Removing Thorns From a Citrus Tree: Safe, With One Exception

Thorns on a lemon or lime tree are normal, and removing them will not hurt the tree. An Ask Extension expert answering a question about a thorny young orange tree put it simply: pruning thorns away will not damage the tree, and casual growers can remove them for safety.

The more useful question is where the thorns are growing. Thorns on the main canopy are just a nuisance. A thorny shoot coming from below the graft is rootstock, and that whole shoot should go.

Why citrus trees have thorns

The Ask Extension answer notes that thorns develop at the nodes, often on new grafts and fruiting wood. Many juvenile citrus have thorns that mature trees often do not. Mature trees grow thorns less often than newly grafted trees.

Two other common situations produce extra-thorny growth:

• Trees grown from seed. UF/IFAS Extension warns in its Florida Dooryard Citrus Guide introduction (HS 884) that a seedling tree may grow straight up with little branching and be very thorny. It adds that even budded Meyer lemon, Bearss lemon and grapefruit trees can be thorny.
• Juvenile wood. UF/IFAS explains in Citrus Propagation (HS1309) that fruit from seed-grown trees usually takes many years because of juvenility. The same guide tells propagators to prune the budding area clean of thorns, so removing them is routine nursery practice.

A thorny seedling lemon on a windowsill is not a sick plant. It is behaving like a young, seed-grown citrus.

How to remove thorns safely

1. Wear thick gloves. RHS advises this whenever you prune citrus, because they are often armed with sharp thorns, in its citrus growing guide.
2. Use clean, sharp pruners or snips. Cut the thorn off close to the stem without tearing bark.
3. Cut the thorn only. Thorns develop at the nodes, where the leaves and buds also sit, so take care not to nick the leaf or bud next to it.
4. Take only the thorns that are in the way. There is no need to strip every thorn. On a young tree, many will be less frequent on later, mature growth.

Removing thorns does not damage the tree. Pruning whole shoots is a different job with its own effects on growth and fruit, covered below.

Check for rootstock shoots below the graft

Most nursery citrus is grafted: a fruiting variety budded onto a separate rootstock. UF/IFAS describes this in Citrus Culture in the Home Landscape (HS132). It advises removing suckers from the base of the tree because they are likely to be the rootstock variety, will not produce desirable fruit, and interfere with tree development.

How to find the graft union, from the Ask Extension answer:

• Look on the lower trunk for a diagonal scar or a change in bark colour or trunk width.
• Shoots below that line may have a different leaf shape from the rest of the tree.
• Vigorous, thorny shoots from low on the trunk are the usual suspects.

To remove them:

1. Snap off soft green shoots by hand while they are small, close to the trunk, without tearing the bark.
2. Cut woody shoots with sharp, clean bypass pruners, flush with the trunk. UF/IFAS advises flush cuts because stubs may be attacked by rot organisms.
3. Do it as soon as you see them. The Ask Extension expert advises removing suckers before they become established, regardless of season.

UC IPM’s cultural tips for growing citrus gives the same instruction: prune off any suckers that arise below the graft or bud union. RHS advises removing any shoots arising from the main stem below the crown on potted citrus.

Thorny water sprouts in the canopy

Vigorous upright shoots can also appear above the graft. UF/IFAS calls these water sprouts. They are slow to bear fruit and crowd more productive limbs, so it recommends removing them. UC IPM says young citrus often produce very vigorous shoots that can be shortened for a tidier shape.

On an indoor tree, prune lightly. RHS notes citrus flower on the tips of new sideshoots, so heavy pruning gives a bushy plant with little fruit. UC IPM adds that branches newly exposed by pruning can sunburn, which matters when the tree goes outside for summer.

When to expect fewer thorns

UF/IFAS notes that budded trees bear fruit earlier than seedling trees. UF/IFAS warns that a tree grown from an orange seed may take 8 to 15 years to bear fruit. If your thorny tree came from a supermarket seed, expect thorns and patience. If it came from a nursery, keep an eye on what grows below the graft.

If your indoor citrus is dropping leaves after a recent repot or move, see our indoor citrus transplant shock guide.

Related guides

Other indoor citrus problems we cover: honeydew residue, sunburn.

References

• Ask Extension: Orange Tree (thorny shoots), #804177
• UF/IFAS Extension: Your Florida Dooryard Citrus Guide - Introduction (HS 884)
• UF/IFAS Extension: Citrus Propagation (HS1309)
• UF/IFAS Extension: Citrus Culture in the Home Landscape (HS132)
• UC IPM: Cultural Tips for Growing Citrus
• RHS: How to grow citrus