Grow what the supermarket does not sell.

Supermarkets sell what ships, stores and looks the same every week, which is a sliver of what grows. Each spring you can grow a cucumber the size of a grape that looks like a tiny watermelon, a round yellow cucumber, purple and white carrots, a tomato the size of a currant and a purple basil, all from a packet, in gardens right across the country. Most go in after the last frost, though the carrots can start earlier, since they do not mind cooler soil.

The vegetable aisle is not a list of vegetables. It is a list of vegetables that survive a truck, a cold room and a week on a shelf and still look the part. The many other edible plants and varieties beyond that range are left to people with a packet of seed and a spare square metre.

None of the five below is difficult, given suitable conditions and a little care. Each grows much like a common cousin you already know. They are just too small, too odd or too soft for the big supply chains to bother with, which is the best reason we know to grow them at home.

1. The cucamelon: a watermelon the size of a grape

The cucamelon, Melothria scabra, also called mouse melon or Mexican sour gherkin, is a grape-sized fruit striped like a tiny watermelon that tastes of cucumber with a sour, citrus edge. It grows like a cucumber: a fine climbing vine with small yellow flowers that wants a trellis or a wigwam, full sun and regular water.

It is frost tender and wants warm soil to germinate, around 22°C, so it is sown after the last frost once the soil has warmed. In Brisbane, Sydney, Perth and Adelaide that can be a direct sowing from early spring into October. In Melbourne, Canberra and Hobart start a few seeds in a pot indoors in early spring and plant out when the frosts are done. Once away it can crop steadily through summer, usually from about ten to twelve weeks after sowing. Pick the fruit small and firm, eat them whole, drop them in a gin and tonic, or pickle a jar.

2. Lemon cucumber: round, yellow and older than the ones in the shop

Lemon cucumber is an heirloom that grows round and yellow, picked at about the size of a lemon while the skin is still pale, with a mild, clean flavour and a thin skin. It is grown much like any other cucumber, on a trellis, in warm soil, with steady, even moisture. You rarely see one for sale, which is a good part of its charm at home.

3. Carrots in purple and white

Orange is the newcomer. Purple and yellow carrots were grown for centuries before orange became the standard, and the old colours are still in the seed. Cosmic Purple carries a deep purple skin over a bright orange heart, so every slice is a bullseye, and Lunar White is pure white through. Both are sown and grown like any carrot, which means the fine-seed rules apply: sow thinly in a shallow drill, cover with sieved mix and keep the row damp for the two to three weeks it usually takes.

The colours appear at the sink, not in the bed, which makes them the best crop in the garden for children and sceptics.

4. Yellow Currant: the tomato the size of a currant

A currant-type tomato is a rangy, indeterminate plant that sets trusses of six to eight fruit no bigger than a fingernail, sweet and low in acid and in quantities that outrun the bowl. Nothing that small packs or ships, so it stays in home gardens. Grow it like a cherry tomato: in punnets in early spring, out once the soil reads 16°C and the frosts are gone, with a frame to climb.

5. A purple basil, and a red leaf for the summer patch

Purple Fire is a sweet basil with deep purple leaves, used just like the green kind and a striking colour in a salad. Red Garnet amaranth is the other summer colour: a heat-loving plant whose young red leaves are picked as a summer green in the weeks when spinach and lettuce have given up, with dozens of seed heads to follow if you let it run. Both are sown once the nights are mild.

Why the shop does not sell them

Shelf life, shipping, uniformity and yield per hectare. A supermarket vegetable has to look identical every week, travel across the country and sit for days without losing its shape. For the most part these are simply varieties the big chains stock less often, if at all, and some you may still spot from time to time. None of that is a mark against flavour. It is a description of the supply chain, and a packet of seed sits outside it.

A note for every zone

Most of these are warm-season crops sown in spring, and the start date is the main thing that shifts. Carrots are the exception: they are happy in cooler soil, can go in earlier, and in the hottest zones do better as a cooler-season crop.

• Brisbane, Gold Coast, Sunshine Coast: direct-sow most of it once the spring soil is warm. The cucamelon and the amaranth in particular love the heat, and the cucamelon wants really warm soil, about 22°C, to come up well.
• Sydney, Perth, southern WA and Adelaide: sow from early spring into October as the soil warms.
• Melbourne, Canberra, Hobart: start the cucamelon, the tomato and the basil in pots, sow the carrots direct, and plant the tender ones out after the last frost.
• Darwin, Cairns and the tropics: the cucamelon and the amaranth take the heat and humidity; the carrots are a dry-season crop.
• Alice Springs and the inland: after the last frost, with shade cloth on the worst afternoons and steady, even watering.

The What to Sow Now page has the month-by-month chart for your postcode.

Grow it: seeds for this lesson

The seeds behind the five ideas above, most of them well off the shelf. A couple have interstate shipping limits (the Yellow Currant tomato, for one, does not ship to WA), shown on each product page.

Cucamelonlooks like a tiny watermelon, tastes of cucumber and lime.See the seedsCucumber Lemonround, yellow and grown like any cucumber.See the seedsCarrot Cosmic Purplepurple skin, orange heart.See the seedsCarrot Lunar Whitepure white right through.See the seedsTomato Yellow Currantone of the smallest tomatoes in our range and one of the sweetest.See the seedsBasil Purple Firea purple sweet basil for the salad bowl.See the seedsAmaranth Red Garnetred leaves for the summer patch, sown once the nights are mild.See the seeds

Grow one thing each spring that you cannot buy. It changes how the rest of the garden feels: less a cheaper version of the shop, more a place to grow things you cannot easily pick up on the way home, and there is real satisfaction in that. For the rest of the sowing list for your area, our What to Sow Now page covers every zone.

Frequently asked questions

Do cucamelons taste like watermelon?

No. They look like one and taste like a cucumber with a squeeze of lime. The surprise is the point.

Do I need two cucamelon plants to get fruit?

No. Each vine carries both male and female flowers, so a single plant fruits on its own, though two or three on a trellis give a better picking.

Will purple carrots stay purple when cooked?

Boiling can wash some of the colour out of any purple carrot, so raw, roasted whole or lightly steamed keeps the most. Cosmic Purple is known for holding its colour well after cooking.

Are these harder to grow than the ordinary kinds?

No. Each one grows like its common cousin: cucamelon and lemon cucumber like a cucumber, the carrots like carrots, the currant tomato like a cherry tomato, the basil like basil.

Can I grow them in pots?

The cucamelon, the basil and the amaranth are happy in a large pot with a frame for the vine. Carrots want a deep pot of fine mix. The currant tomato is indeterminate, so give it a frame; it does well in a large pot on a patio or in the ground.

When will I pick the first ones?

Once the soil is warm the lemon cucumber crops from about two months after sowing, the cucamelon from about ten to twelve weeks, the currant tomato and basil in between, and the carrots from about ten to thirteen weeks. Cold soil stretches all of it, which is the subject of Lesson 4.