Last week, I taught my Houseplants 101 Class at the Rochester Brainery. (Another class should be coming up this Spring, keep a watch!) A lot of great questions were asked but one in particular pushed me to write this blog.
The question was, “How often should we change the soil?”
My reply was, “you don’t need to. Just aerate and add fresh soil to the top”.
The reason this response wasn’t completely right is because it required more information.
We are currently in the middle of January. We have cold, dark weather. Our plants are currently in dormancy due to this seasonal change. My response was specific to the present. Poke holes (aerate), top off with fresh soil, and that should hold over until the Spring, when its safe to replace the soil entirely.
Why we should replace soil annually
The organic materials in the soil naturally break down. Due to this break down, the soil becomes more acidic. Acidity is the by-product of microbial decay processes. Most plant species grow best at a soil pH around 7 because at near-neutral conditions they are
best able to access needed mineral nutrients. When this happens, it’s recommended to “repot” your plant. Carefully remove the plant, discard the soil and sanitize the container. Add the plant with fresh soil mix back to its original container. This will neutralize the pH and correct the acidity issue. It is not recommended to do this in late fall or winter months as the plant will not easily adjust to its new environment and could possibly die. Your plant can wait a few months. [You can also up-pot if your plant is outgrowing its current container]
Another result of organic materials breaking down is soil compaction. When air is displaced from the pores between the soil grains, the soil becomes dense. Dense soil means that roots cannot move to find nutrients, oxygen, and water. Ultimately, the roots suffocate.
Most tropical foliage plants enjoy well-aerated soil. Expect to aerate every few waterings. Succulents and cacti naturally grow in sandier soils so you don’t need to aerate them unless you’re noticing that they don’t hold water as well as they used to (but this could also be solved by repotting).
You can aerate the soil with a sanitized chop stick. I use a metal one that I wipe clean with rubbing alcohol between each plant. This will allow more oxygen to flow through the entire root ball and the soil will become more evenly moistened.
This video below is an excellent example of a gentle way to aerate your soil.
We didn’t get in depth with soil mixing in our class but sustainability is important to my mission. I’m including eco-friendly, organic ways, along with commercial ways to mix soil.
There are 3 main components:
1) Growing Medium- You could grab a houseplant soil mix or organic compost from a local garden center, which is sterilized to remove weeds and disease. If you’re local, I recommend Community Composting
2) Moisture Retention - Coco coir made from coconut husks is an excellent, eco-friendly option for moisture retention. Peat moss is also moisture retentive however there are negative environmental effects that should be taken into consideration when utilizing this product.
3) Drainage- Organic amendments to improve drainage would be bark, sand, pumice and porous gravel. Inorganic amendments would be perlite or vermiculite. Perlite is made by heating bits of a glass-like material until they expand into puffy, lightweight particles.
It holds no water, aside from the little that clings to the surface of each particle. Vermiculite is mined and may contain asbestos. Most of the mines that are safe are located outside of the USA. Be sure to read the packaging.
When mixing, I like to keep the ratio as close to 1:1:1 as possible. The fun part about you’re own mixing is trial and error. You can create mixes and see what works best with what plants you have.
And, SURPRISE! The Botanist creates sustainable, eco-friendly, organic soil mixes for Tropical plants, Succulents and Cacti, and Epiphytes such as Orchids and Bromeliads. The mixes will be available for purchase starting February 1st.
Planty Love + Light,
Shelby Rae, The Botanist