Heirloom tomatoes are the tomatoes your grandparents grew: open-pollinated varieties passed down for generations, grown for flavour rather than for shipping well or looking uniform. They come in strange shapes and colours — ribbed, striped, green when ripe, almost black — and the flavour is the point: rich, sweet, acidic and complex in a way modern supermarket tomatoes rarely manage.
Heirlooms are not the easiest tomatoes to grow. They are mostly indeterminate and vigorous, many are more prone to cracking and disease than modern hybrids, and their fruit can look, frankly, ugly. But for flavour they are unmatched, and because they are open-pollinated you can save seed and grow the same variety next year. This guide covers the extra care heirlooms repay: steady watering, good airflow, honest expectations, and picking at peak flavour.
Heirloom Tomatoes at a glance
| Growing factor | What this crop needs |
|---|---|
| Sun | full sun |
| Soil pH | 6.0–6.8 |
| Days to germination | 7–14 |
| Days to maturity | 70–85 |
| Spacing | 24–36 inches |
| Water needs | high |
| Cold tolerance | tender |
| Family | Solanaceae |
Starting seeds
Heirloom Tomatoes seed is best started indoors. Sow in trays or modules filled with fine seed compost, barely covering the seed, and keep the tray warm and moist — germination takes 7–14 days. Give seedlings as much light as you can once they appear. Our seed-starting calculator can work out your sowing date from your last frost, and the germination-time calculator helps you plan around the 7–14-day germination window.
Because this is a tender crop, timing follows the frost: in Zones 3–6 start indoors and plant out only once frosts are past and the soil has warmed; in Zones 7–9 the warm season is long and a second sowing is often possible; in Zones 10–13, which are frost-free, grow it through the cooler months with afternoon shade in the hottest weather. Check your dates with our frost-date calculator or the last-first frost lookup — and when in doubt, ask your local extension service.
Start heirloom seed indoors, germinating in 7–14 days in warm conditions. Heirloom seed is often saved at home, so germination can be more variable than bought hybrid seed — sow a few extra and thin to the strongest.
Transplanting and planting out
Harden seedlings off for a week before planting out: put them outside for a few hours a day, increasing the time and exposure, and bring them back in at night. Plant out at the final spacing of 24–36 inches apart, in holes the same depth as the pot. Water each plant in well and mulch around (not against) the stems to hold moisture. Our plant-spacing calculator shows how many plants fit your bed at 24–36-inch spacing.
Soil and feeding
Heirloom Tomatoes grows best in soil with a pH of 6.0–6.8, so test your soil before you plant — a cheap test kit tells you more than guessing ever will. Work in plenty of compost or well-rotted manure to improve structure and feed the soil life, and make sure the bed drains freely. Our soil-volume calculator and raised-bed soil calculator work out how much soil or compost your bed needs.
Feed generously through the season: work compost into the bed before planting and side-dress with a balanced fertiliser once plants are growing strongly. Hungry fruiting and leafy crops repay feeding with visibly bigger harvests, but too much nitrogen gives leaf at the expense of fruit, so follow the label. Our fertiliser calculator works out how much to apply.
Heirlooms are heavy feeders, so dig in plenty of compost before planting and feed with a tomato feed once fruit has set. Mulch thickly — heirloom fruit sits close to the ground on sprawling plants, and mulch stops soil splashing onto leaves and fruit.
Watering
This is a thirsty crop. Water deeply and regularly — shallow daily sprinkles encourage shallow roots and stressed plants. Aim to keep the soil evenly moist, especially while fruit is swelling, and mulch thickly to slow evaporation. Water at the base in the morning so leaves dry by evening, which also keeps disease down. Our watering calculator gives a starting point for your bed size and soil, and the watering schedule generator can build a routine around it.
Sunlight and temperature
Give Heirloom Tomatoes full sun — at least six hours of direct sun a day, and more is better in most zones. Sun drives flavour and yield in this crop, and plants in shade stay leggy and unproductive. Our sunlight calculator can check whether your spot gets enough sun.
It is tender, so cold is the enemy: a single frost can finish it. Wait until frosts are past and the soil feels warm before planting out, and keep fleece or cloches handy for a late cold snap. In warm zones it will keep producing until the first cold nights of autumn.
Pests and diseases
The pests and diseases to watch for with Heirloom Tomatoes are aphids, hornworms, flea beetles and whiteflies.
Aphids cluster on tender new growth and under leaves, sucking sap and leaving sticky honeydew.
Hornworms are big green caterpillars that can strip a plant overnight.
Flea beetles chew tiny shot-holes in young leaves.
Whiteflies cloud up from the undersides of leaves when disturbed.
Prevention beats cure: rotate crops so the same family does not grow in the same bed year after year, clear debris at the end of the season, and inspect the undersides of leaves weekly. Our pest identifier helper can help you name a pest from its damage, and the plant-disease checker can narrow down a leaf problem.
Companion plants
Good companions for Heirloom Tomatoes are marigolds, basil, onions and lettuce.
Marigolds are the classic companion: their roots and scent deter several soil pests, and their flowers bring in pollinators and beneficial insects.
Basil is said to improve the flavour of its neighbours and its scent confuses some pests; it also makes good use of the same sunny, well-watered bed.
Onions help mask the scent of their neighbours from pests, and their upright leaves take little light from the plants beside them.
Lettuce is a shallow-rooted, quick crop that fills the gaps between taller plants without competing hard for nutrients.
Plant companions in the same bed rather than in a separate corner — that is how they do their work. Our companion-planting finder can suggest more pairings for your bed.
Harvesting
Heirlooms are ready about 70–85 days after sowing, and picking is a matter of judgement, not colour: many heirlooms are green, striped or dark when ripe, so learn what your variety looks like ripe and pick when the fruit gives slightly to a gentle squeeze. Pick when fully ripe for the best flavour — heirlooms picked under-ripe never develop their full taste. Handle them gently: thin skins bruise easily, and a bruised heirloom rots fast.
Pick every few days and eat or process heirlooms quickly — they do not keep like supermarket tomatoes, and that is the trade-off for flavour. At the end of the season, save seed from your best fruit: scoop the seeds into a jar of water, let them ferment for a few days, rinse and dry them, and you have next year's seed for free. Because heirlooms are open-pollinated, saved seed grows true as long as varieties have not crossed.
Common problems and fixes
| Problem | Likely cause | Fix |
|---|---|---|
| Fruit cracks around the shoulders | uneven watering | Water evenly and mulch; pick fruit just before fully ripe in wet weather. |
| Fruit looks misshapen or lumpy | catfacing from cold weather at flowering | Plant out only when nights are warm; nothing to do once it appears. |
| Dark spots spread on leaves | blight | Remove spotted leaves at once, water at the base, and rotate beds yearly. |
Fruit cracks around the shoulders
Likely cause: uneven watering. Heirlooms crack more than hybrids because their skins are thinner and their growth is less even. The cause is the same: a dry spell followed by a rush of water.
Fruit looks misshapen or lumpy
Likely cause: catfacing from cold weather at flowering. Catfacing — lumpy, scarred fruit with ridges and holes at the blossom end — happens when flowers form in cold weather. It is common on heirlooms and harmless: cut the scarred part away and eat the rest.
Dark spots spread on leaves
Likely cause: blight. Many heirlooms have little blight resistance, so the disease can move fast in wet weather. Remove spotted leaves immediately, water only at the base, mulch to stop soil splash, and give plants generous space.
Frequently asked questions
What makes a tomato an heirloom?
An heirloom is an open-pollinated variety that has been passed down for generations — usually at least 50 years — and grown for flavour rather than uniformity or shelf life. Because they are open-pollinated, you can save the seed and grow the same variety next year, which you cannot do reliably with hybrids.
Are heirloom tomatoes harder to grow?
They can be. Many heirlooms are more prone to cracking and blight than modern hybrids, and their fruit is often oddly shaped.
How long do heirloom tomatoes take to grow?
Heirloom tomatoes take 70–85 days from sowing to maturity. They are mostly indeterminate, so they keep growing and fruiting until frost, with the first ripe fruit arriving in midsummer and production continuing for months.
Can I save seeds from heirloom tomatoes?
Yes — that is one of the best things about heirlooms. Scoop seeds from a ripe fruit into a jar of water, let them ferment for two or three days, rinse and dry them thoroughly, and store in a cool, dry place.