Dietes grandiflora (Wild Iris or Fairy Iris) as it is commonly called is originally from Southern Africa where it grows along coastal areas from South Africa through to Mozambique, it is widely used in landscaping.
Grown for the evergreen foliage as well as the colourful flowers it is easy care and makes a great plant for mass planting in full sun to a little shade. The flowers of D. grandiflora are white with a yellow markings and mauve sepals.
The large flowers of Dietes grandiflora last around 3 – 5 days which differs from those of Dietes iridoides which last a single day.
Another common name is ‘Fortnight Lily’, it gets this from the flowering cycle which takes around 2 weeks.
This is a large plant, clump forming and reaching up to 1.5m (4 – 5 ft) in height. The foliage is sword shaped and held upright.
How To grow Dietes grandiflora
Once established this is a very low care plant. However they will need to be divided after 4 – 5 years to promote good flowering.
When planting a spacing of around 40cm apart will be suitable as the plants will spread reasonably quickly to cover the area.
Planting Dietes grandiflora
- Plant in full sun for best flowering
- Choose a well drained soil.
- Water in well after flowering.
- Mulch around the plant to maintain a cool moist root run.
- Fertilise using a general purpose slow release fertiliser once a year.
- Water during long dry spells during summer to maintain appearance.
The flowers appear from spring through summer and stems will actually produce flowers over a few years, so although the spent flower heads themselves should be removed , the flower stems themselves should not be pruned away.
How to Prune Dietes grandiflora
Dietes commonly called the Fortnight Lily will eventually become a little tatty looking. New foliage mixed in with old dead foliage and it is very difficult to just prune away the old brown foliage.
Pruning Methods
Every few years you will need to refresh the foliage of your Dietes plant and there are two methods of doing this.
1 .The whole plant being pruned right back to ground level.
This can be done in winter or early spring.
- Use your power hedging shears, hand held shears a pruning saw or as last resort secateurs or pruners.
- Prune back to around 6 inches (15cm) or even lower.
- After pruning its time to fertilise and water, within a month or so new growth will appear and the clump will be revitalised.
- You can also selectively trim away spent flower spikes and dead foliage. Remembering that the flowering spikes can produce flowers over a long period.
2. A slightly harder method, but in the long term a better solution is to dig and divide the whole clump.
You can do this in late winter.
- Dig the whole plant roots and all.
- Remove the newer parts of the plant that are around the edge in good sized clumps.
- The centre part is the oldest part of the plant and you may just as awe dispose of that.
- Use some garden snips to remove any dead foliage and also the oldest part of the rhizome, which will be the part that was attached yo the centre of the clump.
- Renew the soil with compost and aged cow manure, replant the fresh new clumps, water in and your Dietes will be good to go for another 4 – 5 years.
Summary Information
- Botanical Name – Dietes grandiflora
- Common Name – Wild Iris, Fortnight Lily
- Origin – Cape province of South Africa
- Family: Iridaceae
- Position – Full sun to a little shade.
- Soil – Well drained.
- Height – To around 80 cm in height
- Spread – Clump forming over time
- Flowers – White with mauve and yellow
- Flowering Time – Spring to summer,
- Foliage – Strap like evergreen foliage, mid to deep green in cooler.
- Frost tolerant – Mild frosts
- Drought tolerant – Yes
Dietes grandiflora are available for sale from the following participating nurseries
862 Midland Highway Mount Rowan Vic 3352
We offer over 245 varieties of Fuchsia, tubestock, pots, baskets and standards. Mail order specialists. Open 7 days by appointment.
www.brenlissaonlinenursery.com.au