That’s about the right ratio. When potting almost any plant I blend about one part of the white, rocky, pumice to three parts potting soil. I’ll add even more pumice to plants that want especially good drainage; plants like natives, most succulents, potted bulbs and many Mediterranean species.
Correspondingly, is pumice good for plant?
There are many advantages to growing plants in pumice. It reduces water runoff and fertilization by increasing soil absorption in sandy soils. It also absorbs excess moisture so roots don’t rot. Additionally, pumice improves aeration and stimulates the growth of mycorrhizae.
In respect to this, should I mix pumice and soil?
If you add pumice to the soil, it ensures that the water is drained without being stored in the soil for too long, and that the soil never really dries out. Another thing that is very good with pumice is that it creates an airy and fine structure in the soil so that all fine hair roots can crawl out without obstacles.
Can I use pebbles instead of pumice?
No. Pumice is best (I explain why below), but many other options work: perlite, decomposed granite, rice-sized bits of gravel and even chicken grit. Aim for about two parts inorganic coarse-grained sand or fine crushed rock to one part organic (i.e. plant-based) material (like compost).
Pumice is also a bit heavier than perlite. This means there will be less waste, and you won’t lose so much product to wind, rain, and routine watering. Since pumice doesn’t decompose, this means that you won’t need to replace it, which can help cut back on cost.
Cover the drainage hole in the bottom of the planter with a felt layer or separation-cloth. This will allow excess rainwater to drain through whilst retaining the clay hydro granules/pebbles in the bottom of the planter. Place a layer of clay hydro granules in the bottom to act as a water reservoir.
The best mixing ratio of the three ingredients is two parts sand, two parts gardening soil, and one-part perlite or pumice. Translating this to cups makes it 3 cups of sand, 3 cups of soil, and 1.5 cups of perlite or pumice. The purpose of pumice or perlite is to aid in aeration and drainage.
Pumice is naturally rich in micronutrients that are exceptional for healthy succulents. Unlike the feather-weight, lookalike perlite, pumice will not float up through the potting soil with each watering. To improve the drainage of your succulent soil, simply add pumice!