what type of rocks attract heat during the day and release it at night?

Question

heard of a gardening technique that uses rocks to release warmth at night and the plants like that, so i would like to know what rocks are best for that
and best place to locate them
thanx a million

how to choose a best answer they are all good

Answer 1

Any rocks do that. You need dark colored rocks to hold the most heat. The lighter colored ones hardly retain any heat at all.

You can find them at lakes, along the side of creeks and streams, or you can buy them at any gardening store.

Answer 2

"Dark colored rock will retain heat in the landscape and may offer some frost protection (reradiated heat) for fruit trees in the spring (it also may encourage early breaking of dormancy)."
http://www.tindaraorchids.com/index_tindara.htm?mediums_mixes.htm~rbottom

Rock mulch is an excellent choice where a more formal look is desired, or in locations where wind can blow away wood-based mulches.
Since it tends to retain and radiate heat it's not the best choice to go along the sunny side of a house. It's also not a good choice around heat-sensitive plants. On the other hand, dryland plants with hairy leaves and succulent stems do much better in rock mulch than in wood-based mulch, which keeps the soil too moist and promotes root rot.
http://www.denverwater.org/cons_xeriscape/xeriscape/RockMulch.html

The amount of water in and the permeability of the surrounding country rock is also a factor. If the country rock is permeable and contains groundwater, heat will be able to move by convection.
http://www.tulane.edu/~sanelson/eens211/contact®ional_metamorph.htm

Good luck! Hope this helps.

Answer 3

If you just need some warmth for plants you could use a heat sink. I use this in my greenhouse to help retain heat in the winter. I use one gallon plastic milk containers, spray paint them black and fill them with water. The sun heats the water and the color helps to contain the heat. You could use this type of heat sink and then cover the bottles with dark colored rocks for extra warmth.

Answer 4

Like the prior person said, goto the darkest rock for maximum absorption. and the places you get the rocks is entirely up to you (either buying or finding) Just remember that when you take a rock from the "wild" you affect the erosion on a minuscule scale...