Pelargonium for Europe, a german company that distributes Geranium in more than 10 countries in Europe, shares basic tips for an adequate look after of these plants and ensure their best blossoming.
Some routines to take into account to take care of this flower from South Africa are: best period to cuiltivate, location, pot size, watering and fertilising.

Timing
The ideal moment to take Geranium to the exterior is when nights stop being very cold, that is, moderate temperature, typical in spring or summer.
Location
Geraniums come from the Southafrica Cape, so they feel comfortable in a warm place with sun, or partial shadow. In fact, it is a sun lover and high tempertatures are a great benefit for its growth. Despite these plants do not need many maintenance, it is not a big problem if it rains.
Pot
Geraniums develope specially well when they have big space. If they are too close from each other or the pot or jardiniere is too small, they never will get their full flowering potential. A window box or any other receptacle should have a minimum depth of 18 centimeters and the plants should be separated, at least, 20 centimeters.
Watering
As temperatures increase and Geranium grows, also its water needs gets bigger. It is very important that plants don’t get completely dry, but neither a water excess because it could cause rotted roots. For those reasons is better to water plants regularly and with normal quantities. -Standard watering guide is: 500 mililiters per plant, in a 20 pot of centimeters.
Fertilisation
The expert from Pelargonium for Europe recommed using slow delivery fertilisers, which provide nutrients to the plant in an effective, controlled way, and prolonged in time. Manufacturer instructions will indicate how long the nutriets will last. The best option is to look for a 9 month life product and the temperature should be of 20º C. During the summer the temperature is higher and the fertiliser will run out before. In that situation, the experts recommedn use standard fertiliser once a week. If the leaves present a yellow colouring, it means the process is not being efficient.
Maintenance
Remove regularly dry flowers and yellow leaves will help the plant to be in good condition and moreover, will help to produce new flowers..
Preservation
To achieve a good preservation for the next year, the greenhouse effect has to be carried out. Before first night frosts come, the plant should be prunned to 15 centimeters, and the place for them to have, ideally, between 5º C and 10º C.
Source: Pelargonium for Europe.