Tips From a Pro on Hellebore Production
As the first plants to bloom in spring, hellebores demand attention and will earn a special place in your perennial assortment. There are many different types of hellebores on the market today. It is important to become knowledgeable about these varieties before beginning a program to be sure you get the results you expect.
Pay Attention to the Hellebore Variety You Choose
Three main categories of hellebore are sold in the U.S.: niger spp., orientalis spp., and hybrids. Growers often do not get the results they expect when growing hellebores due to the varieties they have chosen. Varieties grown from seed, such as many orientalis spp., can take two years or more to bloom. Other varieties may bloom too early for their market; many niger spp. start to bloom in November. Unless a grower wants a Christmas crop, this is too early.
With new developments in breeding, hybrid varieties are becoming widely available as they are bulked up in tissue culture. Some series such as Frostkiss are bred for production, so they are easier to fit in with other varieties growers produce. Hybrids grown via tissue culture will normally bloom in under a year and in general are later to bloom than niger spp., most start to bloom around January. The production tips in this article are geared toward the hybrid category, specifically the Frostkiss series, but the basics can be used for most hellebore crops.
Quick Tips for Growing Hellebores
To successfully produce hellebores, try these 10 tips:
1. Hellebore liners can be planted in two seasons, spring and fall, when they are actively growing.
2. Hellebores are dormant in the summer months. It is not recommended to pot liners during this time.
3. Hellebores need a well-drained, coarse soil with lots of aeration. Keep pH at 5.5. A peat-based soil with decomposed bark works best.
4. Shade plants at 30% in the summer months to prevent overheating and/or burning of foliage.
5. Water hellebores early morning or late evening.
6. Opposite of many plants, hellebores need more fertilizer in the fall to help them initiate flowers.
7. Keep hellebores actively growing. If they stop growing because of low fertilizer, it can set growth back by two to three months.
8. Flower initiation occurs with shortening of days in the fall and lowering of temperatures, at around 40°F to 50°F.
9. Keep hellebores frost-free during the winter in a cold greenhouse, at 32°F to 45°F, to prevent flower delay.
10. To delay flowering, keep the crop very cold, just below freezing. This can delay flowering by one month or more.
Transplanting and Finishing
Whether crops are spring or fall planted, pot them as early as possible in the season. This is particularly true in the spring, as hellebores only actively grow when the temperatures are cooler, so delaying planting can stunt the overall finish size of the crop and decrease the flower-bud count. At Pacific Plug and Liner, we offer a 72-cell liner to plant in the spring and a large 32-cell liner to plant in the fall. For growers not wanting such a long crop time or for growers wanting to avoid over-summering hellebores, fall planting is highly recommended as it can cut the crop time in half. If planting in the fall, growers must make sure the liners they use are large enough and have enough age on them so that flower buds have already formed. This will ensure the hellebores will bloom the following spring. If the liner is too small, lack of flowers may result in a poor quality finish.
When potting liners, it is important to fill pots to the top with soil, to prevent burning the hellebore roots. When planting liners, plant a little deeper than the soil surface. This will help to increase flower bud development.
If overwintering under plastic, be sure to use a white polyethylene versus a clear polyethylene to keep plants from burning on fully sunny days.
Despite what most growers think, hellebores need a steady feed throughout the growing cycle with an electrical conductivity (EC) of 1.2 to 1.5. A slow release, eight- to nine-month fertilizer is recommended for spring planting. In the fall, hellebores start initiating flowers, so they need extra nitrogen and iron during this time. This can be supplied using a liquid drench, keeping EC levels at 1.2 to 1.5.
For most of their crop life, hellebores should be kept pot tight. This seems like the wrong thing to do as growers have been trained to space crops as soon as the foliage starts to touch. Hellebores enjoy cool roots, so keeping plants close together causes the foliage to shade the pot and prevent root burn. Plants can be spaced in stages as the foliage starts to overlap because some varieties grow wider and will need more spacing than varieties such as Frostkiss, which is more upright and does not stretch when grown pot tight. Once plants start to flower in the spring, they can be spaced a bit more to give flowers room to develop.
Never pinch a hellebore; every leaf of the hellebore is helping to form flower buds of the future. Removing the leaves decreases the flower count and overall finished quality. Only remove damaged leaves at time of shipping.
Diseases and Pests
Hellebores are tough plants and rarely get diseases. The main disease issue seen is Botrytis in the flowers. Prevent this by keeping plants dry and in an area with good airflow. Watch for aphids and spider mites.