If you have moisture-loving plants or are starting new seeds, you may want to consider using vermiculite to help keep them moist and healthy. This mineral assists in absorbing and retaining moisture and aerating the soil. But what is vermiculite exactly, and when should you use it?
Our experts explain everything you need to know about vermiculite, when to use it, its pros and cons, and how to use it correctly in potted plants.
Vermiculite is a mineral made up of magnesium, aluminum, and iron silicates and is used as a soil amendment, says Jane Dobbs, expert gardener and gardening team lead at Allan's Gardeners.
"Vermiculite has excellent water-holding properties, which makes it beneficial in both indoor and outdoor gardening," Dobbs says. "It absorbs and retains moisture, gradually releasing it to plants as needed, ensuring the soil stays evenly moist. This is great for plants that like consistent moisture."
"Besides absorbing water, [vermiculite] attracts potassium, magnesium, and calcium, which are essential for plants," Dobbs continues. "It's great for plant propagation and for potting plants that like moist compost."
Gene Caballero, co-founder of GreenPal, says vermiculite is most effective in seed-starting mixes or potting soils because it enhances water retention and aerates the soil, helping root growth and seedling development. "You should incorporate vermiculite into the soil at planting time or when mixing potting soil," he informs.
Dobbs states that vermiculite improves soil aeration and drainage for various plants, too. "It also helps regulate moisture levels, which is especially beneficial for plants that require consistent moisture, such as herbs and vegetables," she says.
While vermiculite can benefit plants, the EPA recommends certain precautions when using the product, such as:
So, keep these things in mind if you decide to use it on your potted plants or in your garden.
"When it comes to potted plants, vermiculite is an excellent addition to compost for houseplants as it helps to retain moisture and nutrients," Dobbs says. "Its sponge-like properties keep moisture and release it gradually, enabling plant roots to access water as needed."
For houseplants, Dobbs recommends mixing 1 part vermiculite with 2 parts potting mix. "This will provide a light and airy growing medium that will not become compacted over time, allowing for better root growth and water penetration," she says.
Vermiculite can be beneficial for the right types of plants. However, there are some pros and cons to consider before using it. Dobbs breaks down the pros and cons of vermiculite so you can decide if it's best for your potted plants and garden:
Vermiculite offers quite a few benefits to your plants, such as:
Although it has its perks, there are some significant cons to consider before using vermiculite, such as:
Dobbs says despite their similarities, perlite and vermiculite are very different. "Vermiculite excels at water retention, which allows it to hold essential nutrients that plants can absorb," she says. "On the other hand, perlite is more effective for drainage, making it ideal for alleviating heavy, compacted soil," she explains.
"During the winter months, perlite is particularly beneficial for clay soils," she continues. "Both are excellent for mixing into potting mixes, suitable for gardening and do not decompose in the soil, ensuring long-lasting benefits."
Caballero also says there are significant differences between the two. "The pros of vermiculite include its ability to retain water and help distribute nutrients. However, it's less effective for drainage than perlite, making it potentially unsuitable for plants prone to root rot," he informs.
"Vermiculite is best for moisture-loving plants, while perlite, made from volcanic glass that's heated and expanded, is better for improving drainage and is favored for plants requiring dry conditions," he continues. "Each serves a specific purpose depending on your garden's needs."
Dobbs says there are several alternatives to vermiculite that can be used for gardening and other purposes. "Some popular substitutes are perlite, coconut coir, peat moss, and rice hulls," she says. "Each of them offers different benefits in terms of moisture retention, aeration, and drainage for potted plants."
"These alternatives are more sustainable and environmentally friendly compared to vermiculite, which is a non-renewable resource," she continues. "Our plants' specific needs, such as their moisture requirements and preferred soil structure, will determine which one to choose."
Many gardeners choose vermiculite to aid plants in retaining moisture and provide a boost for seedlings. However, you can also try some of the recommended alternatives if you feel it's not the right choice for your beloved plants.