Growing Geraniums

Latest Update 10th October 2016.

Geraniums (Pelargoniums)
  • Geraniums are actually Pelargoniums, but what's in a name.  These extremely hardy small shrubs flower continuously all year with beautiful clusters of flowers in a wide range of colours.
  • To keep them in good shape, they need to be trimmed back every few months, and to keep them flowering, just break of the spent flower stems.
  • I like to replace my Geraniums with new plants every year.  They are very easy to propagate from cuttings and strike very quickly and reliably in an Ecopropagator.  However, they will live on happily for a number of years if they are kept well trimmed.
  • The photo above shows a vibrant rich pink geranium growing under the protective canopy of my olive tree.


  • Binomial Name:                                      Pelargonium hortorum.
  • Family:                                                   Geraniaceae.
  • Garden bed type:                                     Drip line irrigated. 
  • Recommended soil pH:                             6.0 - 8.0.  
  • Plant Spacings (centres):                          300mm. 
  • Climate:                                                  Warm Temperate.
  • Geography:                                             Southern Hemisphere. 
    Growing Conditions:
    • Full sun.   
    • Minimise soil disturbances to maintain a natural soil structure.  
    Feed the Soil.  
    • In September, remove old mulch, fallen leaves and other decaying organic material.  Dispose of them in the compost heap.   
    • Drench the soil with aerated compost extract, and apply a 60mm thick top dressing of home made compost.  
    • Cover with fresh straw mulch.
    Growing Instructions  
    • They can be propagated from softwood cuttings as soon as the plant starts to grow vigorously in spring.  
    • I cut off shoots about 100mm long and strip them of their leaves until there is only one small leaf cluster left at the top of each cutting.
    • I push these cuttings 50mm into soft soil in one of my Ecobeds, water them in and forget them until Summer when they are ready to plant out.
    • Select a spot to plant your new shrub and remove any decaying organic material to the compost heap. 
    • Drench the soil with aerated compost extract, and apply a 60mm thick top dressing of home made compost. 
    • Cover the compost with fresh mulch.
    • Leave for a few weeks to boost microbial activity.
    • Move some of the mulch to one side and dig a hole twice as big as the new plant's root ball.  Place the plant in the hole and back fill with compost.  Water it in well.
    • Water the plant every few days until it is established, and then allow the drip irrigation to take over.  
    • When replacing an old Geranium, choose a spot which hasn't grown them for at least 3 years.
    • They remain vigorous plants for several years if kept compact by frequent trimming, but I like to replace them with new cuttings every year. 
    • Deadhead the flowers and give the plant a light prune from time to time during the growing season to maintain a compact shape and encourage masses of new flowers.
    • Spray the foliage with aerated compost tea twice a year in late autumn and late spring.
    Organic Pest Control.
    • My Geraniums have been pest and disease free for many years, but can be effected by the following:-
    • Caterpillars.
      • When mixed with water, Bacillus thuringiensis becomes a potent (organically certified) killer of butterfly caterpillars.  It is sprayed onto the plants leaves, and when ingested, kills them by releasing toxins into their gut.  They stop feeding and die within a few days.
      • I use aerated compost tea as a foliar spray on all my ornamental plants.  I don't claim this is as effective as the bacillus, but after one year using this spray, I seem to have less pests of any kind on my plants.
      Aphids (greenfly).
      • I usually just rub them out when I find them with my fingers, but if there are lots of them, I remove them with a jet of tap water.  They seem unable to regain their place on the buds and shoots of my Geraniums and (I guess) starve to death where they land.
      • I spray my Geraniums with aerated compost tea every month, and I am sure this increases the plants resistance to aphids, but I still get some on the new shoots in between sprays.
    • Powdery mildew. 
      • A monthly foliar spray of aerated compost tea was a spectacular success last year with no sign of powdery mildew on any of my plants.
      • Alternatively a solution of 1 part cows milk to 9 parts water makes a reasonably effective organic pesticide against powdery mildew.  However, it needs to be applied early before this fungi gets well established, and frequently to keep it in check.
    • General:
      • Regular foliar sprays of aerated compost tea boost the natural defences of Geraniums by colonising the leaf surfaces with beneficial microbes.  These microbes defend the plant against airborne pests and diseases.
      • Similarly, proper soil preparation including regular applications of home made compost and aerated compost extract boost the community of beneficial microbes, which defend the plants roots against plant pathogens.