Tree · Rutaceae
Lemon
Citrus limon
Give it full sun, deep but infrequent water, and protection from frost, and its glossy branches carry fruit for decades.
Full sun
Every 7–14 days
USDA 9–11
6–20 ft · 1.8–6 m
Overview
The lemon is a small evergreen tree in the citrus family, its branches dense with thick, glossy, deep green leaves that give off a sharp citrus scent when crushed. Waxy white blossoms, tinged purple in the bud, open along the stems, and from them swell the tart, bright yellow fruit with their dimpled, oil-flecked rind. The species came from Asia by way of the Mediterranean and grows where winters stay mild, in zones 9 to 11, often carrying flower and fruit on the same twig.
In the ground or in a large pot, a mature lemon builds a rounded, twiggy crown reaching 6 to 20 feet (1.8 to 6 m) tall, with many forms carrying stiff green thorns along the shoots. Dwarf types stay far smaller and denser. Nearly every tree is grafted, and you can often spot the swollen graft union as a knuckle low on the trunk, above which the leafy top and below which the rootstock meet, which is why a seed-grown lemon rarely matches its parent.
Up close the lemon rewards a second look, from the leathery sheen of each leaf to the pebbled, fragrant skin of the fruit. The main risks are frost, soggy roots, and a short list of citrus pests and diseases. Get the drainage and the watering rhythm right, watch the pale, tender new flush where trouble starts, and the tree fruits for many years.
Care
The short version: the glossy-leaved lemon keeps its deep green shine with all-day sun, no exposure to frost, a thorough soak once the upper few centimetres of the mix feel dry, a gritty free-draining loam full of organic matter, and a citrus fertilizer given monthly across the growing months.
Light
The lemon craves full sun, ideally 8 hours or more a day, which packs the crown with blossom and fruit and keeps the leaves a deep, even green. In partial sun or bright indirect light indoors it grows on, but stretches leggy with wider gaps between the paler leaves and sets a thinner crop.
Water
Water deeply, then wait until the top few centimetres of soil dry out before the next drink, usually every 7 to 14 days. Citrus resent both drought, which crisps the leaf margins, and soggy roots, so the rhythm matters more than the volume. A potted tree dries faster and needs checking more often in heat.
Soil
Plant in well-drained sandy loam rich in dark organic matter, never letting the roots sit in water. A slightly acidic pH of 5.5 to 6.5 keeps the foliage feeding well and green. Drainage is the one thing a lemon will not forgive.
Temperature
The lemon thrives in warmth and holds across roughly 28°F to 100°F (-2°C to 38°C), though frost near the low end blackens and curls the tender new growth. Keep a potted tree above freezing through winter and it comes through unmarked.
Humidity
Average humidity of 30% to 60% suits a lemon, so there is little to fuss over. Indoors, the dry air near a heater can leave the leaf tips crisp and brown, where an occasional misting or a pebble tray helps.
Feeding
Feed monthly through the growing season, spring into late summer, with a citrus-specific fertilizer higher in nitrogen. The added iron, zinc, and manganese keep the leaves a solid green and head off the yellowing citrus are prone to.
Pruning
The lemon needs little shaping. Prune lightly in late winter or early spring to cut out dead, crossing, or weak wood and any suckers below the graft union, which often carry sharper thorns, and thin the twiggy canopy to let light and air through.
Repotting
Move a container tree into a pot one size larger every 2 to 3 years. Pale roots circling the pot or poking from the drainage holes, water running straight through, or growth that stalls and yellows despite feeding all tell you it is time to size up.
Size & spacing
A lemon tree builds a rounded crown 6 to 20 feet (1.8 to 6 m) tall with a spread of 5 to 15 feet (1.5 to 4.5 m), so give it open room, or pick a compact dwarf for a tight spot or a container.
When to plant
The lemon runs on warmth and stalls at frost. Young trees go out in spring, once the cold has passed and the soil has warmed. The waxy white blossom opens mainly in spring, and the green fruit slowly swells and colours over roughly 6 to 9 months, ripening to bright yellow with peaks that often fall in winter.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Plant: spring, after all danger of frost has passed and soil has warmed
- Harvest: Blooms mainly in spring but is everbearing in mild climates; fruit ripens roughly 6 to 9 months after bloom, with peaks often in winter. Trees are typically grafted onto rootstock rather than grown from seed.
Hardiness
USDA hardiness zones: 9–11
Temperature: down to -7°C
Troubleshooting
Most lemon trouble writes itself on the leaves first, whether a pest is scribbling through the pale new flush or a fungus is blistering the older, deep green foliage. Reading those early marks lets you step in before the tree slips. Match the look of what you see below, then deal with it while it still helps.
Splotchy uneven mottling, bare dying twigs, and warped bitter green fruit
The leaves turn patchy with uneven islands of yellow and green, twigs die back bare, and the fruit hangs small, lopsided, hard, and stubbornly green, all the marks of Huanglongbing, or citrus greening, a bacterial disease the Asian citrus psyllid carries and one that slowly kills the tree. There is no cure, so a confirmed tree has to come out to protect its neighbours. The blotchy mottling straddles the veins unevenly, which sets it apart from a tidy nutrient shortage, and any suspected case belongs with your agricultural agency for testing.
Fix:
- There is no cure; remove and dispose of confirmed infected trees to protect the area
- Report suspected cases to your state department of agriculture or extension office
- Manage the Asian citrus psyllid vector
Shiny sticky coating, soot-black crust, and hard little domes on the bark
Rows of tiny hard bumps stud the stems and the undersides of leaves, glued in place and shining with a sticky film, while a sooty black film dulls the glossy foliage nearby, and these are scale insects drinking sap and dribbling honeydew. Wipe or prune away a light run, then coat the rest with a narrow-range horticultural oil for full cover. Knock back the ants too, since they tend the scale and drive off the predators that would clear it.
Fix:
- Wipe or prune off light infestations
- Apply horticultural or narrow-range oil for thorough coverage
- Control ants to allow natural predators and parasitoids to work
Translucent greasy welts swelling under older leaves
Turn an older leaf over and you find raised, translucent blisters in murky yellow-brown, slick to the touch as if smeared with grease, and this is greasy spot, a fungus that swells up after warm, humid spells and drops the leaf. Rake up and bin the fallen foliage where the spores overwinter, and thin the canopy a little so the leaves dry faster. A copper or oil spray timed to the summer flush helps where it is advised for your area.
Fix:
- Rake and remove fallen leaves that harbor spores
- Improve airflow through pruning
- Apply a copper or horticultural oil spray timed to summer leaf flush where recommended
Glinting silver ribbons etched into puckering new leaves
Thin silvery lines wander like snail tracks across the youngest leaves, twisting them into curled, puckered shapes, and this is the mark of the citrus leafminer feeding inside the soft new flush. Pinch off the worst-mined leaves and hold back on nitrogen and light pruning, since both push out the tender growth the larvae bore through. On an established tree the scribbled damage looks worse than it is and rarely costs fruit, so a light hand beats a spray.
Fix:
- Prune off and dispose of heavily mined new flush
- Avoid excess nitrogen and frequent light pruning that forces vulnerable new flush
- Use horticultural oil on new growth; protect natural parasitoid wasps by avoiding broad-spectrum insecticides
Toxicity
The pale, juicy flesh and its sharp juice are safe for people, but the rest of the tree is not pet-friendly. The oil-flecked peel, glossy leaves, and pale seeds hold essential oils and psoralens the ASPCA flags as toxic to cats and dogs, and the same compounds can upset other animals. Keep rinds, prunings, and any concentrated citrus oils away from pets.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · Birds
Safe for
People
Cats Mild
A cat that bites into the glossy leaves or oily peel usually shows vomiting, loose stools, strings of drool, and a flat, listless mood. Concentrated citrus oil left on the fur can also leave the skin beneath sensitive to sunlight.
Dogs Mild
A dog that gnaws the bark, leaves, or peel tends to get an upset stomach, diarrhea, and a slump in energy. The strong oils pressed from the rind can leave the skin reactive in sunlight, so keep those products off the coat.
Horses Mild
The oils and psoralens held in the peel and leaves can turn a horse's gut sour and leave it dull. Most horses spit out the bitter, aromatic foliage, so real trouble is rare.
Rabbits Caution
The pungent oils packed into the peel and leaves clash with a rabbit's delicate digestion. Keep the rind and greenery away, and treat even a scrap of the juicy pulp as a rare nibble.
Livestock Caution
Cattle, goats, and sheep rarely mouth citrus, but the oily peel and leathery leaves can irritate the stomach if they do. Keep prunings and windfall fruit out of grazing ground to be safe.
Birds Caution
The concentrated oils in the fragrant rind and leaves are best kept from pet birds, whose systems handle such compounds poorly. A small taste of the plain, juicy flesh is the most they should ever have.
People Flesh safe
The pale, juicy flesh and its sharp juice are everyday kitchen staples, safe to eat and drink. Handling a lot of the oily peel can leave skin sensitive to sunlight, so rinse your hands before heading into the sun.
Keep peels, leaves, seeds, and any concentrated lemon essential oils away from pets, and avoid applying citrus oil products to animals.
Helpline numbers
United States
ASPCA Animal Poison Control: (888) 426-4435 (fee applies)
Poison Control: (800) 222-1222
Canada
Poison Centres: 1-844-764-7669
Varieties
Hundreds of lemon selections exist, differing in thorn, leaf, and the shape and skin of their fruit, but a few turn up in nearly every garden and grocery aisle. These are the ones worth knowing by name.
Eureka
Eureka is the familiar grocery lemon, its branches nearly free of thorns and hung with fruit right through the year in mild climates.
Lisbon
Lisbon is a vigorous, sharply thorny tree that loads its branches in heavy seasonal flushes and shrugs off both cold and heat better than Eureka.
Meyer
Meyer is a lemon-mandarin cross bearing rounder, sweeter, less sour fruit wrapped in a thin, smooth, orange-tinged rind, and it stays small enough for a dwarf container tree.
How to propagate
Lemons are nearly always multiplied by grafting, though you can also strike a semi-hardwood cutting or sow the smooth pale seeds if you accept the trade-offs each route brings.
GraftingDemanding
Active growing season, late spring to summer · A season or more for the graft to take and push growth
Grafting is the standard commercial route, slipping a bud of a chosen lemon scion under the bark of a vigorous, disease-resistant rootstock during the active growing season from late spring into summer. It takes a steady hand, and the swollen union needs a season or more to knit and push fresh shoots. The reward is a tree that fruits true and carries the toughness of the rootstock.
Stem cuttingsModerate
Spring to early summer from semi-hardwood growth · Several weeks to a few months to root
A firm, half-ripened semi-hardwood cutting taken in spring or early summer will push pale white roots in several weeks to a few months. The tree then grows on its own roots, which is simpler than grafting, though it gives up the disease resistance and vigor a good rootstock would have brought.
SeedModerate
Sow fresh seed from ripe fruit · Many years to reach fruiting size, if ever true to type
The smooth, teardrop seeds prised from a ripe fruit sprout readily, but the seedlings come up variable, often bristling with thorns, and take many years to reach fruiting size, if they ever fruit true to the parent. For that reason seed serves breeding work and rootstock raising far more than a tree you mean to harvest.
Myths
Seeds scooped from a ripe supermarket lemon grow into carbon copies of the parent tree.
Shop lemons are grafted onto a separate rootstock for disease resistance and reliable fruit, so the smooth pale seeds inside will not copy their parent. What grows instead is a slow, variable, often thorny tree that may never fruit the way you hoped.
A lemon's fragrant oil and glossy foliage cannot hurt a cat or a dog.
The ASPCA lists Citrus limon as toxic to cats and dogs, thanks to the limonene, linalool, and psoralens concentrated in the fragrant peel, glossy leaves, and pale seeds. Keep the rind, foliage, and any concentrated citrus oils well out of a pet's reach.