I’m really enjoying experimenting with re-sprouting vegetables from kitchen waste!
Just as celery bases and carrot tops can be cut specially and then planted to regrow without the need for seeds or seedlings (see my March 6, 2018 post), the same can be done with cabbages and root onions. Simply cut a core out of the root end of each vegetable, as shown in the first image above, and then set the cabbage cores out on offset spacing centers (see How to Grow More Vegetables… for full details on offset plant spacing).
The onions can then be planted separately on 4-inch spacing centers or interplanted among the cabbages on offset centers as shown in the second photo (cabbage cores are circled in orange). The photo shows the cores set out on top of the soil, so you can see the spacing, but in reality, you’d want to dig a little hole for each core, and then cover everything with an inch or so of soil so that the sprouts will be protected as they start to grow. If you interplant onions with cabbages, consider 6”-spacing with 12”-center spaced cabbages (shown here), 7.5” with 15”- center spaced cabbages, and 9” with 18”- center spaced cabbages.
One of my favorite cabbages is the Greyhound variety (so called because it looks like a greyhound’s ear) because it grows so rapidly! It is planted on 12-inch offset centers and only takes about 2 months to mature—much less than the 90- and 120-day maturing varieties (which go on 15- and 18-inch offset centers respectively). Each Greyhound cabbage is smaller, but the yield per day per unit of area is about the same as for the larger varieties, as many more cabbages can be planted in a given area and take much less time to produce.
For the highest root onion yields per unit of area/time, consider the Walla Walla variety. It’s delicious and sweet, and for us, its yields have tendency to double, plus it does not make your eyes water when you are slicing it! Also in the higher yield category is the Red Torpedo Onion. The roots are the same diameter as regular onions, but can be up to twice as long.