Pinching Out Tomato Sideshoots: Why It Matters and How to Do It Right

By late July, a lot of first-time tomato growers end up with the same plant: a dense, tangled bush of stems and leaves, two metres of foliage, and a handful of green fruit buried somewhere inside it. Sometimes the opposite mistake happens: a grower pinches out what they're sure is a sideshoot and weeks later realises they removed a flower trussThe flowering, then fruiting, stem cluster on a tomato plant; each truss ripens its fruit together. Full definition →, and a whole cluster of future tomatoes with it. Both trace back to pinching outRemoving the soft growing tip of a stem to stop upward growth and make the plant branch out sideways instead. Full definition → sideshoots on cordonA fruit tree or bush trained as a single main stem with short fruiting side-spurs, usually grown at an angle against a wall, fence or wire. Full definition → tomatoes. Done correctly and consistently it turns a sprawling plant into a productive one; done wrongly, or not at all, the result is the difference between a good crop before autumn and a plant still mostly leaf when the frost arrives.

Why sideshoots matter: the plant only has so much energy

A tomato plant makes its food in its leaves and spends it on growth (stems, leaves, roots) and fruit. It doesn't prioritise fruit automatically. Left alone, a cordon tomato puts out a sideshoot at every leaf joint, and each grows its own leaves, flowers and further sideshoots, branching over and over through the season.

Every one of those extra growing points competes for the same water, nutrients and sugars as the fruit trusses lower down. More foliage also means a denser canopy, which shades the leaves and trusses underneath, slows air movement and makes conditions damper and more favourable to fungal problems like blight. In a damp Scottish summer, anything that keeps leaves drier and air moving through the plant does double duty. An unpruned cordon will still ripen some tomatoes, but the same energy is spread across far more demands, so what does ripen tends to arrive later and in smaller amounts than on a pinched, single-stemmed plant.

Removing sideshoots while small redirects that energy toward the main stem and its trusses, and keeps the plant to a single stem that's manageable on a support. Pinch with clean hands, and wipe secateurs between plants when you have to cut rather than snap, since plant viruses can pass on sap-covered fingers and blades.

Cordon or bush? This decision comes first

The two types are grown in opposite ways, so check which you have before pinching anything.

Cordon (indeterminateA tomato's growth habit: determinate (bush) varieties stop at a set height; indeterminate (cordon) varieties keep growing until stopped or frosted. Full definition →) tomatoes are grown as tall, single-stemmed plants that keep growing upward for as long as the season allows. They need tall supports and the sideshoots removed regularly. Most tomatoes sold as young plants or seed for greenhouse and outdoor growing in the UK are cordon types, and this technique applies to them.

Bush (determinate) tomatoes are more compact, stop growing upward once they've set a certain number of trusses, and their sideshoots should be left to grow. Many of those sideshoots carry flower trusses themselves, so pinching a bush variety the way a cordon is pinched removes fruiting stems the variety was bred to produce and can noticeably cut the crop. It's one of the more common beginner mistakes, because the two habits are opposites.

Seed packets and plant labels normally say "cordon," "indeterminate," "vine," "bush" or "determinate." If you can't tell, a cordon keeps extending a single obvious main stem past its first few trusses, while a bush variety branches into several roughly equal stems and stops getting taller. For which Scottish-suited varieties fall into each category, see best tomato varieties for Scotland.

Telling a sideshoot from a flower truss

This identification step trips up more first-time growers than anything else about tomato pruning. A sideshoot and a flower truss both appear near where a leaf meets the main stem, and early on they can look alike.

A sideshoot grows from the leaf axil, the V-shaped notch exactly where a leaf stalk joins the main stem, at roughly a 45-degree angle, so it looks like a smaller third branch sitting in the fork. When it should be removed it's a short stub a couple of centimetres long, with a tiny fan of embryonic leaflets, usually a lighter, fresher green than the foliage around it. It has no flower buds and no thickening at the tip. If left, it becomes a second, competing main stem.

A flower truss comes off the main stem itself, not from a leaf axil: trusses form along the stem between leaves, in a fairly regular pattern for the variety. Early on it looks like a small, knobbly cluster on a short stalk, with no leaflets fanning out. As it develops it thickens and shows a tight cluster of tiny yellow flower buds, which a sideshoot never produces.

When in doubt, look at exactly where the growth is coming from. If it's rising from the crook between a leaf and the stem, then it's a sideshoot. If it's coming from the stem on its own, independent of any leaf junction, with no leaflet fan, leave it: it's very likely a truss. Waiting two or three days rarely costs anything. A sideshoot left an extra few days is still easy to snap out, while a truss removed by mistake is fruit the plant will never produce.

When and how often to pinch out

The RHS advises checking the plant each time you water for shoots sprouting from the joint between leaf and main stem, then pinching them out or snapping them off. Teagasc gives about 3cm as the size to snap them off. Checking roughly once a week works better than trying to catch up on a plant that's got away. At 2 to 3cm a sideshoot snaps off cleanly between finger and thumb with a light sideways bend, leaving barely a mark. Left for a few more weeks it thickens, and removing it means cutting, which leaves a larger wound and an easier entry point for disease.

Check behind the leaves and lower down the stem, not just the shoots visible from the front. Sideshoots missed at 3cm are the ones found weeks later as thick, semi-woody stems. A pinched-out joint often throws up a new sideshoot from the same spot within a week or two, so recheck the same leaf axils on the next pass. In strong midsummer growth, a weekly check may not be quite enough and a quicker look every few days is worth it.

Pinch on a dry day if possible, or once the foliage has dried off. A fresh wound on wet leaves is probably an easier entry point for grey mould (botrytis) and other fungal problems, and botrytis thrives in still, humid air, so a greenhouse with poorer natural ventilation is where this matters most.

Rather than composting the sideshoots, a healthy one pinched at 8 to 10cm or so, with its lower leaves stripped and the cut end stood in water or damp compost, will typically root within one to two weeks and grow into a new plant genetically identical to the parent. It's a free way to raise a late-season plant, a spare in case of losses, or extra stock to give away.

Stopping the plant: how many trusses is realistic in Scotland

Sideshoot removal isn't the only cut a cordon needs. At some point the growing tip has to go too, a step called "stopping" or "topping": removing the growing point two leaves above the top truss you want to keep, so the plant puts its remaining energy into the fruit already set.

The RHS counts trusses: remove the growing point once the plant has set seven trusses indoors or four outdoors. Teagasc, the Irish national agriculture advisory body, whose maritime climate is a useful comparison for western Scotland, works to a date instead: pinch out the growing point in August, two leaves above the last flower truss. The tomato growing guide covers the full comparison.

Scotland's own season is tighter than either reference alone. The Met Office says Scotland usually sees around six days of air frost in April against England's under four, so tender plants like tomatoes typically go outside later relative to the calendar than a UK-wide or Irish timeline assumes. A later start without a correspondingly later autumn frost means a shorter ripening window for an outdoor cordon in most of Scotland, which is why the safer choice outdoors is to treat the lower end of each range as the working number. The dates and the inland figure below are rough guides rather than published figures.

The under-glass figure of 7 needs no downward adjustment for Scotland, because a greenhouse or polytunnel is protected from the frost timing that shortens an outdoor season. *The inland and upland row is a starting estimate, so check it against the local last frost date on Scotland's frost dates for your plot.

For the full tomato-growing process, sowing dates, feeding and staking, see the tomato growing guide. For getting fruit to set in the first place, see hand-pollinating tomatoes and squash.

Common questions

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