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.
Four easy steps to grow Ranunculus so they don’t die
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.
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.
I recently tried to push the timing of a ranunculus succession to see if I could get them to bloom around the beginning of May. Unfortunately, it didn’t work with my Zone 3 garden. I found that the corms that I started at the beginning of February were really stressed and didn’t do well, or, if they bloomed, they just bloomed at the regular time.
The corms I started on February 15th actually did not do too bad and started to bloom a week or two earlier than usual. Overall, I think starting at the beginning of March is the best time because the struggle of starting a bit earlier is not worth the number of usable blooms that I got.
One more thing to consider: because I started everything so early the bugs that prayed on my ranunculus were really thankful because I had given them food a lot earlier than expected. The bug pressure was much higher than I anticipated.
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 tried growing all my ranunculus in the greenhouse and I found that it fried out my corms. This is because we’re still working on our soil and it’s so early in the season that we don’t have our irrigation set up. The combination of poor soil that tends to get anaerobic plus not enough water plus this, that, and the other thing, resulted in a complete disaster. That’s not to say that if you have a hoop house that you can reliably get water to or soil that holds water better that it won’t work. I know many people are able to successfully grow ranunculus in greenhouses, but for my particular situation, it isn’t going to work.
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.)
FREQUENTLY ASKED QUESTIONS ABOUT RANUNCULUS
1. 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. (I still have not gotten it together enough to try out a fall succession, so I have no additional notes on this. I just know it can be done because I’ve seen other Zone 3 growers do it).
2. 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.
3. 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. Once the corms are completely dried you can put them in a box, bag, or anything that won’t have excess moisture and store them in a dry place.
It’s definitely worth it to pull and save your ranunculus corms. This year when I did it, I found that a lot of my corms grew baby corms, and a surprising number even had 2-3 babies! With the price of ranunculus corms these days, this is an economic way to grow your stock. (Just please don’t save things like Butterfly ranunculus corms that have patents on them that say that you cannot save them).
4. WHERE TO PURCHASE RANUNCULUS CORMS?
Ranunculus corms are generally sold in both the fall and spring. These are things that you might find in a big box store, but by the time you find them, it will be too late to plant them to get successful blooms. So it’s best to buy them from a supply or specialty shop online. In Canada, you can get specialty wholesale ranunculus from Unicorn Blooms. Dahlia May Flower Farm and Antonio Valente Flowers both sell the same varieties of corms as Unicorn Blooms in home gardener quantities.
I have also purchased corms from Whistling Prairie Flowers, Sarah’s Cut Flowers, Tundra’s Flower Farm, Veseys Seeds, and West Coast Seeds. There may be other places as well, but wherever you shop, just be on the lookout for corms sometime in September and then again sometime in March.
I hope you feel inspired to try growing some ranunculus this spring!
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