Orchid Manoeuvres in the Dark

Elizabeth Bailey of the Tauranga and BOP orchid societies came for a cup of coffee yesterday morning – the deal was that I would provide morning tea and she would provide enlightenment on how I might improve my growing of some of my orchids.

Something I can grow – Sarchochilus hartmannii

I’ve tried to choose only those orchids that will be happy growing outside year-round (albeit under a verandah) – so things like the gorgeous Vandas are beyond my spectrum – but I am also relying on the plant sellers to be realistic about what will and won’t work. However, I’m darned if I can get the Australian Dendrobiums (reckoned to be “easy”) to reflower, even the New Zealand-discovered Pukekura which one local grower described as “bombproof”. (See note at the bottom for some of its history.)

And despite growing outside and being covered in flowers at Te Puna Quarry Park, my Coelogyne cristata alba (photos of a plant in full bloom) has hardly increased in size since I bought it. “Don’t worry,” says Elizabeth, “lots of people find it tricky.”

Why does it do so well at the Quarry Park? My expert shrugged her shoulders. Which I suppose is why people are fascinated by orchids. They need their owners to learn something, they can surprise you with their adaptability and the reward when they flower is bliss.

So now I’m on a mission to:

  • Repot Dendrobiums into hanging baskets and spread them along the fence that’s under deciduous trees (the plastic pots sold as water lily pots in garden centres are ideal as they have lots of small drainage holes and so don’t need a liner but I will need to make wire hangers for them).
  • Water my Dendrobiums more (although it is better to be an under-waterer than an over-waterer with orchids), starting by soaking the pots in a bucket so the bark is soaked.
  • Buy or make* a spraying oil. I have the odd scale insect, nothing major, but these pests suck the vitality out of a plant. Oil suffocates them so is the most effective treatment.
  • Use a fertiliser that’s higher in nitrogen. I have been using a liquid seaweed fertiliser at half-strength in rotation with Brigitta Orchid Food. Elizabeth recommends one that’s higher in nitrogen as well. Phostrogen (a British horticultural society has useful advice on its use) is a popular choice with orchid growers and is available again after seemingly disappearing for a bit. It’s no longer imported into Australia and Debco claims its all-purpose fertiliser is essentially the same thing.
  • Buy BioBoost. Made at the New Plymouth wastewater treatment plant, it is the bee’s knees, Elizabeth says, when it comes to slow-release fertiliser. Palmers in Bethlehem has it, in 8kg and 25kg bags. Farmlands is also listed as a stockist.

The point of getting the fertilisers right is that almost all orchids are grown in a medium (bark, sphagnum, etc) that gives them nothing in terms of food, it’s just something for their roots to hang on to and allows us to have them in a pot or basket. In the wild they don’t grow in soil either but can collect food from bird droppings, leaf litter, etc., when it rains.

It’s also useful to understand that orchids with “bulbs” (properly called pseudo-bulbs) can store food and water (e.g., Cymbidiums and Zygopetalums) as can those with canes, such as Dendrobiums. Orchids that have only roots (Sarchochilus, Phalaenopsis) feed through their leaves and roots so need more food/water, more often than those with storage chambers.

Bifrenaria harrisoniae, an orchid native to Brazil

Fortunately, I am doing all right with some plants and so far this year have had flowers on both Sarchochilus, Osmoglossum pulchellum (a sweetly scented flower), Cymbidiums, Coelogyne fimbriata, Dendrobium kingianum and Dockrillia pugioniforme, the first time this creeping orchid has flowered for me. One Bifrenaria harrisoniae has a fat bud (I expect more in later summer), while indoors my white Phalaenopsis (bought from Eric Jones) is sending up its second flower spike for the year and the parent plant of the pink one (from Mega Mitre 10, separated into three plants after its last flowering) looks like it might have a flower spike too.

* I have found this spray recipe for scale on the net: Mix 1 tablespoon of vegetable oil (canola, sunflower, etc) with 1 tablespoon mild dish-washing liquid and 900ml (1 US quart) of water.

Note: Dendrobium Pukekura was discovered in the 1960s among a collection donated to Pukekura Park in New Plymouth by Fred Parker. The plant had been given to Mr Parker by a Japanese doctor, who was known to have used Den. moniliforme as a parent. It is generally accepted that the other parent was Den. regium. Others have suggested that it could be Den. Nobile. Information supplied by George Fuller, curator of Pukekura Park, 1965–1990 (from the RHS quarterly supplement to the International Register of Orchid  Hybrids (Sander’s List), January-March 2011).

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