that flower in the early part of the year do so on the previous year’s ripened wood and therefore need no . that flower in the latter half of the year do so on young wood that has been produced the same season, and therefore need hard every year.
That in a couple of sentences is the answer to the question of the pruning of clematis, which to many people is still a bit of a mystery. However, it is not quite so simple as that, as some of the early-flowering varieties flower later on in the summer on young wood which they have made since they flowered in the early part of the year, which makes it all rather confusing. The thing to do is to find out when the main flowering is, and the way to do this is to leave the plant unpruned for a year. Then if it blooms freely from April to June it is a variety that does not need pruning and belongs to the Patens and Lanuginosa group. Thesewill often flower during the summer and autumn on the young wood but this does not matter, we have found out when the main flowering period is and until the plant gets out of hand it can be left alone, unpruned, but trained, if there is plenty of room, to give each vine the space in which to produce its blooms without overcrowding. When they do get out of hand they can be pruned back hard after their main flowering period, which is May and June.
If, however, your clematis starts to grow in the spring and keeps on and on and does not produce anyuntil July or August, and then keeps on flowering continuously until the end of September or October, then it belongs to the Jackmanii or Viticella and needs hard pruning every year. This can be done any time during the winter but must be done before the end of February as clematis start to grow very early in the year, in January if the weather is mild, shoots begin to swell and by the beginning of March are well on their way up their supports.
To return to the first section (those that flower in the spring and early summer on the previous year’s wood). In this group there are large number of small-flowering species and they have only one flowering period, with no second blooming as the hybrids do. If all early-flowering clematis bloomed only in the spring and early summer then we would know where we were and what to do, but alas, the large-flowering hybrids that bloom in May and June will confuse the issue by producing a second flowering period on the young wood during the summer and autumn. These species, which only bloom once in the spring, include such varieties as C. calycina, C. alpina, C. macropetala, C. montana, C. spooneri and their varieties. They all produce thousands of small flowers on the previous year’s wood and they need plenty of room for expansion, except perhaps the alpina varieties which are not very rampant growers. If you have plenty of space then they can be allowed to ramble at will, creating a very pleasing picture in the spring. However, if you have only a small garden and wish to grow these charming early-flowering species, then a certain amount of pruning is necessary to keep these plants in bounds. This can be achieved by pruning directly after the plant has flowered. The plant can be pruned quite hard and as the growing period of the early-flowering varieties is after they have flowered, the plant has all the rest of the summer in which to produce its flowering wood for the next spring. In this way even such rampant varieties as the montanas can be grown is a fairly small space, and even if the plant looks like swamping its allotted space it can be stopped by nipping out the growing tips when it has filled its area. When pruning like this it is a good thing to encourage the plant by giving a good soaking of a liquid fertiliser before pruning and afterwards, this gets the young shoots moving. Species do not need so muchas the large-flowering hybrids, especially the early-flowering ones, so if the area is limited and the plant is a strong healthy one these two feedings will probably be sufficient, but keep an eye on the growth during the summer, well, and if it looks as though a little help is necessary give it another soaking of a liquid fertiliser.
The Patens group will be the next to flower. These are the varieties that produce those huge exotic blooms in May and June, such varieties as Lasurstern, Nelly Moser and The President. They send out side snoots from the previous year’s growth and it is on these that the enormous plate-like blooms appear. No pruning is necessary once the first-year pruning has produced a bushy plant, but careful training is essential, otherwise the shoots will simply rush straight up the wall or support and develop into a horrible tangle at the top. Training clematis shoots can be a tricky operation, the young shoots are very tender and very brittle, too much bending and off they snap. Do not worry too much should this happen, as the plant will soon send out another shoot, maybe even two, which will be an added bonus. On a well-established plant one can do a little light pruning in March or April,back any dead shoots, but a word of warning, a shoot may look dead and after the secateurs have snipped through it we realise to our horror that there were green buds further up the . So start from the tips of the shoots and work your way back just to make sure that you do not inadvertently cut off any flowering buds. A lot of dead ends can be removed at this time of the year, but it is not absolutely essential as the flowers and new growth will soon cover up any dead patches.
Double varieties such as Duchess of Edinburgh, Belle of Woking, Countess of Lovelace and Vyvyan Pennell will be flowering at the same time, these belong to the Florida group and also
need no pruning. Doubles are not everyone’s choice but they are quite popular, especially since Vyvyan Pennell appeared on the scene. Double flowers only appear on the old wood, later on the plant will produce single flowers on the young wood during the summer, flowers that do not resemble the spring-flowering efforts in the least, often causing people to sometimes think that their plants are wrongly labelled.
The next group to flower is the Lanuginosa group which causes more confusion than any other, mainly because many of them flower just as freely on the young wood as on the old (just how infuriating can clematis get!). So with this group you can do as you please about pruning, if you leave them alone, training as well as one is able, then you will get the best of both worlds, spring and summer displays., however, will destroy the large blooms that are so effective in the late spring. However, you can cut down the plant once in a while, when it is impossible to train any more or the birds have made too many nests, but you will still get a good show in the summer. If you have a very good plant furnished with several coming from the base you can try a bit of ‘relay pruning’. With this method you cut down half the plant one year, which shoots up with young growth to provide a summer , leaving the other half to produce the big early blooms. Then the following year you reverse the process by cutting down the other side and leaving the part you pruned the year before, thus keeping the plant in perpetually good shape, and obtaining the best of two worlds. You may run into a little trouble with training during the summer, but if you can keep the new shoots of the pruned side away from the non-pruned side all will be well. Such varieties as Henryi, Madame le Coultre, Mrs. Cholmondeley and William Kennett are to be found in this very large section.
The Jackmanii and Viticella groups can be treated as one for the purpose of pruning. They all flower continuously on the young wood and all need hard pruning every year. That means cutting down to the lowest pair of buds on each, often to within a few inches from the ground, especially with young plants. Inevitable this point will get higher from the ground every year, as more shoots are produced, but it does make for a very bushy plant, with many more flowers every year. Therefore during the winter, preferably in January if the weather is open, proceed with a pair of secateurs to your summer-flowering varieties, bend down and cut through all the as low as possible. Do not look up! If you do you will see lovely fat buds swelling beautifully at the top of the plant and you will be tempted to leave them. Should you do this you will find that later on in the summer all your plants have bare stems at the bottom of the plant without a single as far up as those big fat buds you left the winter before. If left unpruned, your Jackmanii varieties will start to grow from where they left off the year before. This means that if your plant grew up to 8 feet the previous year it will start growing from that point, leaving all that 8 feet below as bald as a coot! They can be left, especially if being grown in trees where a bare stem at the bottom does not matter, but when you want to clothe the wall, do please hard.
Relay pruning can be used quite effectively in this section to vary the times of flowering. Cut down half the plant at the proper time for pruning, January or February. Leave the other half of the plant until the end of March or if the spring is cold, the end of April, then cut the second half down. This will result in a much longer flowering period as the first pruning will flower from June to September, and the second pruning will flower from July to October. Varieties in the Jackmanii and Viticella class include such famous and well-known varieties as Comtesse de Bouchaud, Jackmanii, Perle d’Azur, Ernest Markham and Gipsy Queen.
The late-flowering species need little or no pruning unless this lack of space crops up again, in which case they can be cut back hard as with the Jackmanii varieties. The herbaceous varieties should, however, be pruned hard every year as in any case the previous year’s wood often dies back to the ground, so one should cut down the dead stems when clearing up in the garden during the winter. Viticella varieties also do best if pruned hard, as like the Jackmaniis they will start to grow from where they left off the previous year. But the flammula, tangutica, rehderiana or paniculata varieties can be allowed to ramble at will, provided you have the room.