Fertilising Orchids - Wayne's tips after 40 years growing

by Wayne Turville – February 12, 2024

I don’t know of any other subject on the culture of growing orchids that is more hotly disputed and full of misinformation. So many different stories, techniques and opinions. Maybe this blog will stir up some ideas and discussions!

I think I’ve got it right after 40 years experimenting.

This article may be a bit drawn out, but it to show how a lifetime of orchid growing changes your mindset and how I’m still learning after all this time.

Through the 1970 and 80s all the go was Auqasol and Thrive…weakly & weekly.

Alternatively we used Fish emulsion and Nitrosol with an ocational seasol (Liquid Blood and Bone) for an organic natural hit, once again weakly & weekly. A sprinkling of Dolomite lime once a year.

On writing this I get a warm feel good about how much I enjoyed rotating these ferts and fondly remember the ocean smell of the seasol and the earthy musk of the Nitrosol and the beachy Fish emulsion. Even a bit of the old Charlie Carp was tried (ground up pest fish). All balanced up to create quite a smosgasboard of delights for my orchids. I even used to add trace elements once a month in the form of a powder dissolved in the watering cans.

Evert saturday morning i would mix up a differnt fertilizer and apply it with a watering can. About 30 minutes work, but then i only had 300 orchids not 300,000. My thoughts were that if th blends were not exactly right then another fert the following week would fill the nutritional gap.
This worked fine for the first 10 years until the collection became a little large and all those watering cans wern't so much fun anymore
By this stage in the 1990s i had 12 small glasshouses joined together in our big backyard

In the late 80s most were using a Fertigator to feed their orchids. These were brass and hose fittings that had a hose in a bucket of strong fertizer. I think it was called venturi pressure feeding.

At one stage in the mid-80s I borrowed an EC meter (which measure electroconductivity – how much salts are dissolved) and found that the Fertigater method was all over the place. Sometimes dangerously high and other times no fertiliser at all. It seems it depended on the pressure going through the hose!

So what next? Small and mid-sized nurseries were using a gizmo called a "Gewa". So I started trying to buy a second hand one of those.

They work by water being channelled into a reservoir inside the steel canister, but on the outside of a very heavy duty bag. The bag was slowly squeezed by water pressure and concentrated fertiliser solution was funnelled out a valve and mixed with fresh water flowing through to the hose. By turning a valve on the top you could adjust the strength, although an Ec meter was needed to verify the correct strength. We all called this device R2-D2 for obvious reasons. At over $1600 new, it was never a cheap option, but it worked perfectly for the next ten years for me.

Even in the early days of AON from 2001 we used the GEWA every week of the year. Eventually a thoughtless staff person (possibly me!) left the lid open and tried to fertilize. The bag prolapsed up through the lid and ruptured and the item was too old to be replaced.

So what do we do these days? Keep it simple! Tip the fertilizer into the giant rain water tanks, mix to correct strength using an EC meter and just pump it on via the overhead sprinklers. Ta Da! And that’s how we still do it today after 18 years at AON Nursery.

And when you get it right this happens!

So as I mentioned, I used to use the Smorgasbord technique to fertilize until the idea that if I used every product, the orchids would have to be getting all they needed. Unfortunately it’s a fairly unprofessional way to feed your orchids and this came to bite me many years later.

At this time I worked for a large (huge actually) cut flower nursery and all I thought I knew was laughed at on a commercial scale.

At this particular nursery they has a full time staff person who arranged all the 15 acres of roses and carnations to be both drip fed and foliar fed.

Leaf matter was sent to Holland for analysis and a formula was sent back to the nursery every 4 weeks with a feeding program to follow.

Massive sacks of Calcium nitrate, potassium phosphate ,numerous trace elements (all different coloured powders) were blended and dissolved in massive 1000 litre vats and using an electronic dositron, the solution was blended into the water pipes headed out to the igloos.

Below is a crop of Miltoniopsis I grew for Collectors Corner Melbourne

The above crop was a hard one to grow as the crop needed plenty of calcium to grow well and keep the extra large tissue like blooms healthy and fungus free. We asked for a rep from to come and talk about the available options for tank based feeding via the watering lines. The world standard for orchids was a product called Peters Soluble from the USA and Holland. It came in High N for growth periods and Hi K for blooming months. It had more calcium than any other soluble fertiser and that appealed to me, Ive always been a big fan of calcium, and its effect on disease control via strong cell walls. So we started using Peters 30/5/20 + 7 Ca by the sack, using an EC meter to get the strength right.