Planting Potatoes in the Greenhouse


red seed potato with roots

At the farm where I work we have a small, unheated greenhouse. Just as last season ended, I decided to try to use compost to heat the greenhouse just a little - just enough to help along the greens and herbs that were overwintering there. 

The greenhouse has three rows: two rows of soil along the outer edges, and a gravel path in the middle. The row on the left I reserved for the compost, and the row on the right held the plants. Every time I visited the farm over the off-season, I piled a little more manure and hay on the greenhouse compost pile. This should be about the time in this post where I tell you that it was a grand success and post a screenshot of my amazingly detailed spreadsheet of manure application and temperature readings. Butttt... I didn't make a spreadsheet or take temperature readings. Since this was a sort of last minute plan, and nothing hinged on its success or failure (the greens would have grown, albeit more slowly, anyway, and we don't have any scheduled groups touring the garden in the winter months), I didn't record any data. But, I will tell you that the spinach is getting really big, so big that I may just harvest it instead of transplanting it outside in the next week or so. The fennel and cilantro show no signs of being worse for wear. The mache only has the tiniest touch of frostbite.The dill seeds I sprinkled on the soil over the winter are now transplant-sized seedlings. And, here's where I get to the point: the potatoes I planted in this big pile of poo are beginning to root.

Where to Find Seed Potatoes

Normally, you plant potatoes in the spring after any danger of frost has passed and the ground has warmed a little. If you have a farmer's market near you, you might check with some of the vendors - they often sell seed potatoes in the spring. Another option is just using the bag of potatoes that's sitting on your counter sprouting eyes. Guess which option I used? 

Readying Potatoes for Planting

You can plant an entire potato, but you'll get a lot more potatoes if you cut them up into pieces about 1" square. Whether you're using seed potatoes or the sprouted ones from your pantry, you should be able to see the eyes. Try to cut your potatoes so each piece has one or two eyes on it. This is a task to do just before you plant - try not to wait more than a day between cutting your potatoes and planting them. 

How to Plant

Each piece of potato you plant will grow new potatoes. For every one pound of potatoes you plant, you can expect to harvest five pounds. You probably already know that potatoes grow underground. So, they need some space and some soil to grow in. Some people plant their potatoes in a hill, mounding dirt on top. Others dig a ditch and plant in rows. Some layer leaf mulch, potato pieces, and soil until they've run out of potato pieces to plant.

My Method

I like the hill method myself, and used that last year in one of the farm's raised beds. This year, in the greenhouse, I layered manure with potatoes until I had a well-insulated pile of manure-y compost that would break down and keep the potatoes just warm enough until it was time to grow. This isn't something to worry about if you're planting in the spring - your potatoes will just keep on chugging along underground for 80-ish days until one day you poke your spade into the dirt and pull out a fully grown potato! I was taking a chance planting them over the winter, but I was confident that as the manure broke down, the heat from that process would help keep the potatoes from freezing.

I've been watering the potato/compost pile frequently, and today I decided to check on their progress. I carefully sifted through the top layers of hay and compost and came up the glorious sight pictured above - a potato piece WITH ROOTS. I have had a garden and/or worked on a farm for years and years, and I am always so happy to see little seedlings pop up, or the healthy white roots on seedlings when I transplant them. I know these things will grow, but it's still so awesome to watch it happen. And, now I know - a little insulation via the greenhouse and compost is enough to help these potatoes get an early start. An early start means I'll get to eat fresh from the dirt potatoes a couple months earlier than I normally would (and I'll be planting an outside batch, too, in May).

Normally I tell new gardeners to plant either what they use the most (like herbs, tomatoes, greens) or what is most expensive to buy at the store and will save them money if they grow it at home. Potatoes are inexpensive, but the flavor from potatoes you grow versus the ones available at the grocery is night and day. Normally, for me, potatoes are a vehicle for sour cream and butter. They don't have much of a flavor. Home-grown potatoes are DELICIOUS. They are absolutely worth growing if you have the time and space. Plus, they're fun to dig up. It's like a little treasure hunt. That you get to eat. 

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