• A hand full of black lava gravel, small angular pieces of porous rock. The smallest are the size of sand grains, while the largest are around a centimeter.
  • A birds-eye view of a bowl of multi-colored lithops, with black lava gravel as top dressing. The dark rock makes the plant colors of purple, orange, white, and green pop.
  • Four brown paper bags full of black lava sand arranged on a garden table, demonstrating the different sizes available. The smallest is three quarters of a pound, approximately three cubic inches. The second smallest is twice that volume, one and a half pounds which is approximately four cubic inches. The third largest is five pounds, approximately six cubic inches. The largest size is fifteen pounds, which is approximately eight cubic inches.
  • A huernia procumbens succulent in a small black two and a half inch pot with black lava top-dressing.
  • Diagram indicating the lava gravel provides good heat retention over winter, but can lead to plant burns if used in direct summer sun conditions
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Black lava sand, coarse-grain horticultural grit

Black lava sand, coarse-grain horticultural grit

$4.00 USD
$4.00 USD
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Size

SIZE 1/8" avg grains, 1/4 inch down to fines (silt)
Units: 3/4, 1.5, 5, or 15 lb

The sand has been washed and sorted to remove foreign materials and any obvious light-colored chunks. This material is mined in northern Arizona, and characteristic of the region's material I have found some tiny bits of peridotite/olivine mixed in!

Black lava sand is finely crumbled volcanic rock. It is a key component of DIY Pon mixes for succulents, cacti, aroids like hoya and philodendrons, bonsai, and carnivorous plants. The fine gravel can also be used in terrariums and fairy gardens. It is a decorative lightweight top-dressing that helps hold moisture in soil. Alternatively, mix it into the soil like perlite for a lightweight grit.

There are many cacti and succulents that are happy to be planted directly in lava sand or lava rock mixed with other rock types to create an inorganic soil—it more closely mimics low-nutrient natural growing conditions. The porosity of volcanic rock keeps it lightweight, so roots stay airy and dry. At the same time the porosity retains moisture well similar to LECA, so lava rock soils drain immediately but light moisture remains available to the plant. This makes it much more difficult to lose a plant to the soggy conditions that cause root rot. (And dissuades fungus gnats!)

How much do I need? If you aim to use this as a potting medium, a 2.5" square pot holds about 4.75oz, and a 4" round pot takes about 15 oz.

3/4 lb - best for one or two plants, fairy gardens, testing out the substrate.
1.5 lb - best for small plant collections, mixing with other substrates, terrariums.
5 lb - best for more advanced gardeners and larger projects.

🌟 15 lb BULK size now available!

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