How to Grow Tomatoes: The Single-Stem Vertical Method

How to Grow Tomatoes: The Single-Stem Vertical Method

Try Growli: Not sure whether your plant is a cordon you should prune or a bush you shouldn't? Snap a photo with the Growli app and we'll identify the variety and tell you exactly how to train it.

A single tomato plant grown sprawling on the ground gives you a tangle of leaves, poor airflow, and a handful of disease-prone fruit. The same plant grown as a single vertical stem — what UK gardeners call a "cordon" — can produce far more fruit in a fraction of the footprint, with cleaner foliage and fewer fungal problems. This guide walks through the method three experienced growers in three different climates all converge on, and corrects two of the most stubborn tomato myths along the way.

If you're still planning your beds, start with our guide on the square foot gardening spacing chart — vertical tomatoes are what make tight raised-bed spacing actually work.

What is the single-stem (cordon) method?

The single-stem method means training an indeterminate tomato up one main stem, removing every side shoot so all the plant's energy flows into fruit instead of foliage. Grown vertically as a cordon, a tomato takes up very little ground and crops heavily on a tall support. Grown loose on the ground, the same variety throws out a mass of scrambling, leafy stems that are hard to support and produce fewer fruit.

According to the Royal Horticultural Society, cordon (indeterminate) tomatoes "naturally produce side-shoots… and these side-shoots should be removed to keep plants growing vertically on just one stem." That single change — vertical instead of sprawling — is the heart of the method. It quadruples how many plants you can fit in a bed and dramatically improves airflow, which is your first line of defence against blight and other leaf diseases.

Indeterminate vs determinate: which tomatoes to prune

Prune side shoots only on indeterminate (cordon) tomatoes — never on determinate "bush" types, where removing suckers cuts your yield. This is the single most important thing to get right before you pinch anything.

• Indeterminate / cordon: keep growing taller all season and fruit continuously along the main stem. These are the ones you train to a single stem and pinch. Most cherry tomatoes and many slicers fall here.
• Determinate / bush: grow to a fixed size, set most of their fruit on their branches, then stop. According to UNH Extension, determinate types need essentially no sucker removal — taking off those side shoots removes the very branches that carry the crop.

Check the seed packet or plant label for "indeterminate," "cordon," or "bush" before you decide. When in doubt, the Growli app can identify the type from a photo.

How to choose a disease-resistant variety

Start with a variety bred to resist the diseases common in your area — late blight and early blight ruin more home tomato crops than any pest. Variety choice is a free, do-nothing-extra layer of protection.

For genuine late-blight resistance, Mountain Magic and Juliet are well-documented performers — Mountain Magic carries resistance genes that hold up well against modern blight strains, and Juliet is a reliable, crack-resistant grape type. Note that some popular cherry varieties marketed as "disease resistant" are actually resistant to other diseases: Sungold, for example, is prized for flavour and productivity and carries Fusarium resistance, but it is not specifically late-blight resistant. Super Sweet 100, Lemon Boy, and Early Girl are dependable, heavy-yielding beginner choices, though you should still expect to manage blight in a wet season through airflow and base watering rather than variety alone.

A quick note on flavour: in side-by-side taste tests, a vine-ripened homegrown Sungold consistently beats a supermarket cherry tomato — the difference is real, not just gardener bias.

When to plant tomatoes outside

Plant tomatoes outdoors only after your last frost, once nights stay reliably above about 10°C (50°F). Tomatoes are frost-tender; a single late frost can kill an unhardened transplant.

In USDA zone 7A (much of New Jersey), that's typically the second week of May. In much of the UK, mid- to late May is the usual window outdoors — earlier if you're growing under glass. If you started seeds yourself, do it 6–8 weeks before your last expected frost; you can hold healthy seedlings in their trays for a few extra weeks if cold weather lingers. For the full indoor routine, see our guide to seed starting indoors with a heat mat, light, and watering.

How deep should I plant a tomato?

Bury the transplant deep — up to the first set of true leaves — because new roots form all along the buried stem. This is unique to tomatoes and a few of their relatives, and it builds a much larger, more drought-resilient root system.

Strip the lower leaves first, then either dig a deep hole or lay the plant sideways in a shallow trench and bend the top up (a "trench planting" that works well if your soil is cold deeper down). Almanac and multiple Extension services confirm that the buried section of stem produces additional roots. A leggy, stretched seedling is actually an advantage here — you simply bury more of it.

Good soil makes those new roots count. If you're filling a fresh bed, our guide on the best soil for raised vegetable beds covers the drainage-and-fertility balance tomatoes need.

Stake at planting, then prune and lean

Drive your stake or set your support at planting time — never push a stake in weeks later, when you'll spear the root system you just buried. A single-stem tomato gets tall and heavy, so commit to support on day one.

Once the plant is established, work through it weekly:

• Pinch side shoots. Side shoots appear in the joint (axil) between the main stem and a leaf — a distinct shoot growing at roughly 45°, not the leaf itself. Snap or pinch them out while they're small. The RHS advises checking "each time you water."
• Remove the lowest leaves. Strip the bottom leaves as the plant grows so foliage doesn't touch the soil. This cuts the path for soil-borne fungal spores to splash up.
• Lower and lean (optional). For very tall cordons, string-trained growers let the stem lean along the support as it climbs, keeping fruit at a workable height.
• Top the plant. When the stem reaches the top of its support — or has set roughly four to five trusses outdoors — pinch out the growing tip so the plant ripens what it has rather than chasing more flowers it can't finish.

What actually causes blossom end rot

Blossom end rot is caused by disrupted calcium uptake, almost always from uneven watering — not by a lack of calcium in your soil. This is the myth worth getting right, because the usual "fixes" don't work.

The sunken black patch on the bottom of the fruit does mean the developing tomato isn't getting enough calcium. But according to University of Minnesota Extension and Iowa State Extension, the soil usually has plenty of calcium — the problem is that the plant can't move it to the fruit when the water supply swings between bone-dry and soaked. Calcium travels with water, and fruit at the far end of the plant loses out.

The practical takeaway:

• Water consistently — a steady supply during dry spells matters far more than any additive.
• Mulch to even out soil moisture between waterings.
• Skip the Epsom salts. Epsom salts are magnesium, not calcium, and don't help. Extension sources note that adding calcium to the soil is "generally ineffective" because the soil isn't the bottleneck.

Our guide on how to water a vegetable garden covers the deep, even watering rhythm that prevents this in the first place.

Why are my tomatoes splitting?

Tomatoes split when a dry period is followed by a sudden flush of water, so the fruit swells faster than its skin can stretch. It's the same uneven-moisture root cause as blossom end rot, showing up as cracks instead of a rotten base.

Extension and RHS sources note that fluctuating water and temperature drive cracking, and that soils high in nitrogen but low in potassium make it worse. To minimise splitting:

• Keep soil moisture as uniform as you can — water during dry spells rather than waiting for rain to do it unevenly.
• Mulch to buffer the swings.
• For container plants, feed with a high-potassium "tomato feed" once fruit sets; pots have limited root volume and can't find their own nutrients the way in-ground plants do.
• Pick fruit promptly as it ripens, before a heavy rain hits it.

How to water tomatoes the right way

Water tomatoes deeply at the base, in the morning, and never overhead. Wet leaves are how fungal diseases like early blight get started.

Penn State Extension recommends watering "at the base in the morning to minimize how much and how long the leaves are wet," and mulching immediately after planting so soil-borne spores don't splash up onto the foliage. Morning watering lets the soil drink before midday evaporation and lets any stray splashes dry through the day. A drip line or a slow soak at the base beats a sprinkler every time.

Companion planting for tomatoes

Basil, carrots, and marigolds are the classic tomato companions — and good airflow between plants matters as much as which neighbours you choose. Companions won't replace pruning and base watering, but they help.

• Basil is a long-standing tomato partner and conveniently likes the same warm, sunny, well-drained conditions.
• Marigolds are often planted between tomatoes as a trap and deterrent crop.
• Carrots are a traditional low-growing companion that uses the space beneath staked tomatoes.

For the bigger picture on keeping pests and disease down without harsh sprays — from sterilising your pruners between plants to netting and trap crops — see our organic pest control for the vegetable garden guide.

About the sources

This guide draws on three documented real-world growing journeys for hands-on context: a nursery-and-bed-build walkthrough from Epic Gardening (Kevin) in southern California; a season-long, weighed-harvest first-year garden from a UK gardener (Alex); and a 15-year backyard gardener (Team Grow) in USDA zone 7A, New Jersey. Every specific and safety-relevant claim — blossom end rot, fruit splitting, pruning rules, planting depth, and watering — was verified against university Extension services (Minnesota, Iowa State, Penn State, UNH) and the RHS, and softened where those sources could not confirm a figure.