How to Plant, Grow, and Care For Ranunculus

We all know how popular roses are. Thousands of books have been written about them and millions of rose bouquets have been gifted. They’re certainly loved for their beauty, but there’s another flower out there that creates as much, if not more, of a stir due to its beauty as well. Have you ever heard of a rose lookalike called the “Rose of Spring”?

Long ago, a species of flower from the vast family of Ranunculaceae (also known as the buttercup family) lived naturally in the arid coastal regions of the Mediterranean in a swath all the way up to Turkey. This species was Ranunculus asiaticus, or the Persian buttercup. This wild, fairly plain flower in mostly shades of yellow and red would go on to become the ancestor to the many-petaled, full, lovely, and mesmerizing flower we know today as garden ranunculus.

The garden ranunculus, or florist’s ranunculus, originated in a swath of land that covers Cyprus to Turkey and Iraq to Iran. Before breeding and selection, the Persian buttercup was a relatively small plant that acted naturally as a groundcover due to its spreading nature. The flowers were single, or rather, had one row of petals, and bloomed in shades of red and yellow.

The ranunculuses growing in gardens later were known as the Turkish or Double Turban forms. These flowers were bred and selected over time. In the mid-1800s, breeders in France developed a semi-double ‘French’ strain. The French strain was noted for having a blotch in each bloom. About fifty years later, a peony-flowering fully-double strain was developed in Italy.

This was how the garden ranunculus was until the 1920s and 1930s, when a man named Luther Gage began breeding them. He had purchased a farm in California and began growing freesias, anemones, and gladioluses in 1922. Ranunculus seeds were purchased from England, and then it was off to the races.

Mr. Gage would go on to develop cultivars under the name Giant Tecolote Ranunculus. The difference? Large, double flowers in a variety of colors compared to the French varieties at the time.

Later in the 1930s, Frank, Earl, and Edwin Frazee would begin 60 years worth of collecting seeds and breeding new varieties on their farm that was also located in California.

Today, ranunculus are grown as cut flowers mostly, though there are some shorter bedding varieties that are sold at plant nurseries in the Spring.

Plant Propagation

Ranunculus is a tender perennial flower that grows from fleshy, underground structures called tubers. Botanically speaking, a tuber is a starchy underground stem or rhizome with buds or “eyes” that produces shoots that become leaves and stems.

Sometimes the tubers are mistakenly referred to as corms, which are a modified underground stem. In fact, in much of the cut flower and plant nursery world, you will repeatedly see ranunculus tubers referred to as “corms”, not tubers. So, don’t get confused!

They can also be propagated by seed and is done so by many nurseries and greenhouses to sell as bedding plants.

Starting From Seed

Fill a seed tray or pot with loose, well-draining media. Moisten the media, plant your seeds, and then cover the seeds lightly. Keep a humidity dome on top to hold moisture while seeds are germinating.

The temperature should be around 50 to 60 degrees F for optimum germination. Avoid germinating seeds in temperatures that are warmer than 68 degrees F, so no heat mat is needed. Remember, ranunculus are cool season flowers. Seeds should germinate in 10 to 14 days, but germination may be slow and sporadic.

Transplant your seedlings when there are 4 to 5 true leaves present.

Dividing Tubers

If you have ordered ranunculus as tubers, most of the time the supplier will have already divided the tubers so that they’re at the optimal size for planting. However, if you are eager to save your tubers and divide them, then you can do easily!

After the plant has died back in early Summer, you can dig up the tubers. You’ll know that the plant has went dormant when the leaves have yellowed and browned. If you have been growing your ranunculus in a pot inside your home, in a greenhouse structure, or in a raised bed outside, make sure you stop watering your plants when they start to go dormant. You don’t want the tubers to rot, and they won’t need any water at this point.

Dig up or pull on the decayed plant stems and leaves and the dried up tuber should come up easily. If your ranunculus have grown like they should have during the season, you’ll notice that the tuber clump you planted in early Spring should be larger than it was. Often there will be little sections with their own buds off to the side of the original tuber blump. Using your fingers, you can gently wiggle these apart.

Most of the time these divisions are fairly small, but when planted they should grow in size. The larger the tuber, the more vigorous the plant will be the following season. The plants will be larger and produce more flowers. Over a few years you can increase your stock if you’d like. Fortunately, they store well also.

Save only the tubers that are healthy. If you see any signs of decay or mold, or if the tuber is mushy, discard them.

Make sure you are not dividing and saving ranunculus that is under a plant patent, because it is illegal and unethical to do, even if you are just a home gardener.

When to Plant

Because ranunculus are winter hardy to USDA zones 8 to 10, they will not survive temperatures below 25 degrees F. There are a few varieties touted to withstand temperatures down to 23 degrees F.

They perform poorly if temperatures are above 70 degrees F for some time, and they are also intolerant of temperatures above 80 degrees F. Growing this plant can be a little tricky for most gardeners. Think of them as cool season flowers that don’t like hard freezes for long periods of time.

To successfully grow and enjoy ranunculus in your garden, you’ll need to “pre-sprout” the tubers in late Winter or early Spring. Pre-sprouting means you are taking the dormant tuber and adding just the right amount of moisture that the tuber begins to “wake up” and produce root growth.

In warmer zones, you may need to plant in the Fall. Wait until soil temperatures have dropped below 70 degrees F, with night temperatures around 45 to 50 degrees F for optimal growing conditions. Make sure they receive lots of sunlight. At least 8 hours is preferable for growing over the Winter.

I pre-sprout my ranunculus in late January and plant them out in the field with protection in February, but my last expected frost is around April 20th. If you do not have a way of protecting your ranunculus from hard freezes, then you should aim to pre-sprout them later so that you are planting them outside about a month before your average last frost date.

If starting from seed, you’ll need to start them fairly early. It can take 4 to 6 months for ranunculus to flower after starting them from seed, so likely starting them about 16 weeks prior to your estimated last frost is best.

How to Pre-Sprout Ranunculus

The best way I’ve found to accomplish pre-sprouting is by soaking my dry, dormant tubers for no more than four hours in water. Some experts will say you should keep water moving to avoid any possible disease from settling into your tubers, but others will say it’s not necessary.

After soaking the tubers, I fill a tray with moist seed-starting mix and place the tubers onto the mix with their pointy octopus-like “legs” pointing down. I then cover the tubers with a light layer of moist seed-starting mix.

Once complete, I use another black tray and flip it over the top of my bottom tray in order to keep humidity high. I set these trays on my cool basement floor. From there, I check on them daily to ensure they do not dry out and so I can discard any tubers that begin to mold and rot.

In about 1 to 2 weeks, you should start to notice tiny white roots beginning to emerge from the tubers. In 3 to 4 weeks, these tubers will be ready to be planted outside under some sort of protection.

I plant my tubers into raised beds in my unheated high tunnel. This is greenhouse-like structure that is covered in plastic, but it is not heated like a greenhouse typically is. If I know there will be a particularly cold night that dips into the low 20s, I will typically cover the ranunculus bed with a layer of frost cloth. This helps insulate the bed even more.

Another option is to wait until about a month before your average last frost and cover your ranunculus only on those nights that it is forecasted you’ll have a hard freeze. Using an old bedsheet will work fine as a cover if you don’t want to order frost cloth or don’t have any on hand.

How to Plant

Plant tubers or transplants at about 8 inches apart. If you crowd your plants by decreasing spacing, you may end up with more disease. Some commercial cut flower growers will plant as close as 4 inches apart, but that is for smaller tubers.

Tubers can be buried shallow. 1 to 2 inches below the soil surface is perfect. Make sure if you’re planting tubers that plant with the claw-like tubers pointing down. It will be easy to see the correct way to plant if you have chosen to pre-sprout your tubers, as the roots and shoots will have already begun to grow.

How to Grow

When growing ranunculus, there are several things to make sure you prepare for. You want to have the right planting location, soil, water, and climate that can actually allow these beautiful flowers to thrive. Let’s take a look at everything you need to know.

Location

Ranunculus prefer full sun (at least 6 to 8 hours of direct sunlight per day). In warmer climates, it may be advisable to grow them in part shade.

Soil

Ranunculus prefer light, sandy loam soils that are well-draining. Soils with higher clay content may hold too much moisture and cause the tubers to rot in the ground. They prefer slightly acidic to neutral soil pH.

Water

Keep your ranunculus on the drier side, as excess moisture and humidity can cause disease. Using mulch or straw can help conserve moisture. The soil should be moist when plants are getting established, but afterwards a light watering of 2 to 3 times a week should be sufficient.

As plants begin to go dormant, cease watering your ranunculus. The leaves will begin to yellow rapidly when the plant is beginning to go dormant.

Climate & Temperature

Ranunculus prefer temperatures of 50 to 60 degrees F. They can typically withstand temperatures down to 25 degrees F, but will shut down if day temperatures are 70 degrees and above for a lengthy period of time.

In my experience, my ranunculus were still blooming even after temperatures were above 80 degrees F, but the plants became covered in powdery mildew because I was irrigating frequently and the temperatures were so high. As a result, the quality of the blooms was severely reduced.

Fertilizer

You can fertilize with a slow release fertilizer or some gardeners like to use a combination of fish emulsion and kelp. Fertilize a few times during the growing season and your plants will perform well. Wait until the plant has become established before fertilizing so you don’t burn any newly formed roots or leaves.

In my experience as a cut flower grower, I have never fertilized my ranunculus. They are grown in raised beds of compost and that has worked out well for me. I do not treat my ranunculus as a perennial, though. If I were saving the tubers for next year, I would likely try to fertilize more than I do now.

Maintenance

Once established, ranunculus are fairly low maintenance. No pinching or pruning required! Cull any plants that appear to be diseased. Deadhead the faded flowers by cutting at the base of the flower stem almost at the soil line. This will signal the plant to push out more blooms!

When & How to Harvest Cut Flowers

Ranunculus will flower approximately 60 to 90 days after planting tubers, and they will flower 4 to 6 months from sowing if you’re growing them from seed.

To harvest for cut flowers, it is best to cut the stems when the buds are in the “marshmallow” stage. This is when the bud has cracked open and is showing color, but the petals have not unfolded.

The bud will feel soft and squishy when squeezed gently. This is the best stage to harvest for optimum vase life, but you may harvest later as well. They will open faster if the petals have begun to unfold already. Expect cut flowers to last about 8 to 10 days in a vase if you are harvesting at the optimal time.

Cut the stems near the base of the plant. After you cut, the plant will send up more shoots. Usually you will get at least 3 to 5 stems per tuber on average. Some newer varieties can produce 9 or more stems per plant.

How to Harvest or Lift Tubers For Storage

Wait until the plant has went dormant before digging up tubers. The plant foliage will yellow and die back after hot temperatures set in. Make sure the foliage has fully died back before lifting the tubers.

Grabbing the dead foliage and stems, gently wriggle the whole plant out of the soil. If your soil is loose, this should be fairly easy. You may choose to use a small hand trowel also.

Clip off the dead stems and leaves from the top of the tuber, and if you want, you can trim the roots as well. Some gardeners will say that you can store the tubers without washing them. Others will say that you should spray the tubers off well and soak them in a 10% bleach solution. Make sure to dry them out after washing before storage.

To store tubers, you can place them in a paper sack or a mesh bag and store them in a cool, dark, dry place. A basement or cellar is perfect, or even a cool area of a garage. An ideal temperature would be around 50 degrees F for storage.

Popular Varieties

Varieties of ranunculus come in white, pale pink, yellow, orange, salmon, crimson, violet, and various shades in between. Let’s dive into some of the most popular or beautiful varieties!

‘Amandine Barby’

Double flowers of bubblegum-pink are brilliantly beautiful on this variety. The stems are strong and, overall, the plants are vigorous. Plants reach about 10 to 15 inches in height. If you love pink, this is the variety for you.

‘Amandine Chamallow’

Another vigorous performer with strong stems, ‘Chamallow’ produces flowers in a range of soft colors, namely blush, cream, and pale pink. This variety is popular amongst florists for weddings, and once you see it in person, you will know why. The plant reaches 10 to 15 inches in height, though some stems may reach up to 2 feet tall or more. The blooms are quite large.

‘La Belle White Picotee’

These blooms are truly unique! The double flowers have a white base with pinkish-purple tips. Each flower is unique and such a delight. Each tuber can produce about 9 to 15 stems per plant.

‘Cloni Success’ Series

The ‘Cloni’ varieties of ranunculus are especially coveted for their giant blooms that are much larger than standard varieties. The ‘Cloni Success Hanoi’ variety is white tinged with the palest of pink.

‘Cloni Success Grand Pastel’ has blooms that reach 4 ½ to 5 inches across in a soft peachy blush color. ‘Cloni Success Fragelino’ has a bloom the shade of fresh strawberries. The ‘Cloni’ varieties are cloned, patented plants.

‘Cloni Pon Pon Minerva’

The petals of this ranunculus take are textured like carnations, frilly and fringed. The form of this flower is beautiful but the peachy pink color is stunning as well! Just like with other ‘Cloni’ varieties, these ranunculus are vigorous with tall stems and larger flower heads.

‘Bloomingdale’ Series

This series was bred by Sakata Seed America in 1983 and is usually propagated by seed in plant nurseries. Plants of this series are dwarf in habit, only reaching 8 to 10 inches in height, with leaf sizes that are smaller as well.

‘Bloomingdale’ varieties are said to tolerate temperatures as low as 23 degrees F. The flower blooms are double and about 3 inches across. Colors available are red, rose, pink, yellow, purple, whtie, and bicolor shades. This variety is an excellent choice for growing in a pot due to its compact nature.

Pests & Diseases

There are a few pests and diseases that are common for ranunculus. With proper maintenance, both pests and diseases are fairly easily managed for this garden favorite. Let’s take a deeper look at the most common ranunculus pests and diseases you’ll encounter.

Aphids

These common pests are tiny insects with piercing, sucking mouthparts. They come in shades of green to gray, and their juvenile stage (called a “nymph”) looks like a miniature version of the adults. Aphids suck sap from plants and produce sugary excretions called honeydew that develop sooty mold growth, which creates unsightly black spots on the leaves and petals.

Aphids can also transmit viruses. Most of the time you will see aphids clustered underneath the base of the ranunculus bloom or sandwiched between petals. They can quickly become a nightmare if ignored due to how quickly they reproduce and grow.

To control aphids, encourage natural predators like lady beetles or lacewings. You can also purchase these beneficial insects and release them into your garden.

A forceful stream of water sprayed onto the plant will also knock off adult aphids and kill small aphids, and if all else fails remove any heavily infested plants altogether from the garden. There are sprays you can purchase from a garden or hardware store that may also reduce aphid populations.

Cutworms

Early Spring is a time when many caterpillars begin to hatch from eggs and feed on plants. I see them every Spring on my ranunculus and anemones. They damage the plants by boring into the stem or eating through the flower buds. Sometimes the damage isn’t noticed at first, but as the bloom begins to unfurl you will see holes in the petals or petal edges that appear to have been chewed.

One of the most common caterpillars I’ve seen that have done damage to my ranunculus have been cutworms (which mature later into moths after they pupate). There are many different types of cutworms, some with spots, some with stripes, etc. Most are smooth in appearance and can reach 2 inches long when fully mature. Typically, they will curl into a ‘c’ shape when disturbed.

Picking off the caterpillars can be effective if you are very proactive. Cutworms like to be active at night. Oftentimes I will come out in the morning and find damage, so I’ll poke my finger in the soil around the plant and usually find one curled up in a ‘c’ shape near the base of the plant.

Sometimes you’ll find them resting in between the petals of the flower as well. Maintaining a 3 to 4 foot barrier of bare soil around your garden or raised bed can also make your garden less attractive to cutworms. Remove weeds, as these are alternate host plants for young cutworm larvae. Tilling will also expose and kill larvae and pupae in the soil.

Powdery Mildew

A disease that likes hot, humid conditions – powdery mildew is a common problem. Infected plants have a powdery, white growth that appears first on the leaves and then works its way to stems and flowers.

Severe infestations will cause the leaves to turn yellow and die. Powdery mildew is extremely common for ranunculus, especially as the plants begin to die back for the season because the temperatures are usually climbing.

Promoting good air circulation will help prevent powdery mildew problems. You can do this by increasing the spacing between plants. Also, watering in the mornings and avoid overhead watering if possible. Water at the base of the plant by hand or by using drip irrigation.

Botrytis

Botrytis has many forms, but the form known as crown rot can affect tuber health. Botrytis causes molding and rotting of the tubers. Water-soaked tan spots with irregular shapes are also signs of botrytis on the petals. Eventually, the spots will have fuzzy gray fungal growth. The petals will stick together and become matted.

To prevent botrytis infestation, promote good air circulation through your garden bed by increasing plant spacing and also avoid overhead irrigation. Discard any infected tubers immediately.

Plant Uses

The main use for ranunculus is for cut flowers. They are highly sought after in the floral industry because of their beauty. My customers love to watch as they unfold in their vase. Their buds seem small, but when they open their many-layered petals are magnificent. Even the single and semi-double varieties are endearing.

Ranunculus is also often grown in pots in early Spring for the home gardener. They pair well with Spring flowers like larkspur, pansies, ornamental cabbage, salvia, nigella, snapdragons, and more.

A great companion flower for ranunculus is Anemone coronaria. Anemones have similar growth requirements, and in my experience anemones are a little bit easier to grow.

Frequently Asked Questions