You might not have heard of calibrachoa (ca-libra-KO-a) before, but these heavy bloomers are often loved at first sight.
In USDA hardiness zones 9 to 11, they’re wonderful perennials but are considered annuals throughout most of the US.
Calibrachoas are commonly grown in containers due to their higher moisture needs, often making it harder to ensure they’re kept well-fed.
There’s a lot of debate about what NPK to use for this plant, but many of the recommended fertilizers lack what this plant needs for its numerous flowers.
Note: Since this plant genus only hit the market in the 1990s, there’s still a lot we don’t know about it, and the many cultivars that have sprung up since further muddy the waters.
The following recommendations are thus based upon all currently available information on this plant and may change as our understanding of calibrachoas grows.
Best Fertilizer for Calibrachoa
It is recommended to feed calibrachoas a balanced liquid fertilizer every two to three weeks.
However, there are a few additional details to consider.
When purchasing fertilizer, you’ll see three numbers on the package.
Known as the NPK ratio, this indicates how much of the three most vital nutrients is in the fertilizer.
These three nutrients are:
- Nitrogen (N) – Essential for the development of foliage.
- Phosphorus (P) – Promotes healthy blooms.
- Potassium (K) – Needed for strong stems and a good immune system.
Additionally, fertilizer has many other important nutrients, such as calcium and iron.
These are generally found on a much smaller label somewhere on the packaging.
Calibrachoas need a lot of nitrogen and will show visible signs of distress if they don’t get enough, usually in the form of yellowing leaves.
Potassium is another important nutrient for calibrachoas due to the number of blooms they create.
This can be a problem with many fertilizers with high nitrogen, as they’ll often have a lower phosphorus level.
Granular vs. Liquid-Soluble
Another important consideration is whether to use a granular slow-release or liquid-soluble fertilizer.
Those who argue for granular fertilizers often claim they require less effort since the granules will slowly break down over time.
Unfortunately, the nutrients within these granules don’t break down at the same rate, resulting in the plant getting too much of one nutrient and not enough of another at any given time.
Meanwhile, liquid-soluble fertilizers are designed to be diluted in water and can be given while you water your plants.
The soil must be slightly dampened before applying the fertilizer to avoid the risk of chemical burns and improve saturation.
However, the nutrients contained within are instantly available to the plant.
Even more importantly, diluting a liquid fertilizer is easy, allowing you to fine-tune the dosages to meet a specific plant’s needs.
Choosing and Using a Calibrachoa Fertilizer
We’ve found that the overall best fertilizer to use on calibrachoas is a 10-10-10 NPK liquid soluble fertilizer.
Follow all instructions on the package and dilute to half-strength.
You must apply the fertilizer once every 2 to 3 weeks during the growing season.
Pay attention to your particular plant and adjust the frequency until you find a feeding pattern that works just right.
Note that some calibrachoa growers like to add slow-release granules at the time of planting and then switch to liquid fertilizer.
While not necessary, these plants prefer acidic soils, so adding an acidic fertilizer to a fresh potting medium can help lower the pH.
If you choose to do this, you will want to start using the liquid fertilizer every three weeks, then increase it closer to two weeks as the granules wear down.