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Brightly-colored in shades ranging from common pinks and reds through deep dusky blues and violets, geraniums are a common sight in most gardens today.
The term “geranium” itself is a bit misleading, because there’s actually two separate genuses that are considered geraniums. But we’ll go into that in more detail shortly!
Whether you are simply looking for a plant which can create a plethora of bright and wildly-colored flowers, or a plant that smells like cinnamon or spices, you can find a geranium that will suit you. So let’s explore this aromatic and beautiful plant at length!
Products To Eliminate Geranium Pests/Diseases:
- Neem Bliss 100% Cold Pressed Neem Oil
- Safer Soap
- Monterey BT
- Garden Dust
- Hydrogen Peroxide
- Microbe-Lift BMC Fertilizer
- Mosquito Bits
- Ladybugs
- Lacewings
- Beneficial Nematodes
- Beneficial Parasitic Wasps
- Bonide Copper Fungicide
Geranium Overview
All About Geraniums
There are two types of plants that are called geraniums: true geraniums that are part of the Geranium genus and plants which are Pelargonium genus. Both are part of the Geraniaceae family, and are related if not identical.
Geraniums are also susceptible to an extremely wide range of fungal, bacterial, and viral diseases (see article for complete list). Most common are botrytis cinerea, various leaf spots, various root rots, galls, rusts, and mosaic viruses.
Both of these plants are often confused for one another.
The majority of what gardeners consider to be geraniums are actually Pelargonium genus plants. True Geraniums are often referred to as crane’s bill or wild geraniums, and sometimes as hardy geraniums as they’re a bit more cold-resistant.
We’ll cover a bit of both here!
Types of Geraniums
The majority of plants grown in the average garden bed are going to fall into the pelargonium category, simply because that’s the category which has become most known as geranium. But we’ll cover a few true geraniums as well.
Here’s a short list of some of the different types. Between the two categories, there’s nearly 700 types of plants, but we’ll list some of the most popular!
Pelargonium x hortorum
‘Garden Geranium’, ‘Zonal Geranium’, ‘Malva’, ‘Malvon’
These are the most common geranium type found at your local garden center. They create large clumps of pink, red, or white flowers atop a tall stem that rises above its fan-shaped leaves.
A hybrid, Pelargonium x hortorum is a cross between Pelargonium zonale and Pelargonium inquinans.
Pelargonium peltatum
‘Ivy Geranium’, ‘Ivy-Leaf Geranium’, ‘Cascading Geranium’
Fleshy, rounded leaves create a base from which stems rise, each holding 8-9 pink or streaked pink flowers in a clump. The ivy geranium is a popular variety especially in areas prone to wildfires, as it tends to be less flammable than other flowering plants.
The flowers tend to have five petals, some varieties streaked from the center of the flower up along the petals. Ivy geraniums tend to be more susceptible to some forms of disease, but can make for beautiful garden plants.
Pelargonium graveolens
‘Scented-Leaf Geranium’, ‘Stork’s Bill’, ‘Rose Geranium’, ‘Sweet-Scented Geranium’
This species is known for the rose-like aroma which its leaves produce. Velvety and soft, the leaves themselves are coated in fine downy ‘hairs’ which help hold their scent.
The flowers tend to bloom with the upper two petals being much more dramatic than the lower three, almost reminiscent of some forms of pansy. However, it is the scent which continues to draw people back, and Pelargonium graveolens var. graveolens is heavily used in the perfume industry.
Pelargonium domesticum
‘Martha Washington Geranium’, ‘Regal Geranium’, ‘Show Geranium’
These bushy evergreens make up another large segment of the American plant market’s geranium supply. Popularized here by the varieties known as “Martha Washington”, they are heavily-flowering specimens which create large and attractive border plants.
However, not all Pelargonium domesticum are larger plants. There are some very attractive miniature-type geraniums in this category as well. Their main popularity stems from the heavy production of flowers which these plants do each year.
Pelargonium crispum
‘Angel Geranium’
Sometimes referred to as ‘pansy-faced geraniums’ in the United States, the angel geranium tends to be a popular bicolored species. Similar in growth habits to Pelargonium domesticum, Pelargonium crispum has been bred to become more bushy and compact with smaller flowers.
Some cultivars may have a citrus-like scent to their leaves. They can be cultivated to produce an oil that is used for perfuming.
Other Scented Pelargoniums
There’s a huge selection of scented pelargonium species, all of which are grown heavily for perfuming purposes. Scents range from almond and apple through mints, citrus scents, nuts such as hazelnut, spices like cinnamon or nutmeg, and even celery.
While there’s simply too many species to mention that fall into the scented category, these can be extremely popular amongst growers for those unique aromas.
Geranium phaeum
‘Dusky Crane’s Bill’, ‘Mourning Widow’, ‘Black Widow’
Native to Europe, the dusky crane’s bill has a deep violet flower with a protruding stamen cluster emerging from petals that are turned back. This gives it a bill-like look, leading to its name.
Popular varieties of this species include “Lily Lovell” and “Samobor”, both of which are commonly cultivated in European gardens.
Geranium maculatum
‘Wild Geranium’, ‘Wood Geranium’, ‘Spotted Geranium’, ‘Spotted Cranesbill’, ‘Old Maid’s Nightcap’
This wild plant has its origins in and around the plains regions of the United States, but has been successfully cultivated in gardens as well. Its roots are used in herbal medicine, especially among tribal groups.
One popular variety which has won the Award of Garden Merit from the Royal Horticultural Society is the “Elizabeth Ann” cultivar.
Geranium pratense
‘Meadow Cranesbill’, ‘Meadow Crane’s-Bill’, ‘Meadow Geranium’
With varieties such as ‘Mrs. Kendall Clark’ having received the RHS Award of Garden Merit, the meadow cranesbill is another popular geranium variety. Native to Europe and Asia, it is widely cultivated worldwide.
This species is extremely cold-hardy, and can tolerate temperatures that dip into the single-digit negatives. That makes it much more popular as a garden plant in the snowier regions of the world.
Care of Geraniums
Overall, geraniums are pretty easy to care for. Most of your work will be comprised of deadheading hundreds of spent flowers to encourage more blossoming. The tips below will show you the best conditions for your plant to thrive in.
Light and Temperature
Geraniums are typically a full-sun plant in most conditions. They require lots of light to create all of their vibrant flowers! However, they’re surprisingly adaptable, and can be in partially-sunny conditions. For best flower production, aim for 6-7 hours of sunlight per day.
Most geraniums are quite tolerant of warm weather, but in desert climates, shade during the hottest part of the day is recommended. When the weather’s over 90 degrees, try to ensure they get a nice break from the scorching sun.
If growing your geranium indoors, aim for 6-7 hours of sunlight per day and supplement with a grow light if needed. Ideal growing conditions for indoor plants are 65-70 degree temperatures, but they’ll accept up to 85 degrees without any significant slowing of growth.
Water
All plants require water, but geraniums tend to be especially sensitive to over-watering and under-watering conditions. If the soil is right, they’re not difficult to maintain.
Water your geraniums only when the soil is dry to the touch. Just stick your finger into the soil a few inches, and if it seems a bit on the dry side, go ahead and water. If you find moisture about an inch below the surface, wait a little longer before watering.
Outdoor plants usually have a minimum of one deep watering weekly, but may require more watering during the hot summer months.
Plants in pots (both indoor and outdoor) should be given a deep watering once the soil has dried out. Allow the water to flow through all the soil until it comes out the bottom of the pot, then stop.
Hanging pots or outdoor ones may require more frequent watering, so be sure to check these regularly. Indoor plants often require less watering than outdoor ones, but will need more watering if the humidity level indoors is low or during the hotter months.
Soil
There’s no doubt that geraniums like a drier soil. Don’t use bark-based or coir-based soil as it generally holds too much water around the roots.
I recommend a blend of equal parts potting soil, compost, and perlite for your geraniums. This ensures that there’s plenty of perlite there to provide airflow in the soil and keep it from being too soggy.
If you’re lacking potting soil, don’t panic! You can make a potting mix out of equal parts garden soil, peat moss, and perlite, and then use that to blend your geranium soil.
In addition, most geraniums prefer an acidic pH level. Something in the 5.5 range will make your geraniums quite happy.
Fertilizer
A good, balanced fertilizer is what’s recommended by most geranium societies, applied every 4-6 weeks. If you’d like to fertilize more often, make a half-strength dilution of your fertilizer and fertilize every 2-3 weeks.
Trying to encourage heavy flowering? You can switch to a 5-10-5 fertilizer and add fresh compost over the surface of the soil each fertilization. The compost provides additional nutrition, but that extra phosphorous encourages the plant to flower rapidly.
Propagation
Geraniums can be propagated from both cuttings or from seed.
We all know how to plant seeds, so I won’t get into huge detail there. But geranium seeds don’t need to be planted deeply. Just enough soil to cover them is fine! And they germinate best with soil temperatures of 75 degrees Fahrenheit.
Cuttings can be taken year-round, but it’s best to wait until the plant’s not currently blooming.
To take a cutting, find a healthy stem and cut it just above a leaf node (a swollen place on the stem). Remove all but the tip leaves, and then make a second cut at the base just below a leaf node, leaving yourself with a 4-6″ long cutting.
Place your cutting into a sterile container of warm, damp potting soil. Water it thoroughly, then place it in a bright location, but not in direct sunlight. You do not have to cover geranium cuttings, as that can cause them to rot.
Water when the soil dries out, and your plant should take root within a couple weeks.
Repotting
It’s surprisingly easy to repot geraniums, although older plants require a bit of pruning first.
Begin by preparing your growing medium. I recommend a mix of potting soil, compost, and perlite to ensure it’s well-draining and nutrient-dense. Moisten it slightly, just enough to make it damp to the touch but not muddy.
Trim back the branches and stems of your geranium plant to a 4″ length, trying to be sure that you cut just above a node on the branch. It will grow back quickly!
Gently tilt the old pot and slide the geranium out. Unwind any roots that have started to circle around the rest of the root clump, and trim if necessary. If any roots show signs of rot, trim those out as well.
Set your plant into its new pot at about the same height it was planted before. Hold it in place with one hand, and fill around it with fresh growing medium. Then, give it a good watering, being sure that you water until you have water freely flowing out the base of the new pot.
Be sure to place a couple inches of mulch on top of the soil to slow down water evaporation, and water when the soil beneath the mulch feels dry.
Pruning
Half of your pruning for your geraniums will be spend deadheading spent flowers. It seems like a neverending task, but to encourage more flowering, you should absolutely do it!
To deadhead flowers, look at the stem beneath the flower, and trim back to just above a leaf node. That way, the plant will produce new growth at that node area and continue to blossom.
In late summer or into the fall, once the plant has begun to die back, it’s time to prune perennial geraniums. Trim the plant to 2-3″ above the soil’s surface. Whenever possible, cut just above a leaf node to encourage future growth, but shape it down low.
Mulch around the base of the autumn-pruned plant for winter root warmth, and it will grow back slowly during the winter and much more rapidly come springtime.
Geranium Problems
There’s quite a few pests that geraniums have to contend with, as well as a number of diseases. While you’re not likely to experience these problems constantly, here’s how to handle them if and when you do!
Growing Problems
Geraniums are warmth-loving plants. If the weather gets too cold and the plant is not protected, it can cause yellowing or reddening of the leaves, wilting, and possibly even plant death.
To prevent these problems, be sure your geranium is kept warm during the winter. If it’s under 50 degrees, consider using a cold frame or other outdoor protection, place it in a greenhouse, or bring your plant indoors if it’s in a pot.
Oedema, also known as edema or corky scab, is another problem that primarily affects ivy geraniums. When the air is cooler than the soil temperature but humidity both in the soil and air are high, it can cause oedema.
This condition creates watery blisters on leaves that rupture and turn yellow or brown, and can be mistaken for forms of rust. To prevent oedema, keep the air humidity low and don’t overwater. Air temperature should be kept at or above the soil temperature as well.
Speaking of overwatering, improper irrigation is a regular issue for geraniums. Overwatering can cause leaf yellowing, but so can underwatering. Check the soil if your plant starts developing yellowed leaves, and if it’s too wet, reduce your watering frequency.
Underwatering can cause reddening of leaves, or crisped edges of leaves. Again, check the soil and if it’s dry, water your plant.
Some nutrient disorders or deficiencies may also cause reddening or yellowing of leaves, but checking your irrigation status first is usually the best choice. If your irrigation level is good, then move on to having the soil analyzed and checking for signs of plant disease.
Sucking Pests
There are a number of sucking-type pests that go after geraniums for their inner juices.
Aphids are quite common in gardens, and they like geraniums almost as much as they like our edible plants. They group on the underside of leaves and along stems.
Scale insects, especially two types of mealybug (the citrus mealybug and Mexican mealybug) and the cottony cushion scale, are also prone to attack your geranium plants. These can create little fluffy, cottony masses on the leaves and are easy to identify.
The twospotted spider mite will also attack geraniums, although they typically only go after plants in drier conditions. These can create web-like masses on the leaves.
Thrips, especially western flower thrips, can often be found on the flowers or buds of geraniums. These may also be found on the leaves.
And finally, there’s whiteflies. You may find clouds of tiny white bugs flying above your plants, and that’s a sure sign that they’re present. Their larvae will be hiding on the underside of leaves, sucking the juices out of them.
On the bright side, there’s a couple things you can do to conquer all of these pests. Spray your geraniums regularly with neem oil to keep them at bay and to smother their eggs. Release ladybugs and lacewings around your garden during spring and summer to help kill them off.
You can also use insecticidal soaps like Safer Soap against these pests, if neem oil isn’t available. But I honestly recommend keeping neem oil at hand for the sucking pests at all times! A weekly or biweekly application of neem keeps them at bay.
Caterpillar Pests
A huge list of moth larvae feast upon geraniums, too. And unless we want a plant’s leaves to look like Swiss cheese, they need to be controlled quickly and effectively.
Armyworms, particularly the beet armyworm, are quite fond of geraniums. While they’ll go towards edible plants first, they’re more than willing to feast upon your geraniums next if they’re not dealt with.
The bollworm may be more of a curse to cotton growers than to home gardeners, but if you live anywhere near cotton farms, you’re susceptible. These hungry little caterpillars will chew through your leaves.
Cabbage loopers are common throughout the United States and in many other countries. Like armyworms, geraniums are not their primary choice, but they’re certainly not unwilling to chew huge holes in your leaves.
The geranium or tobacco budworm is a moth larvae who specifically targets both geraniums and tobacco, along with petunias and other common flowering plants. Widespread through the western United States, it’s found in lesser numbers worldwide.
Another larval pest that targets geraniums is the geranium plume moth, which is also widespread throughout the western USA. The adult moth has frilled wings and looks like a cross between a moth and a butterfly. Their caterpillar form is particularly destructive to flowering plants.
The oblique-banded leafroller is a moth that’s native to North America. Its larvae feed on an extensive range of plants. While geraniums are one of their targets, so are roses, rhododendrons, strawberries, carnations, honeysuckle, and azaleas. These also attack trees like willow and pine!
The omnivorous leaftier is sometimes called strawberry fruitworm because it attacks strawberries. But it will happily consume geraniums as well, and it’s best to keep a watchful eye out for this moth and its caterpillars.
And finally, there is the variegated cutworm. Like all caterpillars, these small larvae feed on plants. However, they’ve earned their name by eating through stems, causing the stem to topple over as if it were cut. These can be absolutely deadly to young geranium plants.
Like the sucking insects, there’s one primary control method that I recommend for all of these. Spraying or powdering your plants with bacillus thurigiensis, also known as BT, will eradicate a couple hundred species of caterpillars.
I recommend Monterey BT as a spray, or Garden Dust as a powdered form. Both will work quite effectively without harming beneficial insects.
Other Pests
The Fuller rose beetle, aka the rose weevil, is as inclined to consume geranium plant matter as it is to go after roses. The adults will eat the plant’s leaves, where larvae go after the plant’s roots. A bad infestation can easily kill your geranium plants.
It’s important to control these beetles in their adult form, before they can lay eggs. Neem oil is considered to be an effective deterrent against the Fuller rose beetle, and can smother their eggs.
Once larvae form, beneficial nematodes in the soil will also attack the weevils, as will parasitic wasps.
And at the end of this long pest list, we have the sciarid fly, known as the dark-winged fungus gnat. While the adults are mostly just an irritant, their larvae will live within your soil and do root damage to your geranium plants.
Using the common household version of hydrogen peroxide as a soil drench is quite effective at killing the larvae of fungus gnats, as is neem oil.
A species of BT that’s not in most commercial sprays or powders, Bacillus thurigiensis var. israelensis, can also be used to kill fungus gnat larvae. You can find this in Microbe-Lift BMC Fertilizer if you need to fertilize your plants. Alternately, water in some Mosquito Bits to get it in your soil.
Fungal Diseases
Fungal issues like Armillaria root rot, botrytis blight, Alternaria leaf spot and other leaf spots, pelargonium wilt, and verticillium wilt are common problems for geraniums.
Armillaria root rot is caused by the fungus Armillaria mellea. It causes stunted growth and wilting on geraniums, as well as leaf drop. Honey-colored mushrooms may form at the base of infected plants, although that’s more common on trees. Destroy infected plants and remove all root material.
Botrytis cinerea creates greyish, mold-looking spore infestation across leaves and can be fatal to plants over time. Treatment is a bit complex, so I recommend you read my article on how to handle botrytis cinerea infestation.
A variety of leaf spots tend to be caused by fungal growths, and many of them cause damage to geraniums. The worst of these is alternaria leaf spot, which causes brown spots with a yellowish halo around them. Use a liquid copper fungicide to treat these conditions.
Geranium rust, occasionally referred to as pelargonium rust, can cause yellow spotting with dark brown pustules filled with fungal spores. Neem oil can help protect your plants’ foliage from developing this disease.
Finally, we come to the last fungal issue for geraniums, verticillium wilt. Wedge-shaped yellow patches on leaves will form. Quickly thereafter, the entire leaf may yellow, wilt, or simply fall off. Plants will become stunted and may have limp branches.
Geraniums showing the symptoms of verticillium wilt should be removed completely and destroyed. This fungus lives in the soil, so new plants susceptible to verticillium should not be placed in that soil unless it’s fully heat-sterilized.
Bacterial Diseases
Bacterial infection for geraniums tends to be uncurable. Prevention is your best defense.
Bacterial leaf spot or bacterial blight are some of the most common diseases of geraniums. There are multiple bacteria, but the most prevalent are Xanthomonas campestris pv. pelargoni, the Psuedomonas species Pseudomonas cichorii and Pseudomonas syringae pv. syringae, and Ralstonia solanacearum.
Most of the bacterial leaf spots and blights are spread by water splashing onto the leaves or through infected soil. While there are some chemical bactericides which may be partially effective, these bacteria are notoriously hard to wipe out. Destroy infected plants.
Blackleg is a common infection for geraniums which turns the stems a distinctive black color and causes them to wilt, as well as causing root rot. Plants infected with blackleg will not recover, and should be destroyed.
A pair of gall types also tend to strike geraniums.
Leafy gall causes a cluster of strangely-shaped leaves to appear right at the soil line. This bacteria is transmitted through the soil, and infected plants should be destroyed. Avoid planting new geraniums in that spot.
Crown gall causes distorted growths or galls directly on the plant’s stem. These galls make it difficult for the plant to take up water or nutrients. Plants with galls should also be destroyed, and again, avoid planting geraniums in that spot.
Viral Diseases
There is also a long list of viral diseases which can affect geraniums. Like the bacterial diseases, these have no known remedy. Infected plants should be destroyed to prevent viral spread.
Two mosaic viruses, the cucumber mosaic virus and tobacco mosaic virus, can spread via aphids, virally-infected seed, or via human hand on tools. These cause mottling and streaking of the geranium leaves, as well as blistering or crinkling of the leaves.
Curly top, also referred to as beet curly top virus, causes thickening of the leaves and twisting and deformation. Leaves may yellow, as well. Younger plants often will die off quickly, while older plants may hold on for a while.
Impatiens necrotic spot virus and tomato spotted wilt virus were originally considered different strains of the same virus, but now are viewed separately. Both cause a wide variety of symptoms including yellowing, spotting, discoloration, stunting, wilting, and stem death among others.
Pelargonium flower break causes stippled yellowing of leaves, leaf edge browning, and yellow veining. This disease is widespread in greenhouse environments.
Finally, there is the tobacco ringspot virus. Transmitted by everything from nematodes to honeybees, this virus causes irregular yellow splotches on leaves, crook-shaped stems with drooping flower heads, browning and rolling of leaves, and other symptoms.
Most of these viruses are transmitted by pest populations. If you keep your plants free of pests, you will greatly reduce your chances of plants developing these viral infections. Destroy any plants which are infected to prevent spread of the diseases.
Whether you’re growing them for their luscious scent or their showy blooms, geraniums are definitely worth growing! What’s your favorite variety of geranium? Let me know in the comment section!
