Growing Parsley in Containers: Pot Depth, Watering and Light

Depth matters more than width

Parsley sends down a taproot that will go 8 to 12 inches (20 to 30 cm) if it can. In a shallow herb trough the root reaches the base within weeks, turns sideways, and the plant spends the rest of the season as a small, easily stressed rosette that bolts at the first hot spell.

Give it at least 8 inches (20 cm) of depth, and 10 to 12 inches (25 to 30 cm) if you want plants that keep going through a hot summer and into winter. Width only decides how many plants you can fit, and it is the less important of the two numbers.

Drainage is the other half of the same issue. Parsley wants steady moisture but rots at the crown in standing water, so use a free-draining potting mix rather than garden soil, and never stand the pot permanently in a saucer of water.

One dry day changes the flavor

Container parsley that wilts hard, even once, comes back with tougher leaf stalks and a distinctly stronger, more bitter taste. It also moves closer to bolting each time it happens. Consistency is worth more here than any feeding regime.

Check by weight rather than by looking. Lift the pot: a well-watered 10 inch (25 cm) pot is obviously heavy, and one that has gone light needs water regardless of whether the surface looks damp. In high summer that will be daily for small pots and every other day for larger ones, and in winter it may be once a fortnight.

1. Water until it runs out of the base A splash on the surface wets the top inch (2.5 cm) only, and the taproot is nowhere near it. Water until it drains, then stop, and let the top inch dry before the next one.
2. Mulch the surface Half an inch (1 cm) of fine bark or compost on top of the pot cuts evaporation noticeably and keeps the crown clean when you water.
3. Move pots out of afternoon sun in high summer Six hours of sun is plenty. In the hottest weeks a spot with shade from early afternoon holds the leaves softer and slows the drying.
4. Start feeding at six weeks Potting mix runs out of nitrogen after about six weeks. A balanced or nitrogen-leaning liquid feed at half strength every two weeks keeps the leaf coming.
5. Re-pot or re-sow rather than rescue A pot-bound plant with a coiled taproot will not recover. Once growth slows and leaves shrink despite feeding, start a new sowing instead.

Indoors it is a light problem, not a heat problem

Parsley on a kitchen windowsill almost always fails from lack of light rather than cold. It wants five or more hours of direct sun; a north-facing sill in winter offers a fraction of that, and the plant answers with long pale stalks and small leaves that never taste of much.

A south-facing sill works from spring through autumn. Through winter, either accept slow growth and pick sparingly, or run a grow light for twelve to fourteen hours a day about a foot (30 cm) above the plants. Room temperature is rarely the issue: parsley is happy anywhere between 50 and 75F (10 and 24C).

Turn indoor pots a quarter turn every few days. Parsley leans toward light strongly, and an unturned pot ends up with all the leaf on one side and a bare crown facing the room.

A supermarket pot of parsley is dozens of seedlings crammed into one plug and is not a plant you can grow on. If you want to keep it, split it into three or four clumps within a day of buying and pot them separately in deep pots.

Winter, and what a pot lets you do

The advantage of container parsley is mobility. A pot from a late-summer sowing can be moved to a sheltered wall, a cold frame or an unheated porch, where it will keep giving leaves through most of the winter. Parsley is hardy well below freezing and will survive outdoors in most temperate gardens, but growth stops and the leaves become brittle, so shelter buys you picking rather than survival.

Remember the trade-off. A pot that spends winter cold has been vernalized just as thoroughly as a plant in the ground, so it will bolt in spring. Use it hard through late winter and early spring, and have the next sowing under way before it goes over.

Notes worth keeping for containers

Record the pot size and depth alongside the sowing date, and note any day a pot dried out badly. When one batch tastes coarse and another does not, that record almost always names the reason, and it is the fastest way to work out which of your pots are simply too small for the position they sit in.

It is also worth logging the date you started feeding and the date leaf size visibly dropped off. The gap between the two tells you how long your particular compost lasts, and next season you can start feeding before the plants ever check.