Therm-O-Rock Super Coarse Horticultural Vermiculite | 4cu ft - Super Coarse (36/PL) - OMRI Listed

Super Coarse Vermiculite for Aeration in Heavy Container Mixes, 4cu ft

Dense, poorly aerated container soil restricts root growth and drains slowly no matter how carefully it's watered, and adding more water only makes a compacted mix heavier rather than looser. Therm-O-Rock Super Coarse Vermiculite corrects this at the particle level: its large, accordion-shaped particles expand soil structure while holding both water and air within their internal layers, so a heavy mix drains and breathes without losing its ability to retain moisture.

This 4cu ft bag is sized for growers blending their own bulk potting or container mixes rather than buying pre-mixed soil, and it ships 36 bags per pallet so commercial growers and nurseries can order at the volume a mixing operation needs.

Key Features & Benefits

• Coarse accordion-structured particles — open up heavy mixes while holding water and air within the same particle.
• OMRI Listed — approved for use in certified organic production.
• Prolongs nutrient release — buffers nutrients in the root zone between waterings rather than letting them wash straight through.
• 4cu ft bag, 36 per pallet — packaged for bulk ordering by commercial growers and nurseries mixing their own substrate.

Who Should Use Super Coarse Vermiculite

This grade fits growers and nurseries blending their own bulk container or potting mixes who need extra porosity and drainage without sacrificing water retention. It's suited to commercial-scale mixing rather than small single-container use, given the 4cu ft bag size and per-pallet packaging.

About Therm-O-Rock

Therm-O-Rock East manufactures horticultural perlite and vermiculite, including graded vermiculite products sized for soil conditioning and bulk container-mix production.

Frequently Asked Questions

What does the Super Coarse grade mean compared to finer vermiculite?

Super Coarse refers to the particle size — larger flakes than medium or fine grades, which open up soil structure more aggressively in heavy mixes. Finer grades are generally better suited to seed-starting or rooting mixes where a lighter, more uniform texture matters more than maximum porosity.

Why add vermiculite instead of only using perlite for drainage?

Perlite improves drainage and aeration but holds very little water itself, while vermiculite's accordion-shaped particles hold water and nutrients between waterings as well as improving airflow. Many container mixes use both together rather than relying on either alone.

Is this vermiculite OMRI Listed?

Yes, this 4cu ft bag is OMRI Listed and approved for use in certified organic production. That status applies to this specific product and package, not to vermiculite as a category.

How is this vermiculite packaged for ordering?

It ships in 4cu ft bags, 36 bags to a pallet, which is the standard format for growers and nurseries buying in bulk for their own mixing operations. Smaller-volume buyers can still order individual bags rather than a full pallet.

What happens if a container mix has too much vermiculite in it?

An oversized share of vermiculite can hold more water than a crop needs, so it's typically blended in at a percentage that fits the grower's existing mix recipe rather than used as a soil replacement. Adjusting the ratio down is the usual fix if a mix stays too wet between waterings.