Tomato

Cordon or Bush: What You Are Actually Growing

A tomato seedling bought in spring gives few clues about what it becomes. Solanum lycopersicum reaches 0.9 to 1.8 m tall and spreads 0.6 to 0.9 m at a fast rate, and in its native range it grows as a short lived perennial; almost everywhere else, the first frost ends the plant for good (Missouri Botanical Garden). Cordon, or indeterminate, varieties keep extending all season and can reach 1.8 m, so they need a tall cane, string or stake from the start. Bush, or determinate, varieties stay shorter and bushier and suit a pot or growing bag without any support at all (RHS). Training a cordon plant like a bush, or the reverse, wastes the pinching and staking effort the variety was never bred to need.

Sowing and Hardening Off

Seed sown for a greenhouse crop goes in from late February to mid March; for an outdoor crop, late March to early April is soon enough. Either way the seed needs a temperature of about 18°C to germinate and usually takes about a fortnight to emerge (RHS). Prick seedlings out once they carry a couple of true leaves, then keep them at a minimum of 16°C as they grow on. Do not move plants outdoors, even under cover, until daytime temperatures are reliably above 16°C, and harden them off gradually first so the leaf tissue can adjust to outdoor light and wind before it has to cope with both at once.

Spacing, Pots and Site

In open ground, space plants 45 to 60 cm apart so foliage can dry between waterings. In containers, one plant needs a 30 to 45 cm pot on its own, or two plants share a standard growing bag (RHS). Missouri Botanical Garden's profile calls for full sun and an average, medium moisture, well drained soil, and notes the plant does best in a moist, humus rich, fertile loam, the opposite of a soil that dries out between waterings or stays waterlogged after rain. A greenhouse border or a warm, sheltered patio bed both meet that brief; a shaded corner or a spot that floods after heavy rain does not.

Watering Without Triggering Blossom End Rot

Blossom end rot, the sunken, leathery patch that appears on the base of developing fruit, is a calcium deficiency inside the fruit itself, not usually a lack of calcium in the soil. Because calcium does not move freely within plant tissue, even a short gap in watering followed by a heavy soak is enough to interrupt calcium uptake at the exact moment the fruit needs it (Alabama Cooperative Extension System). The same extension guidance keeps soil pH at 6.0 to 6.5 and aims for around 1.5 inches of water a week once plants are fruiting, applied evenly rather than in a single deluge after a dry week. RHS adds that containers dry out fast and may need watering daily in hot weather, and that the same fluctuating moisture that causes blossom end rot is also what makes ripening fruit split its skin.

Feeding for Fruit, Not Just Leaves

Once the first fruit trusses start to swell, RHS recommends switching to an organic, high potassium liquid feed applied every 10 to 14 days. Feeding earlier, before any fruit has set, mostly grows leaf and stem at the expense of flowering, since nitrogen-heavy growth compounds are what young plants pull from a balanced feed. Fortnightly feeding through the fruiting period is enough to keep trusses filling out without pushing the soft, disease-prone growth that comes from overfeeding.

Pinching Out Side Shoots on Cordon Types

Cordon tomatoes throw out side shoots from the joint between each leaf and the main stem, and RHS advice is to pinch these out or snap them off as soon as they appear, keeping the plant to one productive stem rather than a sprawling, self-shading bush. Once a plant reaches the top of its support, or has set seven fruit trusses under glass or four outdoors, RHS advises removing the growing point two leaves above the top truss so the plant stops putting energy into new growth it will not have time to ripen. Bush varieties are not trained this way; their side shoots are part of how the plant produces its fruit.

Diseases, Pests and the Toxicity Confusion

RHS lists tomato blight, most common outdoors in wet summers, along with grey mould and glasshouse whitefly as the recurring problems on both cordon and bush plants. None of these explain a dog or cat getting sick after chewing a stem: the ASPCA lists tomato plant foliage, stems and unripe green fruit as toxic to dogs, cats and horses, with solanine as the toxic principle and hypersalivation, inappetence, gastrointestinal upset, weakness, dilated pupils and a slowed heart rate as the clinical signs. The same ASPCA entry is explicit that ripe fruit is non-toxic, so a pet stealing a red tomato off the vine is a different situation from one chewing on the leaves or an unripe green fruit still on the plant.

Harvest and Ripening

Cropping starts from midsummer onward, with cherry varieties ripening faster than large slicing or beefsteak types, and greenhouse plants typically cropping earlier and for longer than the same variety grown outdoors (RHS). Pick fruit as soon as it is fully coloured rather than leaving it on the vine, since ripe fruit left in place slows the rest of the truss and adds to the same moisture-driven splitting that comes from irregular watering earlier in the season.