How to Grow a Lemon Tree in a Pot, Anywhere

A lemon tree in a pot will fruit year round — flowers, green fruit and ripe lemons on the plant at once — and will survive a cold winter indoors that would kill it in the ground.

Two decisions make or break it: buying a grafted tree rather than growing from a pip, and getting the watering right in a container.

Why not from a pip

A lemon pip germinates easily and grows into an attractive plant. It will also:

• Take 5 to 15 years to flower, if it ever does
• Produce fruit unlike the lemon it came from, because citrus does not come true from seed
• Grow long thorns during its extended juvenile phase
• Reach a large size before doing anything useful

A grafted tree — a named variety joined to a selected rootstock — fruits within a year or two, stays true, and can be sized by the rootstock. That is the entire reason grafted citrus exists, and it is the same logic as apple trees.

Growing from a pip is a good project. It is not a route to lemons.

Choosing a variety

Ask what rootstock it is on. Flying Dragon is dwarfing and keeps a tree manageable in a pot without reducing the crop — worth seeking out specifically.

The pot and the compost

• Large, but go up gradually — one or two sizes at a time. An oversized pot holds wet compost the roots cannot use.
• Terracotta suits citrus well, since it breathes and dries the rootball.
• Generous drainage holes, and never standing in a saucer of water.
• Free-draining mix — a proprietary citrus compost, or a loam-based compost with about a third grit or perlite. Not ordinary multipurpose on its own, which stays too wet.
• Slightly acidic, roughly pH 6.0 to 6.5.

Repot every two to three years in spring, teasing out circling roots.

Watering, which is where they are lost

Check before you water. Top two inches dry, then water thoroughly until it runs from the base, and let it drain completely.

Frequency varies enormously — twice a week in high summer, once every two or three weeks in winter. Watering to a schedule rather than to the compost is the fastest way to kill one.

Citrus roots need oxygen. Permanently damp compost causes root rot, and by the time the leaves show it the roots are usually gone. Growing in pots covers the general principles.

Rainwater if your tap water is hard. Citrus dislike alkaline water and it gradually raises the pH of the compost, which locks up iron — the same mechanism that yellows blueberries.

Feeding

Citrus are hungry, and they need trace elements ordinary fertiliser does not supply in the right balance.

• Summer citrus feed — higher nitrogen — from spring through autumn, roughly weekly to fortnightly while in growth.
• Winter citrus feed — lower nitrogen — when growth slows.
• Watch for interveinal yellowing — yellow leaf with green veins — which means iron or magnesium shortage and is very common in hard-water areas.

Light, warmth and overwintering

Full sun outdoors in summer. Move the pot out once nights are reliably above 50°F, and harden it off over a week or two.

Overwinter cool and bright. 50 to 60°F is the target, in the brightest spot available — a conservatory, porch, unheated greenhouse or cool spare room.

Move it gradually. Sudden transitions in either direction cause leaf drop. Two weeks of progressively longer or shorter exposure prevents most of it.

Reading leaf drop

That last one is worth knowing: a lemon tree sets far more flowers and fruitlets than it can carry, and drops the surplus. It is not a fault.

Pruning and fruit

Prune lightly in spring — remove crossing branches, dead wood, and any shoots from below the graft union, which come from the rootstock and will take over if left.

Lemons fruit on new wood, so light annual pruning encourages cropping. Fruit takes six to nine months to ripen and holds well on the tree, so harvest as needed rather than all at once. Colour plus a slight softness is the signal; unlike a tomato, a lemon does not improve after picking.