A balanced fertilizer 10-10-10 contains 10% nitrogen, 10% phosphorus, 10% potassium). The remaining 70% of material is filler. Because geraniums have thick, nearly succulent stems, they can survive dryness when kept properly during winter. To overwinter geraniums in dormant storage, dig up the entire plant before frost and gently shake the soil from the roots. Yellowing leaves indicates that you may be watering too frequently. Use a well-draining soil, like SummerWinds Potting Soil , to ensure proper moisture. This is especially true for zonal geraniums. Wintering geraniums causes plants to produce larger flowers as plants mature in years. Provide bright light, cool air temperatures and water only when soil is dry. Take Some Cuttings. To store dormant plants, dig them up in the fall, shake soil off the roots, and place plants into open paper bags. Put the plants in your brightest window. Ideally the temperature should be between 45-50 F. Geraniums are a favorite flowering plants in the garden, so itâs no surprise many gardeners want to enjoy blooms from the same plant year after year. With some newspaper, a cardboard box, paper bag, or a sunny windowsill, you can keep these tender perennials for the winter and have fresh blooms next spring and summer. If you have too many large geraniums to dig up, or storage just isnât feasible, you may make cuttings to root indoors. Iâll walk you through the options and provide winter care tips. Bright light is critical for geraniums to remain healthy throughout the winter, as low light results in tall, spindly plants with yellow foliage. There are several ways to overwinter geraniums ( Pelargoniums) from your garden. Allow soil to dry to some extent between waterings, then water thoroughly. Roughly 4-6 wkly soak the roots again and hang up again. Check plants carefully before bringing indoors to make sure youâre not ferrying insects inside. For geraniums and other annual flowers, a good option is a âbalancedâ fertilizer which has equal amounts of nitrogen (N), phosphorus (P) and potassium (K). Over-wintered geraniums prefer temperatures that are in the 60- to 75-degree Fahrenheit range. During the winter, water much less, but do not let the roots dry out entirely. Geraniums do best when given a period of dormancy through the winter months, during which they use less water and do â¦ I tried different ways to overwinter my geraniums last winter and found the best results to be the easiest. Garage. (You can also tie groups of soil-less â¦ How to Care for Geraniums. You can learn â¦ Place your potted geranium in a location in your home that is bright and sunny, but not too warm. Theyâll take root over the winter months and will be ready for transplanting outdoors come spring. Be sure to water your Geraniums thoroughly, but allow the soil time to dry (equivalent to a damp sponge) in between watering. Water your geraniums once a week, or when the surface soil becomes dry. Place the plants inside open paper bags or hang them upside-down from the rafters in a cool, dark location for the winter. When You take in the geraniums shake off all soil from the roots, soak the roots in a bucket for an hour and then hang upside down in a cool place i.e. 2. Overwatering may cause your geranium stems to rot at the soil level.