Why your tomatoes are struggling, and how to fix it

Tomatoes are the crop people take personally. Everybody has a go at them, plenty of people have a bad year at them, and a bad year is usually four or five small things stacking up rather than one big one. So before you decide you're no good at tomatoes, work down this list, because the fix is nearly always in here somewhere.

Start with the variety

A lot of disappointing tomato seasons start at the seedling rack. Cherry tomatoes are the forgiving ones and they're where a beginner should start, because they set fruit in conditions that make the big ones sulk and you get something to eat while you're learning.

For a full-sized tomato, Grosse Lisse is the old reliable here. Rouge Marmande and Oxheart are worth a go once you've had a season under your belt, and San Marzano is the one to grow if you're making sauce rather than slicing.

When to sow

Tomatoes go in once the frost risk has passed, which around here means October through to December. You can start seed earlier under cover on a warm windowsill and plant out when the nights lift, and that's how you get a head start without losing the lot to a late cold snap.

Give them full sun. North is the aspect you want and the western afternoon sun is the one that scorches in a heatwave, so a bit of temporary shade over the hottest few days in January is not cheating, it's just sensible.

The soil

Tomatoes are fussy about where they put their roots down. They want rich, free-draining soil with plenty of organic matter in it.

• Dig compost or well-rotted manure through the bed before you plant anything.
• Blood and bone or a pelletised manure gives them a solid start.
• Aim for a pH around 6.0 to 6.8. If your beds already grow decent vegetables, don't go measuring for the sake of it.
• Move them. Planting tomatoes in the same bed year after year builds up disease in the soil, and rotating them around is free.

Watering, and why it matters more than you think

Consistency is the whole game with tomatoes. A plant that dries right out and then gets flooded is the plant that splits its fruit and gets blossom end rot, and both of those are watering problems wearing a disguise.

• Water in the morning so the plant has a drink before the heat and the foliage dries off during the day.
• Water at the base, not over the leaves. Wet leaves overnight are how fungal problems get started.
• Deep and less often beats a daily splash, every time.
• Mulch. It holds the moisture steady between waterings, and steady is what you're after.

Blossom end rot, and the eggshell myth

This is the one worth getting right, because the internet has it wrong.

Blossom end rot is that sunken leathery black patch on the bottom of the fruit. It is a calcium problem, but it is almost never a shortage of calcium in your soil. It's that the plant can't move calcium into the fruit fast enough, and the usual reason for that is the soil drying out and rewetting in swings.

So crushed eggshells will not fix it. They break down far too slowly to make any difference to this season's crop, and if the calcium in your soil was fine to begin with, adding more does nothing anyway.

What does fix it is mulch and a steady watering routine. Going easy on high-nitrogen fertiliser helps too, because pushing a lot of fast leafy growth makes the plant compete with its own fruit. Fruit already affected won't recover, so pick those off and the next ones will come through clean.

Feeding

Tomatoes are hungry. Feed them fortnightly with a liquid seaweed or fish-based feed while they're growing, then once flowers appear, swap to something high in potassium, because potassium is what builds fruit rather than leaves.

Pests and the other usual trouble

• Aphids. Blast them off with the hose early. Ladybirds turn up on their own if you're not spraying everything, so leave them to it.
• Fruit fly. This is the serious one and it is not the little flies in your kitchen. Worth reading up on properly before it costs you a crop.
• Caterpillars and chewing insects. A tomato dust handles most of it. Read the label for the withholding period and stick to it.
• Not much fruit and plenty of leaf. Too much nitrogen. Back off the fertiliser and feed for fruit instead.

Pruning and support

Take the lower leaves off so nothing is touching the soil, which cuts down on disease coming up off the ground. If you're growing an indeterminate variety, the kind that keeps climbing all season, pinch out the side shoots in the leaf joints so the plant puts its effort into fruit instead of into more plant.

And stake them properly at planting time rather than trying to rescue a sprawling one in February.

Nobody starts out good at tomatoes. Everyone I know who grows a good one has a couple of seasons behind them that they'd rather not talk about, and that's genuinely how it goes.

Shop related products

• D.T Brown Tomato Grosse Lisse Seed Pack. The reliable full-sized tomato for around here.
• D.T. Brown Tomato Red Cherry Seed Pack. The forgiving one to start on.
• Brunnings Potash Power 2.5kg. Switch to this once the flowers appear.
• David Grays Tomato Dust 3-in-1. For chewing insects and fungal problems. Read the label.

Did you know we also carry Oxheart, Rouge Marmande and San Marzano tomato seed in store, plus bamboo stakes in a range of lengths, and none of that is on the website. Give us a ring on (08) 8536 4333 to check what is on the stand.

The rest of the garden range is on the website, and there is more again in the garden centre.

More from the garden

• Growing heirloom tomatoes, and when to sow them
• Fruit fly, and what to actually do about it here
• The native bees your tomatoes need

Still learning, still growing four cherry tomato plants because I cannot be trusted with fewer. Candeece.

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