Minimum pot size by crop
University of Maryland Extension groups vegetables into three sizes by the potting mix each plant needs. The figures below convert its US gallons and inches to litres and centimetres, one plant per pot unless it says otherwise.
| Crops | Mix per plant | Depth | Australian pot |
|---|---|---|---|
| Tomatoes, capsicum, chilli, eggplant, cucumbers, pumpkins and other winter squash | 30–38 L | 30–40 cm | Larger than a 400 mm pot (27 L); a 500 mm pot holds about 55 L |
| Dwarf tomatoes, capsicum and eggplant, zucchini, cabbage family, beans, beetroot, silverbeet, carrots; rosemary, parsley, lavender, fennel | 15–23 L | 20–30 cm | A 400 mm pot (27 L) |
| Basil, coriander, thyme, mint, garlic, radishes, spring onions, English spinach, lettuce and salad greens, Asian greens, peas | 4–11 L | 10–15 cm | A 250–300 mm pot (7–12 L), or a trough |
| Strawberries | – | 20 cm | A trough or strawberry pot at least 20 cm deep |
| Potatoes | About 115 L | – | A half wine barrel (about 110 L) or a large grow bag |
| Dwarf fruit trees | 95–115 L | – | A half wine barrel or larger |
The "Australian pot" column uses the typical volumes of standard tapered nursery pots, which are sold by top diameter: about 3.5 L for a 200 mm pot, 7 L for 250 mm, 12 L for 300 mm, 27 L for 400 mm, 55 L for 500 mm and 110 L for a 600 mm half wine barrel. Because pots taper, a "300 mm pot" holds far less than its width suggests; the potting mix calculator works out any pot exactly.
Citrus and other fruit trees
Guides differ on the minimum for citrus, because it depends on the tree. Tui, in New Zealand, says to look for pots of at least 40 litres, four times a 10 L bucket, and names half wine barrels as an ideal size. ABC Organic Gardener sets the bar higher: 100 litres for a naturally dwarf citrus such as 'Meyer' lemon or one grafted onto a dwarfing rootstock such as 'Flying Dragon', and 200 litres for a lemon or lime on a standard rootstock. It lists too small a pot as a common mistake. For other dwarf fruit trees, University of Maryland Extension suggests 25–30 gallons of mix, about 95–115 litres.
Why bigger pots are easier
- They hold more water. A small pot of mix in summer sun can dry out between morning and evening; a large one buffers a hot day. That matters most for crops such as tomatoes, where uneven watering causes blossom end rot.
- But they take far more mix. Doubling the diameter of a pot multiplies its volume by about eight, so price the mix before you buy the pot; the potting mix calculator does both.
Several plants in one container
Add up the minimums. A 60 L trough can hold two plants that each need 23–30 L, or several herbs at 4–11 L each, as long as it is deep enough for the deepest-rooted one. For crops grown close together in a trough or raised planter, the plant spacing calculator gives the count and the raised bed sizes guide the soil for larger planters.
Questions
What size pot do I need for tomatoes?
At least 30–38 litres of mix and 30–40 cm deep for a full-size tomato, according to University of Maryland Extension; dwarf varieties manage in 15–23 L. That is bigger than a standard 400 mm nursery pot, which holds about 27 L.
What size pot for a lemon tree?
At least 40 litres, according to Tui, and ideally 100 L for a dwarf lemon such as 'Meyer', according to ABC Organic Gardener. A lemon on a standard rootstock needs about 200 L.
How many litres is a 300 mm pot?
A standard tapered 300 mm nursery pot holds about 12 litres to the brim. A 400 mm pot holds about 27 L and a 500 mm pot about 55 L.
Can you grow potatoes in a pot?
Yes, in a big one: University of Maryland Extension suggests about 115 litres of mix. Tui's method is to plant at the bottom and add mix as the shoots grow until the container is full. See when to plant potatoes.
Sources and method
- University of Maryland Extension, Types of containers for growing vegetables – minimum mix and depth for large, medium and small crops, potatoes, strawberries and dwarf fruit trees. Converted at 1 US gallon = 3.785 L and 1 inch = 2.54 cm.
- Tui, What size pot can I plant citrus in? – at least 40 L.
- ABC Organic Gardener, Potting lemons and limes – 100 L for dwarf citrus, 200 L on standard rootstock.
- Pot volumes: the typical nursery-pot figures used on the GardenMaths potting mix calculator.
Last reviewed 23 September 2026 · Report an error