Wednesday, September 12, 2012

Half hardy climbers

Providing it fits in with my 'exotic' theme I always like to try something new in the garden and the use of short lived, half hardy climbers has offered plenty of opportunities over the years.  Even with my relatively mild Plymouth climate their long term survival isn't guaranteed - but they are fun to try even if they only last for a season.  Some last longer, of course, but the one thing they all have in common is their ability to grow freely and flower well in their first year or on annual growth from perennial roots, providing a display up whatever support is available.  Some can be grown from seed, but others are better from cuttings or bought in as young plants.

I've grown a number of different Thunbergia as summer annuals.  This year's feature has been Thunbergia 'Sunshine Susie Red and Orange', a cutting grown variety readily available as small plants early in the season.  Three of these in terracotta pot are growing well up a simple cane framework attached to two downspouts on my house wall.  They've easily reached 8ft / 2.5metres and have produced a continuous sprinkling (it's been too cool and wet for more) of 2in / 5cm reddish orange flowers with contrasting black eyes.

Thunbergia 'Sunshine Susie Red and Orange'
This one should be perennial, with a rootstock capable of taking a degree or two of frost.  I'll cut down the top growth later in the year and store the pot in my shed over the winter and hope for regrowth next year.  This is a process I've used with a couple of other Thunbergia, both of which I kept going for a couple of years before harsh winter reality intervened.  Best of the two was T.gregorii, a true orange.  This even survived outside for a year or two.

Thunbergia gregorii
Thunbergia 'Lemon Queen' was a little more tender and only lasted two seasons - but was still very attractive and far more subtle than the rather strident colouring of the other two.  It took me back to my days as a teacher, growing Black Eyed Susie, Thunbergia alata, for longer term class experiments.

Thunbergia 'Lemon Queen'
There is a triumvirate of seed grown favourites that I keep coming back to in the garden.  Not every one every year but often enough to regard them almost as residents.  Some are - for a year or so if the perennial rootstocks survive one of our milder winters.

Eccremocarpus scaber now comes in a variety of colours, from rarely seen white, through more common yellow, the orange form I've illustrated below, and back to scarcer red.  It's a bit pot luck with a packet of seeds - and who has the room to grow a couple of dozen seedlings on to find the elusive white or red forms?  Not me, I'm afraid.  For all that, even the commoner yellow and orange forms are attractive as they wend their ferny annual foliage through whatever support is handy.  They will seed around and can survive for a number of years through self sowing but plants are rarely as impressive as seed sown early in the year - even the previous autumn - and then grown on in some protection until late spring planting.
Eccremocarpus scaber
Similar early sowing can produce impressive specimens of Cobea scandens by later summer.  This is more vigorous and definitely needs siting in a position where it will not swamp the host plant(s).  It doesn't self sow with me but I have had the rootstock survive a winter to produce a good sized climber the following year.  I've only grown the normal form with it's 3in / 7.5cm bells that open pale cream and darken to their seductive deep purple colour after a short time but there is also a white form if you are looking for something a little different.

Cobea scandens
I keep coming back to Mina lobata about every three years.  Related to the Ipomea indica I grow on the south facing house wall (sadly unlikely to flower this year after our miserable summer) this has interestingly attractive spikes of flowers that open red and fade to white after pollination.  Sadly, the hummingbirds that would pollinate this in the wild are not a feature this side of the Atlantic and the job is probably handled by bees and long tongued moths.

Mina lobata
I should really add a fourth to this seed grown group.  The climbing / trailing form of the annual nasturtium, Tropaeolum majus, was a feature of the garden for years, self sowing annually and producing trails of 6-8ft / 2 metres or more by the end of summer.  In warmer climates it can even climb trees but is far more restrained in our cooler summers.  Sadly the two bad winters before this last one seem to have destroyed the stock of freely produced seeds and for the first time in a while I don't have this in the garden.  I must re-introduce it next year.  It can be a bit of a pest - but the flowers in their various reds, yellows and oranges are well worth the occasional need to cut back the trails of foliage.

Tropaeolum majus - climbing / trailing form
Passion flowers, with the notable exception of Passiflora caerulea which has been in the garden for fifteen years now, are mostly just too tender to thrive outside through every winter.  However many do make excellent pot plants, grown up an framework inside the pot or allowed to grow up an external support on an annual basis, the top growth being cut back in late autumn and the pot being stored under cover through the winter in just frost free conditions.  I've had a lot of pleasure from two over the last few years.  'Lavender Lady' is almost hardy with me, only succumbing in the harshest of the recent winters while the extremely dramatic looking Passiflora antioquensis 'Hill House' was a bit more tricky.  Time to try them both again, I think - or one or more of the other varieties.  They do add exotic interest to the garden and, in a normal winter, surge back to fast growing life in spring when given a minimal amount of cold season protection.

Passiflora 'Lavender Lady'

Passiflora antioquensis 'Hill House'
Though not amenable to the extensive cutting back of the more vigorous passion flowers the same treatment works for the evergreen Pandorea jasminoides.  It would undoubtedly flower more abundantly given free reign against a hot, sunny wall but just isn't quite hardy enough with me to survive such treatment.  I've seen it growing well in other south west gardens which enjoy a more favourable micro climate but for me it has to be pot growing and winter protection or nothing.  Still worth while, though, the heads of tubular white flowers with their rosy eyes providing excellent contrast to the glossy evergreen leaves.

Pandorea jasminoides
There are many others I could - and probably will - try but even this limited selection has added greatly to the garden scene over the last few years.  I warmer climates they would be permanent features, commonplace enough to be ignored.  Here, in cool, damp Plymouth they are exotic additions - but surprisingly easy to grow.  For a summer, at least.


  1. A beautiful selection of half hardy climbers there! Must say Cobaea scandens is my favourite but the rest don't trail behind too far. We have the red flowered Eccremocarpus scaber in our garden and that has remained evergreen last winter, sailing through -10C. We can send you some seeds if you want :)

  2. Hi
    I got a thunbergia orange beauty climber in a pot outside my front door, it's still got quite a few flowers on it, I just wanted to know when, if & how I should I take I in?
    Many thanks

    1. The first mild frost should put paid to the top growth. I'd cut it down at that stage and overwinter the pot somewhere cold but frost free (I use a shed). With luck it will regrow as the weather warms next spring.

  3. After I initially commented I appear to have clicked the -Notify me when new comments are added- checkbox and from now on
    each time a comment is added I receive four emails with the same comment.
    There has to be an easy method you can remove me from
    that service? Appreciate it!

    Look at my blog :: tree climbing

    1. I think you'll need to delete your original comment. There is no setting I can find in Blogger that allows me to switch off the Notify box for an individual comment.

    2. Should have said. I can delete the comment but, out of courtesy, I'll give you the option to do it yourself.