Comparison: Best Buy Organic Potting Soil (Updated | Dec 1st)

Indoor mixes are formulated to retain moisture longer and often contain additives like yucca extract or mycorrhizae that help with root health in confined spaces. Outdoor mixes usually include a quick‑release natural fertilizer and a coarser texture to improve drainage for larger containers and exposure to the elements. Choose the product that matches the environment where you’ll be planting, keeping in mind that indoor soils also tend to be pet‑ and gnats‑safe.

Back to the Roots indoor mix is 100 % organic, peat‑free, and emphasizes moisture control with yucca extract and dolomitic limestone for pH balance, plus it adds mycorrhizal fungi for root development. Miracle‑Gro indoor mix includes responsibly sourced peat, coir, and a quick‑release natural fertilizer that feeds plants for up to two months, focusing on nutrient boost rather than long‑term moisture management. The Back to the Roots option is generally more eco‑friendly, while Miracle‑Gro offers faster feeding.

Peat‑free mixes, like those from Back to the Roots and Wonder Soil, reduce carbon emissions because they avoid harvesting peat, a non‑renewable resource. They often use upcycled plant material, wood fines, or coco coir, which provide good aeration and water retention. While peat‑free soils perform well for most houseplants, they may require occasional supplemental fertilization compared to peat‑based blends that naturally hold nutrients.

Mycorrhizal fungi form a symbiotic relationship with plant roots, improving nutrient uptake and drought tolerance. Back to the Roots indoor mix and Espoma’s Potting Soil both list mycorrhizae as a key ingredient, whereas Miracle‑Gro mixes rely more on fertilizer. If you want long‑term soil health and stronger root systems, choose a product that explicitly includes mycorrhizae.

When comparing price‑to‑volume, the 25 qt. Miracle‑Gro Outdoor mix (fills three 10‑inch containers) often offers the lowest cost per quart, followed by Wonder Soil’s compressed coco coir that expands fourfold. Back to the Roots provides 12 qt. bags, which are slightly more expensive per unit but include premium organic additives and a satisfaction guarantee. Consider both price and the specific features you need for your garden.

Back to the Roots indoor mix is marketed as pet‑ and people‑safe, containing no bark or compost that typically attracts gnats. Wonder Soil also claims to be family‑ and pet‑safe, using coco coir and natural amendments. Miracle‑Gro mixes contain peat and a quick‑release fertilizer, which are generally safe but should be kept out of reach of curious pets and children.

Quick‑release fertilizer provides an immediate nutrient boost, helping seedlings establish faster and supporting blooming in the first few weeks. However, it can lead to faster nutrient depletion, requiring re‑application. Organic mixes like Back to the Roots rely on slower‑release nutrients from yucca extract, limestone, and mycorrhizae, offering steadier feeding over a longer period.

Products that list moisture‑retaining agents such as yucca extract, coco coir, or perlite help prevent over‑watering and improve root aeration. Dolomitic limestone, found in Back to the Roots mixes, stabilizes pH to keep nutrients available to plants. If you live in a region with hard water or plan to grow pH‑sensitive plants, choose a mix that explicitly mentions pH balancing.