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Garden Help Desk: What do I do about onions growing from last year?

By USU Extension - | Apr 22, 2023

Courtesy photo

Many pollinators are attracted to small flowers like those on onion umbels.

I must have missed some of the onions in my garden when I harvested them last year because there are several onion plants growing now in that part of my garden. Should I just treat them like regular onion plants, or do I need to do something special for them this year?

Mature onions that overwinter won’t behave the same as newly planted onions this year, depending on how mature they were when winter arrived. The bulbs that were left behind last year provided the energy for the new growth you’re seeing now. If you were to dig up one of the onion plants, you’d find just a shriveled, dry “shell” of the old bulb around the new growth.

Your onions will probably flower early in the season, which is normal for onions and other biennial plants during their second season of growth. A flower stalk will rise from the center of the plant, bearing a round umbel of white flowers at the top of the stalk.

Take care of your overwintered onions this year the way you care for the rest of your onions. You may be able to use them as green onions for the next few weeks or you can leave them to flower and provide food for pollinators in your garden.

Sometimes onions will bolt (flower) because of stress during their first growing season. Heat stress or a period of frosty weather late in the spring can trigger that flowering. The flower stalk leaves the onion bulb with a very tough, inedible center but the rest of the onion can still be used. Onions that have bolted won’t store well, so plan to use them up right away after harvesting them.

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Onion plants that are stressed early in the growing season may bolt and produce flowers on tall stalks.

Not every onion plant will bolt if it spends the winter in the garden, though. With planning and care, certain sweet onion varieties can be planted during the first few days of August and overwintered as young plants for an early onion harvest in June of the following year before spring planted onions are ready.

We’ve had several calls from people concerned about spiders in their homes. Spiders are most likely to get into homes during the fall when temperatures cool, but there are things you can be doing this spring and summer to reduce spider problems this fall.

Some spider problems are related to the way we landscape around our homes. Dense plantings along the foundation can provide habitat for many kinds of insects and where you find insects, you’ll usually also find spiders hoping to catch an easy meal. This doesn’t mean you shouldn’t include shrubs, perennials, and annuals in your landscaping. It does mean that you should schedule time each spring and summer to keep this area clean- remove weeds and dropped twigs and leaves, don’t let litter or clutter accumulate around the foundation and under your shrubs, and clean up annuals and perennials at the end of the season. Light pruning under any foundation shrubs will make this job easier. If you’re putting in new landscaping, think about how you can make this an easier job.

Exterior basement stairwells and basement window wells can also provide habitat for insects and spiders. Clean out any clutter and plant debris in these areas in the spring and again in the fall.

In addition to reducing shelter for insects and spiders near the foundation of your home, you can take some good exclusion steps now to discourage indoor spider problems in the fall and winter.

  • Inspect your doors and windows inside and out, looking for any small openings or gaps that may provide access for spiders and insects.
  • Window and door frames should fit into walls tightly and doors and windows should fit into their frames tightly. Use caulk to seal any small gaps around the frames.
  • Window screens should be in good condition and fit tightly as well. White duct tape can be used to seal off the tiny gap between screens and window frames.
  • Weather stripping, door sweeps, and should be in good condition.
  • Use caulk to close any small gaps where the natural gas line and AC refrigerant line come into your home.
  • Repair any ventilation openings along the top of the foundation, if needed.

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Mature onions that are left to overwinter will use the energy from the onion bulb producing new green growth in the spring and leaving behind the shriveled, dry remains of the bulb.

Will clean foundation plantings and good exclusion give you a completely spider-free home? No. Spiders may still occasionally find their way indoors, but laying some sticky spider traps on basement windowsills and along baseboards next to exterior doors can give you an added measure of prevention.

Dense shrubbery provides an attractive hangout for insects and the spiders that prey on them.


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