The next soil trial has started (4th of May). Taking the learnings from the previous trials, I’m trying lighter blends. Whilst the 50/50 sandy loam/compost blend worked brilliantly for tomatoes, the blend has a very high water holding capacity. Not all plants will tolerate this. Finding a blend with a good water holding capacity, that wicks efficiently but importantly can also drain giving it good air-filled porosity is the aim of this trial.

As per previous trials, WaterUps Square Planters will be used. The trial will be conducted in a greenhouse to get a more stable temperature and humidity. The planters will be against the north facing side to get the most sun.

BioGro Premium Wicking Mix has performed exceptionally in every trial I’ve run. I also grow a wide range of plants in this soil mix. However, it is only available in 30L bags and it is not organic.

With that in mind and in collaboration with Jeffries, 5 of the soil blends are Jeffries with the remaining soil BioGro.


1 – Jeffries VG* + sandy loam

2 – Jeffries VG* + sandy loam + rock dust

3 – Jeffries VG* + coir

4 – Jeffries Veggie and Garden Mix

5 – Jeffries Special Soil

6 – BioGro Premium Wicking Mix

Jeffries VG* is based on the Veggie and Garden Mix but has been modified.

The soils will be run in duplicate. In previous trials, the location of the soils wasn’t randomised and I noticed differences based on the proximity to the side of the greenhouse. The dark colour of the WaterUps Square Planter (Monument) results in warmer soils in the planters closer to the side of the greenhouse. This trial the soils were split into 2 rows of 6 with 1 of each blend in each row. The location of the soil blend was then randomised.

Planting plan

1 – Leeks – will be thinned to 2 plants

2 – Celery – will be thinned to 1 plant

3 – Purple Bok Choy – will be thinned to 1 plant

4 – Purple Choy Sum – will be thinned to 1 plant

5 – Pak Choi – will be thinned to 1 plant

6 – Basil ‘Blue Spice’

7 – Basil ‘Red Italian’

8 – Basil ‘Thai’

9 – Basil ‘Sweet’

The thinking behind this plant selection is to have some fast growing Asian vegetables, slower growing leeks/celery and some out of season herbs (basil). As this trial is in a greenhouse, the average temperature will be higher, humidity will be higher so there will be less stress on the plants. The Asian Vegetable will be harvested entirely and then re-planted, if there is enough time remaining in the trial.

To simplify things, only 1 fertiliser will be used. Culchar is an organic fertiliser from Jeffries with BioChar.

From the Jeffries website “Give your garden a boost of biology to effortlessly have the plants of your dreams. Jeffries CulChar is a NASAA organic certified fertiliser that contains sustainably sourced Jeffries BioChar. Produced in South Australia, Jeffries CulChar is perfect for garden beds, veggie patches, lawns, pots and roses. It’s honeycomb structure holds nutrients and water then slowly releases them over time as the plant needs them. This means you are getting more out of each fertiliser application and watering. Overall, your plants become more resilient and produce richer, fuller blooms.”

I used Culchar in the last trial and it performed well. I’ve also been using it in my own vegie patch and in clients gardens and the results have been impressive. As per the dosage and application rates from previous trials as advised by Jeffries, each planter will have 20g added prior to planting, mixed through the soil. Every 6 weeks another 20g will be added to the soil surface and then watered in daily for 3 days.

Day 14 Update

The Asian vegies were the first to germinate, as to be expected. This occurred first in the BioGro soil followed very quickly by the Jeffries VG + coir blend and the Jeffries VG + sandy loam blends. The Jeffries Veggie and Garden Mix was a few days behind and the Jeffries Special Soil last with only very small seedlings barely visible on Day 14.

The basil has been germinating over the past few days in all soils bar the Jeffries Special Soil. No sign of the leek or celery in any soil.