Potpourri on a bush, lemon geranium (Pelargonium crispum) leaves are loaded with aromatic oil. Crush them, and a burst of lemony fragrance fills the air. In U.S. Department of Agriculture plant hardiness zones 10 through 11, where it's perennial, lemon geranium perfumes the garden all year. Elsewhere, a potted plant spends the summer outdoors and comes inside when fall temperatures drop below 50 degrees Fahrenheit. Pampering, especially with the watering can, isn't necessary for this easy-care geranium.
Water When Dry
As plants adapted to the sandy, dry soils of South Africa's Western Cape, lemon geraniums do poorly when overwatered. Water only if the top 1 to 2 inches of their soil or growing medium is dry. Water outdoor plants on sunny mornings, so their leaves have time to dry thoroughly before nightfall.
Overwatered lemon geraniums produce weak, soft growth. To keep potted plants healthy, stop watering as soon as water runs out of their drainage holes, and empty their overflow saucers immediately. Always use pots with drainage holes for these plants.
Fertilizer and Epsom Salt
Lemon geraniums don't need much fertilizer. From the time their new growth emerges in late winter or early spring until they die back in fall, fertilize them with balanced, water-soluble 15-30-15 fertilizer at one-half the label's recommended rate.
One fertilizer brand, for example, recommends mixing 1 tablespoon of granules in 1 gallon of water. During the growing season, lemon geraniums would get 1/2 tablespoon of this brand mixed in their water before every other watering session. In-ground and container plants receive the same dose. Use one-half the label-recommended amount of your specific fertilizer.
Between fall and late winter, or if the weather is cloudy and cool for a lengthy period, limit fertilizing to every eighth watering session.
One teaspoon of Epsom salts added to every fourth fertilizer application keeps lemon geranium's foliage healthy and green. Magnesium-deficient plants develop yellow margins around arrowhead-shaped, green centers.
Cut Back on Pruning
If you're happy with the size and shape, pruning a lemon geranium is optional. When necessary, cut the growing tips back to a leaf node to stimulate new shoots for a bushy, well-shaped plant.
Don't prune until the geranium is at least 6 inches tall, with four or five leaf nodes on each stem.
Use clean, sharp scissors disinfected between cuts in a solution of 1 part household bleach to 9 parts water so you don't accidentally spread disease.
Expect new shoots to bloom within two months. After that, snipping off old flowers and leaves or unruly growth keeps the plant tidy.
When life gives a garden geranium lemon-scented leaves, bugs ignore it. Move the plant inside, and it's a different story.
Pear-shaped aphids mass by the hundreds on new stems and leaves. Mealybugs on the stems and leaves resemble cotton wool. Four-winged whiteflies swarm from the plant when disturbed, and all three cover the plants in sticky, transparent waste. Fine webbing on the leaves' undersides means a spider mite attack.
For early insect control, set the plant in the shower or sink and hit it with a strong water spray. Spray a heavily infested geranium with organic, ready-to-use insecticidal soap until all its surfaces drip, and repeat weekly or at the label's recommended intervals until the pests are gone.
As a precaution, wear protective clothing and eyewear and a respiratory mask when spraying the soap.