r ranson wrote:
can the whole system be set up for under ten bucks?
With a little creativity, yes. Cover the outside of one or more canning jars with foil, paper and tape, or paint. Basically, as long as it holds a decent quantity of water, is opaque or covered to keep the light out so you don’t end up with an algae farm, and has an opening that is it can be made sufficiently narrow to hold the weight of the cup, you’re in business. Make a cup to hold the plant by cutting long, wide slits in a yogurt cup. Growing medium can be some clean, small gravel. Coconut coir works great, too, if you have that somewhere. Or cut up loofa sponges. Light can be supplied through a good window or even just a basic lamp.
So far, cost is $0. Cool.
The one off-premises input you need for hydroponics is nutrient solution. It needs to be specific to hydroponic grows, especially with Kratky—the plant is always in the solution, so an imbalance can kill it. To be under $10, look for small containers of it or split a larger one with someone (or someones). They’re sold in concentrates and it takes very little per container.
The other sticky bit that may incur a cost is starting seeds. Gravel won’t work for that purpose, though it works just fine for the technique that Anne mentioned in restarting from the cut stalk if you have the right type of lettuce. (Iceberg, no, romaine, butter, and “red leaf” or “green leaf” yes.) Coconut coir can
work, but it’s a bit fiddly to keep the seeds from dropping out before they have a chance to germinate. I’ve used rock wool and compressed hydroponic “sponges” successfully, but it doesn’t fit into the under-$10 category unless you split a package with someone. There are other materials that will work with seeds, and perhaps someone else can comment on those.
I currently do lettuce in a second-hand Aerogarden I picked up from someone on Facebook Marketplace for $20. Bought a liter of nutrient solution a few years ago and I’ve used maybe a quarter of it. This system works really well for me.