Gardening glossary
Loam
Loam is a soil texture class, not a brand or a product. By the USDA definition, loam contains roughly 40% sand, 40% silt, and 20% clay. That balance gives it the strengths of all three particle sizes while smoothing out their weaknesses.
Sand contributes drainage and air space. Silt holds moisture and nutrients without compacting. Clay grips onto cations (calcium, potassium, magnesium) and slowly releases them to roots. Mix them in roughly equal-ish proportions and you get soil that drains within a few hours of heavy rain but stays evenly moist for days, accepts a spade easily, warms quickly in spring, and never bakes into brick.
How to tell if you have loam: do the ribbon test. Wet a handful of soil and squeeze it. Sandy soil falls apart. Clay forms a tight ribbon longer than 2 inches. Loam forms a soft ball that crumbles when poked, and a ribbon under an inch long.
Most home gardens don't start with true loam. You probably have sandy loam (drains too fast, dries out quickly) or clay loam (holds water too long, slow to warm). The fix is the same in both directions: add organic matter. Compost, leaf mold, aged manure, and cover-crop residue gradually shift any soil toward loam-like behavior. Two to three inches dug in each year for a few seasons is transformative.
Bagged "topsoil" and "garden soil" are almost never true loam — they're usually screened mineral soil with some compost mixed in. For raised beds, build your own blend: roughly one-third quality topsoil, one-third compost, and one-third coarse mineral amendment like coarse sand or perlite. That is loam-adjacent and will grow nearly anything.