Soil Science Made Easy
Matching the right plant with the right soil is just as important as finding it the perfect light conditions. However, as intimidating as the phrase "soil science" is, the process of finding or forming the right growing medium for a plant is more intuitive than systematic.
Plants are looking for five things when it comes to soil – Moisture Retention, Drainage, Aeration, Stability, and Nutrients.
Identifying a plant's needs when it comes to these big five factors starts with identifying the plant and its origin in the wild. Many tropical plants grow in light, nutrient rich loam in the understories of jungles, while succulents and cacti tend to flourish in rocky, sandy soil that drains as quickly as it gets saturated. Understanding a plant's origin is the first step to imitating those growing conditions at home.
This isn't an exact science – there is no secret ingredient or ratio.
Provide a growing medium that is close to home for your plant and it will thrive.
At Tula, we love pre-made all-purpose and succulent/cacti soil mixes. A good all-purpose soil is an excellent growing medium for most tropical plants, and the same goes for a succulent/cacti mix for arid plants. However, a general all-purpose mix can also be amended with various ingredients to match any indoor plant.
Here is a collection of soil amendments and their uses.
Bark: Aeration, Stability. Large plant matter like bark helps tropical plants bind easily to a soil mix while allowing for air pockets that promote healthy roots. Mix 25% with all-purpose soil for tropical plants and epiphytes.
Coco-Coir: Moisture Retention, Aeration. The peeled and ground husk of coconuts makes a fantastic, eco-friendly soil lightener. It also retains moisture well. Mix 25% with all-purpose soil for tropical plants, and up to 50% for epiphytes to mimic a canopy environment.
Compost: Nutrients. Compost functions as a light, natural fertilizer in indoor plants. Mix up to 10% into growing medium when potting up any new plant. You can also use it to replenish nutrients in soil that has been with a plant for a long time. Simply sprinkle onto the soil around the base of the plant.
Moss: Moisture Retention, Aeration, Stability. Mosses like sphagnum moss and sheet moss can help leaven soil and act as excellent root-stabilizers for tropical plants. Mix 25% with all-purpose soil for tropical plants, and up to 50% for epiphytes to mimic a canopy environment. You can also pile moss around the base of tropical plants to provide moisture-retentive mulch.
Monto Clay: Aeration, Drainage, Stability. This is a Tula favorite. Cacti and succulents love bigger stones to cling to that allow air to reach the roots. For a great cactus mix, combine 25% Monto Clay with 25% sand and 50% all-purpose soil. Increase stability on top-heavy cacti even more by providing a top-dressing of Monto Clay around the base of the plant.
Perlite/Pumice: Aeration, Drainage. When we plant cacti or succulents, we need to aerate the soil without retaining moisture. Perlite, a crystalized volcanic glass, is super light and absorbs almost no water. Air passes easily through soil with lots of perlite, allowing roots to breathe. Mix up to 25% into an all-purpose mix to make a quick, functional succulent/cacti mix.
Sand: Aeration, Drainage. When it comes to cacti, sand feels like home. Be sure to purchase washed sand or silica sand – sand from the beach, for example, has a high salt content that can harm plants. Mix up to 50% into an all-purpose soil for a natural cactus mix.
Stones / Lava Rock: Aeration, Drainage, Stability. Larger stones and lava rocks function well as root-binders and drainage promoters in cactus/succulent soil. Like with Monto Clay, you can combine 25% stones with 25% sand and 50% all-purpose soil for a great cactus mix.