For many gardeners, growing plants from seeds and cuttings becomes something of an obsession. Not only do you have the joy of nurturing tiny plants, but there's the challenge aspect of it all - can I get this to grow in my garden? And as most of us have to garden on a budget, it becomes natural to view the grocery store as a source of unusual planting material.
I have been growing plants from kitchen groceries for a number of years now. The first thing I tried was dragon fruit - a truly tropical plant that would never survive outside in my climate. The dragon fruit is an unusual plant to grow from groceries, because it is a cactus. The fruits have an enormous number of seeds inside, distributed throughout the flesh. Separating them out isn't hard, but it's a slow process if you try and save them all. I found that nearly all of the seeds germinated after I cleaned them and sowed them in a little bit of potting compost, so you'll have plenty of seeds to share with friends. Dragon fruit cacti are quite slow growing, and prickly, but they have an attractive trailing habit. I suspect it will be many years before they get large enough to fruit, but in the meantime they make an attractive (and easily cared for) houseplant.
Another fruit that I've had lots of success with is lemons. Store bought lemons tend to have quite a number of pips, and if you rinse them off and plant them in compost then they have a very good germination rate - although you will have to be patient as they can take up to two months to begin growing. Citrus plants make very good houseplants, with their attractive glossy leaves. When they flower, they have a very attractive scent and are very beautiful. After a few years your plant should be old enough to fruit. Most lemon plants will grow fruit that are perfectly edible. Some other citrus plants grown from seed (such as oranges) may produce fruit that is not very nice to eat, but you can't tell until they start fruiting. You may find that a home grown lemon bush is spinier than a named variety from the garden centre, but if you grow several seedlings you can keep the ones that you like best.
A fun project for children is to grow their own peanut plant. You can plant peanuts from the grocery store, but you have to buy the ones that are still in their shells - once the nuts have been cracked the seeds quickly dry out and will not germinate. Shell the nuts before you plant them, though, or germination will be patchy. Peanut seeds are easy to plant - push them quite deeply into the compost with your finger. They need a much larger pot than you would imagine, because they have a special trick up their sleeve. The peanut will grow into an attractive little plant, and in due course it will produce beautiful yellow flowers. But after that it does something very unusual - the stems bend down to plant themselves in the compost, and the new peanuts form under the soil. When the plant dies back at the end of the season you can tip it out of the container and search for the new peanuts in the compost!
Kids will also enjoy watching an avocado stone grow. The traditional way of starting an avocado stone is to suspend it over a jar of water, so that it's base is kept wet. If you keep it warm enough then the avocado will start to sprout roots into the water. And then after a couple more weeks it will start to spout leaves as well. If you want to, you can plant the sprouted stone in compost and keep it. Your avocado plant won't fruit for you, but they make nice houseplants. They need to be kept pruned because - given the chance - they try and grow into a very large tree. You can also start an avocado stone by planting it directly into compost. Again, if you keep it warm then it will probably grow, but it will be longer before you see any growth if you can't see the roots.
If you want to grow a free houseplant that will reliably produce edible fruit then save the seeds from a store-bought pepper (sweet or chilli). They're easy enough to start into growth early in the year, and provided they get enough light will grow into bushy plants that are happy on a windowsill in a container. They have pretty white flowers that are self-pollinating, and will be followed by fruit. All peppers are ornamental plants, with fruits that start off one colour and change to another. Chillies are especially pretty because they have lots of small fruits growing at the same time. You may find that the fruits your plants grow aren't like the one you saved the seeds from, because many commercially grown peppers are hybrids and don't have seeds that grow true. But the fruits will be edible, and you might find that you've grown a very nice pepper. Save the seeds from it, and the chances are much better that next year your plants will be the same.
These are just a few of the plants I have enjoyed growing. Once you start to grow your own houseplants from kitchen groceries, you will discover that the possibilities are almost endless. There's a large array of plants from around the world that will happily grow from pips, stones and seeds. Some of them will even bear edible fruit for you. But even the ones that don't will be exciting, unusual and attractive and will amply reward you for your time and effort.