Recently, I have been helping a friend who wants to replant a courtyard, which is sheltered by an enormous tree in a neighbour's yard: this provides welcome shade in summer but also means that its huge root system robs moisture from the borders in the courtyard. My friend already had some suitable plants in place for this challenging situation: bromeliads, which only really need enough soil to prop them up, and which survive in very dry, shaded spots; and Clivia, including some of the lovely creamy-yellow ones (flowering now!), which have large, fleshy roots that seem to be able to spread out sidewise in a garden bed and cope with competition from trees and lack of moisture.
So adding a few different bromeliads that she didn't already have was my first idea, including the lovely silvery-leaved Aechmea fasciata, which has tousle-headed pink inflorescences that last for ages, and another favourite, Aechmea weilbachii, which has attractive purple and red flowers from late autumn until early spring. There are so many bromeliads available these days, with an endless variation of leaf colours, patterns and shapes, as well as unusual flowers, and I have seen wonderful effects achieved by massing them in dry shade.
I then thought about the family Asaparagaceae, which contains a range of very resilient plants, many of which thrive in dry shade in Sydney: particularly those with rhizomatous roots. A number are foliage plants that give a lush and interesting presence throughout the year. One of the toughest is Aspidistra elatior, known appropriately as the cast-iron plant, a rhizomatous perennial with long, wide leaves, growing up to about 50 cm or more tall. Over time, it will grow into a wide clump. There is a white-striped form that is a good foliage plant too. Liriope muscari also belongs to the Asparagaceae family and has cultivars that are very robust plants for dry shade, with shallow root systems that cope with tree competition. There are a number of different variants, all with arching clumps of shiny, strappy, evergreen leaves, which may be plain green or gold, or striped with white or limey-gold, and all bloom in autumn, with pretty spikes of tiny, bell-like purple or white flowers. Most are 30-60 cm in height, but 'Evergreen Giant' grows to 80cm or more and is an excellent foliage plant in shade, giving the effect of an ornamental grass.
Still in the Asparagaceae family is Ruscus aculeatus, a very tough, evergreen rhizomatous subshrub (ht 75 cm). Sometimes known as the insect plant, it has tiny flowers in the middle of its spiky 'leaves' (which are actually stems), looking for all the world like little bugs. It forms an impressive mass, and will grow in difficult spots where few other plants will thrive, including in dry shade with root competition from big trees! Another Asparagaceae plant I suggested for the courtyard was clump-forming Arthropodium cirratum, sometimes known as the renga renga lily, which will provide dainty sprays of white star-shaped flowers in mid-spring. To echo these pretty blooms, I also chose the groundcover plant Saxifraga stolonifera, sometimes known as mother of thousands. It has rounded leaves with pretty silver veins, and spreads by stolons. Its tiny white blooms, which are like a cloud of miniature moths, appear at the same time as those of the renga renga lily, so they look good grown together. It forms an excellent carpet.
Rhizomatous Begonia are also excellent groundcovers in dry shade, and they also pair well with the Saxifaga, with a similar 'fleshy' look. My friend already grew some of these, so I suggested these be included in the courtyard, with a few extra ones. There are so many different cultivars, with varying leaf patterns and hues. Grown together, they form a very effective tapestry effect. They have delicate blooms in spring: an added bonus. Other possible groundcovers in this situation could be some of the low-growing Acanthaceae plants, such as long-flowering Justicia scheidweileri or Ruellia makayona, which both have attractive, silver-marked leaves and pretty flowers, no matter how much shade they are subjected to! Fancy-leaved Tradescantia, such as deep purple Tradescantia pallida 'Purpurea' or silvery Tradescantia sillamontana, or even Tradescantia zebrina (shown in the photo above) are all very useful for filling in gaps in dry shaded areas.
I look forward to seeing how the plantings evolve. Of course, another solution to the problem of a dry shade site with tree root competition is to grow all the plants in pots. These need regular watering; however, there are some easy-to-install automatic drip systems for pots available these days, which can be set to come on regularly with a timer. I would be interested in hearing other suggestions for plants for dry shade in Sydney gardens!
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