Onions and potatoes…not only do they taste great together – they grow great together! A few weeks ago, we planted our onions (yellow 1015, otherwise known as Texas Sweet) and potatoes (red LaSoda) in one of our raised beds. We planted the onions from seedlings, and prepared seed potatoes.
To prepare the potatoes, they were quartered – making sure there were a couple of eyes in each section, dipped in sulfur powder (you may know it as the stuff you sprinkle on yourself to keep chiggers at bay), and then left in a cool, dry, dark place to callous over. By callousing over the cut parts of the potatoes, excess moisture evaporates and the chance of mold growing underground where the potato was cut is reduced. Usually, 7-10 days is sufficient for callousing.
Since the onions didn’t require any special work, they got planted a couple of weeks earlier, at the top of two rows we’d made in the bed. They were planted about an inch deep, and roughly four inches apart from one another. These are bulb onions, so we wanted to make sure there’d be plenty of room for them to grow nice and big. The potatoes, once they were ready, got planted in the furrow made between the two rows of onions, cut side down (eyes up), about four inches deep and roughly six inches apart. Six inches may seem a little close, but our goal was to plant all our sets, and that’s how the spacing worked out in our raised bed.
So why plant these two together? It goes like this: as the onion grows, to help facilitate bulb production, we’ll start removing some of the soil off of the tops of the bulbs. Meanwhile, the potato plant grows upwards, but the potato is formed off of the part of the stem that is underground. So as the potato grows upwards, we’ll use the soil we’re removing off of the onion to help bury the potato plant stem so there’s more stem to swell into more potatoes! Pretty nifty, eh?
Finally, at the end of the bed we have a boxlike structure made of wood. There, we’re experimenting with growing the potatoes really tall – covering the stems with compost as the plant grows upwards. We’ve planted five potato pieces in there – one in each corner, and one in the middle – and our drip line extends into the box area. As the plants grow up and we add more compost, we’ll lift the drip line (we’ve left a little play in there) so it stays near the top of the soil.
It’ll be a few months before we can harvest the roots and tubers of our labors, but it’s good to keep in mind that if you plant a short-day/spring/sweet onion, it’s not considered a storage onion. If cured properly, it may last a couple of months, but the high sugar content works against long storage. So it’s best to cook ’em up and eat ’em quick!