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HOW TO GROW RANUNCULUS IN ZONE 3 (SO THEY DON’T DIE!)

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If you’re growing cut flowers in your garden and hoping for some earlier spring blooms, you’ll quickly realize that there aren’t a lot of options for those of us in short growing seasons with cool climates. Enter Ranunculus. It looks like a garden rose and brings a welcome hit of colour to spring bouquets, and it’s something less expected than the standard daffodils, tulips, and lilacs.

Plus, Ranunculus can withstand temperatures up to – 5°C/23 °F. A huge win!

The downside? Growing Ranunculus requires a few extra steps and fussing that beginner gardeners might not be prepared for. These finicky flowers took me a few years to get the hang of, but now that I’ve made a bunch of mistakes, you don’t have to.

Here are four easy steps to grow Ranunculus so they don’t die.

pink and white ranunculus flowers

1. Soak the Corms

The first year I failed at growing Ranunculus, and it was largely because I didn’t realize you had to soak the corms first. My dried-out little corms never stood a chance.

Soak for a minimum of 4 hours to a maximum of 24 hours before planting. Less soaking time is ideal. If you soak them any more than 24 hours, your corms could turn to mush.

The second year I tried Ranunculus, I soaked them, but kept forgetting about them, drying them out, and rehydrating them. It was a mess and I don’t know what I was thinking, but I know that I was 7 months pregnant, super tired, and the world was going crazy because it was March of 2020. So I cut myself some slack, and thankfully some of those corms were tough and handled my abuse.

soaked ranunculus corm ready for potting.

2. Pre-Sprout in a Cool, Dark Place

While pre-sprouting is optional, I’ve had better results when I do it. Once you’ve soaked your corms and put them in trays, find a cool, dark room for them to sit in for around two weeks. Check on them every 3 days to see if they need more water or not. This is tricky. Too much water and they’ll rot or get mould. Too little water and they’ll start to dry up and won’t sprout. Aim for slightly moist. (Sorry to use that word!)

Here’s a short video so you can see the soaking and pre-sprouting process:

3. Start Indoors

Ranunculus need around 90 days for maturity, so technically, I could put them directly outdoors in May when I plant the rest of my garden. However, this is a bad idea because they would then be blooming in the warmest part of the year–not ideal for a cool-loving flower.

I start mine in early March for blooms in June. This is about the earliest I can start them without a greenhouse considering the temperatures they need.

[Update: In 2022 I am trying to get ranunculus to bloom for a wedding I have booked for May 7th. It could be a long shot, but I’ll let you know if I’m successful or not.]

ranunculus greens poking through the soil.

4. Harden off with a Hoop House for Best Results

I have a small hoop house my husband made me that lets me put my Ranunculus outdoors with some confidence. I have a few garden bricks to pop up the house on hot days, so they can slowly get acclimatized to the wind.

In fact, I now harden off almost all of my flowers this way because it works so well.

Now that we’re out at the acreage, I’m hoping to grow all of my Ranunculus in the greenhouse, where I think they’ll have a much better chance at survival.

Whatever you do, you’ll need to have some sort of frost fabric or cover for your plants, as you’ll be setting them outside well before your last frost. (Ideally, mid-late April, depending on the weather.)

Ranunculus seedlings in a hoop house grown in zone 3, Saskatoon SK

When is the Best Time to Start Ranunculus?

March 6th. Kidding. . . sort of. If you want blooms in June, you need to start in early March. You can technically start Ranunculus anytime as long as you have 90 days for it to grow. However, it doesn’t really like the heat, so starting on the optimal planting day in May for everything else means that your blooms may not do as well in the late summer heat.

If you’re planning on a fall succession, you’ll need to start those corms in late June or early July, and have shade cloth on hand to get them through warm summer days.

Can you Grow Ranunculus in Containers?

Yes! And in a way, it’s actually better that you do. The first year I tried Ranunculus, part of the reason I failed was that I planted them in a flower bed that had a lot of competition from weeds and nonsense perennials. The soil mix in containers means you’ll get better results.

In 2020, I devoted a raised bed to them and I got great results. So whether you’re planting in-ground, in containers, or as part of a square foot garden, it can work.

How do you Store Ranunculus Corms?

In short, the process is similar to how you save and store dahlia tubers. Once they’ve died back and yellowed, carefully pull the corm back and gently remove excess soil. Let them dry in the sun, then try and remove more excess soil. Store in a box with peat moss over the winter in a cool, dry, and dark place.

I hope you feel inspired to try growing some Ranunculus this spring! And if you have any of your own tips and tricks for growing Ranunculus, let us know in the comments!


If you need more help with your cut flower garden and putting everything together, you’ll love Cut Flowers Made Simple. It’s the cheapest and easiest way to start a cut flower garden in your backyard or use it as a way to dip your toes into flower farming.

Learn more here.


Kristen Raney

Kristen Raney

Kristen is a former farm kid turned urban gardener who owns the popular gardening website, Shifting Roots.  She is obsessed with growing flowers and pushing the limits of what can be grown in her zone 3b garden.  She also loves to grow tomatoes, but oddly enough, dislikes eating them raw.

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Kristen

Welcome!

Hi, I'm Kristen and I help new gardeners learn to grow their own vegetables and beautify their yards. I also share recipes that use all that delicious garden produce. Grab a coffee (and your gardening gloves) and join me for gardening tips, simple recipes, and the occasional DIY, all from the lovely city of Saskatoon, Saskatchewan.

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