Considered the “Rose of the Spring”, ranunculus is one of the most popular spring blooms that we grow, especially for spring wedding work. They are tender blooms that like a long cool period to establish a robust root system. However, they cannot tolerate a hard freeze, making them a little tricky to grow outside of zones 8-10 but it can definitely be done!

When to Plant

Ranunculus are best planted in the fall in zones 8-10. In colder zones, they can be spring planted but they will be more prolific if started in the fall under cover, such as a hoop house or low tunnel. If planting in the spring, plant as early as the ground can be worked but have frost covering ready should you experience an unexpected late freeze. Corms can be stored in a cool dry place in your house until you are ready to plant. Just be sure that rodents can’t get to them!

Pre-Sprouting Ranunculus

Ranunculus corms look like little brown octopus. It’s amazing how these strange little creatues can produce such gorgeous blooms. They just need a little wake up call to do so. We do this with a process called pre-sprouting, which hydrates the corm and begins the rooting process. Pre-sprouting is typically done for both ranunculus and anemone corms.

Sort and Soak - The pre-sprouting process begins with soaking the corms in water for 4 hours. Ranunculus require about half the soaking time as anemones take. While the ranunculus are soaking, it is important to oxygenate the water the entire time. We use an inexpensive aquarium air pump with multiple bubbler stones. We often soak multiple varieties together, keeping them separated in labeled mesh bags.
Dip and Dry- As soon as we remove the ranunculus bags from soaking, we dip them in a santizing solution, such as Oxidate, to kill any bacteria or mildew. They then get laid out in individual trays to dry slightly for a couple hours. Be careful not to let them completely dry out.
Sprout and Store - After soaking, anemone corms can be planted out directly but allowing them to pre-sprout in a relatively controlled environment gives the plants a jump-start and will bring you blooms 3-4 weeks earlier. Another benefit of pre-sprouting is the ability to weed out any duds or unhealthy corms (sorry, but there are always a couple) prior to taking up valuable greenhouse or garden space.
We pre-sprout in 72-count trays in order to keep the corms separated from one another to avoid the spread of any rot or disease from one corm to another. The 72-count trays get a small layer of sterile potting material (we prefer ProMix or sometimes use a 50/50 combination of peat moss and perlite). The potting material should be damp enough to wring out a few drops when squeezed but not overly wet.
Place the corms with the “octopus tentacles” down, one per cell. Once full, loosely cover with planting material just so that the corms are fully covered (not deep). Leave the trays in a cool place (40-50°F) where there is not a risk of rodents for 10-14 days. Check on the trays regularly to make sure the soil is moist but not soggy.

Ready to Plant

At the end of the pre-sprouting period, the corms should have doubled in size and grown hair-like roots 1/8” - 1/2” long. Carefully remove several from the trays to check. If planting in beds, the sprouted corms should be planted 2-3” deep and 6-9” apart. The corm should be completely submerged in soil with any plant growth above the soil line. We use 6” agriculture netting to perfectly space our ranunculus with one going in the center of each 6” square. We plant our butterfly ranunculus 12” apart in rows because they are a larger plant. Prior to planting, be sure to prepare the growing beds with 2-3” of compost and fertilizer.