We are often asked about plants that suddenly have a flower which is different to the normal colour of the parent plants. There are several reasons why you can get a new flower colour. The most common cause is a plant mutation which then changes the growth habit or flower colour of the parent plant. Often a new shoot displays different characteristics to the parent. These new shoots are known as 'Sports'.
Sometimes it is a good sport, sometimes it is not so good. A problem of course is that gardeners who find a 'sport' on one of their plants, automatically assume that it is a 'good' sport. Interesting it may be, and maybe even a very different colour to normal. That in itself, does not make it a brilliant new plant of your very own!
Like all things in life, there can be good sports - and bad sports.
Sports - or mutations - do not always materialise in the form of colour differences. Sometimes a new shoot with a 'different' characteristic will be just as important. For example, most climbing roses, started life a a sport or mutation on a well known parent rose. That is how we have got 'Climbing Iceberg' and 'Climbing Ena Harkness'. Someone was observant enough to realise that the vigorous shoot sent up by the ordinary floribunda rose 'Iceberg', was not mistaken as a 'sucker' but as a very valuable vigorous shoot that enabled it to 'climb'. The shoot was then propagated by the normal process of budding, and we ended up with 'Climbing Iceberg.
R. Iceberg. The Climbing Iceberg, started life a a 'sport' of the ordinary Bush Rose - Iceberg.
In the case of Ena Harkness - a gorgeous red with a disappointing flower habit of 'drooping' instead of staying upright - the new vigorous shoot that was found and 'converted' into 'Climbing Ena Harkness', both gave us another climber to add to the catalogue, but also its droopy flower habit, fits in very well with its re-birth as a climber!
Reverting to Type
Virtually all variegated plants started life as ordinary green or whatever - sending out a variegated shoot - a sport - which was then propagated to give us the variegated plant form. Euonymus 'Emerald and Gold', and E. 'Emerald Gaiety' are two such typical examples.
One of the problems with variegated plants, is that they often send out green shoots - which are normally more vigorous than the variegated parent. If they are not cut out, then they will soon take over the whole plant, and you will be left with a mass of mainly green shoots.
In this case, the green shoots are where the variegated plant has 'reverted' back to its original parentage! So, the new green shoot is not a 'new' plant or sport, but simply a desire within the plant to find its original 'roots' again!
Self Sown Seedlings explains how ne plants are often 'discovered' by garden seedlings.