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Pot Sizes

Printed From: British Clematis Society Forum
Category: Clematis
Forum Name: Postings
Forum Discription: General chat and help about anything Clematis
Printed Date: 24 Oct 2018 at 5:32am
Software Version: Web Wiz Forums 9.06 -

Topic: Pot Sizes
Posted By: trogre
Subject: Pot Sizes
Date Posted: 24 May 2011 at 8:04pm


Following on from Roy`s advice that clematis should not be planted direct from 9 cm pot I have this question. Now sometimes  and normally if you buy on line a plant whatever it is will come in a 9cm pot, not sure of litre size but must be around ½ litre.

Normally when the plant is too big for the pot which is normally seen by roots growing out of bottom you transplant into next pot size up and so on.

If you want to want the final placement to be a container on the patio would it be the correct thing to transplant into bigger pot when needed and then plant this pot into the container which would be filled up with soil to hide the pot.

You then can after a few months or whatever take pot out of container and again check roots and again go through the process again until you reach what Roy suggests a 4 litre pot until final placement in container, am I on the right thinking or not.

One other thing as I have as yet not found a good site which will translate pot size  from cm to litres. Wilkinson`s sell a 28cm pot but it did not tell me how many litres. I did find out in the end that this equalled 10 litres but no site that is comprehensive.

Thank you

Posted By: trogre
Date Posted: 24 May 2011 at 8:14pm
Just thought of a problem to my idea of planting bigger pot into container.You will have the clematis growing up support and would be difficult to lift pot out without causing damage,mmm,perhaps back to the think tankSmile

Posted By: Nunn00123
Date Posted: 25 May 2011 at 4:33pm


A great many of my clematis are seed grown, either from wild collections or from deliberate crosses, these are all grown on into gradually increasing sizes of pots, part of this process includes pruning back the plants and pinching out growing tips to encourage the development of more shoots, the result is a bushier plant. Whilst the plant is in the pots smaller than 2 litres it is not allowed to grow above the top of a 3 foot cane. Some plants that I wishe to get into flower early to see their potential, may be allowed to grow on to flowering size in the greenhouse in two litre pots. After flowering a few may be selected for growing on, which means taking cuttings, growing on into 4 litre long tom rose pots and then into the garden or a larger container. At this stage a suitable support will need to be introduced to suit the growth of the plant, but it is not necessary or desirable to remove the original supporting cane at this stage.
I would not advise planting an existing pot into a larger container, as roots will quickly grow through the small pot making it almost impossible to remove the small pot.
There is always the problem of overwatering in a large container, the relatively small root system is then left to rot in soggy compost, this is the main reason for the advice of not overpotting your plants.
When changing containers to a larger one (about every two or three years) or when the ultimate size of pot is reached it will be necessary to tip the plant out of its container and pot on. This is best done with group three clematis when pruning in late February, but leave groups one and two until they have completed their first flowering, at this stage they can be cut down to a manageable size and if replanting into the same pot they will require root pruning, this can be done by hosing soil off the rootball and selectively pruning away some of the root system. Note white or creamish brown roots are live, but black roots are generally dead. Root growing tips are usually white.
Roy Nunn

Posted By: Nunn00123
Date Posted: 26 May 2011 at 4:21pm
When buying plants mail order I usually tip them out of the container they arrive in and if they have a good root system I will generally wash off all soil and repot into a compost that I think is suitable for the plant, into the next size pot, so going from say 9cm to a one litre or two litre pot. They then spend about a week in the shade and then move them to a cold greenhouse. Some plants received are nothing but rooted cuttings that have just been potted on. Often these spend their first week in my propogation area, then to the greenhouse bench. It has been known for me to send plants back that are not of good enough quality, or are not as specified.
The pots I generally use for Clematis are 9cm square x 10cm deep.
1 litre Long Tom is 11cm diameter at the top x 13cm deep.
2 litre Ditto is 13cm dia x 18cm deep.
3 litre Ditto is 15cm dia x 20cm deep.
4 litre Ditto is 18cm dia x 23 cm deep.
Unfortunately there seems to be no universal sizing system for pots, as metric, imperial lateral measures are used as well as cubic capacity, in the US Gallon sizes are referred to, which is totally confusing to me.
The containers that I grow my clematis in vary from minimum 30 cm dia x 30cm deep, for smaller Clematis, usually frost proof clay (Yorkshire), but I also use Chinese Glazed Clay pots but line them with a suitably sized plastic pot. To 45 cm dia by 45 cm deep of similar type. I do not use the clay pot feet as I have found that they tend to result in the pot falling over in wind, but stand them in groups of three for stability. I do not go above 45 cm pots as they tend to be difficult to deal with when repotting, which will need to be done after a about three years.
Good Planting and growing.
Roy Nunn

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