Geraniums are quite easy to care for, but this doesn’t stop many from panicking when they find out their prized geraniums might not be geraniums at all.
This is because the most popular geraniums are actually from the genus Pelargonium (pe-lar-GO-nee-um), which was separated from the main Geranium (jer-AY-nee-um) genus in 1789 but never lost the common name.
However, while there are some subtle differences between the two general, care requirements are almost identical with the exception of temperature needs.
One of the biggest concerns is fertilizer, which one would expect geraniums to need in abundance.
Yet these plants are actually not heavy feeders, especially the hardy geraniums (Geranium spp.), which are cold tolerant perennials adapted for life in the mountains.
Too much fertilizer can actually lead to chemical burns and health issues, so moderation is key.
Here’s what you need to know to ensure your geraniums get just the right amount of food to give spectacular blooms every year.
Best Plant Fertilizer for Geraniums
As mentioned, geraniums don’t need heavy fertilization, and liquid fertilizers tend to work best, as they’re less likely to be leeched from the soil.
It’s also possible to use homemade compost-based mixes if you wish to go totally organic.
The Numbers Game: Different NPKs for Different Jobs
While you can give your geraniums a balanced liquid fertilizer on a bi-weekly or monthly basis, it’s a good idea to switch things up depending on the time of year.
When it comes to the NPK ratio, these three essential nutrients play different roles, meaning you’ll need more or less at certain times of year.
- Nitrogen is essential for healthy and abundant foliage, as well as stem growth.
- Phosphorus encourages root growth and is essential for blooms, but too much can lead to a potassium deficiency.
- Potassium is essential for a plant’s general health and physical strength.
New plants will do best if you give them a 5-10-5 for their first feeding, since they need to develop stronger root structures.
A balanced fertilizer (10-10-10 as a slow-release fertilizer or 20-20-20 as a liquid water-soluble fertilizer) is perfect for most geraniums, both grounded and potted.
You’ll know if you’re short on nitrogen if your geranium will get yellow leaves. Phosphorus may likewise result in yellow or red leaves and a failure to bloom. Potassium deficiency will cause the lower leaves to die and the stems will become more flimsy.
In addition, geraniums need several macro and micronutrients to thrive which are present in most good plant food.
Of these, the ones to pay attention to most for these plants are:
Nutrient deficiencies in any of these can lead to problems faster than other micro and macronutrients.
The good news is these deficiencies can often be fixed with very simple remedies.
- Calcium can be replenished with crushed eggshell or bone meal
- Iron, manganese, and zinc are available in a supplement form and are often present in compost.
- Magnesium is easily boosted with a teaspoon of Epsom salts.
You can also augment the soil with coffee grounds (and the coffee filters or crushed leaves) to help encourage beneficial microorganisms and further boost plant health.
But there’s one other important thing you should know about fertilizing your plants, and that is how much your soil already has available.
A soil test is important for outdoor plants because it can warn you of potential problems before they happen.
For example, a soil test that shows a high amount of phosphorus means it’s best to cut back a little on the phosphorus content in your fertilizer, as too much will cause potassium deficiencies.
For indoor plants, this isn’t as important, as commercial potting mixes are generally pre-balanced and will be changed out every three years to replenish the soil.
When Or How To Fertilize Geraniums
Fertilizing geraniums isn’t difficult, but you should always pay attention to the product label, as different brands may require different concentrations.
Also, when transplanting a new geranium outdoors into freshly composted soil, you can skip the first fertilizer dose, as the compost will provide sufficient food.
Generally speaking, your geranium will require a dose of fertilizer every 4 weeks.
However, there are a few specimens that are heavier feeders and some that require even less.
If you aren’t sure how much your particular geranium plant needs, begin with a monthly feeding and adjust if you see signs of food issues, such as leaf color, legginess, or bloom color and adjust the feeding by plus or minus one week (depending on your plant, feedings may end up being as often as every 2 weeks or as infrequent as every 6 weeks).
Note also that hardy geraniums are mostly perennials and will go through a dormant phase, so you will need to cut back on feeding in the fall and resume in spring.