Propagating Clematis

Clematis crispa seedlings

I’m frequently asked “How do I propagate clematis?”  Propagation is defined as a multiplication or increase, as by natural reproduction.  In horticultural terms it is the process of creating a new plant via layering, cuttings or germinating seeds 

Gardeners choose to propagate plants for several reasons: to satisfy the challenge of producing their own plant, because the plant is not readily available at their local nursery or because it is a relatively inexpensive way to obtain a duplication of a favorite plant. 

I am going to only briefly discuss propagation of clematis by seeds and cuttings because it is an intricate and lengthy procedure that is covered in many books written on this subject alone.  These books give you concise step by step instructions needed for success.  There are even college courses that are dedicated to this topic.  These courses describe propagation techniques for commercial nurseries as well as home gardeners and show how to do plant propagation by tissue culture, seed, cutting, layering, grafting, and division. 

Crossbreeding is not an easy operation because it involves careful parent selection and exact timing.  It also requires a lot of patience, but I believe the end results are well worth the wait.

Growing Hybrid and Species Clematis by Seed

Growing a hybrid clematis by seed is most challenging because of the time involved for it to germinate.  These little seeds, if they were successfully pollinated, can take anywhere from 18 months to 36 months to germinate.  Yes, three years is a long time!  But it is also an exciting prospect because these future hybrid clematis ‘babies’ do not necessarily exhibit any of the same attributes of their mother’s flower. These seedlings can often vary in flower color, size, shape and plant vigor.  This means, with time, you could potentially be the owner of a unique American clematis cultivar.

Growing a species clematis by seed is a much easier procedure.  These seeds will produce an offspring just like its mother.  They are also much quicker to geminate, some even sprouting in only 30 days.

Both species and hybrid clematis seeds must be ripe before you gather them.  The best time to sow the seed is immediately after it has ripened.   This will vary depending on when the flower blooms.

If you would like to try your hand at propagation by seeds here are a few simple guidelines:  

It is essential that you are fanatic about your hygienic habits when planting your seeds.  This requires you to use a sterilized planting mix that is specifically made for seedlings.  Disinfect your containers with horticultural disinfectant or a bleach solution to prevent diseases like damping-off.

Place the planting mix in small 3” containers and cover your seeds with 1/8” of the mix.  Moisten and cover with a piece of glass.  Place your containers in a shady location such as the north side of your home where the temperature is 60° to 70° or in a cold frame for colder parts of the country.  Never allow the soil to dry out completely. 

Transplant the sprouted seedlings carefully only after they have developed secondary leaves and they are about 2” high.  To acclimate them properly move them gradually into a sunny location.  Continue to pinch back the tips to promote healthy thick stems.  And, of course, exercise a lot of patience because this is not going to be a speedy process.

Propagation by Cuttings

Many gardeners want to share their plants with fellow gardeners and neighbors.  This time-honored practice of giving cuttings has gone on for generations.  This is reportedly how we now have our American Clematis ‘Betty Corning’ because when Mrs. Erastus Corning II saw this bell-shaped mauve clematis in her Albany neighbor’s garden, she asked her for a cutting of this pretty little clematis. 

In terms of propagation, taking cuttings from clematis stems is a more difficult procedure than germinating clematis seeds.  I suggest that it is probably easier if you want a particular clematis to try and purchase it first for faster enjoyment.  However, if taking cuttings is a reproduction technique you would like to try your hand at because you are a die-hard gardener or the clematis your friend has is not readily available, this is the answer for you.

You will need the following items before you take your cuttings: 6’’ containers, a sharp clipper or knife, a sterilized planting mix, a rooting hormone that contains a fungicide, labels and large plastic baggies.  Before you start you will also need to disinfect your clippers or knife and the containers if they have been used before.  Use horticultural disinfectant to prevent spreading any diseases.  You should use a sterilized planting mix that is specifically made for seedlings and for planting cuttings.  The manufacturer has already sterilized it and using a heavier mix or native soil would more likely rot out the cuttings.  Fill the containers with the planting mix to one-inch below the rim and tamp the mix down lightly.  Water thoroughly.

Now you are ready to select your stems for cuttings.  The best time to take your cuttings is in the morning hours of summer months.  Avoid any sick or weak stems, the very young tips of a clematis, and stems that are starting to turn brown.  You want to select clematis stems that are healthy, vigorous, green and firm.  Take your clippers or knife and cut some appropriate stems.  Remove and discard any flowers or growing tips.  Cut each stem into three to four inch pieces.  Each piece should have one pair of leaf joints (nodes) at the top of the cutting.  Cut off one of these leaves.

Next, dip the cuttings into a rooting hormone.  Be sure to follow the package’s instructions exactly because these rooting mixtures contain a hormone which, if you put too much on, can actually inhibit it from rooting instead of promoting roots.  Use a pencil to make a planting hole.  Insert each cutting into a hole and leave the leaf joint (node) uncovered at the top of the soil line.  Firm the planting mix around the cutting to eliminate any air pockets.  Water again with a fine spray.  Label each pot with the cultivar name and date of planting.

Insert four drinking straws or bamboo canes into each pot.   These will act as miniature tent posts when you cover the pot with a plastic bag.  Make sure the bag doesn’t touch the leaves.  Secure the plastic bag around the pot with a rubber band to maintain a moist, humid atmosphere for your new cuttings so they will not wilt.  Place the pot in a warm, bright location in your home, out of any direct sunlight.

Check on your cuttings regularly.  Take the plastic bag off daily and turn it inside out to provide ventilation and prevent the build-up of excessive condensation, which can cause the cuttings to rot.  Remove and discard any decaying leaves. 

Once the cuttings have rooted, in about four to eight weeks, start exposing them to a drier atmosphere by slitting a few openings into the sides of the plastic bag.  To check for rooting, gently tug on a cutting.  Now acclimate these cuttings to the open air by transplanting each cutting into its own pot for about a month.  They are finally ready to be exposed to a shaded outside location for another month.  Before these new plants will be ready to be planted directly into the ground, they will need to be hardened off for at least a year by leaving them in their containers and gradually exposing them to sunlight.  Good Luck!

FYI: If you are really interested in an in-depth look at clematis hybridization from seeds please visit Bryan Collingwood’s excellent website.