Growing Ranunculus From Corms: 9 Pro Tips and Tricks
Ranunculi are delightful in the spring-cutting garden and any other place you plant them! Growing these from corms is easy, and with the right environment and a bit of knowledge, you can have these beautiful buttercups lighting up your yard in no time! Cut flower gardener Melissa Strauss has some tips for starting your own ranunculus from corms this spring.
Contents
I added ranunculus plants to my spring cutting garden a few years ago, and they have been an excellent addition! These members of the buttercup family have attractive foliage and simply wonderful blooms. Their long, slender stems make them great for floral arrangements, but they look just as nice if you leave them in your beds as ornamentals.
While you can grow them from seeds, it’s not ideal if you want to see flowers in the first season. They may bloom in late summer to fall in cooler climates, but planting ranunculus corms will give you those flowers much faster.
Corms are the small network of tubers that these plants develop under the soil. Planting corms that are already developed allows your ranunculi to focus energy on leaves and flowers. Planting from roots isn’t complicated. Here are a few factors that contribute to their success that I would love to share with you.
Buy From a Reliable Retailer
First and foremost, if you’re going to purchase a large number of ranunculus corms, the source is important. They are more costly than seeds by quite a margin. If you’re investing in these, it’s a good idea to purchase them from a known and trusted source.
Now, I am all for buying interesting and rare beauties from just about anyone to give them a try. I generally go for a small number if I’m purchasing from a new retailer. Then, if they work beautifully, you have a new source for the next order that you can depend on!
Store Corms Properly
When you receive your roots, you may choose to plant them right away. If it’s not the optimal time of year, though, you may need to hold onto them for a while. Knowing how to store them best will go a long way in how well they come out of dormancy.
If you need to hold them for more than a week or two, storing them properly will keep them safe from sprouting in the meantime. The ideal storage situation involves staying dry, most importantly. A cool spot is usually good for keeping plants in their dormant state. Just keep in mind that these need to stay dry.
Soak Corms
As with many seeds, tubers, and roots, ranunculus roots benefit from soaking before you plant them. Soaking rehydrates them after storage and gets them on the road to sprouting sooner. It’s also important to avoid over-soaking them, as this leads to rotting.
Wait until the day you intend to plant them to soak them. Soak in room temperature water for about four to six hours. Don’t add fertilizer to the water. This is not necessary. If you add anything, it should be a fungicide to help prevent root rot. You can also choose to dip them in a sanitizing solution at the end of this process to help avoid fungus and bacteria.
It’s a good practice to change the water every hour. This keeps bacteria to a minimum. Don’t overdo it because they can begin to break down and decay if they remain wet for a significant time. Overnight is too long. They should just plump up and become smoother. They may expand but don’t worry if they don’t double in size. They don’t always expand that much.
Pre-Sprout
Pre-sprouting is optional, but it can give you a head start on flower development. On average, pre-sprouted ranunculus corms will flower a few weeks sooner. Set up to do this immediately after you soak them so they don’t dry out completely. Remove them from the water and lay them aside on a towel to dry just slightly.
You’ll need a tray and some loose potting mix. Seed starting mix is a good medium to use. Spread some moist potting mix on the bottom of the tray, lay your corms on top. Then, sprinkle another layer of moist potting mix on top.
Place your tray in a cool, dark spot, and mist the soil to keep it moist but not wet. It should take about two weeks for them to sprout.
There are two great benefits to pre-sprouting. This gives you the opportunity to weed out any duds. With the ones that don’t sprout, you can toss them or give them a bit more time. It also gives you a head start on blooming. Pre-sprouted ranunculus will flower about three weeks early compared to those planted at the same time that are not pre-sprouted.
Plant With the Right Side Down
If you’ve pre-sprouted, it should be obvious which side is up. When you plant your roots, it’s important that they face the right way. The vegetation sprouts from the top, which is where the small, finger-like tubers connect. Basically, plant them with the fingers pointing down.
Water, Soil, Sun
Ranunculus corms need loose, well-drained, slightly acidic soil. They do well if you mix in compost for added nutrients. Heavy soil that stays soggy will contribute to root rot, so make sure your drainage is good.
In terms of exposure, your ranunculi will need full to partial sun. About four to six hours is ideal. They prefer cool weather, so if you plant them in full sun, they may stop flowering early and burn up before they are able to produce healthy roots.
These plants like moisture, but they don’t like wet feet. Keep the soil lightly moist, and as long as the drainage is good, they should be happy.
Deadhead
Most flowering plants benefit from deadheading, and ranunculi fall into that category. Removing the spent blooms helps the plant redirect nutrients and energy into producing more flowers. Snip spent blooms at the base of the stem to maintain a tidy appearance.
Leave the Leaves
After they finish blooming, the foliage will eventually turn yellow and die back in the heat of summer. In the meantime, it’s best to leave the leaves intact. They continue to photosynthesize and contribute to forming strong, healthy roots for next year. Allow them to die off before snipping them off at the ground level.
Zones 4-7 Store For the Winter
The most commonly sold ranunculi are warm climate plants and only hardy in Zones 8 and higher. That doesn’t mean that you can’t grow them in colder climates. In fact, even here in Zone 9, I dig up my corms and store them for the summer so that I can utilize that space for other plants.
In warmer climates, plant in the fall. Ranunculi love cool weather and are quite frost tolerant. They stay green and happy in temperatures down into the low 20s (around -7°C). In cool climates, plant them as soon as the ground is workable. They won’t survive in frozen soil, but they like the cold just fine.
If you need to dig them up in the summer, wait until they naturally die back. Remember, those leaves support the development of the roots you will plant next year. When the leaves die back, use a garden fork or spade to gently loosen the soil and lift out the corms.
Wash them thoroughly, doing your best to keep them intact. They will hopefully have multiplied, so you’ll want to gently work them apart, separating individual clusters. Remove as much soil as possible and then lay them out to dry.
Place them on a tray or paper towel in a cool, dark spot for several days. Then, store them in paper or mesh bags, keeping them cool, fairly dry, and in the dark until planting time comes back around!
