I bought two large potted Martha Washington geraniums in the spring of 2019. With the arrival of fall/winter, could you tell me if I can bring them inside the house over the winter? If so, how should I be caring for them? I put them in my sunroom, which faces west. The leaves are very green and firm. I know they do not like direct sunlight, but I’m not sure if that only applies to when they are outside during the heat of the summer. Should I be cutting them back, changing the soil? Should I give them fertilizer, and if so, which kind? The blooms were profuse when I bought the plants in May. I am not sure if I can get that level of bloom back again for next spring.
Thank you so much in advance for your help. I looked on the internet, but I could not find the answers I was looking for.
Martha Washington geraniums can definitely be overwintered indoors. In fact, they are often considered to be the ideal variety of geranium to grow indoors and can be grown as a houseplant year-round. In general, they prefer cooler overall temperatures compared to the more common cultivated geraniums that are widely available at garden centres, and they need cooler night-time temperatures (10-15 degrees celsius) to bloom.
You may notice some temporary dieback or yellowing of foliage as the plants adjust to their new indoor environment, but this is a normal occurrence and no cause for concern. For the best chance of flowering, Martha Washington geraniums should be grown in direct sun (but protected during hot summer months), especially if grown indoors. Your west-facing sunroom sounds ideal. Due to the lower light levels in winter, they will require less watering than during the summer. Fertilize very lightly over winter – ex. once every four waterings – with a balanced fertilizer that is formulated for flowering plants and diluted to at least half the recommended concentration, according to package instructions. Your local garden centre should be able to recommend a suitable brand.
In terms of pruning and repotting, neither is necessary over the winter, as growth will naturally be slower than during summer. However, if you find that the foliage is becoming leggy or otherwise unshapely, feel free to cut it back to keep the plants bushy. You can even root the cuttings to create more plants, if you wish. In spring, you can repot the original plants into new soil and larger containers, if you notice that the plants have become root-bound. Click here for more information on repotting.