What will survive winter - need help

I'm finding it difficult working out which of my plants will survive winter or rather which are annual and which perennial. My confusion stems from the fact that I'm getting conflicting opinions from various reliable sources,(RHS books and good web sites) however it may just be me not understanding it all properly. For example I have a bacopa snowflake in one of my hanging baskets which I bought in spring from a pretty good local garden centre. However some sources say its perennial and some quite the opposite. It is still flowering but basically is now over what I want to know is if its going to live because if it is I will leave it for next year however if not I want to replace it now with some winter colour and then find something else perhaps bacopa again for the spring and summer.Some of you know that I live in London and have a large balcony however space is a problem and although I can bring in some of my geraniums and pelargoniums I cant really bring in much else. Therefore overwintering is a problem and I have to make a decision as to what I bin now. I have the same question for my Bidens ferulifolia - Dahlia roxy - Dianthus warden hybrid - Coleus - and Campanula monic. I have many other questions with regard to other plants which although I know are not annuals for example my Hibiscus Diana, Hibiscus syriacus oiseau blue and Fuschia (possibly cascade) which I simply cannot bring in and which will have to stay out on the balcony. The only comment I can make here is that I'm about 90' - 100' up in the middle of London over looking the Thames and I should think a heavy frost is unlikely. What do I do with these or will they be perfectly OK where they are?
I have questions about my roses which I will post under a separate heading but any help on the above would be very welcome.

 

Charlie I think the problem is that many plants that are really tender perennials are sold in the UK as annuals. I do not know Bacopa - and I have only looked on one site but that site confirmed my opinion. It said Bacopa Snowflake was a perennial with a frost tolerance down to -2C.

There are quite a lot of these so called annuals that are really tender perennials - even the common Petunia is really a perennial. It is further complicated by the fact that some of these perennials may lose their vigour in the second year, so are best grown as new plants from seed or cuttings even though they are perennial.

The good news is that if a plant is technically a perennial you should be able to take cuttings and overwinter these. This may solve the space problem.

If I am looking for info on a plant I usually Google 10 or even 20 sites and take an average. As you say there is so much contradiction out there, but if I look at enough sites a consensus seems to appear.

 

I am having the same problem with bacopa, after consultation with the experts [see Bacopa seeds, 19th Sept] I have deided to try taking cuttings, bringing some into greenhouse, and leaving one outside with protection eg fleece. Next year, try the variegated one if you can find it, gold and lime foliage with the same white flowers.
The following is all experience and not definitive! Bidens and Dianthus should be OK if no frost, and will often set seed if left in situ. I think most Campanulas are hardy. Don't know about dahlias, I think they have to be lifted and overwintered as corms[?]. Coleus are usually more tender, but easily grown from seed if you can't take it in as a houseplant. Fuschia should be OK if you protect it with fleece, hay etc so its roots aren't frosted, but cut it back soon, mine are beginning to look sad now, except for the larger ones. I have two Hibiscus syriacus which have been fine unprotected in pots over 2 winters, but we haven't had more than 2 hard frosts. If you haven't room indoors, any survivors will be a bonus. Good luck!

 

The last few winters have been pretty mild, but as you probably know the Met Office is forecasting a bad winter this year - so I am taking some extra precautions. I am going to bring as many dubious plants into the house as possible rather than leaving them in an unheated summer house.

 

Thank you Liz and Peter very much for all that it has been very helpful. I'm now starting to understand the perennial/annual issues - What I do know is that its not an exact science!
My Bacopa is just a lovely plant and sits in a hanging basket however, its begining to have a few bits die off. What do I do here? Do I prune it back or just let as is. I assume it will all go brown as winter progresses? Taking cuttings and overwintering is not really that easy for me as I dont have a green house, however I do have some room and I was intending to bring in my geraniums and pelegoniums after I've trimmed and de-leafed them. However my big question here is is it worth doing this or if by doing it am I going to get as good or better blooming plants from the originals. Because quite frankly if I'm not I might as well bin them and buy new ones next spring.
The RHS book says with Dahlias you should cut back and pull up the bulbs and overwinter inside. I only have one Dahlia (that I want to keep anyway)Roxy which is beautiful so I'll give it a go.
My Fuschia is still flowering quite vigerously and looks pretty good apart from some of the leaves are yellowing and beginning to drop. Are you saying (Liz)cut it back now or wait until its stopped flowering?
My Bidens has died (I think)why I dont know it was so prolific and healthy and then it all started to go brown. So I cut it as per a pudding bowl hair cut and left it, maybe it's ususal for it to do this and it will spring back into life next year. I read it was an annual!
Anyway thanks again for the input and any more help would be much appreciated.

 

Best rule I know about overwintering plants - is to try them and see. But take some cuttings and see. The biggest killer overwinter for things like dahlias for instance is less the frost and more the wet. Always remember that plants don't read books - and with a balcolny garden, dependant on aspect, you micro climate will be very different from a ground garden.

 

Charlie - I have had a closer look

Most Dianthus are hardy though I do not know about Warden. I saw the picture of your Campanula Monic on another forum - I do not know it - but it is not like the normal hardy border types. It looks like a house plant and I saw it on a list of houseplants on another site. I would say not hardy.

Coleus is very tender - zone 11 (London is zone 8 or possibly zone 9 depending on heat given out by close buildings) and my A-Z of tender perennials says needs a minimum of 10 to 15C over winter and will not stand frost at all. Dahlia will stand down to -5C if well mulched in a border. But it is always a gamble to leave them out, and pots are colder than a border.

Depending on the variety your Fuschia may be hardy enough. I have them outside in Yorkshire but do not cut them down till the spring as although the foliage will be dead it offers some protection to the crown. But in a small space you may prefer to cut it back for tidiness and protect it with some fleece.

Why not take some cuttings as well if you can - for a gardener it is the challenge not the cost.

 

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