How to Overwinter Geraniums 

A garden favorite, the tender geranium, commonly known as the pelargonium, is a colorful addition to the flower bed or container garden.

Typically cultivated as annual plants, pelargoniums are hardy in USDA Zones 10 and warmer, such as the warm climates of Southern California. This means fans of the pelargonium in cooler climates must purchase new plants each spring. However there is another option.

Learning how to overwinter geraniums enables you to keep the same plants year after year, and in some cases even increase the size of your plant collection.

This guide to how to overwinter geraniums not only explains why this is a useful skill to acquire but also takes you through 3 reliable methods.

Colorful and attractive pelargoniums are easy to protect during the winter months. 

What are Pelargoniums?

Pelargoniums, also known as tender or scented geraniums have been cultivated as houseplants in the United States since the 1820s.

Different from the hardy perennial geranium, pelargoniums aren’t typically grown as houseplants.

Pleasingly easy to protect, unlike other plants, pelargoniums do not go through a dormant period during the winter months. This makes it easy to keep them going through the winter months before they flower again the following spring.

Why Should I Learn How to Overwinter Geraniums?

There are several reasons why you should learn how to overwinter geraniums.

Firstly, purchasing new plants every year can be an expensive process. It can also be frustrating if you find an attractive cultivar one year, but are unable to source it again the following year. Learning how to overwinter geraniums enables you to cultivate your favorite cultivars year after year. In fact, some plants are so resilient that they can be passed down through different generations of the same family.

Learning how to overwinter geraniums is also more affordable than purchasing new plants every year. It is also fun to take cuttings or learn how to protect plants during the winter months so that they can return again the following spring.

There are many benefits to learning how to overwinter geraniums.

3 How to Overwinter Geraniums Methods

Learning how to overwinter geraniums is an easy, rewarding process. There are 3 reliable ways to do this. These are:

• Taking indoors and caring for the plants as a houseplant,
• Storing dormant bare roots,
• Taking and propagating cuttings.

All 3 methods are explained below. Whichever method you choose, it is important that you start the process before the first frosts of fall affect the plants. Pelargonium plants affected by frost quickly die.

How to Overwinter Geraniums as Houseplants

Moving your plants undercover for the winter months is probably the easiest way to overwinter geraniums. It is also a good way to save the entire plant. However, unless you have a lot of room to dedicate to the plants near a window that is filled with lots of bright, direct light this method may not be practical.

When learning how to overwinter geraniums it is important to remember that these plants like to be cool. A temperature averaging between 55 and 65 ℉ is ideal. No extra humidity is needed.

A drafty, west facing window is the ideal position to place the plants for the winter.

Before bringing your plants inside for the winter, inspect the foliage for signs of disease or infestation. Treat any infestations with an application of homemade insecticidal soap.

It is important to treat any issues before you move the plants inside. Moving unhealthy plants undercover can endanger any healthy houseplants that you have. Do not overwinter unhealthy plants.

One of the most common diseases affecting zonal pelargoniums is rust. An increasingly common problem, the disease thrives during damp summers and falls. While unsightly it is easily treatable. Affected leaves can be removed and discarded, this helps to control the spread. You can also treat affected plants with a Dithane945 fungicide.

Cut back the plants before you bring them in for the winter. Pelargoniums do not have a winter dormant period, cutting back in the fall encourages fresh growth to slowly emerge during the winter enabling the plants to flourish from early spring onwards.

Moving pots inside or undercover is an easy way to protect the plants. 

Place the plants in a bright, sunny position, no more than 3 ft from a window or light source. Light is an important aspect of learning how to overwinter geraniums. If the plants get too little light they may become leggy or, in the worst cases, fail.

During the winter months aim to keep the soil evenly moist. It should not be wet or damp. Remember pelargonium plants continue to grow during the winter months. While the plants can survive a short period of drought they will not thrive in overly dry soil. A regular drink of water helps to promote growth. If you struggle to gauge the moisture content of your soil, a soil moisture sensor is a useful investment.

Ventilate the air around the plants regularly. Aim to keep the surrounding atmosphere dry. This helps to prevent issues such as mold or powdery mildew. Opening the window on warmer days also helps. On colder days plugging an electric fan heater in on colder days not only moves air around whilst also increasing the air temperature.

In general pelargoniums do not need to be kept overly warm. They simply need to be kept frost free. This means that growers in milder areas can overwinter the plants in a greenhouse. In cooler areas a greenhouse heater with an adjustable thermostat, such as the AKUSAKO Electric Greenhouse Heater, is a useful investment.

Set the thermostat on your greenhouse heater to 41 ℉. If frost is allowed to affect the stems the plants will fail. You can also overwinter geraniums in sunrooms, porches or conservatories.

If the stems start to stretch, pinch them back. It is important to keep the plants fairly compact over the winter months.

Pinching back the plants prevents them from becoming too leggy during the winter months.  

When spring arrives, resume fertilizing the plants and harden off, moving them permanently outside when the temperature is consistently over 50 ℉.

How to Overwinter Bare Root Geraniums

Overwintering bare roots is the most common method of protecting these sensitive plants during the winter months.

To overwinter bare root plants, once flowering has finished in the fall, carefully dig the plants up. This should be done before the first frosts of the year. Shake or brush any remaining soil from the roots and check for signs of disease or damage. Any diseased plants should be discarded.

Allow the plants to sit in a dry place, such as on a greenhouse shelf or windowsill for a few days to dry out. Drying the roots out before storing them helps to prevent mold.

Once dry, there are a few ways that you can store the bare roots. The most traditional method is to hang the plants upside down. You can also wrap them in newspaper or paper bags and place them on a shelf or store in a cardboard box.

However you choose to store the bare roots, it is important that the storage position is dark, dry and that the temperature remains at around 50 ℉ throughout the winter. The temperature should not be allowed to fall below 45 ℉.

When learning how to overwinter geraniums in this way, it is important to check the roots regularly, at least once a month. Inspect each plant for signs of mold, black leaves or soft stems. Unhealthy sections should be cut away.

Ideally, most of the stem should remain firm throughout the winter storage period. If the stems start to wilt too much, soak them in water before drying out and returning to storage.

Around 6 weeks before your area’s last predicted frost date, you can start to revive the plants by cleaning them up and cutting back the stems to healthy green growth. Once cleaned up, replant the bare roots in pots filled with fresh potting soil. When replanting, bury the stems 2 nodes deep. From these nodes new roots will form.

Keep the soil slightly dry until new growth appears. This usually takes 7 to 14 days. Continue to keep the soil moist until the plants are large enough to be planted outside.

How to Overwinter Geraniums by Taking Cuttings

Our final how to overwinter geraniums method is a good choice if space is limited or you do not want to bring entire plants, that may be diseased or infested, into your home. Taking cuttings is also a good way to double the number of plants that you have for little expense.

You will need:

• A sharp knife,
• Rooting hormone,
• A small pot,
• Rooting media,
• Water.

You will also need either a propagator or a clear plastic bag. Placing cuttings that you are trying to root in a Propagator with Humidity Vents helps to control temperature and humidity levels. A consistent environment is vital if you want your cuttings to succeed.

Your rooting media should be fresh and well draining. Coarse sand, perlite or vermiculite either on their own or mixed evenly with potting soil are all ideal.

Taking and rooting cuttings can be a messy process. If you do not have a potting bench, place some old sheets of newspaper down before you start.

Use your knife to take a 3 to 4 inch cutting from the tip of a healthy stem. Once you have taken your cuttings, the remaining plant can be placed on the compost heap.

Remove most of the leaves, allowing only the top pair or two pairs to remain in place.

Dip the cut end in rooting hormone and plant in a clean pot filled with moist rooting medium. Plant the cutting deep enough that it is self supporting. From the covered leaf nodes new roots emerge.

Place your planted cuttings in a propagator or plastic bag. If you are using a plastic bag use sticks or small HAINANSTRY Garden Bamboo Stakes to support the plastic, preventing it from contacting the cutting.

Position your cuttings in a bright, indirect light close to a sunny windowsill. Check the pots periodically, moistening the soil so that it doesn’t dry out.

Roots typically form in 6 to 8 weeks. A sure sign that roots are forming is the emergence of new growth above the soil.

When the cuttings are large enough they can be gradually removed from their protective covering. Once the plants are large enough, the following spring, harden them off and plant outside once the last frost has passed.

Learning how to overwinter geraniums enables you to enjoy abundant floral displays year after year.

An attractive, sensitive bedding plant learning how to overwinter geraniums enables you to protect and prolong the lifespan of your favorite cultivars. Some of the methods outlined above also enable you to expand your plant collection.