In light of the rumoured approaching summer, and with the hope of warmer weather ahead, I give to you this week a list of tropical plants suitable for a metropolitan environment. City gardens often suffer, not just because of space restrictions or local conditions, but more commonly through lack of imagination. With a little planning you can have your own urban jungle, but of the green kind!
Many inner city gardens have their own sheltered little micro-climate, making them ideal for more tender and exotic-looking plants.
The candidates below are all selected based on their compatibility to the urban environment.
1. Dicksonia Antarctica, otherwise known as the soft tree fern. This hardy semi-evergreen, which can grow up to 6 metres in the wild, can survive acidic or alkaline soils, thus immunizing it against the effects of city pollution. Commonly seen in the gardens of Cornwall, this lush-looking species will spore after several years and, due to the unique nature of the plants trunk, it can provide an ecological foundation for epiphytic ferns and vines – plants that derive only physical support and not nutrition from their host, though they may sometimes damage the host. With consistent trimming, the shoots of previous leaves will rot and amalgamate as the plant thrives with older generations of fronds sealing the trunk to protect it from weather and desiccation. The Dicksonia is best planted in heavily mulched and watered soil, but can flourish in semi-shade or sun, with a cold margin of minus 5 centigrade. However, additional protection is recommended during severe weather periods or prolonged winters by capping the trunk with a layer of straw. This can be removed in spring along with any old fronds that have turned brown. Spray the trunk and leaves with water during periods of dry weather.
2. Cordlyine australis, or Cabbage Palm, is one of the most prevalent monocot species on earth, originating in New Zealand. (Monocot seedlings typically have one cotyledon (seed-leaf), and many plants cultivated for their blooms are also from the monocot group, notably lilies, daffodils, irises, amaryllis, orchids, cannas bluebells abd tulips).
The Cabbage Palm is also commonly known as the Torquay Palm throughout Britain as it can be seen all along the mild coastal resorts of the south-west, where it reaches up to 5 metres in height. But we’re talking city living here, and that’s fine too because the Cordyline thrives either in the ground, or in a pot. It is fire resistant like the Dicksonia and can regrow from shoots, stems or even a trunk stump.
The plant’s season begins in autumn, the leaves now tightened to a spear by summer’s departure guard the inflorescence that unoccupied growing tips produce for the spring. Throughout spring these flowers will serve as a watering ground for a myriad of different insects, honey bees and moths, predominantly, until late summer when the specimens fruits will ripen and provide seeds for bird dispersal.
There is little maintenance – just remove any dead leaves.
3. Trachycarpus fortunei, otherwise known as the Chusan Palm, is another palm tree notable for its hardiness and fertility. Indigenous to the rainforests of Burma, it is one of the most prolific palms in the world and due to its natural habitat in the mountain ranges of Japan and Southern China, it is possessed of an extraordinarily high tolerance to cold weather. The aesthetic value of the plant is enormous, with its interesting fibrous trunk, huge green fan-like leaves and a choice of green or yellow flowering depending on which gender you cultivate, and splashes of blue brown during it's autumn fruiting stage. However when investing in the Chusan, or indeed any palm, it is important to note the scale of the commitment you're embarking on, they're avoided by many horticulturists due to their impractical yield time, meaning that, unless you buy a fairly mature specimen, many home owners may well have moved house before the plant matures! Ultimately they can reach up to 20 metres, but this would take many years. Balanced soil is ideal, not flooded, not sun baked, and preferably sheltered if wind damage is likely.
4. Musa basjoo, the Japanese fibre banana, although now contested to have originated in China's Sichuan province, is named for the commercial potential of its fibres as a textile. It is considered an ornamental plant and, due to its hardiness, can adorn the majority of city gardens. The pseudo-stems that make up its base act as an early warning sign of cold weather on the plant. However, should these stems perish, fear not, as consistent mulching will coax new shoots from the frost resistant rhizome and the plant will rapidly return to its full potential. It is, however, advisable to protect the stems in winter by placing a drainpipe over them and packing out with straw. In the UK it will probably never bear edible fruit, however it could nevertheless easily exceed heights of 4 metres or more. Obviously hardiness will increase with age, but it is advisable to plant deeply - between 30 and 45 centimetres of mulch should be afforded. The light requirements vary depending on your desired rate of growth as the species will do well both in full sun or semi- shade. Of course, the trick is in balancing the level of exposure, so that the delicate leaves will not fall victim to wind damage, whilst allowing enough clearance for sunlight. Rather an androgynous species, it will produce male and female flowers on the same cluster in the springtime, with thick white pods and surrounding petals.
5. Fatsia japonica, native, as the name suggests, to southern Japan, is a large, evergreen shrub with glossy green leaves and creamy, candelabra-like flowers in the autumn. With such an array of taller palms and ferns available to us, we should not neglect the lower storeys of our urban oasis in order to maintain a balanced décor. This evergreen’s growth is shrubby and generally limited to 3-4 metres and so is a perfect filler to the undergrowth level of the garden as they require a cool, humid environment for optimum growth. Intense sunlight will be detrimental to this species, thus it will fit perfectly in any garden with a well established canopy and semi moist soil. Growth supplements or fertiliser should be provided bi-weekly in the spring/summer growing period to guarantee healthy flowering late in the autumn. These white umbel blooms, upon shedding, will be followed by small black fruit.
6. Phormium, or New Zealand Flax, at first glance looks very similar to the Cordyline, except that the Phormium doesn’t form a trunk, but remains a fountain of colourful foliage at ground level with tall orange-red flower spikes appearing in summer.
It derives its name from its English discoverers, due to the fibrous nature of its leaves. The Latin derivative Phormium Tenax translates directly to ‘wickerwork tenacity’.
This species can sustain itself in sun or semi-shade and it is fairly resistant to frost although heavy snow can sometimes flatten them for a while. However, damage of this nature is generally centralised to the base of the central leaves, tender due to their recent emergence, and is merely aesthetic and new shoots soon form to replace them. They perform best in a moist soil, so if you’re a water gardener consider festooning the edges of your ponds and streams with this attractive addition. Should you want to propagate the species, the best method is to divide it. Healthy plants soon grow into a large clump as new fans of leaves develop around the older ones. These eventually develop their own roots and can easily be detached from the parent plant.
7. Passiflora caerulea, more commonly known as the Passion Flower is a South American resident popular among gardeners for its distinctive, exotic-looking blooms, its complicated elements being said to represent the Passion of Christ. The colourful corona was supposed to represent the crown of thorns. The ten sepals and petals represented the apostles (except Judas and Peter), the five anthers were the five wounds on Christ's body, and the three stigmas the nails. The leaves were supposed to be the spear that pierced his side, and the tendrils were the scourges that flayed his flesh. Whatever you believe, there is no doubting the exquisite beauty of this plant. Where supporting vegetation is available this vine can grow up to 20 metres high and will flower all summer long, knotting with the surrounding species and providing a subtle visual bridge between canopy and undergrowth. Passiflora differ from the majority of tropical species in that they thrive in arid soil. They are famous for littering the upper slopes of the Andes mountains and prefer a composition of sharp gravel, medium loam and peat. It is best to plant at the end of the winter season as the most common threat to this species is root rot due to poor soil draining and frost damage. While the Passiflora can resist the short term onset of frost, long exposure will perish the roots. In May, cut back any frost-damaged shoots and keep new shoots tied into supports as the season progresses.
8. Campsis radicans, or the Trumpet Vine, is another mid level species worth considering in a tropical-style garden. In time it forms dense foliage into which other plants can amalgamate and wildlife integrate their nests. It is a creeping vine that in warm weather with cling to practically any surface and layer them fast and thick with tendrils, thus it is ideal for the concealment of arbours or drain pipes that might rob your 'banana republic' of its potential for escapism! When blooming, it will produce colourful trumpet shaped flowers, whose pollen is highly attractive to bird and insect life. When cultivating this vine, it is essential to prune regularly and mercilessly, the Trumpet Vine is infamous for its invasive nature so unless you want the authentic 'jungle' motif, then maintenance must be meticulous. Fortunately the hard work mostly ends there, as this species is especially hardy, surviving temperatures lower than -30 degrees in its North American habitats. It will thrive in sun or partial shade, in practically any soil, but just as the Passion Flower, remember to tie it in regularly.
9. Hedychium, a.k.a. Ginger, is a perennial genus native to Asia, sought after for their scent and colour. For this reason they are best positioned where their perfume can be appreciated. They grow from rhizomes and can get up to between 120cm and 180cm tall, so are perfect as mid level foliage plants, whilst also adding dots of exotic orange, red, white or yellow perfumed flowers to your palette. However, care should be taken that it doesn't overrun your garden, as it has developed a reputation as a weed in Brazilian climates, although of course it's virulence all depends on good sunlight. While the plant performs best in full sunlight, semi-shade will provide a sustainable environment. Whether potted or bed bound, the soil should be well mulched, well drained with rich compost. Once flowering has finished, the stems should be trimmed back and a good thick straw mulch applied. Alternatively, you can lift the rhizomes and store them indoors over winter.
10. Canna Lily is another plant for the mid level ornament to your canvas. It originates from Argentina and will also complement the colour scheme of any tropically themed garden, with its bold foliage that is often variegated or richly coloured, and its vibrant flowering. It needs 6-8 hours of sunlight daily throughout the summer months, though greater exposure threatens the leaves in windy conditions. Plant in well-drained soil and water regularly. As with Gingers, it is best to store the rhizomes indoors through winter as an insurance against frost damage.
And there you have it, a menu for thought when planning your tropical city garden. However, this list is only a starting point - there are countless other species who didn't make it here, including numerous varieties of the ultimate jungle plant, bamboo, that can all certainly survive and thrive in your garden.
By Josh Ellison