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Q&A - Growing Clematis

This section is based on an article that appeared in a recent BCS Journal. It will be updated from time to time as new areas of interest arise.

Please also see the section 'Growing Clematis' for information that may answer general questions.

If you have any questions about looking after clematis, please feel free to e-mail us and we will arrange for them to be answered for you by one of our more experienced members. We do this on the understanding that we may publish the question and answer at a later date without, of course, disclosing your name.                           
Success with cuttings
Improving the bushiness of new plants
Growing Clematis paniculata
Clematis davidiana from seed
Successful seed germination
Cutting composts
Stratifying seeds
Protecting roots from rotting
Registering and Plant Breeders Rights
Growing Clematis WISLEYTM

Why do I lose so many of my cuttings during their first winter?

Professionals will take their softwood cuttings from plants that are indoors, in vigorous growth, often with background heating and some bottom heat. Therefore, cutting material is available to them much earlier in the season, compared to us amateurs who usually take our cutting material from normal plants growing out in the garden. Professional cuttings are probably rooted and potted on before some of us find enough suitable growth on our plants to get cuttings. If our cuttings could be taken earlier, potted on as soon as good roots are evident, they would then have several months in which to develop into real plants before they shut down for the winter. The greatest losses occur with cuttings that have only just rooted by when autumn arrives. Some losses can be avoided by not potting on cuttings after, say the end of August, leaving them in their cutting compost trays until the following March, but, if they were taken late in the season, they still might not be developed enough to survive the winter. Either we must get them into growth earlier, (have them in containers in a heated greenhouse) or accept our heavy losses, or leave this type of propagation to the professionals.

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What should I do to improve the bushiness of my newly planted clematis?

Prune down to lowest pair of growth buds in early March, and pinch out the growing tip on each new shoot as soon as it makes two pairs of leaves. Pinch out again when the shoots from these new leaves have also made two pairs of leaves. If growth also starts again from ground level, this too can be pinched out at same two pairs of leaves. This process can be repeated as often as you wish until mid-May, by which time your plant will already have many branching stems instead of just one or two. Pinching out will obviously delay the start of flowering, but now you will have blooms much lower on the plant and no bare expanse of stem. Many stems, instead of just one or two, also give you much better insurance against losing your new plant to wilt. clematis wilt may still attack it but now, because it is shorter and bushy the wilt may only affect a small part of the plant. Clematis 'H. F. Young' is one of few clematis that build up a bushy plant without pinching out.

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Having fallen in love with the beautiful white flowers shown on the label attached to the plant, I have recently acquired a brand new Clematis paniculata. The leaves are very attractive too. I do not know very much about this plant. Please advise me on the following: (a) what is the best planting/ growing position in the garden or does it need a conservatory?; (b) should the plant be pruned during the first Spring after planting?; (c) does it flower on old or new wood?; (d) how and when should I feed it? and (e) can I grow this through another suitable shrub in the garden? I certainly do not wish to lose this plant - cost me quite a bit! Any other information on my paniculata would be most welcome . My garden is not subjected to too many frosts.

In the Southern counties of England this plant is a candidate for a sunny, protected situation. If you do not wish to risk losing it why not grow it in a pot outside (pot can also be buried), and bring it inside for winter. Further North, it is a good plant for a conservatory or cool greenhouse but rules out those greenhouses in full sun unless in a pot which will allow placing outside in the Summer. I consider this plant special, yet out of the ordinary. I make every effort to grow its successor by means of cuttings or other means, because it is inclined to sulk if things are not to its liking.

It is not necessary to prune the plant during the first Spring after planting. However, if the plant is very weak or spindly pruning may help.

C. paniculata (formerly called C. indivisa) is a single sex plant, needing both sexes for seed production. It was introduced from New Zealand in 1840. It flowers on old wood and makes quick new growths afterwards to ripen for the rest of the summer in readiness for next year's flowers.

Feed the plant at regular intervals (say monthly) using a balanced fertiliser.

Growing through another shrub in the garden may be difficult unless it is planted permanently near the shrub. The leaves tend to hang on tenaciously to their host and cannot be just pulled apart - but painstakingly unhitched leaf by leaf - a lot of work and time!

In 1959 Whitehead wrote about a variety lobata with leaves coarsely toothed or lobed, and has larger flowers, but a more recent contributor states that this difference is only evident on young immature plants and the plant eventually grows out of it to produce the 'normal' ovate (not toothed) leaves.

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I read that C. davidiana can be grown successfully from seed in Gardening Illustrated -a very old gardening magazine (1901). I would like to know more about this clematis, and where can I get some seed of this clematis?

I presume it is C. heracleifolia var. davidiana. This plant is well known as is another equally desirable variety 'Wyevale'. Blue, highly scented, midsummer to Autumn flowering, 1.2 m (4 ft.) high, coarse large leaves, smells and looks like hyacinth flowers. I would recommend buying a plant than raising from seed, unless you want more plants.

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Having sown my clematis seeds with great care I am disappointed that not a single seed germinated. I can only report 100% failure rate!

The most important thing to ensure that the seeds are viable. Try and obtain your seed from a reliable and reputable source or ask an experienced grower to show you how to collect and prepare the seed for sowing from your own plants. Be patient, species and small flowered cultivars can take from 3 -12 months and seed of some large flowered cultivars may take up to 2½ years. Do not over protect the seed pots, they may need varying temperatures to break dormancy.

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I am having great difficulty getting hold of sphagnum peat now, for cuttings. Would you say that sedge peat could be used or should I go on hunting for sphagnum moss peat?

No, sedge peat is not a suitable alternative - too wet really. Any proprietary brand of compost including cactus compost for cuttings will give satisfactory results, but most gardeners make their own mix which usually results in a better drained, more open textured compost. Inert materials such as perlite and vermiculite can be added to at least a third by volume but they must be of horticultural quality to ensure compost remains sterile.

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Is it necessary to stratify clematis seeds before sowing?

No. However, germination of certain seeds ( large-flowering varieties - remember they do not breed true) may be hastened by stratification. After harvesting the seeds, leave them in a dry place for a couple of days before storing them in a paper bag at the bottom of the fridge. In February/March, clean the seeds by removing the fruit tails and other debris. Place the seeds in moist sharp sand in a plastic bag, shake thoroughly and leave it in the fridge for about 6 to 8 weeks before sowing.

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Why do I lose so many containerised plants to a from of root rot, compared to the same plants in the ground. This goes for many types of plants, besides clematis?

The reason is quite likely to be a fungus disease caused by Phytopthora sp. that can attach roots and crowns of many plants. It damages some plants and completely kills others. No real cure is available to normal gardeners in the United Kingdom and it is much better to prevent the problem, rather than to cure it. Scrupulous cleanliness of tools, work surfaces, floors and most particularly, pots and other containers, is the best method of preventing an outbreak. Phytopthora thrives in damp, warm conditions and poorly drained composts are ideal breeding ground (also see The Clematis 1999 - Spring Supplement, pp. 34-35).

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I am very excited about a new clematis hybridized in my garden. I have registered it as 'Barbara Ann's Lace' with the International Clematis Society. Would you be able to give me any direction or advice in the process of patenting the clematis and perhaps marketing it sometime in the future.

The best way to move forward with this clematis is for the discoverer to contact someone who can give an independent evaluation of the merits, or otherwise, of bringing it onto the market. The time to decide if it is worth protecting with Plant Breeders Rights or other form of Licence, is when those involved are convinced that it is so different and excellent, compared to other clematis, that it justifies the cost of protection, ( probably £1500.00 or more ). Normally, unless you expect to sell many thousands of its clones and you are already in the commercial world of clematis, it is not worth protecting a new cultivar. You only get back about 25p for each plant sold, so many have to be sold to even get back what you have paid out.

The procedure for obtaining PBR is not short and the people concerned with testing it for complying with the regulations will need at least 3 good sized plants for a year. If it does not stay perfectly true, ( no variation in shape, form, colour, etc ) then PBR will be refused.

As always in these cases, my advice would be, enjoy what has turned up and spread it around amongst your friends. Presumably, it is either a chance cross or a sport, so unless it has bloomed identically for 3 years, it could bloom differently another year. I would suggest that doing the Lottery is a better way to make a fortune than looking to put PBR on a clematis !! One more thing, I have had wonderful blooms from some of my seedlings in my garden and yet, when grown in other people's gardens or in containers, the result is nowhere near as dramatic. Make sure the special effect that makes this clematis so enchanting is not something to do with the location, soil, etc it is currently grown in.

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We have just become the owners of Clematis WISLEY TM and cannot make up our mind where to plant it. The prime question is outside all year or outside in summer and in an unheated greenhouse during the Nov-April period? a. Is it feasible to plant the new plant (which arrived in a 3 "pot and is now 6 1/2"high) into (say) a 9" (5 litre) 'Hide Tomato Pot" using General Purpose Compost (which will have some chalk in it & to which I could add (say) 2 dessert spoons of ground limestone or the like to make it really alkaline) mixed with (say) 2 dessert spoons of either "6X" or 1 dessert spoon of Rose Fertilise. Then to leave it outside until next May ( but bringing it into the unheated large Greenhouse during the winter) before planting it out to wherever presents itself as suitable? or b. Could it be left in a 5 litre pot (or a largish planting tub) for several seasons? If "yes", for how many? And would that be in the unheated greenhouse the whole year(s) round? c. Any other comment(s) or suggestions, please?

Clematis WISLEYTM is fully hardy and will not need any period in a greenhouse, even an unheated one.

The main problem is that you have a very small plant, no bigger than rooted cutting. It will take the best part of 2 years to make this into a plant that will earn its keep in the garden. Ideally, it should have been set in a maximum of a 2 litre pot and kept there for between 3 and 6 months before planting out in the garden. Over potting it into a 5 litre pot may cause it to sulk and do nothing, so, if time is available it should be placed in a smaller pot, as soon as possible.

There is absolutely no need to add lime to clematis compost. Whilst it is true that C. vitalba ( Old Man's Beard ), thrives on chalk, none of the large flowered clematis are native to this country and will usually be happy in any compost that has a PH between 5.5 to about 8.5 !

Rather than molly coddle your new clematis, it would be better this winter to place the complete pot into the soil, up to the rim level or even deeper, so that it experiences the natural seasons. Lift it out next spring and place it in its final planting position.

Like many other clematis, C. WISLEYTM can be grown in a container, provided it is bucket sized or larger, ( ideally 18 inches deep and the same across ). Two thirds J I No 3, with one sixth extra grit ( 6mm ) and one sixth peat. Mix the whole lot together, adding slow release fertiliser, then fill your container, which MUST have excellent drainage and be kept OFF the ground so that it can drain properly.

Whilst I would agree on Rose Fertiliser, I would steer clear of 6X until you have a fully mature plant or you will burn the roots.

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