Papa Geno's Garden Blog

This is a repeat of the posting I made on January 22, so that the reader coming from my newsletter doesn't have to dig around in the archives. 

Outdoor growing - Scented geraniums (Pelargoniums) are a great addition to any area of your garden. We've used them in beds with brightly colored annuals like marigolds and zinnias, combined with standard geraniums, and in beds dedicated solely to scented geraniums. With few exceptions they need 5-6 hours of direct sun per day. Peppermint (and a couple of other "fuzzy" varieties) can get sunburned, and love light shade. At least a dozen varieties make attractive hanging baskets, and we use several varieties for creating topiaries and espaliers.

 

Growing scented geraniums indoors - Scented geraniums are not picky about temperature, but prefer to be cooler than standard geraniums. A range of 55 to 70 ° F is ideal. If you have them in a south window, sheer undercurtains are the perfect screen to prevent sunburn in summer.

Planting your scented geraniums
Any pot that provides good drainage will do, but we think unglazed clay (terra cotta) is a natural complement to these plants. Start with a 5" or 6" pot, and use a light commercial potting mix, or make your own using lots of perlite and/or sand. These plants are indigenous to a cool, semi-desert area and do not like wet feet, so water them well, and then let them dry out before watering again. In warmer areas (Zones 7-10), you may plant them outdoors after a period of acclimatization.

Scented geranium care tips
Give your geranium at least four hours of direct sunlight a day. Night temperatures should be 50° to 65°; day temperatures are ideally 68° to 72°. Allow the soil to dry out somewhat between thorough waterings. Fertilize every two weeks from March through October and once per month during the rest of the year. Pinch the tips of plants that are not branching on their own in order to avoid tall, leggy plants.

Fertilizing
Take care to not overfeed scented geraniums; overfeeding will diminish their fragrance and they actually don't need a lot of fertilizer. Any well balanced commercial plant food will do; natural fish emulsions and seaweed fertilizers are great for outside use. Use all of them at about 1/2 the strength recommended for houseplants. As with most plants, fertilize more often during periods of active growth, and not at all during the winter months.

Pruning
To prune or not to prune? Prune! Some plants may arrive looking as if they have just had a haircut, which is probably true, particularly late in the spring shipping season. These plants are not damaged - in fact, pruning encourages dense, lush growth. To truly appreciate these plants, you need to prune them on a regular basis.

Propagating
Starting new plants to add to your collection or to share with friends or neighbors is very simple. Use the plant material which you prune off your plants! Put the cut ends in damp sand and you will soon have new rooted plants. Plant into containers or into your garden when they're well rooted.

Winter care
Keep them indoors when it's cold outside! As they are easy to grow inside, scented geraniums make great fall and winter houseplants. They need only a sunny windowsill or a flourescent light and seem somehow to thrive on neglect. If you use a light, keep it turned on 12 hours per day during the winter. Some scented geraniums are large and bushy and will need regular pruning to keep under control.

A couple of weeks before it is time to move them outdoors in the spring, prune them back to a nice shape, repot if rootbound, and fertilize. Because of their lack of fussiness and tolerance of hot, dry conditions, scented geraniums are naturals for American summers. Plant them where and when you would plant standard geraniums - after danger of frost is past. Dig and re-pot about 3 weeks before the first fall frost, and gradually acclimatize them to the house before moving them inside for the winter.

Troubleshooting

Why are my geranium's leaves discolored?
If you notice mottling, streaking, curling, or abnormal color patterns on the leaves of your geraniums, they may have been infected with a viral disease carried by insect pests. Once infected, there is no cure; infected plants should be destroyed to prevent the spread of the virus. A regular program of watering and fertilization will keep plants healthy and best able to ward off viral infection.

What diseases affect geraniums and how can I treat them?
The first step in combating a plant disease or pest is to identify it. Here are some descriptions of common geranium diseases and their recommended treatments:

Southern root-knot nematodes: These microscopic, soil-dwelling worms can attack geranium plant roots and cause stunted growth, wilting and yellowing. Infested roots will display knots or swellings. These worms are most troublesome in warm-winter climates and sandy soils. Nematode infestation can be prevented with a regular program of watering and fertiliztion in conjunction with the use of compost to introduce beneficial soil organisms and crab or shrimp wastes to amend the soil. These wastes contain a substance which encourages the growth of nematode-attacking organisms. Once infested, a plant cannot be treated; however, the organisms remaining in the soil can be killed by solarization. Cover bare soil with clear plastic sheeting for three to four weeks. The build-up of solar heat under the sheeting will kill most pests and weed seeds in the top few inches of soil.

Leaf spot: Leaf spot diseases develop during warm, moist weather and cause leaves to display brown or black spots with yellow edges. Eventually, the leaves may drop and the stems may rot. Cut off and destroy infected plant parts as well as seriously affected plants and any soil their roots touch. Since the diseases overwinter on plant debris, if leaf spot occurs, keep the beds clean and replace the mulch. Because the diseases can spread via water, infected tools, or unwashed hands, avoid splashing water on the foliage and keep your hands and tools clean. Spacing plants widely will promote good air circulation.

Botrytis blight: Also known as gray mold, this fungal disease is spread by wind-brone spores and thrives in cool, moist weather. Stems and flowers will rot and develop gray mold, especially during damp, cloudy weather. To prevent its spread, destroy diseased plant parts. To prevent infection, space plants widely to promote good air circulation and allow the soil to dry out between waterings.

Pelagonium rust: This fungal disease causes small, yellow spots on leaf surfaces or powdery, orange spores on the undersides of leaves. Badly infected leaves and plants should be destroyed. Plants with minor infections can be sprayed with sulfur. Watering early in the day, widely spacing plants, and avoiding overhead watering will help prevent infection.

What pests commonly attack geraniums?

Some common geranium pests include the following:

Geranium aphids: These tiny, soft-bodied, pear-shaped insects suck plant juices and can spread viral diseases. They can be controlled by knocking them off the plants with a strong stream of water, an application of insecticidal soap (pay special attention to treating the undersides of leaves), spraying with horticultural oil, and releasing beneficial insects, such as parasitic wasps, ladybugs, green lacewings, and aphid midges.

Caterpillars: Several species of caterpillars chew geranium leaves. Caterpillars can be handpicked and destroyed or they can be controlled with an application of Bt (Bacillus thuringeinsis) which kills caterpillars, but does not harm beneficial insects. Cultivating the soil in winter will kill overwintering pupae. Attracting or releasing beneficial insects such as ladybugs and parasitic wasps will also help to control caterpillars.

Other pests: Common garden pests, such as mealybugs, whiteflies, and spider mites, can easily be controlled by knocking them off the plants using a strong spray of water, watering plants well during dry spells, and attracting or releasing beneficial insects. More severe infestations can be treated by applying insecticidal soap or neem.

What is the best way to overwinter geraniums?
It is almost impossible to overwinter geraniums outdoors in Zones colder than Zone 8, but quite simple to do so indoors. To overwinter entire geraniums or scented geraniums, dig them out of their beds or window boxes and place them in a bright spot inside. Make certain not to overwater your plants during their stay indoors. Some gardeners prefer to grow cuttings of their plants indoors rather than try to overwinter entire plants. To start to root cuttings, remove bottom leaves and place in a glass of plain water on a windowsill. Make sure to protect all overwintering geraniums and new cuttings from freezing temperatures which can occur if your plants are left too close to icy windows.

 

Why won't my geraniums bloom?
A common reason many flowering plants refuse to bloom is an overdose of nitrogen. Many commercial fertilizers are extremely high in nitrogen. While nitrogen is an essential element for vigorous plant growth, too much nitrogen encourages leafy growth at the expense of blooms. Try supplementing your soil with a balanced organic fertilizer such as our Rose and Flower Food. You might also consider having your soil tested through your local county extention agency. This is a free service which will help provide you with valuable soil improvement suggestions.

What should I do to get rid of the spent blossoms on my geraniums?
The best way to deal with old and withered flowers is to deadhead the plants. Deadheading can be done at any time of year, by cutting or pinching dead buds. You can use any hand tool, pruning shears, or even scissors -- just be sure to avoid new buds and blooms. Deadheading will freshen the appearance of your garden, as well as promote longer lasting and more abundant blooms.

If you are really interested in SGs, I know of one good book – Knowing, Growing and Enjoying Scented Geraniums by Jim Becker and Faye Brawner.  It is available both new and used on Amazon.com as I write this. (January 2006).

Click here to see our 140 varieties of Scented Geraniums.

Papa Geno