Gardening in Hawaiʻi with Tom Timmons: Getting under the skin of bulb onions

I remember the day I proposed to my wife. It was a beautiful spring day, the birds were singing, and nearby, a happy little stream was chuckling a merry tune. I knelt and slid an engagement ring on her finger. She started crying.

I don’t remember if it was because she was so happy, or because it was a pungent Awahia onion ring that I slipped onto her finger?

I have found onions challenging to grow on Kauaʻi. Don’t tell the Board of Tourism, but we don’t get enough sunlight in Hawaiʻi. The longest day of the year is only 13½ hours.

Many varieties of onions scoff at such short days regardless of how sunny those days may be. Many varieties of onions like those long, summer days found in the cool, northern latitudes. If you mistakenly plant these on Kauaʻi, in all probability you will be disappointed with the outcome.

This doesn’t mean that you can’t grow onions in Hawaiʻi. It is important when purchasing onion seeds to select a short-day variety. This variety produces nicely in the state. Some are ready for harvest in as little as 3 months. 

Onions have their own sun clock. When the magic number of sunlight hours is reached, the onion stops producing green growth and begins to form a bulb. The short-day onions require less than 12 hours of sunlight to begin bulb production, which makes them ideal for growing in Hawaiʻi.

When buying seeds, it is important to determine the day-length requirements. The shorter, the better. Many seed distributors include this information on the back of the package. The following example is taken from information provided on a packet of Johnny’s Seeds.

Madalyn Onion. Yellow short-day onion for the South. Excellent uniformity and good bolt tolerance. Dense, jumbo-size bulbs with globe shape. Vigorous foliage. Mild flavor with a touch of heat. For fall planting/spring harvest in the South. Early midseason maturity. Best for short storage.

Once you have selected your onion seeds, follow the seed packet planting instructions. The information is specific to that onion variety. Remember: your garden is only as good as your soil. Take the time to prepare a well-drained, sandy loam soil, that is high in organic matter (compost). 

Keeping your onions well-watered is critical. Onions have a shallow root system that requires 1 inch of water per week.  The more water, the milder the taste. Onions also need a snack several times during the growing season if you want robust onion bulbs. Fertilize with manure, compost, or a balanced fertilizer, e.g., 16-16-16 or 10-10-10.

Finally, after months of patience and TLC, it is time to harvest. Yeah! Liver or tofu and onions for everyone! When the onion necks become soft and the floppy, green tops are falling over, pluck the onions from the soil. Unless you plan to eat all the onions at one meal, it is best to allow them to stretch out on the lānai and sun-cure for a couple of days. 

Hopefully, you will have more onions that you can eat in a short time. It is time to store the extra onions. Depending on where you live, finding a dry, cool place to store your harvest may be challenging. My garage, which has never seen the wheels of a car, is where I string up my onions.

Some people braid the stems together. I use fishing line to loop around the onion stem. I can then hang them where they are not touched by sunlight with a gentle tropical breeze flowing about them. The gentle breeze, or airflow if you prefer, is critical if you don’t want the onion to turn into a rotting, stinking mess. To help you remember: Breeze, Cool, Dark are the rules for onion storage. 

You do not want to store onions in the refrigerator. It is a chemistry thing involving sugars and starches and temperature.  It is not just the fact that onions have thin skins that make them susceptible to the cold, but because extended cold can cause the onion to soften and spoil.

Some people have told me to peel the onion under running water. I don’t like wasting water. You have heard of “cool as a cucumber.” But change that to, remember “cool as an onion.”  I just made that up. I toss the onion in the refrigerator for about 30 minutes to chill it out. Cool onions are not as aggressive tear makers as a warm onion.

While the onion is chilling, I sharpen my knife. A sharp knife seems to produce less tear-making vapors. Finally, according to my wife, I should cut from the top to the bottom. I don’t know why. I didn’t ask. I don’t care. I just do it.

I have only peeled off the top layer of onion skin in this article. It should be enough information for you to successful grow bulb onions in Hawaiʻi. 

I can’t help myself. One last groaner. My wife found me in the kitchen crying the other day. I held up an onion that I had just eviscerated for French Onion soup, and said: “These are tears of happiness.”

Recommended Varieties: The University of Hawaiʻi provided the following list of recommended short-day varieties for Hawaiian gardeners. Granex 33, Yellow Granex hybrid, Mercedes, Rio Bravo, Rio Zorro, Cougar, Sweet Sunrise, Jaguar, Awahia (pungent), Monsoon and Savannah Sweet.

References:

• Randall Hamasaki Hector Valenzuela Robin Shimabuku, Editors. Bulb Onion Production in Hawaiʻi. College of Tropical Agriculture and Human Resources, University of Hawaiʻi at Mānoa. 1999. Pg. 6.

• Jack Tanaka 1960. Awahia: A New Pungent Onion for Hawaiʻi. Hawaiʻi Farm Science Agricultural Science Progress Quarterly. Vol. 9, No. 2.  College of Tropical Agriculture, University of Hawaiʻi. 

• K. Y Takeda, S. K. Fukuda, and R. Hamasaki. Koba Green Onion. University of Hawaiʻi at Mānoa, College of Tropical Agriculture and Human Resources.

• Kenneth Y. Takeda and Richard T. Sakuoka.  Onions-Bulb and Green Bunching. CTAHR Fact Sheet, Garden Vegetable No. 16. University of Hawaiʻi at Mānoa, January 1997.

• National Onion Association.  www.onions-usa.org. 

• Sweetser, Robin. 2018. Onion Planting and Harvesting Tips. https://www.almanac.com/growing-onions

• Johnny’s Seed Company. https://www.johnnyseeds.com

Editor’s Note: Every other week, Big Island Now will feature a guest gardening column by Tom Timmons. He is a certified Master Gardener respected for his gardening experience, but his views are not necessarily those of the University of Hawai‘i.

Other gardening columns by Tom Timmons:

• Choosing a fertilizer of your lawn and plants
• The KISS method of composting
• Why should you play in the dirt?
• Basil – the royal herb