Illumi Lime brings a unique lime punch of color to the Frostkiss series. It blooms from January into April. (Photo courtesy Pacific Plug and Liner)

Hellebores, also known as Lenten Rose, can bloom as early as January in some parts of USDA Hardiness Zone 7, even when there’s snow on the ground.
In a recent GrowerTalks webinar sponsored by Pacific Plug and Liner, long-time hellebore breeder Bart Noordhuis offered “Tips & Techniques for a Stunning Hellebore Crop.” Intended mainly for the Frostkiss hellebore series which he created, the tips could apply to any hellebore.
Chris Beytes, editor of GrowerTalks/Green Profit and host of the seminar, noted the information can be accessed at www.GrowerTalks.com/webinars.
The 14 varieties in the Frostkiss series boast a variety of colors, all with marbled foliage. Propagated by tissue culture, these hybrids are from the niger species rather than occidentalis. They bloom later and hold well into spring.
Frostkiss hellebores also are more heat tolerant, able to handle southern climates, especially when shaded. Because they are produced by tissue culture, uniformity is guaranteed — and they’ll bloom the first year. Seed-produced hellebores generally take at least three years to bloom.
These hellebores are available in 72-cell flats for planting in February or March and in 32-cell packs for planting in early September. Noordhuis emphasized the two narrow planting windows — no later than March and no later than early September.
There is no benefit to start with 32-cell plants, he said. They are all from the same tissue culture planting, with those not sold in spring bumped up to a larger size cell.
Beytes encouraged customers to take advantage of Noordhuis’ offer of technical support customized to the grower’s facility. “He has the most knowledge of hellebores out there,” Beytes said.
Noordhuis recommended planting early for a good crop. Keep the root zone cool at all times. If the root temperature exceeds the leaf temperature, there will be a problem, he warned. Drip irrigation is best.
“Do not water during the hottest part of the day, as this shocks the plant,” he said. “If you let the soil dry, the plant won’t be happy. Water early in the morning and make sure the plant has enough water for the day.”
Suggested pH is 5.4 to 5.5. Noordhuis insisted, “6.0 is not close enough” because pH is logarithmic. Each step up is much more than you might think. Phosphate is not taken up above a pH of 6.
Also, you need a steady EC 1.2-1.5 measured directly in the soil.
A well-drained, peat-based soil with composted bark and “nice air pockets that maintain throughout the growing cycle” is recommended. Noordhuis prefers coarse peat because it lasts longer.
There are two types of bark, he continued. Bark-based soils are made from the whole tree, including the white wood of the center which contains lignin. Lignin absorbs nitrogen, so you end up with nitrogen deficiency. Make sure you use only the outer skin, the bark.
The best pot size for a 1-year crop is one gallon, 8-inch diameter at most. Noordhuis does not recommend transplanting a mature plant because it causes so much stress. It will never come back the same way as planting a new plant.
It’s important to keep hellebores active year-round. Never stop fertilizing — in fall, too, Noordhuis said. Maintain a ratio of 1:3 of phosphorus to potassium in the soil for best flower development.
Start with slow release fertilizer in the spring, then liquid feed in fall when buds are initiating to provide extra nitrogen and iron. He recommended 27-15-12 or 20-20-20.
Micronutrients are important. “In every soil test I’ve seen recently, the microelements are low. That got my attention,” Noordhuis said. If there’s something wrong with micronutrients, it may take four to six weeks to notice, and another four to six weeks to start to fix the problem. Better to get the soil right before you start.
He also cautioned, “Roots cannot tolerate light.” Growers should space pots tightly together in a triangular pattern, filling all spaces. “No straight rows,” Noordhuis insisted. “Keep as much sun off the root zone as possible.” The crop can be spaced apart a bit once flowers form, usually no earlier than November. Keep the leaves touching.
A frequent question is whether hellebores, which are shade plants, need shade year round. Noordhuis said no. Once temperatures are above 80 degrees is time to provide 30- to 35-percent shade. If you use poly tunnels, use white cover, not clear, to prevent sunburn.
Ideal temperature in fall is 40 to 50 degrees F. to trigger flower development. In winter, 32 to 40 degrees F. is ideal.
Some growers use a hoop house to accomplish this. The holding temperature for delayed bloom (to sell flowering plants at Easter, for example) is right at freezing, 32 to 34 degrees F. For flowers around Christmas, force the blooms with a heated greenhouse, but use minimum heat.
Plant growth regulators are not needed or suggested. You can try using a cooler to hold hellebores, but you should test first before committing to a large crop. Remember the cooler must remain cold, a maximum of 34 degrees. Don’t let the temperature fluctuate. Place plants in the cooler once buds have formed, but before they open, on racks with nice ventilation and low humidity — usually in early to mid-December.
Wondering when to trim dead leaves? Remove damaged foliage when flowers develop in December or January, never the rest of the year, he advised. Hellebores grow their leaves in the spring and when you cut leaves in spring or summer, you damage their lungs. “If there’s any green in the leaf, leave it!”
Noordhuis added. “Hellebores have a messy habit. Accept the way they grow.” Plant growth regulators cause stress and result in smaller, fewer flowers.
Frostkiss hellebores make good cut flowers. Keep in mind potted plants get root bound and will produce fewer flowers in subsequent years. Grow hellebores in a field, in a permanent spot, spaced 1 foot between plants, three rows to a bed. Plant 72-cell plants. You’ll have a slow start but way more flowers. Most growers use raised beds, which drain better. Mulch around the base of the plant helps.
Once flowers come out, protect the plants from wind, rain and sunburn.
Let two or three flowers open on a stem before cutting. Put them in water without treatment for 24 hours at 38 to 40 degrees F. to let the plant soak up water, then flowers will last two to three weeks.
Florists are looking for length, 18 inches is nice. Some hellebores can reach that high, but maybe not the first year. Noordhuis said European cut flower growers can get 10 years from a hellebore.
Pests include aphids and snails. Aphids you can’t help. Snails are seen when the growing environment is overly wet, as is botrytis seen in flowers when air flow is low and moisture is high.
Root problems are not normally seen, but can occur if soil is too dense or you are irrigating too much.
A technical guide for growing Frostkiss hellebores can be found at www.ppandl.com/hellebore.