Hardy Geraniums are for the most part what the name implies. They do very well in California’s interior valley and foothills.
Hardy Geraniums are in a class by themselves and are not Pelargoniums. Most varieties grow as low sprawling plants and others as thick ground cover. In the Central Valley of California we have two extremes, freezing temperatures in the winter and many days from May through September where temperatures soar into the 100’s with very low humidity.
Most all of the other members of the Geraniaceae family can not tolerate these extremes but many of the Hardy Geraniums can.
Let’s examine the typical physical attributes of the plant. The plant does not have stems but rather thick rhizomes (runners) just below the soil surface. The root structure is thick and wiry and helps store moisture and food supply to help the plant ‘winter over’ in cold or even snowy conditions.
Most of the Hardy Geraniums are shade lovers here in the Valley but not the ‘Sanguineums’. They can take the full sun and the Oppressive heat with little damage to the foliage. The heat does cause some stress and even the Sanguineums fail to bloom during these periods.
The Hardy Geraniums prefer being planted in the garden rather than in a container but will do well in either situation.
The Sanguineums do well in hanging baskets or tubs and planters as the foliage drapes over the edges.
The Sanguineums are unique too since they produce two distinctively different leaf shapes.
The larger leaves are the growth leaves and the smaller more serrated leaves are borne on the flower stalks.
The plants will retain a token amount of foliage most winters but during long periods of extreme cold all signs of life will disappear. Do not worry, your plant is well prepared for this, remember those thick roots and rhizomes, they stored the moisture and energy needed to produce lush new growth in the spring. Check mid to late February and you will see your plant in action.
Most ground covers are very invasive but Hardy Geraniums spread slowly by growing rhizomes and over time may need limited attention. Making cuttings is easy, just dig up a rhizome and if it is not already rooted, simply treat as any other cutting, you know what to do.
The plants produce a good number of flowers over the season and they do set seed. You can propagate the seed for new plants but using rhizomes to create new plants is faster and easier.
Garden watering is well tolerated but over watering is not, does that sound familiar? Fertilize as you would your other geraniums, these fellows need food too. If you are planting several plants together to create an area of ground cover in your garden space the plants 8 to 10 inches apart when planting. It will take 12 to 18 months for the plants to grow together and form the desired effect. If you choose to plant in a container use the same soil mix that you use for your other geraniums and don’t forget the importance of drainage. I do not recommend planting ‘Cinereum’ in the valley as they do best in a coastal environment.
There are some very good books on the subject and the best and easiest to understand is:
‘Gardening with Hardy Geraniums’
by Birgitte Husted Bendtsen, ISBN 0-88192-716-3, printed by Timber Press, published in 2005.
by Robin Parer, ISBN 978-1-60469-418-5 printed by Timber Press, published in 2016