Geraniums (jer-AY-nee-um) can get a little confusing for first-time owners and even experienced growers sometimes have issues with these plants.
It’s no fault of the individual, but rather the fact that most common geraniums are actually from the genus Pelargonium (pe-lar-GO-nee-um), which was split from the actual Geranium genus in 1789 but still shares the common name.
What’s even more confusing is that true geraniums (also called hardy geraniums or cranesbills) have 400+ species compared to pelargonium’s 280 yet most guides will tell you about only pelargoniums.
Geranium plants are more equatorial yet grow in mountains, so they’re very cold hardy, and grown as perennials.
Meanwhile, pelargoniums are mostly annuals from South Africa and actually need more tropical temperatures, making this one of the most backwards and notable distinctions between the two genera.
But whether you have a pelargonium or true geranium, one thing is certain: they both have very similar water requirements.
What Are My Geranium’s Water Requirements?
Hardy geraniums can be drought tolerant once established, but still follow the same preference for about 1” inch of rainfall per week that pelargoniums do.
The good news is that it’s quite easy to ensure your geranium gets just the right amount of moisture and it will let you know when there’s a watering issue.
Related: Types of Geraniums
Growing Geraniums Starts With Good Soil Preparation
If you want to get the watering right, your first stop should always be the soil itself.
One of the best ways to help ensure your garden doesn’t flood is to add a substrate of gravel underneath the planting area.
This creates a buffer zone that can hold water away from plant roots while working its way down to the water table.
You can also add a base layer of gravel or pebbles in a pot to perform the same function.
Geraniums like a loamy soil with a bit of sandy texture to it, although hardy geraniums can survive in almost any soil.
Whether buying a potting mix or planting in the garden, make sure there’s a decent amount of organic material in the soil as well as some coarse sand or perlite.
Two parts soil to one part organic material and one part aggregate is a good blend to aim for.
What does this have to do with watering, you ask?
The organic material present in the soil (especially mosses) retain some water, which can be useful in drought conditions.
Meanwhile, the aggregate prevents the soil from compacting too much and leaves some air zones.
Perlite and similar aggregates may also hold onto a bit of water, but their main function is to give the roots more space to drink and aid in drainage.
Thus, when your plant isn’t drinking properly, the soil may well be to blame.
The Soak and Dry Method
Once you’re sure the soil is well-draining, you can focus on the watering itself. All geraniums respond well to the soak-and-dry method.
The process is very simple: Since geraniums like 1” inch of rainfall per week, you can simply stick your finger in the soil to see if it needs a drink.
The soil should never be wet or soggy, which is a bigger risk in the garden than in containers if you get a lot of rainfall.
Never water when the soil is this wet.
However, if the soil feels dry 1” inch deep, your geranium is ready for a drink.
Water by hand, avoiding a garden hose or sprayer, as geraniums can get fungal infections if their leaves are wet and it can be harder to judge when to stop watering.
Use room temperature water to avoid shocking the plant, preferably natural rainwater or distilled water.
Pour slowly and evenly around the base of the plant so the soil has time to soak it up.
With potted plants, you’ll know to stop when you see seepage from the drainage holes.
For garden plants, it’s usually a good idea to stop if you see the soil beginning to absorb the water slower.
Two of the most common mistakes are closely related and are sadly still being taught to children.
You should NEVER water on a set schedule and NEVER go quickly.
This can easily lead to overwatering or underwatering.
Several factors affect how often a plant needs to drink, so ask yourself:
- Is it particularly hot or cold out this week? Is there a danger of frost?
- Has it been really sunny or mostly overcast?
- Is the plant entering a dormant phase?
- How humid or arid is it?
- Has the plant been divided recently?
- How much has it rained this week?
As a general rule, plants will need to be watered more often when it’s really hot, sunny, and/or arid out but less if it’s cold, overcast, or humid.
A divided plant will have a smaller root system than one that hasn’t been divided for a year or two.
Using your finger to check how far down the soil is dry can be one of the easiest ways to know if the plant is thirsty, and it only takes a moment of your time, so aim to check one or two times per week based on the above factors and water accordingly.
Likewise, giving a quick pour from a watering can or fast spray from a hose will likely not be enough.
Remember that water and fertilizer needs to soak into the ground and will spread out as it tries to work its way down to the water table, so a slow, long pour will ensure you don’t give the plant too much or too little.
Excess Water The Risks of Overwatering
Overwatering geraniums can lead to root rot, a deadly disease caused by either fungal or bacterial infections that destroy roots so the plant can’t get water or nutrients.
Fungal infections are also a common side effect with these plants, as is a higher risk of infestations.
Depending on the species, the leaves may begin to turn yellow or red as well.
Risks of Underwatering
Hardy geraniums are more tolerant of drought than pelargoniums, but both still need sufficient water.
Yellow or red leaves are the primary sign of underwatering, and the plant may suffer bud drop or begin to lose its foliage as the dehydration continues.