• Home
  • Meet Mary
  • Speaking
  • Writing
  • Contact
  • Northern Gardener Book

My Northern Garden

January 4, 2021 · Leave a Comment

Frost Dates in the Vegetable Garden

How to

Last frost. First frost. Frost free. Hardiness zone. For vegetable gardeners, frost dates are important in determining when you should plant and what you should plant. During my recent interview with author Niki Jabbour on the Grow it, Minnesota podcast, we talked about how she decides when to plant seeds or transplants in her under-cover garden.

Niki Jabbour harvesting in winter from a few of her season extending hoop houses. (Photo courtesy of Niki Jabbour)

“Frost dates,” she said. While some gardeners will take soil temperatures before planting a crop, knowing your hardiness zone and frost dates is the easiest way to plant vegetables (and other plants) at the best time for them to thrive. Here are the basic numbers for vegetable gardeners in the North to know:

Hardiness Zone

Most Minnesota gardeners are in either USDA Hardiness Zone 3 or 4. Some may be close to zone 5. These zones are determined by how cold it gets on the most extreme cold day in your area on average. The USDA last updated the zones in 2012 and many areas of the country saw a shift to a warmer zone at that time.

USDA Hardiness Zones with sample cities from each northern zone.

I live in St. Paul in USDA Zone 4b. That means that at its very coldest my garden should not get colder than -25 Fahrenheit, though it might get to -20. Sure enough, the coldest temperature I’ve ever recorded in my backyard is -23 on the morning of January 29, 2019. (I have a photo of my thermometer on that day, but it’s too blurry to share!)

When you buy trees, shrubs and perennials, the hardiness zone for the plant should be listed on the plant tag. Make sure anything you buy is hardy to your zone.

Last Frost Date

The last frost date is the one vegetable gardeners need to pay attention to in spring. It tells you when is the last date in the spring your area is likely to get frost — generally 36 or so degrees. It’s not a perfect system because a very late frost is always possible. (That’s why gardeners like Niki use row covers, cloches and cold-frames in the spring.) However, it is usually a reliable indicator of when to plant. Once you know your last frost date, you can use the information on seed packages to know when to sow your seeds.

I’ve seen a lot of different dates as the last frost date for the Twin Cities, but to be extra safe, I consider it May 10. (Here’s a chart with a more thorough look at frost dates. Climatologist Mark Seeley thinks the Twin Cities last frost date is now actually at the end of April.) But I like to be careful. So when a seed packet says, “sow seeds outdoors after the last frost,” I’ll probably plant them in the second or third week of May. Knowing this date is very helpful for indoor seed starting, too. The pepper package pictured at right says start seeds indoors eight weeks before last frost. Using May 10 as a safe bet, I’d count back eight weeks on the calendar and plant the pepper seeds under lights indoors about March 22. In mid-May, I’d move them outside, but only if the forecast looked favorable—and I’d probably keep them in a cold frame until June.

Frost-Free Days

Frost-free days are the number of days between the last frost of the spring and the first frost of the fall. It’s generally considered the length of an area’s garden season—unless you use season-extenders like Niki does. In the Twin Cities, the odds are very good we’ll have at least 130 to 140 frost-free days, and very possibly 160. In 2016, the Twin Cities had a growing season of 200 days! That doesn’t mean baking sun and 70s all the time — just that we’ll be above 36 or so. The folks up in Roseau will be lucky to get 100 days frost free.

Observe Your Garden

Beyond knowing your zone and frost dates, gardeners can observe the micro-climate they have in their yard to determine when it’s best to plant. Is your vegetable garden in a low-lying spot? It will likely be slower to warm up in the spring. Do you have a south-facing protected spot? That would be a good place to put a tender plant. Knowing your own garden (and maybe using some season extenders) is the best way to get the most from your vegetable plot.

For more on using cold-frames, hoop houses and other season extenders, check out my interview with Niki on the podcast!

Related posts:

  1. Book Review: Keeping Vegetable Gardeners on Track If growing more vegetables is one of your New Year’s...
  2. Book Review: A Gardener’s Guide to Frost A Gardener’s Reading, 13 of 30 By Philip Harnden (Willow...
  3. How to Create Beauty in the Vegetable Garden During these last cold days of winter (hope, hope, hope!),...
« Best Trees for Birds in the North
Winter Sowing for Flowers and Vegetables »

Leave a Reply Cancel reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Connect

  • Instagram
  • Twitter
  • Pinterest
  • RSS Feed for Posts

Grow it, Minnesota Podcast

Now Available!

My Northern Garden book

mynortherngarden_mary

It’s National Gardening Day! I’m not much for It’s National Gardening Day! I’m not much for special days (sorry, siblings, I missed that one last week) but any excuse to post a picture of a gorgeous peony, I’ll take! 

Peonies are a huge part of Minnesota’s horticultural heritage. They aren’t native but our cold climate is perfect for peonies. They’ve been hybridized in Minnesota for over 150 years, and the state still has several peony breeders based here. If you ever get a chance to go to a peony open day in June, jump on it. Seeing rows and rows of peonies all blooming at once is a northern gardener’s joy. 

Peonies will last forever, too. Plant one in the right place and it will outlive you by decades. What’s your favorite plant? 
.
.
.
#nationalgardeningday #nationalgardenmonth #garden #peony #horticulturalheritage #garden #mygarden #mynortherngarden #gardeninspo #gardenblogger 
#mngardening #minnesota #mnhort
#gardeninglife #coldclimategardening
#stpaulgarden #stpaulmn
#Zone4garden #zone4b #nofilterneeded
This week’s podcast and blog post are about grow This week’s podcast and blog post are about growing summer bulbs. I grow lilies in containers, 1) because they look great and 2) because the rabbits 🐇 can’t get them as easily there. Growing bulbs in containers means you can move them around the garden for extra color where you need it. 

Bulbs aren’t that tricky to grow, though you will have to pull dahlias, gladiolus and canna lilies for the winter. Lilies can stay in the ground. This winter, I left some in their pots and held  them in the unheated garage. They survived and are already putting up foliage. 

Check the 🔗 in bio for links to my interview with Mike Heger as well as the blog post on growing bulbs in containers. 
.
.
.
#bulbs #summerbulbs #lilies #liliesinpots #containergardening #summergarden #garden #mygarden #monalisalily #mynortherngarden #gardeninspo
#mngardening #minnesota #mnhort
#gardeninglife #coldclimategardening
#stpaulgarden #stpaulmn
#Zone4garden #zone4b
In bloom at the big box store: Columbine! These lo In bloom at the big box store: Columbine! These look pretty but most of the in ground columbines are just greening up in Minnesota. That’s one thing to remember when shopping for perennial plants now. If it’s in bloom, it’s a spring plant and will probably be green all summer. Nothing wrong with lots of spring bloom in the garden, but plan for the whole season by picking things that bloom in July, August, even the fall, too. 
.
.
.
#columbine #plantshopping #gardentips #minnesota #mngarden #coldclimategardening #zone4b #springblooms #garden #perennials #perennialgarden #perennialflowers
So many things are suddenly blooming! . . . #spri So many things are suddenly blooming! 
.
.
.
#spring #springinmn #bulbs #forsythia #irisreticulata #squill #earlyspring #garden #gardeninspo
#mngardening #minnesota #mnhort
#gardeninglife #coldclimategardening
#stpaulgarden #stpaulmn
#Zone4garden #zone4b #seenonmywalk
Uff da! This seems really early for daffodils 🌼 Uff da! This seems really early for daffodils 🌼 in Minnesota. Last year, I posted my first daffodil photo on April 12, and it was in snow ❄️! No snow this year, and this tracks with the info I heard earlier this week that we are 10 to 14 days ahead of schedule. I’m enjoying the warmth but can’t shake the memory of 2019’s mid-April blizzard. The joys of cold climate gardening! 
.
.
.

#garden #mygarden #mynortherngarden #gardeninspo #spring #mnspring #daffodil #springbulbs 
#mngardening #minnesota #mnhort
#gardeninglife #coldclimategardening
#stpaulgarden #stpaulmn
#Zone4garden #zone4b
This weeks podcast is about rain gardens with Madd This weeks podcast is about rain gardens with Maddie Poling of @sacredspacegardensmn while rain gardens are great for water filtration, they also can be incredible pollinator gardens, especially if you plant lots of milkweed. Link to the entire episode is in bio. 
.
.
.
#growitminnesota #raingardens #pollinators #pollinatorplants #milkweed #growitandtheywillcome #coldclimate #coldclimategardening #minnesota #mngarden #gardenpodcast #mnpodcast
Fun news 🗞! I have an essay in the upcoming iss Fun news 🗞! I have an essay in the upcoming issue of Gardening for Health, a special interest publication of Better Homes & Gardens. It’ll be on newsstands and in grocery stores, home centers, drugstores and more starting tomorrow. The essay is about why gardening matters, for our health, our spirits and our communities. I haven’t seen the layout yet, but I’ll be prowling my local Barnes & Noble tomorrow! Can’t wait to see it. 
.
.
.
#gardenwriter #gardensmatter #gardeningforhealth #bhgspring #bhggarden #bhgspecialinterestpublications
Wondering what winter burn looks like on shrubs? C Wondering what winter burn looks like on shrubs? Check it out. I’ve got three of these dwarf Alberta spruce. This is the worst case. One has no burn, the third just a bit. This one faces south so it gets the most sun and wind. After it starts growing this spring, I’ll trim off the burn. May need some wrapping next winter. 
.
.
.
#whatswrongwithmyplant #winterburn #evergreen #albertaspruce #dwarfshrubs #dwarfspruce #garden #mygarden #mynortherngarden #gardeninspo
#mngardening #minnesota #mnhort
#gardeninglife #notpretty 
#stpaulgarden #stpaulmn
#Zone4garden #zone4b #coldclimategardening #mnwinter
A pair of crocus cuties. This spring is coming on A pair of crocus cuties. This spring is coming on fast, though we know Mother Nature can slam on the brakes anytime she wants. Enjoy the early blooms and have a great weekend! 
.
.
.
#crocus #springiscoming #minnesotaspring #springbulb #flowergarden #growflowers
#flowersofinstagram #plants #garden #mygarden #mynortherngarden #gardeninspo
#mngardening #minnesota #mnhort
#gardeninglife #coldclimategardening
#stpaulgarden #stpaulmn
#Zone4garden #zone4b
My conversation with Amy from @milkweed.and.daisie My conversation with Amy from @milkweed.and.daisies on the @growitmn podcast got me thinking about annuals that are easy to grow from seed. There are a lot! She grows some I haven’t had in years, like hollyhocks and snapdragons, plus plenty of my favorites. Seven really easy options are listed in a new blog post (🔗 is bio) on the My Northern Garden blog. Cosmos, zinnia and sunflowers may be the easiest of  all. 

The sunflower 🌻 pictured is The Joker. The zinnia photo is one I took of the zinnia beds at the @ballseedgardens I’m not sure about the cosmos, which are from a tour garden. 

Plant any of these annuals in sun and let them grow. Suggestions for annuals to try this year? I’d love to hear them! 
.
.
.
#annualflowers #cosmos #sunflowers #zinnias #growfromseed #growyourownflowers #coldclimategardening #minnesotagardening #northerngardener #zone4b #mnpodcast #gardenpodcast
The 3+ inches of snow from a couple of days ago is The 3+ inches of snow from a couple of days ago is melting, and the crocus continue to bloom. Hang in there, little flower, spring is on the way. 
.
.
.
#bulbs #springiscoming #springbulb #minnesota #crocus #meltingsnow #garden #mygarden #mynortherngarden #gardeninspo
#mngardening #mnhort
#gardeninglife #coldclimategardening
#stpaulgarden #stpaulmn
#Zone4garden #zone4b
Crocus so soon! I was taking apart the holiday pot Crocus so soon! I was taking apart the holiday pot and noticed three crocus blooms in my south-facing front bed. This is a full week earlier than last year, and that felt early to me. They’ll probably get snowed on come Monday. 🌨🌸
.
.
.
#minnesota #minnesotaspring #crocus #earlybloomer #springbulbs #garden #mygarden #mynortherngarden #gardeninspo
#mngardening #mnhort
#gardeninglife #coldclimategardening
#stpaulgarden #stpaulmn
#Zone4garden #zone4b
Load More... Follow on Instagram

Top Posts & Pages

  • Growing Lilies in Containers
  • How to Pollinate a Meyer Lemon Tree
  • Mushrooms Growing in Straw Bales
  • Big Changes in Minnesota Hardiness Zone Map
  • Weed of the Week: Stinging Nettle
  • How to Build a Vegetable Garden Box for Your Deck
  • Conjoined Daisy
  • How to Grow Lemons in the North (Plus a Recipe)
  • Taking the Straw Bales' Temperature
  • Frost Dates in the Vegetable Garden

Post Categories

  • Books/Writing
  • Climate
  • How to
  • Plants
  • Recipes
  • Uncategorized
  • Why We Garden

Copyright © 2021 · captivating theme by Restored 316