How to grow green onions, potatoes from grocery store at home

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Red ripe tomatoes, juicy pineapple and tongue-scorching peppers — the produce aisle at the grocery store is full of possibilities for cooking a great meal, but it can also be a great starting point for a prolific garden.

There are many types of produce on store shelves that can be turned into thriving garden plants through seed saving and propagation, which can help to stretch a grocery bill and make for a fun experiment.

Lauri Kranz, an urban farmer, garden builder and co-owner of L.A. Homefarm — a Glassell Park market featuring produce from local farms — loves growing things from seeds of produce she bought at markets. She enjoys the exponential growth factor of this kind of gardening.

“You can get so much food from the one seed, the one potato,” she said. “I love that.”

Kenneth Sparks, a.k.a. Farmer Ken, an urban farmer and garden trainer who sells his produce at Los Angeles County markets, says it doesn’t take a lot of effort to grow things from grocery store produce, but he said it’s important that gardeners go into the process with a little bit of knowledge. He recommends they research the best times of year to plant certain vegetables and fruits and that they look into their USDA Zone and Sunset Climate Zone to know what to expect from their Los Angeles County microclimate.

Kranz said the supplies you will need will vary depending on what you are growing, but recommends having some organic soil and terracotta pots in a range of sizes on hand for planting and transplanting.

Here’s a look at some great grocery store options.

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Potatoes

Potatoes are among some of the easiest plants to grow from the grocery store and in some cases, a single potato can be converted into multiple plants. Sparks says the key is to look for the eyes on the potato, or those little groovy knobs where a potato sprouts. The potato can be cut into chunks, but each chunk should contain at least one eye for it to develop into a potato plant. Sparks recommends putting the cut segments into something like a grow bag, which is a large, rounded fabric container, but said potatoes can be grown in pots provided those pots are at least a foot deep (though 18 inches or deeper is preferable). The deeper the container, the better the likelihood of getting lots of well-developed potatoes, Sparks said. He said potatoes should also be planted at least a foot apart.

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Sweet potatoes

Sweet potatoes at the grocery store can sometimes be sprayed with a substance that inhibits the sweet potatoes from sprouting. (Potatoes may also be sprayed, but even so just leaving them out on the counter over time can make them sprout eyes.) Sparks said washing the sweet potatoes should be enough to get the spray off, but another option is to purchase an organic sweet potato. He submerges a portion of his sweet potatoes in a jar of water and watches for them to develop growths, also known as slips. Unlike the potato, a sweet potato is closely related to the morning glory, so its growths are more vine-like and will develop sets of roots that will grow down into the jar of water. At this point, Sparks plucks each of the rooted slips off the sweet potato and plants them about a foot apart from one another in dirt that’s at least a foot deep. Each slip has the potential to produce multiple tubers. Because sweet potatoes have a vining habit, Sparks says they can be trellised to be less messy.

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Green onions

Green onions – which are perennials in Southern California’s climate – are a great choice because of their staying power in the garden, Sparks said. He said gardeners can buy a pack of green onions from the store and use the green vegetative growth for cooking before planting just the bulbs. Some online tutorials recommend soaking the green onions in water prior to planting, but Sparks said he just sticks them directly in the ground. After a period of watering, the bulbs will sprout new green growth and gardeners can have green onions all year round – and beyond. Sparks said he has had some green onions that he has been growing since 2021 that have continued to produce and gotten thicker with time. Eventually, the green onions will form blooms at the top of their stalks which will produce seeds that can be sprinkled elsewhere for even more green onions.

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Peppers

The seeds of grocery store peppers can be extracted and then planted following a drying process, according to Kranz. She says she lets the peppers sit at room temperature on a piece of parchment paper, turning them occasionally over a period of weeks. When the peppers are ready, their skin will become almost leathery and wrinkled. At that point, Kranz takes a piece of paper and simply breaks the peppers apart with her hands, allowing the seeds to spill out over the paper. Kranz says she doesn’t use any protective gear during this process but people who are working with spicy peppers may want to wear a pair of latex surgical gloves, particularly if they’re going to touch their eyes later to remove contacts. It can take anywhere from 6-12 weeks for peppers to dry fully, she said, with smaller peppers drying faster than larger ones.

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Papaya

Papaya, with its many seeds, is a great choice for home growing because unlike some other large fruit producing plants and trees, it won’t take a long time to get fruit. Sparks said it’s possible to get papaya from a plant grown from seed in less than a year’s time. He scoops out the seeds from inside the fruit, washes off the gelatinous encasing around the seeds and then plants about 20 seeds in recycled containers, like the rectangular plastic containers that baked goods are sold in. He doesn’t worry about spacing. When the plants are 4 to 5 inches tall, he separates them into groups of three in quart size containers. This is because papayas can produce either male flowers, female flowers or hermaphrodite flowers that have characteristics of both. Planting them in groups ensures greater likelihood of pollination and fruiting. When the plants get to be between 8 inches and a foot tall, he puts the groupings directly in the ground in well-draining soil. Papaya is frost sensitive and doesn’t like extended periods of wet and soggy conditions that are common during California’s wintertime either. If protected from these conditions, a papaya will produce fruit for up to 10 years, according to Sparks.

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Tomatoes

Some people mistakenly believe that seeds of grocery store tomatoes will be sterile, but tomatoes grow from grocery store produce easily. Some tomatoes are hybrids, or the result of a cross between two parent varieties. Plants grown from a hybrid tomato may not produce fruit exactly like what was purchased at the grocery store, in my experience. However, seeds extracted from an open pollinated variety — a tomato variety that’s been stabilized over successive generations to produce identical fruit to its mother plant — is a good choice. Kranz said she generally saves seeds from open pollinated and heirloom varieties (all heirloom tomatoes are open pollinated) and hasn’t had any issues. Many gardeners scoop out the seeds of the tomato and let them sit in water for about 3-4 days until the seeds sink to the bottom of the jar — part of a process called wet extraction — before straining them, washing them off and letting them dry for at least a couple weeks. Kranz said she has gone a simpler route of immediately spreading the seeds out over paper towels to dry for a few weeks.

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Garlic

Garlic can be grown from grocery store bulbs by breaking apart the individual cloves within the bulb and planting them with the pointed side up and the wider root side down. Sparks said that because garlic has a long growing season, it’s usually best to plant it in the fall. Garlic bulbs do need a period of cold in order to grow properly, but that can be artificially induced by throwing the bulbs in the fridge for a few weeks prior to planting. Sparks said if possible, it’s best to find a variety that does well in California — he personally likes California White Garlic — and that given the choice between a hardneck or softneck variety of garlic, it’s generally better to choose a softneck variety because it will perform better in an L.A. climate. Softneck is often what grocery stores carry anyway, but you can tell the difference between the two types in the bulbs themselves. Hardneck garlic has bigger, more uniform cloves and a thicker skin that is easier to peel, whereas softneck has a larger number of smaller cloves with a papery skin that’s hard to peel.

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Pineapple

The tops of pineapples can become pineapple plants of their own if given the right amount of water and protected from frost. Sparks said he cuts the top of the pineapple off just below the crown and pulls off some of the lower blades of the fruit’s green growth.

Some online tutorials recommend soaking the pineapple top in water for rooting, but Sparks instead lets the top sit on his counter for about a day before placing it directly in a soil medium and watering every two to three days. How much water depends on a variety of factors, including temperatures at time of planting, soil and watering systems, but Sparks said something like half of a 2-gallon watering can at each watering time could be sufficient. He said that if people check the soil, and it’s dry in the first 2-3 inches, it’s time to water.

Pineapple plants should be covered in times of frost.

“Keep in mind that it’s going to take two to three years before you get a pineapple off of it,” Sparks said. “They’re slow growing, and in our climate they’re even slower, but it can be done.”