QUESTION: How do you know when to harvest onions? Is there a general rule I can follow or can you determine by the onion tops? -Gerald S
ANSWER: As you near the three month mark, look for changes in growth or appearance on the visible tops of your onion plants. These changes will indicate that your onions are nearing maturity. Pull up an onion when you think that it is ripe to get an idea of the size of your onion bulbs.
Look for a diameter of three to five inches depending on the variety and the size of that variety’s mature bulbs. If the one you pulled up isn’t large enough, leave all of the rest of the crop in the ground to grow longer. If the one you pulled up meets the size estimations, check the rest of your crop for other signs of ripeness.
Gently squeeze the plant about two to three inches above the bulb to check for a soft spot on the top. If there is a soft spot, it is a sign that the bulb is finished growing even if the tops look like they are still growing. Pull any onions that have the soft area on the top and leave any that don’t so that they reach full maturity before harvesting.
If you don’t feel the soft spot on the plants, watch for the tops of the onions to get weak and flop over. According to the National Gardening Association, around 80 to 90 percent of the crop will have bent tops once the entire crop is ready to harvest.
Grow your onions for up to two more weeks after the tops begin dying to ensure maximum maturity. However, if there is a heavy rain in the forecast, go ahead and pull up the onions before two weeks as the rain can damage mature onion crops. Learn more about harvesting onions.