About Onions

• Onions grown in the Tahoe/Truckee area do not typically achieve the size found in the markets.
• Onions are defined as short day, long day and intermediate day onions. Intermediate day onions may do best in our area. Tahoe is on the demarcation line for the limits of long-day and short-day onions.

Starting Onions, Shallots and Scallions Indoors

• Start seeds indoors. Up to 70 days prior to transplanting.
• Place seeds in a light soil mixture, sprinkle a little soil over the seeds.
• Once sprouted (7-14 days), do not over water, and give plenty of light (8hr minimal).
• The larger the seedlings the easier it is to transplant outdoors.
• You can trim roots prior to transplanting outdoors, and store for a couple weeks prior to transplanting (do not water once pulled from soil).
• Onion slips (seedlings) can be planted up to 3 weeks prior to the last expected frost.

Planting, Growing, & Harvesting Onions & Shallots

• You can plant seedlings 2-3 weeks before last frost, as long as soil is workable
• Plant seedlings 1-2 in depth.
• Space 4-6 inches apart
• Plant in area that gets as much sun as possible
• Consider planting in raised rows to increase soil temperatures around plants.
• Onions like loose mineralized soils that easily drain water.
• Onions, leeks and shallots are heavy feeders. Fertilize 2-3 weeks after planting and every other week thereafter. Stop fertilizing when bulbs start to show at soil surface.
• The initial fertilizer applications (2-3) should have significantly more phosphorus than nitrogen and potassium – to encourage root growth.
• Thereafter, high nitrogen fertilizers should be used to encourage leaf production and growth.
• Try to maintain even soil moisture, avoid over watering or letting the soil dry out and leaves wilt.
• A cold snap during the growing season (near freezing for more than 24 hours can cause the onions to bolt (set flowers). If onions bolt, pull plants up and use. Bulbing will have stopped and plant energy will have been directed towards flow and seed production.

Harvesting Onions

• Harvest onions that bolt as soon as possible.
• Late summer or early fall the leaves will start to turn brown and droop or fall over.
• Stop watering and leave onions in ground for a few days
• Pull onions and let dry for 2-4 days in a cool dark area. Trim roots but do not remove stems.
• Cut stem from bulb once the neck and outer skin is dry.

Harvesting Shallots

• Harvest shallots if they bolt
• Shallots are a type of clumping onion and can be pulled and used during the growing season.
• Pull shallots and let dry for 2-4 days in a cool dark area. Do not remove stems or roots.
• Cut roots and stem from the bulb once the neck and outer skin is dry.
• Unused shallots can be left in the ground to overwinter, or pulled, dried and stored for planting the following year.
• If left in the ground to overwinter, cut leaves at ground surface when dry or after a hard freeze.

Planting, Growing, & Harvesting Leeks

• Prepare soil as with onions.
• Plant leeks about 4-6 inches deep, so only the tops of the leaves show above the soil surface.
• Mound dirt 3-4 inches around the plant as it grows. This helps “blanch” the lower stem keeping it white.
• Water and fertilize as you would onions.
• Harvest when needed. You can leave leeks in ground until late fall
• Once pulled, trim roots and upper portion of leaves.
• Store in a damp paper towel in the refrigerator for up to a week.
• Leeks can be chopped and frozen in an airtight container for about 6 months.

Information provided by Dave Long, Lake Tahoe Master Gardener, Summer 2024