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Eastern Idaho is a great place to grow onions, parsnips and radishes and here’s the secret to a successful harvest

In the Garden

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Photos: Lance Ellis |

Onions are a great crop to grow in eastern Idaho. They can tolerate our cool springs and are not overly complex to grow. Onions are moderate users of the three major nutrients, (Nitrogen, Phosphorus, and Potassium) and enjoy a soil mixed with lots of loose, well-composted, organic matter. Overfertilization of onions can lead to lots of top growth and small bulbs. They do not enjoy having wet feet, so a sandy loam soil works best for giving them adequate drainage.

With our short growing season, we have two ways to start our onion plants. The better of the two ways is starting with onion sets or starts, as that gives you a head start.

The other method is directly sowing seed, but this is not recommended due to the shortness of our growing season.

Since onions have a shallow root system, they do not compete well with weeds and can be affected by fluctuations in soil moisture. Keep the moisture level consistent throughout the growing season. Periods of drought during the growing season can lead to stunting and strong-flavored onions. To manage this, a straw mulch can be applied around them, as you see in the picture below, which helps to maintain soil moisture and prevent weeds.

Correct harvesting of onions is crucial. When your onions have had about half of their tops fall over, that is a good sign that it is time to harvest them. Do this by gently pulling them up out of the ground, or digging them if they are rooted firmly in the ground, and laying them on their side in the garden for about a week. If you have a frost coming during the week they are curing, then cover them that night until the frost has passed. This drying time allows them to cure and prepare for storage.

After the tops have become papery, and the skin on the onions is dry and crinkly, clip the tops off so that about one inch above the bulb is left and store it in a cool dry place.

Good varieties for our area include Simco, Copra, Prince, Millennium, Fiesta, Yellow Sweet Spanish, Bennies Red, Red Wing, White Sweet Spanish, Blanco Duro, and Super Star. Something interesting to note is that you cannot order in onion starts due to Idaho’s law. They do this to prevent diseases from coming into Idaho from out of state and damaging Idaho’s onion industry. This may be inconvenient, but we have a low incidence of diseases in onions compared to other states, so preventing issues is well worth the effort.

Harvesting parsnips

Parsnips are also an excellent crop to grow in our area. If you aren’t acquainted with parsnips, they are very similar to carrots in shape and size but have a distinctly different flavor and completely different color. They are white, and not orange or purple like common carrots. They like the same growing conditions as carrots, having a deeply tilled and loose soil so that they can root easily.

Parsnips take longer than carrots to germinate, so don’t despair if the rest of your garden is up and growing and the parsnips are still taking their time to get out of the ground. You can harvest parsnips at the end of the summer, but they do not develop a sweet nutty flavor until late fall and temperatures are cooled down.

I try to avoid having the tops of my parsnips get frozen and rotten, so I will cover them with a couple of inches of mulch till I dig them. Many people leave their parsnips in the ground through the winter, and then dig them in April. If you do this, you should insulate your parsnips with a heavy mulch (like a foot or more) or cover them with straw bales to help insulate them from winter damage. Two varieties of parsnips include Harris Model and Lancer.

Harvesting radishes

Another easy crop to grow in our area is radishes. Popular varieties of radishes include Cherry Belle, Champion, Comet and French Breakfast. Two important aspects of growing radishes is consistent water and harvesting them before they are over mature and start to split. Not providing them with adequate and consistent moisture will stress them, making them bitter, and letting them become over mature before harvest leads to a bitter taste and bad texture. Plant your radishes at different time intervals during the summer so they will mature continually throughout the season, and not all at once.

For further questions on vegetables, contact Lance Ellis at the Fremont County Extension Office at (208) 624-3102.