The Best Seed Starting Mix

A proper seed-starting medium: fine, light and deliberately low in nutrients, which is what germinating seeds need.

A seed carries its own food supply. That is why seed starting mix is low in nutrients on purpose -- the seedling does not need feeding until its first true leaves, and a rich mix at that stage encourages soft growth and fungal problems rather than roots.

Texture is the other half. A fine, uniform medium makes contact with small seeds all the way around, which is what triggers reliable germination. Chunky potting soil leaves air gaps and gives patchy results.

Plan the handover. Once true leaves appear, either start a weak liquid feed or pot on into something richer, or growth stalls.

Skip it if: you are potting on. Seedlings past their first true leaves want a richer mix than this.

Add water and sow -- no mixing, no mess, and the whole pellet plants out without disturbing the roots.

Pellets trade a little control for a lot of convenience. They arrive compressed, expand when you water them, and you sow directly into the top. Nothing to mix, nothing to spill.

Root disturbance is the real advantage. Plants in the cucumber and squash family in particular resent being pricked out, and planting the whole pellet avoids it entirely.

Two practical notes: open or peel the netting at planting time so roots are not restricted, and be aware the medium is peat, which is why coir-based alternatives exist.

Skip it if: you would rather avoid peat. The pellets are peat-based, and coir alternatives exist.

Everything in one box with a capillary mat underneath, which removes the single most common beginner failure: uneven watering.

Seeds fail for two reasons in a beginner's first tray: they dried out, or they were drowned. A capillary mat drawing water from a reservoir underneath removes both, because the medium takes what it needs and no more.

The dome is the other useful piece. It holds humidity during germination, which matters most for small seeds sown shallowly.

Take the dome off as soon as the first seedlings are up. Left on, it holds the still, damp air that damping-off fungus needs, and a tray can collapse overnight.

Skip it if: you already have trays. Refill pellets and a dome cost a fraction of a new kit.

Excellent in containers and as the top layer of an intensively planted bed -- but it is potting soil, so blend it rather than filling with it.

Happy Frog earns its reputation in containers, where a light, fast-draining, biologically active mix is exactly right. In a raised bed it needs a job description.

The sensible use is blending: mix it with compost and a heavier component for the top layer of an intensively planted bed, particularly where you are growing a lot in a small area. Used neat across a whole bed it is both costly and too light to hold structure.

Anything labeled potting soil is designed for the physics of a pot -- limited volume, frequent watering, free drainage from the base. A bed is a different environment, and the mix should match it.

Skip it if: you are filling a bed. Used neat in a large bed it is both expensive and too light, and it will slump.