Beginner Onion Guide
How to Grow Onions in Michigan (From Planting to Storage)
Have you ever grown so many onions you weren’t sure what to do with them? That’s a great problem to have… but a lot of beginning gardeners struggle just to get onions to grow in the first place. Let me walk you through everything I’ve learned so you can go from confused to confident (and maybe even overwhelmed with onions 😄).
🌱 When to Plant Onions in Michigan
In Michigan, onions are planted in early spring - about two weeks before the last frost. In southeast Michigan, that’s usually around mid-April. They can be harvested around mid-July. This is different from garlic, which goes in the ground in the fall (around Halloween).
Onions typically take 85–100 days to mature so planting in mid-April = harvesting around mid-July - mark your calendar!
🌱 Onion Basics (This Explains A LOT)
Onions have a 2-year life cycle:
Year 1: Grow a bulb
Year 2: Send up a flower and go to seed
👉 That’s important because it explains why your onions behave the way they do
🌱 Sets vs Starts (This Is Where Most People Go Wrong)
Onion Sets (small bulbs)
Already in their second year
More likely to bolt (flower)
Usually result in smaller onions
👉 Great if you want seeds… not great if you
want big storage onions
Onion Starts (young plants)
Grown from seed this season
Look like small green onions
Best for large, healthy bulbs
👉 This is my go-to now after
learning the hard way.
My first two years?
About half flowers… half onions. 😬
🌱 Choosing the Right Onion Type
In Michigan, you want LONG-DAY onions (this matters!)
They need 14–16 hours of daylight
Good varieties: Yellow, Sweet Spanish, Walla Walla, Red Wing
👉 These grow larger bulbs and store well
🌱 How to Store Sets or Starts Before Planting
Keep in a cool, dry place and out of direct sunlight
If shipped in a box → take them out immediately and don’t wait more than a couple days to plant. Here's an unboxing video so you get an idea of what to expect: https://youtu.be/VuhqQBxPb9Y
🌱 Soil Prep (This Is HUGE)
Onions are heavy feeders and love rich, compost-filled soil BUT bulbs grow at the surface so they don’t need deep soil
👉 Translation: Feed the soil well and don’t bury them deep
🌱 How to Plant Onions (Important!)
Plant shallow
Cover roots only
Leave the top visible (you should see color: white/red/yellow)
👉 If you plant too deep = smaller bulbs - unless you “spoon” them halfway through growing.
💨 Protecting Newly Planted Onions
Because they’re shallow wind, rain, or hail can knock them loose
My protection trick is to cut tomato cages in half from top to bottom and lay them over the beds. This way I can add frost cloth if needed to shield from late spring snows because… Michigan weather 😅
Planting in ground video here: https://youtu.be/gMAeayW2jDI
Planting in raised beds video here:
🌱 Spacing (And What If You Mess It Up)
Give onions enough room based on expected size BUT
👉 If they’re too close:
Pull every other onion early
Use as green onions
Let the rest grow full size
🌱 Planting from Cell Packs (Nursery Tip)
If you buy starts in cells don’t plant the whole clump. Instead moisten soil and gently separate each plant. Below you can see the onion seeds stuck to the leaves. They don’t hurt anything and will come off when they’re ready!
👉 Each stem = one onion
🌱 Companion Planting Tip
Onions + carrots = perfect combo
Onions grow on top and carrots grow down into the soil. They have the same water needs of 1–2 inches per week.
Bonus: Carrot seeds need consistent moisture → perfect in between onion rows
🌱 Watering & Soil Structure
Water: 1–2 inches per week and avoid soggy soil
👉 Best method: Plant in mounded rows. Channels between rows help drainage AND hold moisture for carrots
🌱 More Leaves = Bigger Onions (Here’s WHY)
Each leaf = one onion layer
👉 More leaves = more layers = bigger onion
That’s why some people trim seedlings early → encourages more leaf growth (And yes… I always want to know the why too 😄)
🌱 What If Your Onions Flower?
It happens - especially with sets since
the plant is in it’s second year.
If they flower you can collect seeds by
letting the flower dry and then
shaking seeds out.
👉 You can grow your own starts next year!
🌱 Harvesting Onions
You can harvest anytime for small onions…But for full, mature harvest look for leaves falling over near the stem and bulbs visible at surface.
Typical timing: Mid-July (if planted mid-April)
See some harvested in this video: https://youtu.be/7tyM2Xya8VM
And in this video:
🌱 How to Cure Onions (DON’T Skip This)
You can use harvested onions right away or up to two weeks later but if you want to store onions for longer, curing is essential.
Steps:
Brush soil lightly from bulbs. Do NOT rinse soil.
Gently lay onions out flat in a cool, dry area - with some space between them. Handle carefully to avoid bruising.
Allow airflow. Using a small fan to move the air helps!
Wait until leaves are fully dry and brown.
Trim dried roots. Handle carefully to avoid bruising. Lay a towel over the work area for a cushion.
Then cut tops to about 2 inches OR braid stems around a string of twine.
Curing video here: https://youtu.be/egAqbx_uasw
If outer skin is soiled or moldy, gently peel off to reach clean skin but don’t over-peel and reach the fleshy portion.
Example video here: https://youtu.be/SPedg36tqm0
👉 Those papery skins protect the onion during storage, so minimizing potential rot sources helps them stay viable longer.
🌱 Storage Options
Mesh bags in cool, dark space
Braided stems - video here: https://youtu.be/yLyrn2XPDqM
Freeze chopped onions
Dehydrate slices or chunks
Make onion powder
Caramelize and freeze
👉 Same goes for the greens: Fresh, frozen, or dehydrated
🌱 Real-Life Tips You’ll Actually Use
😭 Cutting Onions Without Crying - Place a wet cloth nearby. Fumes go toward moisture (instead of your eyes)
🧄 Dehydrating Warning - Run your dehydrator in the garage or mudroom, unless you want your house to smell like an Italian restaurant…
…and your curtains to agree 😆