Hellebores.org: Growing and Propagating Helleborus

Growing and Propagating Hellebores

Basic Cultural Requirements

Most hellebores are relatively care-free plants. As with many ornamental
perennials, adequate soil preparation is the key to long term health and vigor.
Though hellebores will grow in a great variety of soil conditions, a well-drained
base containing plenty of organic matter suits them. Preparing deep beds will
provide the extensive root systems plenty of growing room and potentially many
decades of healthy growth. Ideally, the soil should receive regular moisture
without being waterlogged. However, the plants are surprisingly drought-tolerant
once established and can survive in less than optimum conditions.

Almost invariably hellebores are sold as shade plants. One of the benefits is that
they will tolerate shady conditions, but by no means are they shade-loving plants.
Many of my plants receive full afternoon sun throughout the year, and all of them
receive virtually no shade from November-March. Plants in deep shade will live
but generally exhibit sparser growth and produce fewer blooms.

Growing from Seed

One exciting way to grow hellebores is by sowing seed. Though it is nice to
purchase a beautiful plant and put it in the ground, growing from seed can also be
an enjoyable experience. Germinating seed is quite easy so long as you give
them the conditions they need and exhibit a little patience (well, maybe a lot of
patience is more accurate). Most plants will bloom in their third or fourth year.

Naturally, most hellebores grow in environments with a seasonal cycle. A seed
dropped from a plant is likely to encounter a warm environment and endure a hot
summer followed by a reprieve before a cool or cold winter. In most cases, the
cotyledons emerge from the soil sometime in late winter-early spring. The radicle
may begin to form as early as autumn.

This cyclical pattern has led many to suggest that hellebore seeds require
stratification (a warm period followed by a cold period). I generally follow this
wisdom simply because it seems to work almost without fail, but reports of
germination without a cold period are not uncommon, particularly with very fresh
or slightly immature seed. Germination inhibitors develop in mature seed.

Hellebore seed may take 6-18 months (or more) to germinate; however, if you
start with fresh seed and sow it soon after harvest, then your chances of achieving
high germination percentages are quite good. When sowing in pots, place seed
about a quarter of an inch below the surface and firm lightly. Top dress the pots
with grit and water occasionally, just enough to keep the soil mixture slightly
moist. I plant most seed in the garden in prepared beds. I cover the seeds with a
very thin layer of rotted pine bark to help preserve moisture and then water
occasionally in summer and autumn during dry periods. The natural cycle of
autumn and winter provides the a low-maintenance approach to stratification.
Gardeners who have trouble with rodents and slugs may need to take
precautions, as hellebore seed and seedlings are apparently tasty to such
creatures.

If controlled conditions exist, it is possible to expedite the process. For example,
sowing fresh seed in damp media at room temperature for eight weeks followed
by a cool period in the refrigerator for another eight weeks or so will yield results.
This method is often necessary for seed that is shipped from the southern
hemisphere in winter.

Vegetative Propagation

Acaulescent (stemless) hellebores divide fairly easily. Simply make sure to
choose an established clump and dig up as much of the root-ball as possible.
Hellebores have extensive root systems, often deeper than the height of the plant.
Gently shaking or washing off the excess soil allows for better viewing. Though it
is possible to divide at almost any time of the year in some climates, late spring
and early fall generally provide the most opportune times for many gardeners.

Dividing hellebores is the only simple way to produce more of a special plant.
Careful hand pollination can result in many similar (or even superior) specimens,
but seed-grown plants in many cases will differ significantly from the parent. Even
with controlled conditions, plants grown from seed show amazing variation.
Starting from seed is often the most efficient way to raise a healthy plant; however,
given care and a mild environment, divided plants will also thrive. Division is one
solution to the challenge but is not easy to accomplish on a large scale. With the
caulescent plants particularly, it is simply impractical to achieve good results with
division on a large scale.

Tissue culture has also become an option in recent years. It is still a slow
process however, and it is possible that the efforts of careful hybridization and
selection will out pace it and create better plants in the process. Still, it is a viable
option for mass-producing similar plants.

Diseases and Problems

I have never had a problem with hellebores but there are some problems and
diseases that deserve attention. Two of the most ugly are 'Black Spot' and 'Black
Death', the latter being fatal to the plant and a very serious concern for hellebore
collectors. On old leaves it is normal to see browning and blackening of tissues
as the individual leaves go through their natural life cycles; however, there are
cases where blackening of tissue is observed in otherwise active and healthy
tissue. There is no need to panic, but my policy is better safe than sorry. Let's
hope that if nurseries and growers take this seriously that none of us will have to
worry about it in our gardens. My experience is that healthy plants growing in well
ventilated environments do not show any blackening on actively growing tissue. If
you are concerned about particular plants, you can read more here:

www.rhs.org.uk/research/Sciencereport/Hellebore.pdf
http://www.rhs.org.uk/advice/profiles0401/hellebore_black_death.asp
http://www.rhs.org.uk/advice/profiles0501/hellebore_leafspot.asp
http://www.helleborus.be/index.cfm?fuseaction=art&art_id=1299