Urban gardeners have plenty of things to worry about, not the least of which are pests, sunlight, soil and access to supplies. There's one complaint that trumps them all, though, and that's space. Unlike our rural counterparts we can never seem to find enough space for all the things we'd love to grow and eat. Over the past couple of years, I've spent plenty of time thinking about the space problem and trying to find ways around it. I've grown pumpkins up the side of an unknowing neighbor's house, I've cut the bottoms out of 2-gallon containers and stacked them on top of each other (3 high) to grow asparagus in a container that could travel from apartment to apartment with me, I've packed fire escape stairs with planters (not recommended by the Fire Dept) and so on. However, one of my most clever uses of space has got to be the potato bag. Potatoes need long, stems in order to produce an abundant crop. The longer the stems are allowed to grow, the larger your crop. On farms, potatoes are grown in great hills which get piled higher as the season progresses. My grandmother put tubers in the ground and piled straw on top as they grew until she had what I imagine must have been enormous mounds of straw with potatoes hidden underneath. The trouble with hills is that the base is always wider than the top, taking up much more space than an average urban gardener can sacrifice for the joy of digging up your own potatoes. I'd read all kinds of solutions to this issue - Pam Pierce of Golden Gate Gardening suggested constructing a tower made of chicken wire and planting the potatoes up in layers with straw to allow the stems to grow out the sides. I'll probably still try this idea some day, but in the meantime I needed a quick, tidy fix that didn't require wire cutters. As with most problems, the solution came to me over a cup of coffee. I was sitting in my local coffeeshop (which, if you're ever in San Leandro, you should stop by! Zocalo is the best!) sipping on a fresh coffee and watching the staff roast beans. I happened to notice that they had mountains of burlap coffee bags that the fresh beans come in. A quick inquiry later and I had a deal for trading some of my hypothetical potato bounty for some used bags. When they don't give them to me, they donate the bags for school potato sack races, so I've been careful not to take more than I need!
Here's how it works:
- Roll down the sides of a tall bag like burlap coffee bag or used feed bag until it's only about 12 inches high.
- Choose your location carefully. You want full sun and preferably soil under the bag. Because the bottom of the bag will eventually rot out, you want to make sure to place it where it will stay until harvest.
- Add six to eight inches of soil into the bottom of the bag and bury the seed tubers in soil, making sure they're completely covered.
- Water every few days, making sure the soil stays moist but not wet.
- After a couple of weeks, the green stems will start to peek out of the soil. Once they're about six inches high, add more soil and/or compost, leaves, etc to cover all but the top set of leaves. The stems will continue to grow.
- As the soil line gets higher, unroll the bag to match it.
- Continue adding soil and mulch up to about two feet, then add whatever you have on hand to hold the bag up. Straw and dead leaves work well, as do pine needles.
For new (small) potatoes harvest two weeks after flowering. For larger potatoes, harvest two weeks after the entire plant dies off. By now, the bottom will probably be rotted out of your bag and you can just tip it over and harvest the little tubers from teh bottom of the bag! Inside the bag you'll find more redworms (and possibly slug) than you ever thought possible as well as some beautiful soil full of black gold (aka worm poo). Because rotation is always a good idea, I use that soil and straw to plant my tomatoes in and mulch my tomato patch. Your tomatoes will thank you for this little big of urban compost. In the Bay Area, you can plant potatoes from February to August and it's a good idea to succession plant your potatoes every 4-6 weeks, allowing you to harvest almost year round. This year I tried pushing my luck and planting some potatoes in January and they grew, but they stayed quite tiny and there weren't very many of them. I don't recommend trying it! Also, be sure to only plant seed potatoes that were grown for the purpose of planting. Your run-of-the-mill grocery store potatoes may harbor diseases that can enter your soil.
There's still time left to plant some potatoes so get off your tush and get yours in the garden, on the patio, roof or fire escape today! (email me if you have trouble finding seed potatoes - this is a tough time of year to find them, but I have a few left - firstname.lastname@example.org) Happy planting!