In many parts of California, geraniums (also known by their botanical name as pelargoniums) are treated as perennials. However, in the mother lode, these plants can quickly succumb to our frosty winter temperatures. Here, they are grown as annuals.
Annual geraniums are tough little plants, and there is an easy process for keeping them alive over the winter. This process doesn’t take much time or much storage space.
You may have heard of hanging geraniums up for the winter, but I think the following method is even more successful. It’s amazing what these leafless stems can become in the spring, and look at the money you’ll save when you don’t need to buy new plants.
Follow these simple steps to over winter your favorite geranium plants:
Out Of The Ground – Dig up your geraniums before the first hard freeze (if they survived the recent snow, try this technique now) and shake off the soil from the roots. Don’t wash the roots or worry about getting every bit of the soil removed. The plant will overwinter better without the leaves, as leaves can harbor mold, but not to worry, as most leaves will dry up and fall off within a short time.
Into A Box – Store the stems upside down in a box, and close the top. No one is quite sure why they need to be upside down, but one theory is that it forces the moisture downward into the stem. Whatever the reason, keeping the geraniums upside down improves the survival rate. Be sure to store them in a dry location at a temperature of 50 to 60 degrees. Check for mold every few weeks, cutting off any that you find, and clear away any fallen leaves. The stems should stay firm, so if there are any that are shriveled, throw them out. If the stems begin to look dry, soak them in water for a few minutes, being sure to pat them dry.
Pot Them Up – Leave your stems in the box until six to eight weeks before the last frost. Fill five- or six-inch terra cotta pots with damp, soil-free potting mix, and cut the stem back to healthy green growth. Plant the stem into the potting mix deep enough that two leaf nodes are below the soil line; this is where new roots will emerge. The key to making this work is to water cautiously, only when the soil is dry about an inch down.
Ready To Plant – You will start to see new growth within about 14 days, and within four to six weeks the young geranium plant should be ready for its big summer debut. Geraniums really need to have at least six hours of full sun; otherwise they won’t bloom as well. They prefer to be on the dry side, so don’t include water-holding crystals in the potting soil, or put the pot in a saucer. These plants are heavy feeders, and are very happy being fed every few weeks. Begin with 10-10-10 time-release pelleted fertilizer in the soil at the bottom of the container, so that the roots will have to stretch to reach it. Every time you water during the summer, use a half-strength 10-10-10 liquid fertilizer. Sounds like a lot of feeding, but your geraniums will love you for it. Be careful to only water at the base of the plant as the leaves will hold the fertilizer and water mixture, causing the leaves to spot and scorch.
If you have additional concerns about geraniums or other garden plants, call the University of California Cooperative Extension at 209 533 5696, or email me at firstname.lastname@example.org
Betty Hensley is an experienced Master Gardener who loves propagating new plants.