The results of our test of controlled-release fertilisers will show you which will help your plants maintain their healthy appearance throughout the summer.

Your plants will continue to thrive for months on end if you use a controlled-release fertiliser of sufficient quality, but if you use one of inferior quality, their performance will suffer. Our in-depth research and analysis have revealed the solutions that are ideal for you. Because the granules of controlled-release fertilisers are added to the compost at the time of planting, this type of fertiliser offers the lowest-maintenance choice for feeding plants that are grown in pots. Continue reading to find out which controlled-release fertilisers performed the best in the most recent series of testing that we ran. In addition to this, we delve deeper into the distinctions that exist between controlled-release and liquid feeds.

What exactly is meant by the term “controlled-release fertiliser”?

The controlled-release fertiliser, which typically takes the form of tiny granules resembling ball bearings and dissolves when the compost in your pots is wet and the temperature is high enough for plants to flourish, is typically delivered. These fertilisers are equally as efficient as liquid feeds in maintaining the health of your plants; nevertheless, they are more simpler to utilise because you only need to apply them once throughout each growing season. When you are repotting young plants in the spring, incorporate them into the compost you are using. If you try to guess how much to add, you run the risk of either over- or under-feeding your plants. The directions should be read carefully.

Controlled-release fertiliser

Comparison of controlled-release and liquid feeding systems

In prior years, we put both a Best Buy liquid feed and a Best Buy controlled-release fertiliser through their paces in a series of experiments. We discovered that the plants that were given liquid nutrition grew larger, but they produced fewer blooms; the majority of the growth occurred in the leaves. However, the containers that were originally fertilised with a controlled-release fertiliser and subsequently supplemented with a liquid feed whenever they stopped producing growth that appeared to be healthy produced the most impressive displays over the whole summer. If your plants are showing indications of flagging, our recommendation is that you utilise a controlled-release feed, but in addition to that, you should give them a liquid feed.

Methods that we use to evaluate slow-release fertilisers

Our most recent round of testing consisted of selecting 10 controlled-release fertilisers that boasted the ability to provide nourishment to plants throughout the entire summer. The products that made it into our shortlist were manufactured by well-known companies like as Chempak, Garden Direct, Osmocote, and Thompson & Morgan. These controlled-release fertilisers came in a total of ten different forms, eight of which were loose granules and two of which were tablets produced from the granules. As a control, we produced one set of plants with no fertiliser at all so that we could compare the results of using a poor fertiliser to the results of not applying any at all. In accordance with the directions provided on the label, we combined all of the feeds to create a peat-free compost called Best Buy for patio pots.

Which? controlled-release fertilisers tests

Each fertiliser was utilised to provide nourishment to five 10-liter pots of bedding geraniums (also known as pelargoniums) and five pots of potatoes. In addition, we planted five pots of pelargoniums and five pots of potatoes, but we did not provide any kind of nutrition for them. Three separate times, we examined our pelargoniums to determine their leaf colour, the quantity of blooms, their size, and the overall size of the plants. When we were harvesting the potatoes, we searched for plenty of tubers that were a good size and had smooth skins. There were no signs of scab on the potatoes. Near the end of our study, we gathered compost samples from both one of the pots that had performed exceptionally well and from one of the pots that had performed less well. These were sent out to have their nutritional content analysed in order to determine why the plants that were growing in the pots that were not performing well appeared to be in such poor health. Our ongoing testing with compost continue to demonstrate that the most pricey alternatives are not necessarily the ones that are the most successful.