Most geraniums are grown as annuals in climates with harsh winters, but oh how charming they are when they are let to winter-over!
In Europe, overwintering geraniums on windowsills is a tradition. They won't bloom a lot during the winter, but they will provide some welcome touches of vibrant green and red here and there, and the great thing is, you'll have the same plant next spring, instead of just tossing it in the compost heap.
Here's how to overwinter geraniums:
Bring them indoors
Try to bring them in before the first frost! Once they get hit with a heavy frost, they won't really make it, so this is key! I've procrastinated bringing them in before and lost them, so pay attention and try to bring them in before it gets too cold.
You can trim them by about 1/3 before you bring them in, I like to do this just with my hands, by snipping off the stems at the node.
Ideally, geraniums like to be between 50-70 degrees F. Keep them near bright, natural light in a south or west-facing window, and keep them away from drafts and heat.
Keeping them potted
Geraniums should be potted into light, potting soil (with soil, sand, peat). Heavy garden soil or clay doesn't work well for them. Be sure to provide good drainage by using gravel or stones in the bottom of a pot with a drainage hole on the bottom.
Let the geraniums just barely dry out between waterings! Keep in mind, a terra cotta pot will dry them out more quickly then other types, so just be mindful to keep an eye on the soil. Ideally, they should be moist but not wet at all times. Geraniums are at risk of rot if they are too wet, so I normally keep them a little on the dry side.
Always keep them deadheaded so they can produce more flowers. Take off the stem at the node. Don't use clippers, as geranium's soft stems are susceptible to disease. Just break them off with your fingers.
If you have temperatures warm enough, let them live outside during the daytime on occasion to get fresh air and sunshine.
Alpine geraniums tend to overwinter the best out of all varieties, but regular zonal geraniums do great too. There's no need to feed the geraniums in the winter, they'll be in a semi-dormant state.
Bringing them back outside in the springtime
When all danger of frost is gone, bring your geraniums back outside and fertilize them!
If you have a lot of geraniums, you can keep them bare root in a cellar to overwinter, but if you just have a few, or have space in a greenhouse, keeping them in pots is best.