Pruning Medium Tomatoes: Suckers, Stem Count and Thinning the Truss

One stem or two, and what each costs you

A cherry tomato is usually better on two stems because a small fruit reaches full size on almost any amount of leaf. A medium tomato is a genuine trade-off. Two stems roughly doubles the truss count but divides the same root system between twice the fruit, and on this size of fruit that shows up as tomatoes that finish at three ounces instead of five. If you care about individual fruit size, run a single stem.

Two stems make sense when your soil is deep and rich, your spacing is generous at 30 inches (75 cm), and you would rather have a lot of medium-small fruit than fewer full-sized ones. If you go that route, take the second stem from the sucker immediately below the first flower truss, which is always the strongest on the plant, and then remove every other sucker on both stems without exception.

The weekly sucker round

A sucker is the shoot that grows in the angle between the main stem and a leaf. Left alone every one becomes another stem competing for the same water. Set one day a week and work from the base of each stem upwards in turn, snapping off anything under two inches (five cm) with a sideways push of finger and thumb. A wound that size dries shut within a few hours and never gets infected.

Medium tomatoes throw suckers a little more slowly than cherries do, which tempts people into skipping a week. Do not. The plant compensates for slower suckering with thicker suckers, and a shoot you leave for a fortnight is a half inch (1 cm) across at the base. Cutting that out leaves an open wound the size of a coin on the main stem in the middle of humid weather, which is exactly how stem rot gets started.

1. Push sideways, never pull down Grip the sucker at its base and push it away from the stem until it snaps. Pulling downwards strips a tongue of bark off the main stem that takes a week to close.
2. Work one stem at a time, base to tip Finish the main stem before starting the second one. Jumping between stems is the reliable way to miss a leaf joint.
3. Do it on a dry morning Wounds made in wet, still weather stay open for hours. A dry morning gives the plant the rest of the day to seal them.
4. Carry the prunings off the bed Suckers left lying on the soil are a mold nursery under the plant they came from. Bag them and take them away.

If you find a sucker that has already opened flowers, do not simply cut it off. Pinch its tip out one leaf beyond the truss instead. You keep those fruit and the shoot stops extending.

Thinning the truss: the step people skip

This is the operation that matters most on a medium tomato and it barely applies to a cherry. A truss will commonly set seven or eight fruit. The plant cannot fill all of them at full size, so you get a truss of uneven tomatoes, several stunted, and the whole truss ripens slowly and unevenly. Thin to four or five fruit while they are the size of a marble and the remainder size up properly and color within a few days of each other.

Take out the smallest, the misshapen, and anything at the very tip of the truss, which is always the last to ripen and the first to be abandoned by the plant. Keep the fruit nearest the stem, which have the best vascular connection and reach full size most reliably. It feels wasteful the first time. Weigh the truss at harvest and it will not the second time.

1. Thin at marble size, not later Once fruit is walnut sized the plant has already committed resources to it. Thinning at half an inch (1 cm) across redirects everything into what remains.
2. Remove the tip fruit first The last two fruit at the end of a truss ripen a week or more behind the rest and rarely reach full size. They are the cheapest ones to lose.
3. Take out anything catfaced or ridged Fruit that set during a cold snap is often puckered or scarred at the blossom end. It will not grow out of it, so remove it now.
4. Leave four or five well-spaced fruit Fruit touching each other trap moisture between them and rot at the contact point. Space matters as much as number.

Tying in for weight

A truss of five medium tomatoes at full size weighs well over a pound (500 g), and that weight arrives gradually over two months. On a hot afternoon the stem tissue is soft, and a loaded truss will kink the main stem permanently at the node, which chokes off everything growing above it. Ties on a medium tomato are load-bearing structure, not decoration.

Put a tie two inches (five cm) below every truss while it is still in flower, before the weight is there. Wrap the twine tightly around the stake and loosely around the stem in a figure of eight, loose enough to slide a finger through. Stems thicken visibly between one week and the next, so on every weekly round run a finger under each existing tie and replace any that no longer moves.

1. Tie below the truss at flowering Two inches (five cm) below the truss node, before any fruit has set. Once the fruit is on, the truss is already pulling.
2. Sling heavy trusses to the stake A truss holding five full-sized fruit can be looped loosely to the stake with a second piece of twine so the stake carries the weight rather than the stem.
3. Check every tie weekly Slide a finger under each one. If it will not move, cut it and retie. A tie that grips will girdle the stem within a month.

Leaf removal below the picking truss

Once a truss is being picked, remove the two or three leaves below it. Those leaves have stopped contributing much, they sit closest to the soil where fungal spores splash up, and taking them off opens the base of the plant to airflow. This matters more for a medium tomato than a cherry because the fruit hangs in that canopy for two months rather than five weeks.

Stop there. Stripping leaves above the picking truss is a common and expensive mistake: those leaves are what feeds the fruit still sizing up, and a medium tomato with too little leaf gives you pale, hard fruit with green shoulders that never fully color. It also exposes fruit that has been shaded all summer to direct sun, and sunscald on a fruit you have waited two months for is a genuine loss.

Topping, and counting backwards from frost

Because a medium tomato needs 55 to 65 days from open flower to ripe fruit, you have to stop the plant earlier than you would a cherry. Nine weeks before your first expected frost, pinch out the growing tip on every stem, two leaves above the highest truss you actually expect to finish. Anything that flowers after that point is spending the plant's resources on fruit that will still be green when the frost arrives.

Leave those two leaves rather than cutting flush above the truss. They shade the top fruit from scorch and they are what feeds it. Keep doing the weekly sucker round after topping too, because the joint immediately below your cut will throw a replacement leader within days and it grows fast.

1. Count back nine weeks from first frost At 55 to 65 days from flower to ripe, any truss opening inside that window will not finish outdoors.
2. Pinch two leaves above the last truss Use your fingers on a dry morning. The wound closes within a day and the plant redirects everything downwards.
3. Remove flower-only trusses at the same time A truss still at the flower stage in the final nine weeks is pure drain. Snap the whole thing off and the set fruit fills noticeably faster.
4. Keep suckering after topping The plant will try to replace the leader from the joint below your cut. Take that shoot out on your next weekly round.