How many plants in a hanging basket?

As a guide for bedding plants: a 25cm basket takes about 3 top plants, a 35cm basket about 5 top plus roughly 8 side plants in a wire basket, and a 40cm+ basket about 7 top plus roughly 11 side plants. Wire baskets gain the side plants because you can plant through the moss or coir liner — roughly 1.5× the top-plant count. Use fewer for vigorous plants like geraniums, fuchsias or trailing tomatoes (about 3 per 35cm basket).

Do wire baskets need a liner?

Yes. Use moss, coconut fibre, or pre-formed liners. Liners hold compost in and retain moisture.

How often should I water hanging baskets?

Daily in summer, often twice in hot weather. Hanging baskets dry out very quickly due to wind exposure. Add water-retaining gel.

When should I plant hanging baskets?

Plant in May after the last frost risk. For an early start, plant in April and keep in a frost-free greenhouse until late May.

How often do hanging baskets need watering?

In summer, often twice a day. They dry out faster than any other container because wind and sun hit them from all sides. Self-watering baskets reduce this to daily.

GardenCalcs

Hanging Basket Calculator — Plants & Compost

Work out compost, liner, and plant quantities for hanging baskets.

Basket Diameter

Measured across the rim; the most common sizes are 30-40cm (12-16in).

Basket TypeWire baskets need a moss or coir liner and can be planted through the sides for a fuller display. Solid baskets and pots are top-planted only.

How We Calculate This

Basket volume is approximated as a half-sphere: V = (2/3) × π × r³. The default efficiency factor of 65% allows for the liner thickness, plant rootballs and the watering head-gap below the rim, so the figure stays close to real fill capacity — about 7.3 litres for a 35cm (14in) basket and 10.9 litres for a 40cm (16in) basket, in line with maker spec sheets that quote roughly 7.5 L and 10.5 L respectively.

Plant counts are based on standard UK basket planting guides: roughly 3, 5 and 7 top plants for small (25cm), medium (35cm) and large (40cm+) baskets.

Wire baskets allow side planting through the liner for a fuller display, adding approximately 1.5× the top plant count in the sides.

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates based on standard gardening guidelines. Results may vary with soil conditions, climate, and plant varieties.