There are 3 ways to propagate Clematis. Taking cuttings or ‘snips’ are how Clematis are propagated commercially but may be a little tricky for beginners and take several years to get to the size that they can be planted in the garden.
Layering is an alternative for the home gardener which is likely to produce quicker and more ‘accurate’ results.
Seeds are how species can be propagated but otherwise Clematis do not come true from seed. However, this may be the only way some enthusiasts can obtain different varieties not available for sale in their part of the world.
The propagation of Clematis from cuttings – a discussion of some causes of failure
This web page has been re-produced from an article from The International Clematis Society Journal 1998 by Tom Bennett, edited by Fiona Woolfenden.
Clematis have the reputation of being difficult plants. The notion is widespread enough, when applied to cultivation and pruning, to make amateurs think that propagation is impossible unless practised by the most skilled and experienced professionals. By explaining some of the ways which would-be propagators fail, and the reasons behind some of the genuine difficulties of propagation, I hope to clear away some of the mystique that currently surrounds the subject.
Tom Bennett
Material for cuttings
As with many other plants, the best material to use for softwood cuttings is that, taken early in the year, from 1 year old plants grown under glass. It is vigorous, likely to be free from pests and disease, compact and therefore easy to handle. In an unheated greenhouse in the UK, we would expect sufficient growth on stock plants to be able to take cuttings in mid-April. By starting this early, we can rely on a growing season of six months or more which will produce stronger, more mature plants by autumn and the number of winter casualties will be reduced.
By contrast, any attempt to take cuttings from plants established outside will have to wait until late May for suitable material to develop and, in the case of some cultivars, and plants grown in colder areas, as late as mid-June, Also, without glass, the propagator has less control over poor weather, late frosts, pests and disease.
Although all species and cultivars will root from softwood cuttings, it has been found that certain species can be struck from hardwood material. This is taken between late February and April, before the dormant buds break. It is immaterial whether the stock plants are grown outside or not. C. montana, C. chrysocoma (and their derivatives), C. x jouiniana and C. heracleifolia all root well by this method but there may be others. I have known the large flowered hybrids root this way, but only occasionally. It is interesting that they will root poor results on our part may be due to faulty technique which could be improved if. we cared to experiment. It is not generally appreciated that the amateur is far better placed in this respect than is the professional, for whom time spent on research means money (so too does a failed experiment). This means that commercial growers tend to stick to tried and tested methods, leaving the field free for the dedicated amateur.
Not all shoots are suitable for use as cuttings, even though they may look it. Nodes which contain flower buds in the axils will root but often fall to produce shoots and should be avoided It is easier said than done with some cultivars: C florida Sieboldiana and C. x Aromatica, in particular, produce little but flowering wood and for this reason alone are difficult to propagate. Sometimes cuttings will go blind for no apparent reason. Botrytis, flower buds and the bud drying out have all been suggested as the cause, although I would question the basis of the last one.
I can’t leave this section without mentioning C. Perle d’Azur. A highly desirable clematis, It is always in short supply. Commercial growers will tell you that It is hard to propagate and yet you will find that it roots with ease. The problem here is the remarkably long distance between the nodes (50 cm is not uncommon) which means that for each stock plant, a grower may get only 10% of the cuttings he might get from the average clematis cultivar.
Preparation of the cuttings
Softwood internodal cuttings are easily handled and are economical with material, The shoot tip is too soft but stem below this which is still green (or bronzy) is ideal. If older, hardened wood has to be used, it should be wounded by removing a thin sliver of rind from one side. As shown in the diagram, cuttings consist of one node, a leaf or leaflet(s) and about 5 cm of internode below. All cuts must be cleanly executed with a sharp knife or razor blade (watch your fingers!); ragged cuts will encourage fungal disease, The cut at the base of the internode must be immersed in water immediately; if it dries out the cutting may look fine for weeks but will be reluctant to root. How much leaf to remove is a matter of judgement. The principle is one of leaving the maximum possible, just short of causing the cutting to wilt subsequently from excessive transpiration. Wilting, even for a few minutes, will damage the leaf permanently and weaken the cutting. Before striking, the cuttings will benefit from a quick dip in a suspension of fungicide.
Types of cuttings
Hardwood cuttings can be either inter-nodal or nodal and benefit from being wounded at the base as shown in the diagram. Some believe that wounding should be practised on all cuttings. It certainly encourages callusing which is a precursor to roots. Though not feasible for commercial producers, the time it takes may well reward the amateur who propagates small numbers.
Striking the cuttings
A free-draining compost capable of some moisture retention should be the aim. 50% moss peat 50% sharp medium grit is ideal. A standard seed tray is filled with the mixture and is topped-off with horticultural sharp sand to discourage disease. A common mistake is to use too much peat or to substitute sand for grit. Compost made this way will become soggy after watering and will encourage rot. The compost should be lightly firmed but not watered until after the cuttings have been inserted. Delaying watering means that the cuttings can be pushed into the compost more easily (don’t use a dibber, you shouldn’t need one) and the mixture consolidates well around them, avoiding air pockets. Overlapping leaves quickly develop botrytis so keep them to a minimum. Don’t worry about a little overlap, though – it is fascinating to see how the leaves re-arrange themselves over a couple of days so as to take full advantage of the available light.
Rooting powder does no harm and those which contain a suitable fungicide will help to prevent stem rot. Use in line with the manufacturer’s instructions. 0.5% IBA. is recommended for softwoods; for hardwoods use a stronger formulation.
Care of the cuttings
Hardwoods are easy. They will take moderate frost so, in the UK, at any rate, no heat is needed. Steer clear of close polythene or too much damping down (both encourage botrytis) until the buds break. By this time, rooting should be under way. Use fungicides once a week when you water and shade against strong sunlight When the buds open, syringe as necessary to prevent wilting.
Softwood cuttings need much more attention. They are dependent on their leaves and a fine balance should be struck to allow the maximum light levels whilst preventing scorch. Too little light will prevent rooting as will the loss of the leaf. A most effective way round this is to mask those panes of the greenhouse through which direct sunlight will enter, with a proprietary liquid, brushed or sprayed onto the glass. Failures happen when insufficient shading is used or the shading misses areas through which direct sunshine passes undetected, as might happen, for example at 7.00 each morning, a time when you might never be in the greenhouse to notice. Be mindful too of doors and ventilators through which the sun will penetrate, unhindered and unnoticed for just a few damaging minutes each day. Don’t overdo the shading by applying it everywhere; the cold light that passes through north facing glass does nothing but good and should be allowed to fall onto your cuttings unhindered.
Polythene applied closely over newly-struck cuttings, in order to reduce evaporation and stop wilting, causes the high humidity ideal for fungi and should be avoided if at all possible. Heat can also build up under it particularly if your shading is inadequate, and it is common to see cuttings cook as a result. It is far better to position it so as to allow some air movement around the cuttings and to remove it completely at night to allow their leaves to dry out. After about ten days you should be able to dispense with it completely, providing you still spray the foliage at regular intervals (the frequency will be dictated by the weather) during the day.
Heat from electric soil warming cables, controlled by a thermostat speeds up the process of rooting. By using a bottomheat of 23 degrees C, roots should form within 14 days, without it depending on the ambient temperature of the greenhouse, you might have to wait 40 or more. With bottomheat though, your compost will dry out from the bottom upwards so watch the watering; a container that is soaking at the top will, with insufficient watering, be dust dry 4 cm further down.
Fungicides should be applied once a week. It is important to use at least two different types, in rotation. There are a number to choose from. The idea is to keep the various strains of botrytis guessing and to knock out those types that are resistant to any one fungicide. Botrytis is cunning, though. It usually sneaks in under the leaf canopy which will then begin to collapse in big holes full of brown leaves covered with white, fluffy fungus. Most likely, the day before, a superficial look would have revealed nothing. Cuttings affected in this way will be a total loss even if they have begun to root. Get into a habit of combing through the leaves, gently with your fingers (like you might look for fleas on your cat!). Do this every couple of days and remove all affected leaves immediately: botrytis can spread like wildfire.
After 3 weeks with heat or 5 7 without, your cuttings will need less and less water on the leaves although still plenty at the roots which will, by now, be forming nicely Wean the cuttings as you might harden off seedlings in your propagator. They can be given more air and less heat and, if you are using a thermostat, reduce it by, say, 2 degrees C steps every 2 days until you have reached ambient greenhouse temperature. The process will take a week or ten days.
After care
When the roots are 6 cm long or more or when a shoot is growing strongly from the node (be careful, some cultivars produce small, weak shoots long before they root), you can pot up. This helps to keep up the momentum of growth needed to establish a strong plant for the coming winter. Use the correct grade of compost (the weakest). It is a mistake to use a strong compost rich in nutrients (e.g. John Innes No. 3) as this will scorch the new roots. Another common mistake is to over pot. Far better to go via 0.31 to 1.01 then 2.01, making sure that the roots at each repotting have used up most of the compost provided by the previous one. Pot a new cutting straight into a 2.01 pot and you will most likely lose it.
Adequate watering, shading from strong sunlight, protection from wind and cold nights (by ensuring proper hardening-off when the potted-up cutting makes the move from greenhouse to outside), and wilt prevention are all needed to carry the cutting through its first summer and autumn without undue check.
Don’t plant out the large-flowered hybrids until the second summer, they are best protected over the winter in a greenhouse or frame. On the other hand, some strong growing species (C. montana and C. tangutica and their derivatives for example), together with the viticella cultivars will, if struck early enough in the UK, be ready for their permanent positions by the September of their first year.
Finally, it is worth stressing that all clematis, struck as softwood cuttings under optimum conditions and with the right treatment will begin to root in less than 4 weeks. C. tangutica and C. orientalis can be potted up a month after striking and I have done the same recently with C. Sir Trevor Lawrence in under two months, despite it’s reputation of being a devil to propagate. Naturally, failures will continue to happen with us all but these are due to our mistakes, not (as we may often like to think!), an inherent stubbornness in the Genus.
Tom Bennett
P.S. Tom then gives some tables to assist in identifying common errors in propagation by cuttings, by detailing the ‘ERROR‘ and the ‘SYMPTOM(S)‘. There are only a few copies of the 1988 Journal left. So if you would like your own copy of this interesting article please join the International Clematis Society and send me an email asking me to reserve you a copy. I will send you this journal as your complementary old Journal on joining the International Clematis Society.
Details of how to join are available on the Web page How to Join.
If you are already a Member of the I.Cl.S. see the Web page detailing how to buy copies of Old Journals.
Fiona Woolfenden
Layering Clematis
You might want to try to create a new plant by layering your clematis. Bury a one gallon pot about eighteen inches from the base of the mother plant and fill it with potting soil. Train a new shoot to the pot, and when it is about 3 feet long, bury a bud union in the pot, cover with about one inch of potting soil, and place a small rock over the section to keep it in place. It sometimes helps to nick the buried section and dress it with rooting hormone.
Keep the pot well watered and mulched, and in about a year you should have a new plant with a good root system confined to the pot.
Separate it from the mother plant and plant it in its new location. You can bury the attached ‘tail’ from the mother plant under your new plant and that will form roots to supply the new plant in time.
Bill Bird, USA
Collecting and Growing Clematis Seeds
It is the right time of year in the Northern Hemisphere to be collecting Clematis Seeds and we have had a number of queries recently. Many of you are keen to have a go at growing your own so we hope that this page will help.
Identifying Viable Seeds
Any seed you collect needs to be ‘viable’, that is it has the potential to germinate. Generally viable seed will be visible in the seedhead, this is particularly true of species. If you can’t see any seeds, however small, then probably none have set and so there is nothing to germinate.
With some varieties you’ll find only a few of the seeds in the seedhead are viable and so you’ll only be able to see a few seeds. But for all varieties, wait until the seeds go brown before you collect them as this is the most common indication they’ve ripened and dried and can be safely stored.
It is easy to identify seeds in large flowered hybrids as they have large ‘heads’. Hybrid seed probably won’t grow true to form, often producing a plant which is reluctant to flower at all. However this is how many new clematis are produced, though breeders go to great lengths to make sure they know exactly the parentage of all of their seedlings.
The picture above shows Clematis heracleifolia with some seeds that have ‘set’ and others that have not. Remember if you are collecting seeds, the I.Cl.S. Seed Exchange would love to receive some, please see below for details.
Fiona Woolfenden, Great Britain.
Germinating Clematis from Seeds
Clematis seeds may take up to three years to germinate, but you should get some germination in about six months to a year. Collect ripe seed in the fall and plant in sterile seed starting mix, covering seeds with a thin layer of sand. Place the container into a zip lock polyethylene bag and place it outside in a shady spot (or a refrigerator) for several months during the winter so that they go through several freeze/thaw cycles.
Then place the covered container in a warm location out of direct sunlight and wait for your first seedling. As the seeds germinate, the small plants should be pricked out of the germinating container and planted into a small pot using a sterile soilless mix. Be very careful as the root will be a single long root in the beginning. As it grows larger it will need a larger pot, fertilizer and constant moisture. When the plant has three sets of leaves, pinch out the growing tip to promote branching.
Seeds collected from hybrid clematis will usually not breed true to the parent so you might create a new and exciting cultivar that may be named after yourself or a loved one. The chances of getting a new winner are about one in 200, but acceptable smaller flowers of little commercial value will result. They make great gifts to fellow gardeners if you get too many.
Your seedling will take at least a year to offer its first bloom and another three years to become a mature plant. I usually wait until it blooms before planting it out in the garden. A greenhouse helps. It is a labor of love! Good luck!
Bill Bird, USA.
The Society’s Seed Exchange
The seed exchange is a vital part of our Society and one of the main benefits for Members who live all over the world. The seed exchange enables Members from different parts of the world an opportunity to obtain seed of Clematis plants which is difficult to find in their own countries.The 2021 Seed Exchange List, comprising seed collected during 2020 along with some seed collected and remaining from 2019, is now available. It is available on this website, please click 2021 Seed Exchange List. Seed can be requested by any International Clematis Society member and is provided free, subject to availability. Instructions on how to request seeds are contained in the seedlist. Note, one year old seed should be just as viable as seed collected much more recently.
Instructions on donating seed to the Seed Exchange
The best seed to donate to the Seed Exchange is from species as these are most likely to germinate true to type. Seed collected in the wild, specially from expeditions, is much appreciated by other members. Varieties common in one country are often difficult to find in another.
The seeds that you donate to the Seed Exchange should be ‘viable’, generally the seed in the head will be visible, particularly with species. If it is not then the seed has probably not ‘set’ and will not germinate. On a number of varieties you find one or two seeds are viable and the rest are not. The seeds should be well ripened and dry, this usually means that the seed head will be brown.
We would appreciate if you can put the dry seeds in a paper envelope and mark the outside with the name of the Clematis species or hybrid that you picked them from. If you collected them in the wild please add the name of the place that they were collected from.
The Seed Exchange Administrator is Benedikt Herian who lives in Germany. All members have received a Society newsletter giving details of where to send their seed, but if you have mislaid this, or have any other related question you can get in touch with Benedikt. To protect Benedikt’s personal email address please email: query@clematisinternation.com
If you believe that you will be able to donate some seed but that it is not yet ripe, please contact Benedikt and let him know. The seeds are collected this year and early next year the Society will send its Members a list of the seeds available. Seeds are free to Members but we ask that if you would like to donate some money towards the running of the Seed Exchange that you add a little extra to your Membership Fee.
However please note, new regulations are due to be introduced on 14th December 2019 which would require a phytosanitary certificate to accompany seed sent into the EU from an outside (non-EU) location. To be on the safe side, please send in seed to arrive before this date.