Planting Potatoes Early Under Cover in a Compost Bin (3/26 – Zone 5)


This year I’m going to try something a little bit different. I’m going to start some of our potatoes early under cover in this compost bin. With any luck, we’ll be harvesting potatoes in late May or early June. As a general rule, you can start potatoes outside about 3 weeks before the last frost, but you can start earlier under cover. Today I’ll be starting some of our potatoes 5 weeks before the last frost. Though this will be the first time we’ve started potatoes early under cover, Eliot Coleman starts his in an unheated greenhouse in mid-March on his zone 5 farm. And he covers the plants with 1 or 2 layers of row cover, as needed, to protect them from freezing temperatures. Given Eliot’s precedent, I feel comfortable starting some of our potatoes under cover in late March in our zone 5 garden, especially when I see that only a handful of nights in our extended forecast dip below freezing. We’ll be growing most of our potatoes in raised beds and containers, but I decided to grow some in this bin simply to make the best use of our growing space. This compost won’t be ready for months so I thought it made sense to use this space for multiple functions – making compost and growing potatoes. But before planting, I needed to make sure the compost bin was a suitable enviroment for planting potatoes. So, last weekend I did 3 things: first, I made sure the compost was no longer cooking. The optimal soil temperature range for growing potatoes is 60 to 65 degrees Fahrenheit, or 16 to 18 degrees Celsius. So, at 60 degrees, this compost is in the optimal range. Tuber formation is inhibited at temps above 80 degrees Fahrenheit (or 27 celcius), so I wouldn’t plant potatoes here if the compost was still hot. Second, I set up these 2 hoops to support the plastic cover. I used 2 pieces of 1/2 inch PVC and I attached them together here with a U Bolt. Potatoes can be started outside 3 weeks before the last frost without protection. But I’m starting them 2 weeks earlier than that, so I’ll cover the bed with plastic in order to warm the soil, encourage early growth, and protect the potatoes from the cold. Once the plants emerge, I’ll also add row covers as needed to protect the plants from freezing. I’ll remove all protection when there’s no longer a threat of freezing temperatures. Finally, potatoes like well drained soil and this mucky compost was far from it. So, I needed to take measures to ensure there was sufficient drainage around the potatoes. To improve drainage, I spread a 5 gallon bucket of garden soil on top of the compost. I then added half a bucket of sand and mixed it in. Then another bucket of garden soil, and another half bucket of sand. Sand, in particular, will help improve drainage. Finally, I topped it off with a bucket of vermicompost and red wigglers. The vermicompost adds nutrients, beneficial microbes, and plant growth hormones and the worms will turn the organic matter in the bin into worm castings that I’ll use in the garden later in the year. Ordinarily I wouldn’t add all these red wigglers, but I’m eliminating one of my 5 indoor worm bins and this is the best place for the worms. They’ll eat the decaying organic matter but will leave the potatoes alone. Now I’m ready to get started. Today I’m planting Red Norlands and Yukon Golds – 2 early season varieties. The certified seed potatoes I’m using are all pretty small, so I didn’t cut them before planting. If they were much larger than a golf ball, I’d cut them into 1 ½ inchpieces with at least 2 eyes each. I plan to start harvesting the potatoes early when they’re small, so I space them fairly closely – about 8 inches apart, with the side with the most eyes facing up. After laying out all the potatoes, I cover them with a 3 to 4 inches of garden soil, vermicompost. and sand. When the plants are 8 to 12 inches tall, I’ll hill them up with leaves, sand, and vermicompost. I’ll continue to hill them up as they grow until the bin is full. It’s important to keep potatoes thoroughly covered to prevent them from being exposed to the sun, which can result in green spuds that can be poisonous. Though potatoes are considered heavy feeders, all that we plan to do is keep them moderately watered and mulched. In our experience, vermicompost or compost provides more than enough nutrients and no additional fertilizers are needed. If all goes well, we should be harvesting potatoes in late May or early June. Now let’s get this cover back on. Before closing, I thought I’d share our plans for succession planting potatoes. By spreading our plantings out over a number of weeks, we have a longer period of time in which we’re harvesting fresh potatoes from the garden. Two weeks from now I’ll plant potatoes in this bed. By then this plastic may be removed, depending on the weather. And a couple weeks after that, we’ll plant the rest of our seed potatoes in grow bags like this. We find that growing in grow bags is a great way to grow more food in our small garden. And they give us a lot more flexibility as to where we can grow. That’s all the work I’m going to do in the garden today. Next weekend I’ll plant more lettuce, carrots, and turnips, and we’ll also plant Swiss chard for the first time this year. I’ll also decide if it’s time to start removing the covers from the hoop house, low tunnels, and cold frames, and that will all depend on the weather. Well, that’s all for now. Thank you very much for watching, and until next time remember you can change the world one yard at a time.

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