For large heads, you need ample root space and moisture hold. Recommended container: at least 18–20 inches (≈45‑50 cm) wide and deep per plant when aiming for large yield. Harvest to Table
Some sources suggest a slightly smaller container (12–18 inches wide, 8–12 inches deep) will work for smaller, smaller‑head variants. IMP WORLD+1
If you want largest, lean larger: a 20‑inch wide pot, or half‑barrel, or large fabric grow‑bag (e.g., 15‑20 gal) would allow bigger root space and thus bigger head potential.
Ensure lots of drainage holes: cauliflower hates soggy roots; stagnant water leads to root‑rot, smaller heads, disease. IMP WORLD+1
Material: plastic or fabric pots hold moisture better; clay may dry out too fast. Some growers suggest plastic/metal/cement holds moisture longer. Agri Farming
Soil / potting mix
Use quality potting soil, not garden soil (which can compact, hold pests, and reduce root growth). Gardening Know How+1
Soil mix should be: rich in organic matter, loose, well‑draining yet moisture‑retentive. A mix of compost/peat‑free mix + perlite or coarse sand is ideal. Agri Farming
Soil pH should be around 6.0‑7.5 (slightly acidic to neutral). Lime may be needed if your mix is too acidic. Agri Farming
Add compost or well‑rotted manure at planting (top‑dressing) to provide nutrients. Some growers mix slow‑release fertiliser at planting. Harvest to Table+1
By giving the plant a large home and optimum soil, you give it the foundation to produce a bigger head.
Step 3: Planting / Transplanting
Starting or buying seedlings
You can start from seed indoors ~4–6 weeks before transplanting into pot. Maintain moderate temps, good light. Gardener’s Path
Alternatively buy healthy seedlings from a nursery (strong, 4‑5 true leaves) for faster results. This often less risky than direct seed for container size. Agri Farming
Transplanting into the container
Fill your container nearly full with your mixed potting soil and compost. Leave ~1 inch (2‑3 cm) to top edge to allow watering space.
Remove seedling gently from tray, keep root ball intact. Plant so that the lowest leaves are just above soil surface; firm the soil around gently. rhs.org.uk
Water thoroughly after transplanting to settle soil.
If planting outdoors in cooler spring, guard the signal seedling; if substantial heat is expected soon, consider partial shade until settled.
Spacing and number
One plant per large pot is ideal for maximal size. If you try to crowd two plants in one pot, you’ll likely get two smaller heads rather than one large one. Many container growers do one plant per large container. Reddit+1
By planting carefully and giving one plant the space of the pot, you direct energy into one large head.
Step 4: Care during growth – water, light, nutrients
Light & position
