Geraniums: Grow & Care for Pelargonium

Written by Iris

Oct 14 2021

Geraniums: Grow & Care for Pelargonium
Geraniums (Pelargonium) is native to southern Africa and is now widely cultivated all over the world. Geraniums is a good flower for decorating windowsills, especially in European continent, such as Germany and Austria. In Hungary, the people regard it as the national flower. Geranium's flower language is "accidental encounter, happiness is by your side".

How to Grow Geraniums (Pelargonium)

Geraniums Propagation with Seeds

  • To start geraniums from seed, purchase seeds from a reputable purveyor. Do not try to save seed from an existing plant as the second generation will not grow true to the parent plant.
  • According to experts at Iowa State University Extension and Outreach, you should start seeds indoors in mid-February to get a jump on the 13 to 15 weeks it takes the plants to grow and flower.You may sow seeds outdoors in Zones 10 to 11 at any time.
  • Fill the containers to about 1/2 to one inch below the pot rims.
  • Before sowing, gently scarify the seeds with an emery board to break the seed coats.
  • Place seeds two to three inches apart in larger containers or one seed per cell and barely cover them with 1/4 inch of potting medium.
  • Give the containers a thorough soaking to saturate the potting medium and cover them with clear plastic wrap.
  • To ensure germination, the soil temperature must not go above 75°F, so place containers out of direct sunlight in a room with a daytime temperature of 70-75°F, and 60-65°F at night.
  • Water when the potting medium is dry, you want to keep it moist but not waterlogged.
  • Remove the plastic wrap when you see the first sprouts.
  • After Geraniums germination, the Iowa State horticulturists recommend placing containers four to six inches below a 40-watt fluorescent grow light for 12 to 16 hours per day.
  • When the seedlings have a set of true leaves, thin them out unless they are growing in individual cells. Choose the strongest in each container to keep and pull up or cut the rest down.
  • Alternatively, pot up all of the seedlings into individual six-inch diameter pots filled with soilless potting medium.
  • At this time, you can dilute houseplant fertilizer and apply it to the seedlings every two weeks.
After all risk of frost has passed, acclimate the growing Geraniums plants to the outdoors gradually, setting them out for a few hours each day, for about a week, before transplanting them to the garden or containers. Plants should flower 13 to 15 weeks after the seeds are sown.

Geraniums Propagation with Stem Cuttings

You may also start new plants by taking stem cuttings from existing plants.
A close up horizontal image of a geranium cutting set in a small glass jar filled with water on a white background.
It's best to take Geraniums cuttings from fresh green growth, rather than old woody stems. The best times to do this are in early spring, or just after a new flush of growth following blooming.
  • Sanitize a sharp knife and make a clean cut about six inches down from the stem tip, preferably just above a leaf node. This helps to stimulate the existing plant to grow new foliage.
  • Cut off all but the top few leaves at their points of origin, so you have a length of bare stem about four inches long.
  • Place the Geraniums cutting into a clean, transparent container. Fill the container with three to four inches of water, ensuring that the water isn’t in contact with the leaves at the top of the stem.
  • Choose a location that is out of direct sunlight and change the water daily to keep it fresh.
  • In approximately one month, you will start to see roots growing from the bottom of the stem.
  • Wait until the Geraniums roots are well established, approximately one to two inches long, before transplanting the rooted stem cutting to the location of your choice.
  • Alternatively, instead of placing it in water, you may start your cutting in sterile soilless potting medium.
  • The pros at Purdue University Extension recommend a sterile, soilless potting medium with added vermiculite or perlite, to keep it airy and conducive to root formation.
  • When you have taken your cutting as described above, moisten the cut end and dip it into powdered rooting hormone.
  • Make a three to four-inch hole in the potting medium, and place the stem into it.
  • Firm the soil securely around the stem and place it in a sunny location where temperatures remain between 65-75°F.
  • Keep the potting medium moist, but not soggy. Never allow it to completely dry out.
  • The roots underneath grow first, so it will take longer to notice foliar growth on top. When you see new green growth, it's time to plant the rooted stem.

How to Care for Geraniums (Pelargonium)

Geraniums Soil Care

While geraniums are not very particular about soil pH, selecting a neutral to slightly acidic soil will be beneficial. Also, they prefer potting soil that is moist, well-draining, and high in organic matter.
To achieve these properties, work a 3-4-inch layer of organic matter such as compost or peat moss into the soil before planting. Besides, ensure the composition has a coarse material such as sand or perlite. If this sounds too complicated, you can go for a professionally prepared commercial soil mix.
The main advantage of such potting mixes is natural and enhanced with myco-tone which improves Geraniums root development. However, if you go for this option lookout for fungus gnats especially when you keep the soil too moist.

Geraniums Watering

New Geraniums plantings should be watered daily for a couple of weeks. After that, depending on the weather and soil type, watering can be adjusted to every two or three days. Clay soils hold moisture longer than sandy soils, so expect to water more frequently in sandy settings.
Different plants have different water needs. Some plants prefer staying on the dry side, others like to be consistently moist. Refer to the plant label to check a plant’s specific requirements.
Ideally water should only be applied to the root zone - an area roughly 6-12” (15-30cm) from the base of the plant, not the entire plant. A soaker hose is a great investment for keeping plants healthy and reducing water lost through evaporation. Hand watering using a watering wand with a sprinkler head attached is also a good way to control watering. If the garden area is large, and a sprinkler is necessary, try to water in the morning so that plant foliage has time to dry through the day. Moist foliage encourages disease and mold that can weaken or damage plants.
To check for soil moisture use your finger or a small trowel to dig in and examine the soil. If the first 2-4” (5-10cm) of soil is dry, it is time to water Geraniums.

Geraniums Temperature & Humidity Care

These are warm-region plants that dislike cold temperatures. They thrive at the same temperatures preferred by humans—55 to 80 degrees Fahrenheit. Prolonged temperatures below 55 degrees Fahrenheit will stunt these plants, and temperatures at the freezing point usually kill them. It may be possible to overwinter regal geraniums as far north as zone 7 if you cover them heavily in the winter, but it is generally best to grow them as annuals.

Geraniums Fertilizer

As a best practice, don't fertilize your geranium plants until they are well established and when they are not actively growing (in winter). When you do fertilize, use soluble or slow-release fertilizers which are best for indoor plants.
You can fertilize every 2 weeks using a water-soluble fertilizer at half strength. If you’re growing your plants where light intensity is low or indoors, reduce the amount of fertilizer accordingly. Apply fertilizer according to directions on the label, and make sure that the soil is moist before applying.
An ideal scenario would be to fertilize your geranium plants with a liquid fertilizer that's a 20-20-20 formula, using a rate of 2 tablespoons per gallon of water. But again, it’s better to follow the instructions on the label carefully.

Geraniums Pruning

Prune Geraniums plants freely to maintain the desired size and shape. Pinching plants back stimulates dense, bushy new growth and encourages more flowers.
Remove old flowers to keep plant looking healthy and prevent seed production that drains the plant’s energy at the expense of forming new flowers.
Some plants are grown only for their attractive foliage (such as coleus, dusty miller and flowering kale). Their flowers are not very showy and any buds should be pinched off to keep the foliage looking its best.

Geraniums Pests & Diseases

Pelargoniums are easy to grow, but there are a few things worth watching out for:
  • Poor air circulation and damp conditions favour diseases such as grey mould and rust
  • Pelargoniums can suffer from viruses transmitted by sap sucking insects such as thrips, or on pruning or propagating tools including knives or secateurs
  • Roots of container grown plants are prone to vine weevil larvae damage
Geraniums can also suffer from leafhopper, root mealybug and whitefly
Dense clusters of distorted leafy shoots, often close to ground level, are leafy gall

Geraniums Overwinter 

Geraniums that have spent the summer outdoors can be kept as houseplants, provided they get lots of sun. In northern climes, the sun may not be strong enough in late winter to stimulate buds on some varieties.
Before the first fall frost (find your local frost dates here), lift the plants and, using a sharp, clean knife, cut the stems back in a shapely fashion to about 6 to 8 inches. They should not have to support great masses of leaves in the low-sunlight environment they are about to enter. Save a few stems as cuttings to root—an easy way to multiply your plants.
Transplant the “mother plant” to the smallest pot possible—enough to just fit the roots—using regular potting soil to fill.
Keep the plants in shade for a week, then place them in a sunny spot (they need all the sun they can get) and keep them cool.
During winter, geraniums grow best with night temperatures of 50° to 60°F (10° to 16°C) but will survive if they drop to 32°F (0°C) and/or rise above 80°F (27°C), as long as they are kept relatively dry.
When new growth appears in the spring, cut off all the old leaves.
The only thing more difficult than getting the new growth to appear is keeping it. And here's some help with that:
Water only when the leaves show signs of drooping and provide only small amounts. Do not fertilize or feed the plants. It is critical that these plants get rest.
If you want your overwintered geraniums to bloom for Memorial Day, pinch them back in February. Once warm weather returns and all danger of frost has passed, take the plants outdoors and transplant them to beds or pots, as you wish.

Varieties of Geraniums (Pelargonium)

Other common geranium types are:
Zonal geraniums or Common Geraniums (Pelargonium x hortorum) – They usually have distinct leaf markings. They include selections with tri-colored leaves, silver leaves, leaves with white markings, and fancy-leafed geraniums. Flower colors are usually pink, red, or white.
Ivy-leafed Geraniums (Pelargonium peltatum) -  They have a trailing habit and their leaves resemble ivy plant leaves. They are commonly used in hanging baskets and window boxes.
Martha Washington Geraniums (Pelargonium x domesticum) – They are available from many florists during the winter months as flowering pot plants. Like ‘Mabel Gray,’ they are not heat-tolerant and will not perform as well outdoors as the common geranium.

Geraniums (Pelargonium) FAQ

Why Geranium leaves are turning yellow and brown?

If the geranium leaves are only turning yellow, it may indicate nitrogen deficiency. However, if the yellowing is accompanied by brown discoloration, then, you need to watch your watering. Since this indicates overwatering.

Why Geranium plants are appearing tall and spindly

When the Geranium plants begin to look spindly and taller than usual, it is a clear indication that they are not getting enough light. Expose them to bright light. If the weather is good, you may bring your plants outside for some sunshine. Besides, you can cut back a few stems to encourage compact and bushy growth.