The Q&A Archives: Onions Won't Grow

Question: For two years now, I have attempted to plant red onions in my garden. Last year, they popped up their heads and were very small. This year, we planted them deeper, lots of little bulbs on the one I checked, but still small and don't seem to be producing. My radishes also rotted in the ground. Any ideas what to do to succeed?

Answer: Onions are easy to grow. They perform best in well-drained, slightly acidic, fertile soils in full sun. Heavy soils can be improved by incorporating organic, such as compost or peat, into the soil. Onions require higher fertility levels than most other vegetables. Apply 1 to 1 1/2 pounds of an all-purpose garden fertilizer, such as 10-10-10, per 100 square feet prior to tilling. Four to five weeks after planting, sidedress with additional fertilizer. Sprinkle 1 pound of an all-purpose garden fertilizer per 100 feet of row. Place the fertilizer in a narrow band about 2 to 3 inches from the base of the onion plants.

An important aspect of onion development is photoperiod or day length. Photoperiod, along with temperature, control bulb formation. The cool temperatures and short days of early spring promote leaf and root growth. Bulb formation begins when a certain day length is reached. Short-day onion varieties begin to form bulbs when they receive 11 or 12 hours of daylight, intermediate-day onions need 12 to 14 hours of daylight, and long-day varieties require 14 or more hours of daylight. Long-day varieties are the best choice for gardeners in the upper midwest. Short-day varieties will begin to bulb when the plants are small and not produce large bulbs. Next time you purchase onion sets, make sure you purchase long-day varieties and you should have a better harvest. Onions are typically planted in mid-April and harvested about Labor Day in your gardening region.

Radishes grow best in the cool temperatures of spring and fall. You can plant seeds in early September and they will develop nicely for you. Plant seeds in April and they will mature before hot weather arrives.

Best wishes with your garden!

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