Geraniums are an old garden favorite and are most likely found in pots and flower boxes, but also make good borders around a garden bed. They come in a variety of colors including red, rose, purple, pink and white with green or variegated leaves. The flowers are large with many petals and bloom all summer.
Geraniums need full sun to produce flowers. They can tolerate a dry period but should never totally dry out. Wait until the top 1 inch of soil becomes dry before watering again.
Geraniums grow in regular potting or garden soil. Clay soil requires an addition of compost and peat moss to aerate the soil. Geraniums grow especially well in a soilless mix containing peat moss. To produce the best and most continuous blooms, pH levels, or the level of acidity in the soil, must be kept in the range of 5.8 to 6.2. Geraniums will not bloom above or below this level and leaves will sometimes develop brown spots with low levels. Garden centers carry easy-to-use pH test kits and meters.
Never plant geraniums outside until after the last frost. Temperatures of 50 degrees Fahrenheit or less will stop flowers from blooming and turn the leaves a reddish tinge. Temperatures above 85 F can cause the leaves to lose chlorophyll and stop growth of the plant.
A liquid fertilizer with the numbers 15-30-15 will benefit geraniums during the growing season. Apply per package instructions monthly during the summer, but be sure to avoid spraying the fertilizer on flowers or leaves. If using a soilless mix fertilize every week. Pinch back tips of geraniums in April. This encourages more stems and the plant will become lush and bushy. Always remove wilting and dead flowers or leaves. This will encourage more blooms. Geraniums can be overwintered in an area that stays about 50 F. A garage window works well in moderate climates, as does a basement. The foliage will dye back but rejuvenates when exposed to warm temperatures and sunlight. Geraniums are easily propagated from cuttings by taking a 3- to 4-inch slip of a stem and placing it in rooting medium. When kept moist and in sunlight they will grow enough to be planted in three to four weeks.