I have a perennial sweet pea on my balcony – it’s in a pot and in a sunny spot with sun from 4pm onwards. I have got some blooms from it this summer. However, the bottom of the plant looks very unhealthy. I was watering it every second day at the beginning but when this problem started I just watered it twice a week. It is very unsightly and the bloom on it is disappointing. It is in a deep pot. Mary Morris, Co Dublin
Although properly known as Lathyrus latifolius, everlasting or perennial sweet pea’s common names are a clear indication of one of the ways in which it differs from its much shorter-lived annual cousin, Lathyrus odoratus. The colourful flowers of this hardy, vigorous perennial also lack the strong perfume of annual sweet pea. Native to parts of southern Europe, it’s a naturally large, sprawling plant with a slightly coarse growth habit that likes to scramble through hedges or over sloping banks.
You mention that your balcony gets sun from 4pm onwards, which means it’s in shade for a large part of the day, especially the brightest, warmest hours between noon and 3pm. So, I’d suggest that possibly part of the problem is that the plant is just not receiving quite enough direct sunlight to make this sun-loving species happy. I’d also suggest that its naturally vigorous, untidy growth habit means that perennial sweet pea isn’t the best candidate for a container garden as it needs plenty of space to flourish.
Growing space aside, balcony gardens are particularly challenging for both the plants that grow on them as well as the people who tend them. Conditions are typically more extreme, from colder temperatures and harsher winds in winter to hotter summer temperatures and desiccating breezes. Part of the secret to transforming them into lush, green, living spaces lies in using a careful selection of ultra-hardy, shrubby evergreens (examples include Viburnum tinus, Prunus lusitanica, Sarcococca, Aucuba and Pinus mugo) that can cope with these extremes and tolerate regular pruning to keep them in shape while simultaneously offering valuable shelter for less resilient species.
RM Block
Once you’ve established this shelter belt, I’d suggest adding some hardy perennial climbers and scrambling plants more suitable for growing in large containers. These include various small-leafed ivies, Muehlenbeckia complexa, some of the more compact species of clematis such as Clematis alpina and Clematis ‘Warszawska Nike’, and compact varieties of climbing roses such as R. ‘Gertrude Jekyll’ and R. ‘Mary Delany’. If your balcony is an unusually sheltered one, you could also try growing trachelospermum and passion flower, both of which will cope with light shade as long as they are protected from cold temperatures.
Regular liquid feeding during the growing season and annual top dressing in spring with an organic mulch and a slow-release, pelleted organic fertiliser will also help to keep your plants happy.
