Thursday, April 7, 2022

Learning from potato onions

Daffodils in peak bloom

In the last post, I discussed the two different conversations I’m having with potato onions during this growing season. In one of the conversations I’ve asked the onions to compare survival from spring planting versus autumn planting. I’ve hypothesized that spring planting will result in a higher percentage of plants surviving to harvest and for that reason a higher yield. In the other conversation I’m asking potato onion seeds that Lisa Brunette’s plants produced last year to teach me how to grow them. Both the onions and the seeds have made a first response to my questions.


On November 10 of last year I planted seven rows of 1.5 to 2 inch diameter potato onion and four rows of three different varieties of garlic, mulching all of them with fallen maple leaves. In early March I removed most of the mulch, because I have found from previous experience that if I do not remove most of the mulch then, most of the onions die. As best as I can tell, death results either from rotting before sprouting, or from the leaves of sprouted onions failing to grow above the mulch layer before the energy of the bulb is spent. If I do not mulch after planting in autumn, most of the onions die over the winter from frost-heaving (being pushed above the surface of the soil). Frost-heaving is the bane of lower Midwest winters. Highly variable temperatures during winter cause the soil to freeze and then thaw multiple times before the final thaw in early spring. The mulch keeps the onions from frost-heaving, but it can also cause them to rot through excessive moisture or prevent the leaves from emerging before the energy of the bulbs is spent.


The photo above is the potato onion bed on April 5. The onions I planted on March 6 are closest to the camera and are not mulched. Farther back, in the mulched area, are the potato onions and garlic that I planted last November. While it is not obvious in the photo due to the camera angle, it is clear from looking at the bed that almost every onion I planted in spring is growing well. However, a substantial number of the autumn-planted onions have failed to produce any leaves as of today. Because I know how many rows I planted in autumn and in spring, and I know I planted 8 onions in each row, I know how many onions have so far failed to produce leaves. In the area planted in November, 14 out of 56 onions planted have failed to produce leaves (25%), while in the area planted in March, 4 out of 128 onions planted have failed to produce leaves (3%).



Meanwhile, on March 3 I planted the potato onion seeds that Lisa Brunette gave me. You can see the seedlings that have resulted in the photo above. They are the long thin leaves on the left side of the flat. Later this month I will transplant them into one of the garden beds so they can grow on. I didn’t plant all of the seeds in case something went wrong; the remainder are being kept in the freezer for planting next spring.



Lastly, the photo above shows the flats of seedlings that I will plant in the garden over the next several weeks.


Until next time, enjoy life!


  1. Hi Claire,

    Onions are something of a mystery! The other mystery is why would the daffodil bulbs survive the winter months whilst the onion bulbs do not. I've changed tack in relation to onions and am instead planting the weed-like leeks and chives instead, plus some walking onions. The idea for growing leeks instead of onions came from the writings of Steve Solomon, who you put me onto.

    Onions from what I gather are very site specific and your results surpass my own efforts, although bizarrely some onion bulbs which began producing (is it scapes?) were planted randomly and they seem to be doing OK. There's an old saying about a person: Knowing their onions.

    The other day I came across a reference to potato onions in the local gardening club seed catalogue, and they're related to shallots. Who knew?



  2. Hi Chris,

    Potato onions aren't the easiest crop I grow ;-). The bulbs aren't nearby as hardy as daffodil bulbs, which have no trouble surviving the worst our winters throw at them. No, onions only want a bit of cold, preferably not so much as to freeze the soil. They really, really, really hate our freeze-thaw-freeze-thaw cycles. Nothing kills them faster than that.

    In September I'll have an update on the potato onion conversations. Short form: planting them in early March rather than November worked great. The seed-grown bulbs continued growing until hot weather and the summer solstice arrived. Then they stopped growing. I've left them in the ground, thinking they might revive as autumn approaches and temperatures cool down. A few may have rotted, but most of the bulbs are still firm. Are they alive? I hope so.