all cases, a reaction that forms aluminum hydroxide and hydrogen gas occurs, and may cause expansion and cracking of the concrete or mortar. The common use of calcium chloride (or other alkali compounds), and dampness of the concrete increases the reaction rate. Usually, coating the aluminum with bituminous paint, impregnated paper or felt, plastic, or an alkali-resistant coating will prevent or sharply reduce the corrosion.
Copper (Cu)
Copper embedded in concrete and/or mortar is usually roof flashing. Embedded copper is practically immune to reaction with corrosive alkalis, even if exposed to constant moisture. Copper will not react with dry, hardened concrete and/or mortar. Rainwater leaching, however, may bring chlorides in contact with the metal. Corrosion may occur and result in a green discoloration or runoff. Consequently, chloride admixtures should not be used in concrete if contact with copper is expected.
Lead (Pb)
Lead will always corrode when in contact with fresh concrete and/or mortar. The high pH from calcium hydroxide is the cause of the corrosion. Cured, seasoned concrete or mortar will not react with lead. Corrosion of embedded lead flashing in mortar joints will usually result in the production of a lead oxide, a white discoloration. A special case of lead corrosion, called differential aeration, occurs when a lead strip is partially embedded in concrete so that part of the strip is exposed to air. The embedded section has a different electrical potential than the section exposed to air. The result is that the strip will become polar in the presence of moisture. Gradual corrosion and disintegration of the embedded lead will then follow. In such a case, and in all other cases, the embedded portion should be coated with epoxy, varnish, asphalt, or pitch.
Zinc (Zn)
Zinc is highly reactive with alkalies and will deteriorate to some degree upon contact with fresh concrete and/or mortar. The reaction is limited due to a corrosive film that forms on the outer layer of the zinc. It protects the underlying metal from further reaction. Zinc will not react with dry, seasoned concrete and/or mortar. Embedded zinc will react with moisture and calcium hydroxide to produce calcium zincate. Zinc corrosion may also occur when galvanized iron, in the form of flat or corrugated sheets and rebar, comes in contact with fresh concrete and/or mortar. Galvanized iron is coated with zinc, and will react with moisture and chlorides in the concrete and/or mortar to produce zinc chloride. The result is expansion and cracking of the concrete and/or mortar. The metal should be protected with epoxy, varnish, asphalt, or pitch.

I like Marly's experiments with tubing. Even if the tubing broke down, you could still run wire through the opening. I am going to try that multistrand steel aircraft cable that comes embedded in clear vinyl and see what happens. You can often find it on reels (by the foot) at hardware stores. It's very strong.

Sue