Whether you’re growing flowers commercially or for pleasure, the delicate, double-petaled Ranunculus blooms are sure to turn heads wherever they are.
If you're wondering about Ranunculus Zone, It’s important to know that Ranunculus are winter-hardy only in US hardiness zones 7–11, but zones 3–6 can grow them as annuals. Once you figure out the correct planting schedule for your Ranunculus hardiness zone, you’ll save yourself a lot of effort and time.
Keep reading to learn what the best places to grow Ranunculus are and what your hardiness zone means for your Ranunculus plants.
Ranunculus Hardiness Zones
For such a dainty flower, Ranunculus can withstand relatively cold temperatures. It’s known among flower farmers as a half-hardy plant, which means it can take some harsh weather, but only to a certain point.
Since Ranunculus is a cool-season, spring crop, it thrives in temperatures between 55 and 65℉. The corms—another name for Ranunculus bulbs or tubers—can take the cold down to 25℉; lower than that and they’ll die.
The plant also goes dormant in excessive heat. Summer temperatures exceeding 70℉ for a week will make the tender, hollow stems wither and wilt.
This makes the sweet spot for growing Ranunculus anywhere between zones 3 and 11. Of course, the sprouting, planting, blooming, and overwintering times will differ among these zones.
For the sake of simplicity, we split the zones into annual zones (3a–6b) and perennial zones (7a–11b). Temperatures could vary from year to year, so the schedules provided here are not set in stone.
Let’s dive in deeper and go into detail about the requirements for a successful Ranunculus yield in each zone.
Growing Ranunculus in US Hardiness Zones 3a–6b
Most flower farmers or horticulture hobbyists in zones 3a–6b treat Ranunculus as an annual crop. This means that every year a new batch of Ranunculus corms or seeds will be planted. After the plant dies back, it’s left to compost or the corms are dug up for storage.
Here’s a simplified seasonal timeline that can break down the schedule you need to follow to get the longest life out of your Ranunculus.
Fall is usually when most people who plan on having a Ranunculus run order their corms. Growing from corms is safer and will require less time to get flowers than growing from seeds.
You can either shop for your Ranunculus collection from a local nursery or larger nationwide vendors that offer mail-order corms. Try to avoid mixes with unknown strains, since they can have vastly different thresholds for cold tolerance.
Since Ranunculus is descended from winter-hardy wildflowers, you can pick a variety, like La Belle, that will fare better in the cold.
Steer clear from Amandines, as they were intentionally bred to keep flowering in the summer, which affects their cold tolerance.
In particularly harsh winters where the ground remains frozen until early spring, it’s best to wait until the danger of frost has almost subsided to start your Ranunculus crop.
In the meantime, you can plan your pre-sprouting setup, which consists of:
- An indoor area where the temperature is always between 50–60℉
- Sprouting trays
- Seed growing mix
- A light source
Line the planting trays with about 2 inches of the seed growing mix, then place the corms 1 inch apart. Placing the trays under a source of light for 6 hours daily will help the growing stems be stronger and more wind-resistant.
Seeds will have a similar setup, but just make sure you sprinkle enough of them on the growing mix since they have a low germination rate. Cover them with a sprinkling of the growing medium, just not too much to allow light to reach the growing seedling.
A good time to start pre-sprouting your corms is about 4–6 weeks before the last frost is expected. As for seeds, you can start them in late January or early February so you have a long enough time window for transplanting them into the soil.
Spring is showtime for Ranunculus growers. Once your seedlings are about 4–6 weeks old, you can take them out to your greenhouse, hoop house, or even low-tunnel “caterpillar.” You can also plant them in containers that you can move around to protect the plants from the cold.
It’s highly recommended you don’t put them out in the open as long as there’s any chance of frost. They won’t be able to grow or thrive in these conditions, and you’ll have wasted about a month of work and some perfectly good corms/seeds.
When it’s warm and sunny, you can expose the growing Ranunculus to get some much-needed sunlight. At night, cover them back up or put them inside if you planted them in containers.
You can expect Ranunculus to bloom 90–100 days after they first sprout. So if your Ranunculus sprouted in March, flowers will appear in June. This is a bit later than it does in warmer climates, but you’ll still be able to get 4–6 weeks of gorgeous blossoms.
As long as the temperature doesn’t stay in the 70s for a long period of time, your Ranunculus will keep thriving. As it gets too hot and sunny outside, you might notice wilting and withering.
Some people use shade cloth to prolong the blooming season of their Ranunculus. Others prefer to cut the blossoms as soon as they open so the plant keeps producing more buds. Both of these methods can make your Ranunculus stick around for longer.
By the end of the summer, when the plant has died back, you can either:
- Save the spent flowers for seeds
- Dig out the corms to overwinter them
- Compost the plant
It all depends on how much effort you want to put in, and the scale of your operation. You can always buy more corms or seeds for the following year, especially if you want to experiment with different shades and varieties.
Growing Ranunculus in US Hardiness Zones 7a–11b
Zones 7–11 are the hardiness zones for Ranunculus, where the corms can stay in the ground over winter without dying. Even so, some flower farmers and enthusiasts in these zones treat their Ranunculus as annuals, mostly to bring in new varieties every year.
Since Ranunculus thrives in temperate conditions, regions with a long, cool spring are the best places to grow them. They’re usually planted in the late fall to early winter, and flowers begin to bloom in the early spring.
You can get beautiful Ranunculus blooms for 6–8 weeks in their perennial zone. However, care should be taken during the hottest hours of the day, as the flowers and foliage can get sunburnt. You can use shade cloth for sun protection, as well as a method to make the blooms last longer.
If you plan on keeping your Ranunculus corms in the ground over multiple winters, you should dig them up every 2-3 years to divide them. Aside from being a great way to propagate your Ranunculus plant, it can also keep the corms from crowding that can lead to root binding.
To keep your Ranunculus plants strong and provide enough nutrition for the corms, add slow-releasing fertilizer to the soil for the duration of their sprouting.
When they bloom, you can use a water-soluble fertilizer in a spray bottle. Spray them generously every two weeks to promote flowering and strengthen the growing buds.
Conclusion on Ranunculus Zone Considerations
Growing Ranunculus is possible in different hardiness zones, but the best places to grow Ranunculus are anywhere with a long, cool spring. Those in US hardiness zones 3–6 can grow it as an annual crop, while those in zones 7–11 can grow it as a perennial.
You can count on Ranunculus to bring beauty and wonder into any situation, from simple dinner centerpieces to elaborate wedding floral arrangements. So go ahead and start growing this gorgeous “rose of the spring” to see for yourself!
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