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At Thorncroft Clematis we have been growing and selling clematis plants for over 30 years.
Here is an opportunity for us to pass on some of our best advice on how to succeed with them in your garden.
The care of clematis is a big subject so click on the links below to skip to the parts you will find most useful.
Careful planting is the key to success!
Hardening off (November to the end of April)
Clematis purchased during winter through to April, must be hardened off before planting. Stand the plant outside in a sheltered position during the day but take into unheated cover overnight. An unheated greenhouse, conservatory or even a garage will be sufficient to prevent frost damage to the soft growth. The process should be continued for about two weeks before planting.
Planting Clematis in the Garden
The key to successful clematis growing is careful attention to the planting and soil improvement. Without proper soil preparation, even the best quality plants will not thrive or perform to their very best in your garden. An important thing to remember is that clematis like a soil which holds good nutrient but a soil that drains well, so that they do not become too wet.
1. If planting by a wall or fence - the hole should be dug approx. 12" (30cm) away from its base.
2. If planting by a tree - plant about 2 feet (60cm) away from the trunk leaning the cane of the clematis towards the support, try to plant on the north side where the host plant will then shade the root system of the clematis.
3. If planting to grow into a shrub - dig the planting hole just outside the ‘drip-line’ - this is outside the outer branches and lean the bamboo can into the shrubs lower branches.
Whatever your soil type, whether it is heavy or light, acid or alkaline, it should be improved before planting. A clematis does not need a particular soil pH, just good soil quality.
Clematis Planting method:
To start with water the clematis thoroughly before planting, maybe let it soak in a bucket of water but only while you prepare the hole.
1. Dig the planting hole much bigger and deeper than the size of the flower pot. 18”(45cm) diameter and depth is ideal.
2. Break up the soil in the bottom of the planting hole and add well rotted garden compost or a good quality bag of compost. The best compost for clematis is John Innes No.3 because this is loam based and has a high food content. Compost for clematis needs to hold good nutrient as well as adding it.
3. If using manure, put a layer in the bottom of the hole, fork in well and cover with at least 2" of soil. Make sure it is rotted well and not hot or steaming.
4. Sprinkle one good single handful of bonemeal into the hole and mix into the loosened soil. We stock Bonemeal in a 1.5kg Box.
5. Take the plant from the bucket of water (keep this water for later) and remove the plastic ties from the bottom 6 inches of the plant.
6. Remove the pot then carefully loosen the roots if they are in a tight ball. This is essential to encourage good rooting and breaking some of the roots is not a problem, this will aid the development of new root growth.
7. IMPORTANT - Place the plant carefully in the hole making sure that the top of the root ball is buried about 3” (8cm) deeper than it was in its pot and re-fill the hole with a mixture of soil and compost, firming down by hand.
8. Next place four Westland Gro-Sure Slow Release Plant Food around the base of the plant by gently pushing them into the soil enough to cover them up.
9. Using the remaining water from your bucket, water thoroughly - especially if your soil is light and very free draining. Clematis planted by a wall, fence, tree or shrub, may need regular watering especially in its first year but be careful not to overdo it if planting in the autumn.
If your clematis is planted in a hot position, where the base of the plant will be baked by the sun for a large part of the day, place bark chippings or mulch around the base to provide shade for the root system. This will help to keep the roots cool and moist avoiding the plant drying out so quickly.
We stock a range of useful products which you might need when planting your clematis or when preparing the planting area. Check out what we have to offer including our popular range of Care Packs right here in the Plant Care & Gifts section.
How to Grow Clematis in Containers
Choose a large container, preferably terracotta not plastic, at least 18"(45cm) deep with adequate drainage holes. Put plenty of crocks, stones or gravel in the bottom to ensure good drainage and stand the container on feet or bricks to stop the drainage holes becoming blocked.
The best clematis compost is John Innes No.3 mixed with a good multi-purpose compost about 3 parts John Innes to 1 part multi-purpose. Plant the top of the clematis root deeper in the new container by about 3 inches.
Check container grown plants regularly for watering needs, however be careful not to keep them too wet over the winter, and ensure the pot is draining freely!
Each February remove an inch or two of compost from the top of the pot and replace with fresh compost to which a single handful of bonemeal has been added, and water in. For the best results, put 3 Osmocote Tablets into the pot in March, then from April to the end of September we recommend using liquid tomato feed about once every two weeks.
Every four to five years root pruning may be necessary. During winter time when the plant is dormant take the pot off and cut away 2" - 3" of root from the outside of the root-ball. Cut one third off the bottom, and re-pot with fresh John Innes No.3 compost.
Patio Clematis - Notes
To keep these clematis compact, we recommend HARD pruning in February / March and pruning hard again after the first flush of flowers has finished.
In other words - ignore the 'normal' pruning instructions!
For a comprehensive list of Patio Clematis see our Patio Clematis Page.
Tips for growing clematis.
All these clematis have very fine root systems and will not thrive in heavy soil, which is prone to water-logging. They will actually be happier in poorer soils with very free draining conditions.
The herbaceous Heracleifolia Group require hard pruning each year but this is much better left until April when the weather has improved. Do NOT prune these hard in autumn or winter when tidying other herbaceous plants as the Heracleifolia Group over-winter better with the old growth left intact.
Please do not grow these clematis in open, very windy situations, or in heavy soil which is prone to water-logging, as they will not appreciate it and will fail to thrive and possibly die. Instead, give them the shelter of a wall or sturdy fence and ensure the soil is very free draining. Occasionally some leaves will die off, this is natural and they can be trimmed off.
Evergreen clematis have a natural dormant period which is around mid-summer when they look ‘tired’. In extreme heat, cirrhosas may drop their leaves, whilst napaulensis does so every summer. Do not water too much at this time, but give them two or three doses of liquid tomato feed at fortnightly intervals which will perk them up and will encourage them to produce fresh leaves and flower better later on.
Forsteri Group - Other than in milder climates (especially in the UK) we recommend that you grow all the clematis in this group in free-draining soil and give them the benefit of a sheltered aspect. The compost for containers should ideally be very free draining and mixing in a few handfuls of horticultural grit or perlite will help. Make sure the pot can drain freely and reduce watering in the autumn because they over-winter better if slightly dry, rather than too wet!
3. TIPS for the Florida Clematis
These stunning clematis are very prolific and can flower for a very long time when given the right care and attention, so here are my top tips for the florida clematis.
I would recommend growing florida clematis in large pots because they perform very well and they make a stunning display on a patio. Stand the container on the patio from late February to early October and then move it into a sheltered corner or cold glasshouse to over-winter. They will not need heated conditions during the winter, just shelter and if taking them undercover they will probably continue flowering.
In early March the previous season’s growth should be hard pruned down to approximately one foot (30cm) from the soil level and a fresh ‘top-dressing’ of compost and bonemeal can be applied to the container. Use Osmocote tablets for consistent feeding through the year.
Avoid keeping the florida’s too wet over the winter, on the other hand they must not be allowed to dry out completely. Always ensure the pot drains freely and each year harden the plants off during late March as described above.
When planting florida clematis in the garden they will require the shelter of a south or south – west facing wall, with good free draining soil. A sheet of bubble plastic or a double layer of garden fleece draped across and pegged into position will keep the worst of the winter weather at bay. This protection can be removed during early March so that hard pruning can be carried out, then feed with a single handful of bonemeal and water it in. Replace the protection until the worst of the weather has passed.
For further cultural hints see – Growing Clematis in Containers.
Clematis for Hot Climates
We have many customers who garden in countries with warmer climates like in southern France or even hotter such as South Africa or southern Japan. We are grateful to them for giving us feedback on what does well and what does not in these hotter climatic conditions.
Generally we would suggest the following as a guide to those types that are happier in a warmer climate. However, all individual environments do differ, so we cannot guarantee success in any particular location.
Have a look at our page of plants for Dry / Hot Area's.
Keeping the clematis moist at the root is key. Ensure that the compost does not dry out, nor become waterlogged from too frequent watering, then most clematis will cope with reasonably high summer temperatures.
Growing them in pots or containers of some sort is often a better way to ensure good soil and moist, yet free-draining conditions. We understand, for example, that the local soil in Madeira and parts of South Africa is not ideal. There is really no need to shade the roots - although it can help to retain moisture, it can also harbour slugs and other pests.
Most general advice is still the same as in England; Water the plants daily; feed them every two weeks even when they are flowering, and keep pale coloured types that are prone to fading, in shade. (Guidance on Aspect is given in our catalogues - both printed and online).
As a guide, based on feedback from customers, you may like to try the following:
Most of the species, such as terniflora, serratifolia, viticella and heracleifolia.
Cirrhosa and other evergreens, but they may exhibit summer dormancy, losing their leaves in the hottest months.
The Tangutica Group will be fine in drier soils but high humidity may be a problem.
Montanas generally, although they do need a good supply of water especially as they can become very large.
Most large flowered types, but treat all as hard-prune (Group 3), ignoring UK guidance, to avoid too much dead foliage after the early flowers. They should flower again 6 - 8 weeks later.
The Integrifolia Group and Texensis Groups, but these must be kept moist at the root to avoid mildew problems.
Those not suited are the Alpina Group, especially in hot, humid climates such as Japan.
Clematis for Windy Area's
If you are looking for clematis to grow in a position that is exposed to a lot of wind, those in the following groups will cope best. As well as these groups you can use most Hard prune clematis except the category Florida. Have a look at our Windy Aspects page.
Atragene Group - Spring flowering cultivars with nodding bell-like flowers. They are all very hardy, but require a free draining situation. They do not need the 'rich' growing conditions or deep planting that the large flowered cultivars prefer.
Diversifolia Group - These herbaceous cultivars are clump-forming scramblers, or semi-climbers, derived directly, or indirectly from the integrifolia species. In general, they have non-clinging stems and they can be allowed to scramble in herbaceous borders. Alternatively, they can be used to clamber through open shrubs, small trees, rambler and shrub roses or obelisks. They are all hardy, very free flowering, trouble-free clematis and are highly recommended. All the clematis in this group are suitable to use as cut flowers.
Integrifolia Group - These herbaceous cultivars are clump-forming scramblers, they have non-clinging stems and can be allowed to scramble in herbaceous borders. They are good 'front of border' plants and also make excellent companions in beds of bush roses. They are exceptionally hardy, very free flowering and as with other herbaceous plants, they die back in winter. They are all suitable to use as cut flowers.
Viticella Group - They are all extremely hardy, very free flowering, their pruning is simple and they cannot be recommended highly enough. Especially useful for people new to growing clematis as they are extremely tolerant of what the gardener does to them!
Tangutica Group - The clematis in this group are extremely useful in the garden, providing colour and interest from mid-summer through to late autumn, with most producing excellent seedheads for added interest in the winter months. They cope happily with poorer growing conditions and are drought tolerant.
© Thorncroft Clematis 2016