One way to get them interested in the garden is to grow something that is prolific and let them sell it at a little roadside stand. It doesn't have to be a big one and it would still work if they did it only on the weekends, but people are suckers for buying fresh veggies from youngsters. If you have chickens, add fresh eggs to the mix and they are golden....teenage boys love making a little pocket change as they always need it.
Things that grow well for just about anyone, can be trellised to fit into small areas and produce enough to sell in little baskets are cherry tomatoes, yellow squash, cukes, runner beans. All of those do well whether you use cheap dollar store seeds or not. Then they can grow some low growing crops at the foot of these trellised items~onions, carrots, lettuce, spinach, radishes, and beets.
I'd show them how presentation is everything...all veggies prewashed and neatly packaged, arranged in an attractive manner. If you have a spare strip of ground on which you could grow some zinnias, these make great cut flowers to add to the roadside array. They are sinfully easy to grow, the seed is cheap and you can save seed on those easily for the next year. They are bright and beautiful...always a big seller at weekend farmer's markets.
You have only to look at Pinterest for pics of cute ideas for small roadside stands/displays and then have the boys scavenge for pallets in order to construct it. People LOVE quaint things like that. They like it crisp and clean looking, with little baskets they can carry away....you can find all manner of small baskets at Good Will for $.50-$1 and you can charge more for the basket of produce because of it. Yard sales are an even better place for small baskets...can often get them for 10-25 cents each.
Come fall I'd place an ad in the locals about young teens wanting any free apples available...you'd be surprised as the number of people who have apple trees in their yards and feel the fruit falling each fall is a nuisance, especially when they mow. Have them go pick and offer these apples at the roadside stand as well.
Another thing that will sell and you'd be surprised...little bags of composted chicken poo. City folks will buy anything and they love that stuff for their flower gardens but don't have a source. I've traded a bag of chicken compost for a fall crop of oak leaves, neatly bagged,mulched and waiting for me to haul them away~90 bags of it. Use your chicken feed bags to bag it up and it's even more quaint for them and costs you zip, zilch, nada. Sew the top of the bags closed with some jute twine and put a cute tag on it. People will tell their friends about it.
You could even have some homemade lemonade at the stand...cheap to make, easy to sell. If you sell eggs there, don't forget to have a few framed pics of the prettiest hens you have sitting over that part of the display...have names on the frames.
Teach them how to market their wares effectively, talking about the organic produce , fresh eggs and natural fertilizer, etc. It can all be a fun project for them if done right. Don't forget the small American flag hanging off the stand.
People are hungry for a small slice of Americana out there.
Don't know if 4-H still has this, but when my son was in it, he was able to get a $500 agricultural loan to start a small business for his 4-H project. He started his own lawn mowing business....bought an old John Deere and utility wagon with his money, made a great deal of money, paid back that loan and even helped me get the family car fixed with some of his wages. He was 14 that summer.
