Growing New Guinea Impatiens

Latest Update 11th January 2016.

New Guinea Impatiens.
  • The have uncomplicated pretty flowers which contrast beautifully with their waxy foliage and they love hot weather.
  • However, as they are native to equatorial New Guinea rain forests, they need to grow in moist soil protected from intense mid day sunshine.
  • I grow mine under an apricot tree where they get enough sun, but are protected from the worst excesses of Melbourne's hot dry summers.
  • I keep my New Guinea Impatiens well watered but not drenched, and I avoid watering the leaves.
  • They grow viable seeds if allowed and can also be propagated by soft tissue cuttings.  Cuttings will reproduce the parent plant's physical characteristics more accurately than seed unless you can get hold of open pollinated plants.
  • I treat mine as annuals as they are frost tender and die back in our cool winters.  In climates with warmer winters they can be grown as perennials.
Details.
  • Binomial Name:                                      Impatiens hawkeri.
  • Family:                                                    Balsaminaceae
  • Garden bed type:                                     Drip line irrigated. 
  • Recommended soil pH:                             6.5 - 7.5.  
  • Plant Spacings (centres):                          300mm. 
  • Climate:                                                  Warm Temperate.
  • Geography:                                             Southern Hemisphere. 
Growing Conditions:
  • They will grow in full sun, but are best protected from the fierce midday sun in very hot climates.
  • Dappled sunlight through the shade of a leafy deciduous tree is ideal with early morning direct sunshine.
  • The soil should be rich in decomposing organic materials.  
  • Minimise soil disturbances to maintain a natural soil structure.  
Soil Preparation.  
  • Prepare a new bed for them in spring by removing old mulch, fallen leaves and other decaying organic material and disposing of them in the compost heap.  
  • Apply a 60mm thick top dressing of home made compost, and add a handful of blood and bone fertiliser per square metre and cover with fresh straw mulch.
  • Do not dig the soil.
  • Leave for 4 weeks so worm and microbe activity can build up in the soil.  Remove the mulch before planting your New Guinea Impatiens in Spring.
Propagation.
  • Propagate Impatiens by taking cuttings from robust current years growth as soon as the young plant is big enough.
  • Using sharp disinfected secateurs, take a 100mm cutting from just below a node on a stem with a flower starting to form.  Remove the flower bud.
  • Remove the leaves from the stem leaving only 2 or 3 at the top to continue to grow and feed the plant.
  • Plant the cutting in a medium size pot containing organic seed raising and cutting mix.  Soak the pot in 10mm deep dilute seaweed extract for an hour. 
  • Transfer the pot to an Eco propagation bed and bury it 15mm deep in the sand.
  • Pot up to a larger sized pot as required and keep the plant protected from frost during winter.
  • Replant each Impatiens plant in the prepared bed after all danger of frost has passed during the following spring. 
Growing Instructions 
  • Apply a foliar spray of activated aerated compost tea every month when the edible plants are sprayed and remember to spray the plants in the propagation unit.
  • Remove and compost the spent plants when they stop flowering in Autumn.
Organic Pest Control. 
  • General.
    • It is about 15 years since I last grew New Guinea Impatiens and I don't remember them being vulnerable to any serious pests.  When and if I have a problem, I will try to diagnose it and publish details of my response.
    • However sensible preventive measures like regularly spraying the plant with aerated compost tea will boost their natural defences by colonising the leaf surfaces with beneficial microbes.  These microbes defend plants against airborne pests and diseases.
    • Similarly, proper soil preparation including regular applications of home made compost boosts the community of beneficial microbes and defends roots against plant pathogens.

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