Growing Buttercups

Ranunculus are one of the few flowers I truly dreamed of growing before deciding to start a flower farm. They were a great motivation for me, the epitome of flower production, and I couldn't believe that I would have them in my own hands one day.

Long popular in Europe, they are slowly making their way into flower growing in Quebec. Personally, I didn't even know about them before I became interested in flowers! So beautiful, poetic, and championing longevity once cut, they are a firm favorite with many of you. They are now among our most important crops here on the farm, and we are delighted to share with you today how we grow them in the unique conditions of southern Quebec.

The most important thing to know about ranunculus is that they need cool temperatures. Their ideal growing temperature is around 10˚C. They are native to a Mediterranean climate and therefore intolerant of temperature extremes. Conversely, too hot a temperature will stop them from growing properly and flowering. The critical heat threshold for ranunculus is around 24˚C sustained for a few days. Under such conditions, they will stop growing and flowering altogether.

For years, it was believed that they had to be planted in spring in our latitudes because the soil drops to a temperature colder than -4˚C and that this would be fatal for them. However, we are currently conducting tests that prove the opposite. Certainly our winters are less and less harsh than before, but still. Our ranunculus planted in November have survived several nights at -20˚C and even one at -30˚C. Of course, they are not planted directly outside but rather in a cold tunnel (2 layers of blown-in polyethylene) and covered with 2 floating row covers (p19). During the night at -30˚C, we installed two small electric space heaters under the floating row covers to maintain a minimum of heat. It was -12˚C under the row covers for several hours. They are doing wonderfully after these harsh trials, which leads us to believe that planting in the fall is possible in Quebec, provided they are given a minimum of protection.

The tests are not yet complete and therefore we cannot conclude anything at this time, but it is very promising for the introduction of a new approach in a northern climate and thus obtain a prolonged and more abundant harvest.

Our classic method, on the other hand, is that we plant them very early in the season so they have time to grow and flower before the sustained heat of summer arrives. As with anemones, we grow them in cold tunnels so we can plant them in mid-February, when the ground outside is still frozen but not inside the tunnels. Planting ranunculus and anemones is the first active task of the season, the one that wakes our bodies up from the winter months and makes us tingle with joy at welcoming spring again.

Growing ranunculus isn't the easiest thing to do. BUT! I'm going to break it down and explain all the information step by step. Anyone can do it and enjoy the magic of growing ranunculus themselves!
I explain the process for two different techniques, namely mass cultivation for cold tunnel production and for growing in pots at home.

Soaking (4 hours):

The tubers are sold dry, and at this stage they are full of energy and do not mind the cold. Whether you are growing ranunculus in a cold tunnel or in pots, the first step is to soak them.

First, group the tubers by variety and place them in tulle bags, or any other perforated fabric so that the irrigation water can drain away. Place about a hundred corms per bag so that they are not too crowded, then soak them for 4 hours in clean, lukewarm water. They will double in volume during the process.

If you ever get stuck and need to make them wait a little longer, take them out of the water and simply keep them constantly moist. They are not aquatic plants and will no longer be viable if you forget them there.

For cold tunnel cultivation:

There are two options: plant them directly in the ground or let them pre-germinate before planting in the ground.
Pre-germination is chosen a few weeks before the planting date for the sole reason of getting a head start on the season, so they will already be on their way to glory by the time they are put in the ground. Pre-germination is not a prerequisite for growing ranunculus. If you are growing them in pots at home or, by force, you are planting them in the ground later in the season, there is no need to add this step to the growing process.

Pre-germination in soil (2 weeks):

We only tried the pre-germination method in soil once, a long time ago, when we had a smaller quantity of ranunculus to germinate. Then for several years, we simply did not pre-germinate our ranunculus before planting them in the ground because it required far too much energy, space, and resources for our liking.

1. Two weeks before the planting date and after soaking, the tubers are planted in trays between two layers of potting soil.
2. Place the trays in full sun.
3. The room temperature should be around 10-15˚C.
4. Water properly depending on the level of sun exposure and the level of aeration, that is, let the top of the soil dry out superficially between waterings. We want the soil to be moist but never soggy.
5. Once the roots have colonized all the soil, it is time to plant them in the ground.

Bare pre-germination (4 weeks):

Two years ago, we came up with another way to pre-germinate ranunculus that requires significantly less energy, space, and resources than the soil method. This bare method, however, takes a little longer.

1. After soaking, the bags of tubers are placed in perforated boxes (so that the irrigation water can drain) and then stacked in the cold room where it is dark and the temperature is permanently 4-5˚C.
2. We water them every two days to keep them moist (the floor is concrete with a drain in the center) and we make sure that no mold is present.
3. After 4 weeks, the roots and central stem are clearly visible. It is time to plant them in the ground. Handle the buttercups with care.

And there you have it! This minimal-maintenance technique allows us to pre-germinate up to 10,000 ranunculus tubers in the equivalent of 56 cubic feet heated with a single small heater, instead of requiring 2,700 square feet heated with a large propane system with the in-ground method for the same number of tubers.

Planting in open ground:

Whether pre-germinated or not, the process for planting in the ground is the same. Combined with a cool temperature, rich, well-drained soil is a major asset for the quality and length of the flowers to be born. Our permanent beds always receive a pass with a broadfork , a good dose of compost every other year, and a light annual addition of balanced organic fertilizer. All this, gently incorporated into the soil.

We then mark out 5 rows with small removable markers placed on a rake specially designed for preparing permanent 30-inch-wide beds. Next, the tubers are planted (points down) in a staggered pattern across the rows, 6 inches apart and 2 inches deep. Once planted, they must be covered with soil, watered well if necessary, and the beds covered with a floating row cover to protect them from the last night frosts. Finally, it is essential to ensure that the temperature remains relatively cool (around 10 degrees Celsius) for the rest of the plants' growth and flowering time.

Once plants are well established, aphids can become a significant pest. To prevent them from settling in, we usually introduce beneficial insects as a preventative measure, in this case parasitic wasps, which are responsible for giving them a hard time!

Planting and storing tubers at home:

1. Ideally, they should be planted at the beginning of March. Soak them in clean water at room temperature for 4 hours, then plant them in a pot, with the tips facing downwards. Place the pot in full sun, keep the temperature around 10 to 15˚C as much as possible, and water thoroughly. (spring)
2. When temperatures warm up and a few leaves have emerged from the pot (April), transplant the ranunculus outdoors with light protection for particularly cold nights. You can choose to grow ranunculus in pots throughout the season, but transplanting them gives better results.
3. The tubers grow and then transform their energy into foliage and flowers.
4. When the flowers fade, they are removed. Through photosynthesis, the foliage will then serve to transform sunlight into energy that will be stored again in the tubers so that they can flower again next season. (summer)
5. When the foliage fades, it can then be cut. At this stage, the tubers are full of energy and fall dormant. (autumn)
6. It is then time to dig up the tubers to clean them of any remaining crop debris. They are then dried in a shady, warm, and dry place for 2 or 3 days or until they are completely dry.
7. Store them in a dry, frost-free place until next spring. Check from time to time that no mold is forming. (winter)
8. Go back to number 1!

Personally, I like graphics; they help me visualize the big picture.
Here are two graphs that demonstrate the buttercup cycle. One graph for growing in a cold tunnel and another for growing at home with tubers preserved.

Cycle of buttercups kept at home:

Buttercup cycle in cold tunnel:

Regardless of the planting technique, be aware that sufficient ventilation between plants will prevent the formation of fungal diseases. Under these conditions, ranunculus will take about three months to flower and will bloom between two and four weeks. The vase life of ranunculus is impressive and can easily reach ten days, but for this to happen, they must be harvested at the stage where the buds are just beginning to open and have the consistency of a marshmallow to the touch (as in the photo below). This stage can also be distinguished by the opening of the sepals, the small green protective petals below the flower buds.

Remember to keep it funky!