If you planted long-day onions this spring, you will notice that they are forming bulbs. If you accidentally planted short-day onions, you will be feasting on onion tails for the rest of summer. Right now, both long-day onions such as Copra and First Edition and day-neutral onions like Candy are producing nice large bulbs. You can start harvesting them now, but since they are not mature, they won’t store well. Harvest only what you can eat.
In the Garden this Week
Conquer Powdery Mildew
By mid July, I’ll be getting calls on how to control powdery mildew on lilacs. It appears as a fussy white residue on the surface of leaves and is a severe problem in southern Maryland. Powdery mildew also attacks other popular landscape plants including roses, zinnias, phlox and more.
I’ve heard it said that to make onions set bulbs, you must bend the tails in half. Not true. Long-day onions form bulbs naturally as the daylight hours grow longer; then the bulbs mature as daylight hours grow shorter.
Bending or breaking onion tails is a commercial practice to control bulb size. The ideal onion size for consumers is between one-and-one-half and two inches in diameter. To satisfy size demand, commercial onion growers suspend a wooden timber or piece of pipe beneath the tractor and straddle the onion beds, causing the timber or pipe to sharply bend the onion tails, which slows the growth of the bulbs. Timing is critical, when most of the bulbs are approximately one-and-one-half inches in diameter. If done too early, most of the bulbs will be undersized
For proper storage, onions should be allowed to mature in the ground. The onion bulb is mature when the onion tails turn yellow and begin to dry at the tips. By this time the tunic — the papery skin covering the outside of the bulb — has formed. When harvesting, take care not to damage or remove the tunic, which minimizes the loss of moisture from the bulb, thus improving storage.
I generally spread the onion bulbs on the floor of the garage and allow them to dry for a couple of weeks before putting them in mesh bags suspended for maximum airflow. Onion bulbs are best kept cool and dry.