How to Care for Zonal Geranium (Pelargonium × Hortorum)

Zonal Geranium

Zonal Geranium (Pelargonium × hortorum) is a hybrid that that comes from the from P. inguinans and P. zonale. Because of the similarity in the names, Pelargonium zonale is sometimes confused with zonal geraniums.

But, the two are different plants. Although as mentioned above, zonal geraniums come from Pelargonium zonale, which is actually the horseshoe pelargonium.

In any case, zonal geraniums are very popular here in the United States. And, you’ve likely seem them in gardens as well as indoors.

Like I mentioned in my ivy geranium plant care guide, it is not a true member of the geranium genus.  You can probably tell because its botanical name includes Pelargonium, which means it belongs to that genus. If you want more details about the difference between the plants in the two genera, please read the article.

That said, ivy geraniums are treasured for their beautiful blooms which come in many colors including purple, pink white and red. They are sometimes called annual geraniums as well since they’re often grown as such. This is because they are not winter hardy unless grown in warm climate regions.

However, their stunning beauty makes them staples during the summer, be in garden beds, containers or hanging baskets.

They grow up to 3 feet tall and can come as single or double flowers with 5 petals depending on the variety you get. And, because there are many varieties and cultivars to choose from you can collect them to fill your garden.

Zonal Geranium Plant Care

Zonal Geranium Light Requirements

Zonal Geranium enjoy full sun including direct sunlight. It needs plenty of light in order to produce its amazing looking flowers. As such, if they don’t seem to want to bloom, the first thing you want to do is moving them to a brighter spot.

That said, do be on the lookout for the hottest hours of the day. During these times, it appreciates a bit of partial shade.

Too much intense sunlight can also cause them to stop blooming. So, if your plants are already flowering then their blooms suddenly slow down and stop, check to see when the most intense sun occurs and give them some shade during this period.

Indoors, the sunniest spots do the best.

This means a southern exposure is ideal during most times of the year. You can likewise go on the west side. But, during summertime when there are hot sunny days, moving it to the east keeps it from too much heat.

 

Temperature

Zonal Geranium are quite the opposite of houseplants.

Most houseplants enjoy warm, humid conditions because if their tropical origins. However, geraniums actually struggle with both. As such, it is best to keep them in cool to moderate conditions.

The good news is, they’ll be perfectly happy with average room temperature. Again, you want to watch out for summers especially if where you live can get hot and humid.

Ideally keep room temperatures between 55 to 75 degrees Fahrenheit during the warmer months. If you can keep them in a cooler spot, they’ll be even happier. But, avoid heat as much as possible.

During the winter, they enjoy cooler temperatures. As such, if you live in the colder parts of the country you’ll have an easier time caring for them. In the latter part of the year, try to keep temperature at 60 degrees or lower.

This is one of the reasons why South Florida, which is a great place to garden, actually becomes harder to grow geraniums. Hot weather, humidity and rains (which increase moisture) are problems for them.

 

Humidity

With humidity, your Zonal Geranium does best in low to medium humidity. Again, it doesn’t have a problem with regular household humidity. Since most homes average between 30% to 50%, you don’t need to do any misting (unlike houseplants).

In fact, misting is discouraged. That’s because it can lead to fungal problems and root rot.

Instead, they prefer dry conditions.

If you grow them outdoors, they also like a lot of space. So, don’t plant them too close together or too near other plants.

Indoors, this means keeping them away from most houseplants, which enjoy high humidity. Leaving them in moist conditions will cause their stems to rot and turn black. Similarly, mildew can occur.

 

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How Often to Water Zonal Geranium

Zonal Geranium

As much as your Zonal Geranium does not like humidity, it needs regular watering and moist soil. But, avoid wet, muddy or soggy soil.

Like above, this makes summertime, the crucial periods. That’s because in addition to the heat, water also dries up faster.

Indoors, this means you’ll likely need to water the plant between 2 or 3 times weekly. Outside, you’ll be closer to daily.

As with other plants, the best time to water is in the morning. You want to avoid watering late in the afternoon or evenings because the lack of light and cooler temperatures prevents drying. Thus, the plant ends up sitting in water through the night.

If done on a regular basis, this will lead to root rot.

Interestingly, while your zonal geranium enjoys moist soil, allowing it to dry for 1 to 2 days, then watering after that increases its ability to bloom. While this deprive-then-provide method works really well, be careful not to let its roots completely dry for too long.

When this happens, the plant will deteriorate and start dropping leaves.

Because of this preferences, it is best to let the plant dry then drench it with water. You can do so by allowing the top 1 to 3 inches of soil to dry out between waterings. Then, saturate the soil.

Once you start seeing liquid drip from the bottom of the drainage holes, stop watering and allow it to completely drain any leftover moisture. Make sure to discard whatever liquid that collects in the saucer beneath the container.

 

Soil for Zonal Geranium

Zonal Geranium does best in rich, well-draining soil that’s moist.

As such, when grown in the ground, it appreciates loamy soil. if you’re growing it in a container, peat-based potting mix is ideal.

Make sure not to use garden soil in your containers. Instead, get some high quality potting mix from your local nursery. This ensures that the substrate is sterile and free of any pests or diseases.

In addition to this, keeping soil pH between 5.8 and 6.5 (slightly acidic) will help it grow optimally.

You want to avoid clay soil that gets heavy, compacts and retains too much moisture. This will increase the risk of root rot as your plant will end up sitting in water even if you don’t technically overwater it.

 

Zonal Geranium Fertilizer

For best growth and blooming, your zonal geranium needs regular fertilizing, the same as it needs regular watering.

With them, you can expect large, beautiful, colorful blooms. Without both, you may end up with none at all or lackluster flowers.

That said, they are light feeders. As such, be careful with overfeeding them.

Ideally, use a high-phosphorus fertilizer which promotes blooming. Apply this during the spring and summer once every 2 to 4 weeks.

 

Flowering

Zonal Geranium are grown for their blooms. The best part of this is that their flowers as long lasting.

This is why they’re a big part of many summer gardens. They’ll being blooming from spring and keep doing so until fall (around first frost).

They also produce an amazing variety of colors including white, pink, red, orange and salmon just to name a few. Some also have dual colors.

These flowers are also fragrant which adds another dimension of allure to your garden or home.

While they’re not the biggest or tallest flowers in the world (most are under 2 feet), their beautiful, bright colors and amazing looks make them one of the most popular ornamental plants.

That said, it is important to know how to make them bloom. This involves the combination of:

  • Plenty of bright light. Ideally full sun except for the hottest parts of the day or year, where they prefer partial shade.
  • Rich, well-draining soil.

These are the two most important things to encourage blooming.

Other useful things to consider include:

  • Moderate to cool weather.
  • Low to moderate humidity. Avoid high humidity.
  • Regular watering.
  • Bloom booster (high phosphorus) fertilizer.

 

Pruning

Once the flower fades, it is important to deadhead them. This encourages more blooms.

Make sure to use a sharp sterile pair of scissors or pruning shears. You can use cotton and rubbing alcohol to sanitize the blade to ensure no bacteria is passed.

Similarly, making clean cuts is important. Don’t pull them off using a blunt blade or tear their stems because this can increase the risk of disease.

 

Propagation

Zonal Geranium

Zonal Geranium are often propagated via seed, or cuttings. At home, cuttings are the preferred methos because they it is easier to do and requires much less time before you see a full-grown plant.

The best time to propagate them is during spring.

 

How to Propagate Zonal Geranium from Stem Cuttings

  • Pick a healthy stem with at least several leaves.
  • Cut about 4 to 6 inches of the stem using a sterile pair of scissors or pruning shears.
  • Place the cutting into a small container with fresh, moist potting mix. Make sure the soil you use is well-draining.
  • Water the soil to keep it moist. Avoid overwatering or allowing the soil to get soggy.
  • After a few weeks, the cutting should have started to root. You can test by tugging the plant lightly. If it resists, then roots are developing.
  • Once the plant gets a little bigger you can prepare to move it to a larger container or transplant it outside.
  • When transplanting, make sure to harden them off. Don’t just leave them outside. Instead, make the transition gradual to help them get acclimated.

 

How to Propagate Zonal Geranium from Seed

  • Starting from seed takes much longer. Geraniums are typically slow growing plants. As such, it can take 4 or so months before you’ll start see them flowering using this method.
  • As such, many growers start their seeds indoors during the winter to keep them away from the frost while getting a head start. This makes your planting date in May shorter.
  • Start by placing seed staring mix into a planting tray.
  • Add the seeds over the mix.
  • Add another thin layer of seed starting mix over the top of the seeds.
  • Cover with plastic and keep the tray in a bright location with moderate temperature.
  • Once the seedlings start sprouting, remove the plastic.
  • Wait until the seedlings starts to develop 2 leaves or more, then move them to their own individual containers.
  • Keep the plants in under bright light and water them regularly to keep the soil moist.

 

Overwintering Zonal Geranium

Winters can turn perennial zonal geranium into annuals. As such, you need to overwinter them in order to plant them back outside once spring arrives.

This is something you’ll need to do year in and year out if you grow them in the ground outdoors and live below USDA Hardiness zones 10 and 11.

The reason for this is that while they like cool temperatures they cannot stand frost. As such, winter becomes the time when they rest.

Overwintering geraniums are often best done in dark cool places. You can likewise bring them indoors to keep as houseplants through the winter as well.

If you do, make sure to debug them before doing so. Otherwise, they can bring pests and diseases from outside that will infect your houseplants.

That said, one thing I’ve noticed is that storing them away in a dark, cold place like your garage, shed or basement increases their blooms the next season. So, I prefer doing that.

Here’s how.

  • Take them inside into somewhere dark with temperature that’s 50 degrees Fahrenheit or below.
  • Reduce watering. But, don’t allow them to go completely dry.
  • Cut them back about a third of the way.
  • Allow the leaves to die back.
  • Once spring is near, start gradually increasing water and begin light feeding. You’ll slowly increase this until you get the normal levels come spring.

 

How to Repot Zonal Geranium

If you grow your zonal geranium in containers, you’ll need to repot your zonal geranium once you see its roots start peeking out of the drainage hole. You don’t need to hurry though, as the plant enjoys being a little bit pot bound.

As such, if this happens at any time of the year, you can wait until spring before repotting (which happens to be the ideal time to do so).

Similarly, when you do repot, it is best to move it to a container that is just one size bigger (2 inches in diameter). Make sure to replace the potting soil as well.

One of the best things about zonal geraniums is their versality. While they’re most popular patio plants due to their love of sunlight, they do very well in hanging basket and window boxes as well.

Keep in mind that when growing them in containers, you’ll need to water more and feed them more often than you would in the ground because they’re kept in a limited-sized container.

 

Toxicity

Geraniums are toxic to humans and animals. This means it is important to keep the plant away from the reach of young children, dogs and cats.

This is obviously easier indoors. But, it might be a little more challenging in the garden where kids and pets often like to play around.

If ingested, it can cause vomiting and other gastrointestinal distress.

 

Pests

Zonal Geranium are prone to a few pests. This includes aphids and whiteflies. You’ll likewise occasionally see spider mites, mealybugs and caterpillars try to attack your plant.

With pests, it is very important to deal with them as soon as possible once you notice any signs of their presence. You can use insecticidal soap with water or likewise use neem oil spray.

You also want to isolate them from others so as not to allow them to spread.

 

Diseases

Humidity and excess moisture are the biggest culprits of disease. This is one reason why overwatering and humid conditions are not good for your zonal geranium.

Overwatering can lead to root rot which can become deadly if not found early enough. On the other hand leaf spot and gray mold are caused by too much moisture from humidity or getting their leaves wet without allowing them to dry quickly enough.

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