When is the Best Time to Plant Perennials in Minnesota?
The best time to plant perennials in Minnesota is the spring, but there are certain variables to keep in mind for each particular plant.
Successfully Growing Perennials in Minnesota
The short story is that the best time to plant perennials is in the early spring right after the risk of frost and freezing has passed, but the plants have not yet put on significant growth.
However, you can have success planting perennials any time of the gardening season into late summer or even early fall. No matter when you plant your perennials, in order for them to have the most success we have to cover a few more important details.
In this article we will discuss frost dates and hardiness zones, the difference between bare root and potted plants, as well as some helpful tips to get your perennials off to a great start.
Timing your Perennial Planting in Minnesota
Minnesota is a large state, spanning over 400 miles from top to bottom, which allows for several plant hardiness zones and many different last frost dates.
For us in west central Minnesota, about an hour East of Fargo/Moorhead, we see our last frost date around the middle of May. Way up in Warroad, however, they see their last frost around the end of May. Down in Fairmont, they might have last frost dates as soon as late April or early May.
Each season will vary, and this guide from the DNR should be able to give you an average idea. You can also use this Old Farmers Almanac resource, which is a little more user-friendly.
Minnesota Plant Hardiness Zones
Just as we have a variety of last frost dates, we also have quite the range in hardiness Zones. This map from the U.S. Department of Agriculture can help you determine what your hardiness zone is. Make sure the perennials you are choosing will hold up to our cold climate.
Fall Planting Perennials
Different perennials will tell you they are best planted in the fall. I would avoid late fall, anything late October and beyond, as the plant won’t have enough time to establish its roots.
Early fall plantings have the benefit of cooler temperatures that don’t stress out your plant. They also provide you an opportunity for less work on your end. Fall plants do not require as much watering as spring plantings do. Once the ground freezes, your watering duties are over until the next season.
Additionally, spring-blooming bulbs are a perennial that you should plant in the fall.
Bare Root vs. Potted Plants
You will find most perennial plants available in two options, bare root or potted. Here’s a quick break down of both types of plants.
Bare Root Plants
These are dormant plants that have around one to two years of growth on them. They will arrive just as it sounds, with bare roots. They can look pretty scraggly and half dead, but the roots and branches of the plants should feel firm and flexible. If they have any roots or branches that are mushy or snap right off like a dried twig, go ahead and remove those bits and toss in the compost. .
Bare root plants are often much more affordable than potted options, especially if you are buying in bulk. While you probably won’t find these at your local greenhouse, you should be able to easily order them from many different online greenhouses, seed catalogs, etc. The only downside to bare root plants is they do take a little longer to establish.
When your plants arrive, remove any sketchy bits, then soak the roots in room temperature water overnight.
When planting, dig to a depth where the roots will be well under the soil. Add in a few scoops of compost or bone meal (follow instructions on the package) and mix this into the soil at the bottom of the hole.
Backfill the hole, tamping down the soil as you go. You do not want any air pockets in there. Water the plant thoroughly, not so it is in a mud puddle ,but just a good soaking. Add mulch (just about any type of organic matter such as leaves, grass clippings, wood mulch, etc) around the plant and possibly a weed barrier to maintain moisture and keep weeds at bay.
.For the entire growing season, make sure you are watering the plant weekly, sometimes more often if the weather is especially hot.
Potted Plants
You are most likely to find potted plants at your local garden center or big box stores. Potted plants don’t only give your vegetable garden a head start, they can really make a difference in how quickly your perennial plants establish.
Potted perennials are usually 3-5 years old and come in anywhere from half gallon up to five gallon pots. On average, you are likely to see them in one gallon sized pots. These will cost you more, as the greenhouse that raised them put several more years into establishing and caring for the plant before it gets to you.
With potted perennials you are more likely to see bloom time occur the first season (especially with native plants) or by the next growing season.
Potted plants should get a good soaking all the way through before planting. I like to soak mine in the morning, then plant them early evening once the temperatures cool down and the plants aren’t sopping wet.
To remove them from their pot, gently support the stem and any foliage on the plant, flip the pot upside down. If there are any roots sticking through the pot, snap those off. Gently squeeze the sides of the pot and the soil mass should slide right out.
If the roots are like a thick web along the outside this means it is root bound. Gently pull the roots apart some, fanning them out evenly. You can also snip off the bottom inch or so of the root mass, then pull them apart from there. If you don’t free up the roots, the plant will remain root bound and by next spring it might be dead from basically strangling itself or not being able to get enough water.
Dig a hole slightly deeper than the pot the plant came in. Add in a few scoops of compost or bone meal (follow package instructions) then mix in with the soil at the bottom of the hole. This will provide a rich soil for the perennial to get valuable nutrients to jump start growth. Place the plant in the hole, then fill with dirt, pressing it down firmly all the way around.
Give the plant a good watering, and add in either a 10-10-10 liquid fertilizer (dilute according to the package instructions) or you can also use fish emulsion, again dilute according to the package instructions.
As previoulsy mentioned, new perennials will need weekly watering, more during very hot weather. If you notice any poorly performing plants, odds are they just need more regular watering.
When to Divide Perennials
Aside from bare root and potted as options for getting a new perennial plant, there is a third option, which is to divide an already existing plant and transplant it into your own garden. Nothing better than getting new plants for free!
Just as spring is a great time to plant perennials in general, early spring is a wonderful time to divide perennial plants as well. This should be after any chance of ground freezes have passed, and ideally after any last chances of frost.
The perfect time is when you can see the green of the plants beginning to wake up for the season, but before they begin to put on any new growth.
In this post I talk about transplanting perennials at length, so check that out for more details. No matter the time of year you transplant perennials, you can expect the next year they might not put on too much growth.
Unlike an annual flower that blooms right away, the old adage for perennials is that “the first year they sleep, the second year they creep, the third year they leap”! So expect your newly transplanted perennial garden to take a few seasons before it really starts to shine.
One exception to this rule can be native perennials, which can look pretty incredible after just one full growing season.
More from the Garden
- How to Transplant Perennials
- Remove Rust from Garden Tools (No Nasty Chemicals)
- The Best Fertilizer for Daylilies
- Make a Bean House for the Garden (YouTube video)
Sources
Possibly my favorite book on this topic is Growing Perennials in Cold Climates, by Mike Heger, Debbie Lonnee, and John Whitman. It is a wealth of information for each individual perennial you might want to plant, divide, and care for. All the plants you will find are hardy perennials and will do well no matter where you have your Minnesota garden.
The University of Minnesota Extension website, especially their Master Gardener section is also a wonderful resource with many reference guides available.
Another favorite resource of mine is Northern Gardener Magazine, put out by the Minnesota State Horticultural Society.
