Although geraniums are perennials they don’t fare well in the Dutch winter so it is good to know what you can do to avoid the frost from ruining your summer flowers.
Just because they are frost-sensitive does not mean bedding geraniums should be thrown away at the end of the summer - they're far too expensive for that.
Here are some options that you have to make them last:
1.Overwinter inside as potted plants.
2.Store the dormant, bare roots.
3.Propagate cuttings to make new plants.
Keeping them in pots:
Find a cool spot for them like a spare room or in a cold greenhouse – if you do not have such a place, a book shelf will suffice. Keep them relatively dry.
The best tip that I got from my aunt is that you can actually split and multiply them as you bring them inside. With a sharp knife, you can cut the larger clumps up and place each cutting in a pot.
•Remove the bottom leaves and any spent flower buds.
•Dip the bottom end & any wounds where you’ve removed leaves of the cutting in some cinnamon (as this is an anti-fungal)
•Water them a little making sure that they are moist but not soaked.
•Place them in a cool and light spot, not in direct sunlight (this probably is not too much of an issue in a Dutch home)
•The chances are high that all will grow roots and you will have loads of new geranium plants.
If you do not want to split them then you can just reduce the height of the stems by half, and cut off yellowing leaves and dead flower heads.
I like to keep them in pots inside as it adds some green to the winter.
If you are not splitting them when you dig them out then you can actually keep them in a cardboard box wrapped in a newspaper, this will be in their dormant state. You can cut them and create cuttings in spring, placing them directly into the ground outside.
Soak the roots before potting or planting outdoors.
Tie a small bunch of the dormant plants together and suspend them upside down.
Dust lightly with cinnamon (as this is an anti-fungal) & leave them until the spring.
When do I take them inside? Make sure that you take action before the first frost
When do I plant them out? After all danger of frost is over, this is mid-May for the Netherlands.
How do I plant them out? Plant them in well fertilized soi. Make sure that you soak the roots of the dormant plants before potting or planting outdoors.