Growing Ranunculus in a Cold Climate: Tips for Success in Zones 5-6
When it comes to gardening in New England or other cold regions within USDA Hardiness Zones 5-6, one of the most rewarding challenges is cultivating beautiful ranunculus flowers. Known for their vibrant colors and delicate petals, ranunculus blooms can add a touch of elegance to any garden. However, growing ranunculus in a cold climate does require some special care and attention. In this blog post, I'll walk you through the process, step by step, and share our experiences to help you succeed in your ranunculus growing. From budding gardener to farmer-florist, there's a method for everyone here.
Starting Corms Indoors: One of the key factors for success in growing ranunculus in a cold climate is to start your corms indoors. Typically, ranunculus corms are not planted directly in the ground in late winter or early spring (without solid protection like a high tunnel or greenhouse), as the cold temperatures can be harsh. Instead, it's best to begin the growing process indoors to give your ranunculus a head start.
If you need additional guidance on presprouting, I recommend referring to 'How To Grow Ranunculus & Anemone' a prequel to this post. In that article, I emphasize starting your corms on Valentine's Day without any additional protection such as light frost cloth or a tunnel. It's important to note that this would be our latest start date in our region, but your window of opportunity for presprouting runs from January to February as a gardener or small grower. Professional growers can start earlier with large tunnels or heated structures.
The results presented in this article were obtained in a high tunnel located in zone 5, and I initially provided extra protection with a low tunnel. However, I've since gained more confidence and no longer use the low tunnel.
Outdoor Planting Options: When your corms are ready, you have several choices for outdoor planting in a cold climate:
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High Tunnel (Fall Planting Option): If you have access to a high tunnel or greenhouse, this is the optimal location for your ranunculus. The added protection from the elements allows you to start in the fall by planting directly, without presprouting. Direct planting could be in the ground, bulb crates, bags, or other contained method.
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Low Tunnel with Frost Cloth (Valentine's Day Planting): If a high tunnel isn't available, you can still plant your ranunculus in a low tunnel and use frost cloth for extra protection during cold spells. Plant outdoors around Valentine's Day. In Zone 5, I trialed fall planting with low tunnels in a field and even with additional fabric, it resulted in significant losses.
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Raised Beds with Frost Cloth and Low Tunnel (Valentine's Day Planting): In the absence of tunnels, consider raised beds with frost cloth and an additional low tunnel to shield your ranunculus from harsh weather. Plant outdoors around Valentine's Day.
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Larger Pots/Bulb Crates Indoors (Valentine's Day Planting): For gardeners or growers with limited space, growing ranunculus in larger containers indoors is a viable option. Once overnight temperatures consistently stay above 28°F, you can move them outdoors. For instance, you can plant one plant per 6-inch pot or three plants per 12-inch pot, and ensure they are planted by Valentine's Day. For bulb crates, we've had success with 9-12 corms per crate.
Note to small scale growers! Bulb crate growing can be an easy and effective way of staggering your bloom window or by using a combination of these methods.
In the grand scheme of things, if you happen to experience a frigid winter that delays your planting until March, don't sweat it! These things can happen and it's ok. As late March approaches, keep a close watch on the weather, and if possible, consider planting after a rainy spell. This will help soften the ground, making it easier to get your plants in.
Remember, in growing, you aim for the moon, and even if you fall a bit short, you'll still end up among the stars. So, stay flexible and keep going!
Understand that growing ranunculus in a cold climate involves some risk. However, plants have a remarkable ability to adapt and survive. Even with occasional dips in morning temperatures, well-established ranunculus plants can endure. A brief dip into 20°F in the morning won't harm established ranunculus. Brief is 3-4 hours.
You can expect to start harvesting ranunculus in mid-late April, with a bountiful harvest in May. Ranunculus thrive in cool weather, making spring and fall the ideal bloom times for these stunning flowers. 
Ranunculus is generally peaking for us by Mother's Day. It's such a treat to design with and everyone loves them. It makes up for the relatively short harvest window.
To piggy back on ranunculus planting, know you can apply these exact same methods to anemones with less worry. Anemones are more hardy than ranunculus.
If you're eager to try your hand at growing these exquisite blooms, we offer corms during our annual sale. You can explore our Corm Shop for more details or check out our Cut Flower Plant Starts page to see what's currently available. Happy planting!
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Barb Parry
February 26, 2024
Becky, I found this post very helpful, especially after yesterday’s workshop. I wish I had started with anemones rather than ranunc. but I’m game to give it a go. I’m going to try the bulb crate suggestion. Thank you for sharing your expertise.