Lava mulching comes from one of two kinds of mulches that offer invaluable benefits to your garden and landscaped areas: those that are inorganic and mulches that are organic. All mulches conserve water, even out temperature extremes, help control weeds, make maintenance of beds and walkways easier, increase usability for play and sitting areas, and create a more attractive appearance. Mulching with crushed volcanic lava rock is a way to do the above inorganically and in a very appealing way.
The most common colors used for lava mulching are dark red and black. You can, however, purchase this volcanic rock mulch in any number of colors, depending on where you buy it. Although the color of lava rock may seem to be a minor issue, it does, in fact, require some thought. Dark-colored lava mulches hold heat in the soil, while lighter-colored volcanic rock causes heat to radiate away from it and be reflected back onto the plants.
So you have to consider whether or not your plants and soil need or can tolerate higher or temperatures with regard to which color rock you will be spreading. Some plants such as Delphinium, lupine, primrose and Siberian iris can not tolerate high soil temperatures, so avoid placing lava or other types of crushed rock around them.
A Crown Rot Foe
Lava mulching can be particularly helpful as a preventative for plants that have a tendency to develop crown rot, such as hostas, liriope, and several types of fruit trees. Because the crushed rock provides better drainage, the fungus that is the cause of crown rot has a less likely chance of becoming established in areas where this type of mulch is used.
A Neater Mulch
Another benefit to lava mulching and its drainage characteristics lies in its ability to be walked upon even immediately after laying it and watering in and around it. Organic mulches becomes sodden with water and stick to shoes when trod upon, whereas crushed lava mulching stays neatly where it has been placed.
Lava Mulch vs. Organic Mulch
Some people argue that although lava mulching may be more visually striking than organic mulches, it does not provide the amendment to the soil that bark, stray, hay, or other organic mulches do. This may be true, but the home gardener must also remember that organic mulches, unlike mulches like crushed lava, also encourage habitation by pill bugs, snails, slugs, and other unwanted garden pests. Organic mulching around fruit trees can even provide welcome cover for rodents, while lava mulch would never pose this problem.
Lava mulching is plentiful and costs only a little more than some organic mulches. Once you determine whether or not your area in question can handle the temperature changes brought about by this type of mulch and then which color(s) is/are safe to use, you have cleared the way to apply it in any way you see fit. It does a beautiful job of unifying flower and shrub beds in addition to help cut down on your watering bill. So give lava mulch a try. You just may find it is the perfect mulch for your yard.