Half-Price Quadgrow Fertilizer?

Everyone lives by selling something - Robert Louis Stevenson

I first wrote about the Quadgrow system, a product of Greenhouse Sensation, in June 2022 (see here & here). although I had been using this system since 2015. More recent blog posts on this topic can be seen here, here, here, here, here, here, here, and here. Even our miniature bog garden is housed in a Veg/Salad Planter although the current version of Greenhouse Sensation no longer produces this product.

Greenhouse Sensation also sell prepared nutrients (Nutrigold) for use in all their Self-Watering Planters. These come in two forms, A and B, each bag containing 250g nutrient mix. The contents of each bag are emptied into separate 2.5 L bottles and filled up with water. I use warm water to encourage dissolution.

Photo 1: Nutrigold A (250g Bag)

Photo 2: Nutrigold B (250g Bag)

6 ml of each solution (add B after A) is added to one litre of water for the final dilution that is a used to fill up the self-watering planters. I normally add 60 ml of A & B to a 10L watering can and fill up with tap water.

After many years using the recommended nutrient concentration, I decided to see if lower concentrations could be used as this would save money. At the time of writing (August 2026), a pack of both nutrients costs about £12.

This year I am trying a 50% dilution of the recommended nutrient concentrations; i.e. 30 ml from each bottle made up to 10L in a watering can. In Photo 3, you can see my two 60 ml plastic syringes being used to extract 30 ml from each concentrate (A & B).

Photo 3: Prepared Nutrients A & B (concentrate) with Measuring Syringes

So far the results have been good especially considering the very hot summer we are having. The cucumbers (Photo 4) have been very productive (about 40 cukes per plant) as have the late-planted tomatoes (Photo 4, now harvesting). Bell (or Sweet) Peppers have also grown well (Photo 5), flowered profusely and we have been eating the fruits of our labour for about a month now. The aubergines (Photo 6) are floriferous though we haven't had any produce off them yet.

Photo 4: Cucumber and Tomato in Quadgrows (August 6th 2026)

Photo 5: Bell Peppers in Veg Planters (August 6th 2026)

Photo 6: Aubergines in Veg Planters (August 6th 2026)

Cautionary note: I have just spent 3 days in hospital having a bladder tumour removed and no one has been looking after my polytunnel. Everything has survived well (thanks to the self-watering planters) but the cucumbers are suddenly looking a bit tired. This may be simply that they are coming to the end of their productive life after the hottest summer in UK history. It could mean they are not getting enough nutrients to maintain their large structure; cucumbers are much bigger plants then tomatoes, peppers and aubergines and require copious volumes of water and, possibly, nutrients.

I need to keep an eye on the cucumbers but the tomatoes, peppers and aubergines seem to be doing just fine.

So there you have it. If you can get away with half the concentration of fertilizer/nutrient, then  you will save 50% of the costs.