Growing Hydrangea shrubs plants

Hydrangea plants are one of the most beautiful flowering plants in the world.   They have been used for many years in gardens around the world.     Hydrangea plants were first discovered in Japan around two hundred years ago. From there they spread to growers in England and Europe    There are a number of different varieties, the most popular being Hydrangea macrophylla, however there have been many improved varieties developed in recent years.    The older varieties tend to be larger growing from around 1.5 to 2 m.   The newer varieties are smaller and have improved flowering duration and colours. There are also miniature varieties of only around 30cm tall.  

Hydrangea plants are surprisingly adaptable, growing from cool climates, cool temperate through to warm temperate areas.   They are deciduous shrubs, so losing their leaves in winter, this means they are not very attractive in winter, but most gardeners put up with this because they are so attractive in summer.    Flower colours range from whites, pinks, blues, purples and reds (dark pinks).   Flower colour can be changed via alterations to soil pH on marophylla varieties, we will talk more about this in the following pages.

Where to plant Hydrangea shrub plants

Hydrangea plants will grow in full sun in areas with mild summers, however they tend to be more attractive (reduced leaf burn) when growing in shaded spots where they develop their flowers to perfection.    Most Hydrangea shrubs grow around the 1.5 m in height.   However there are newer varieties which only grow around 1m or less.   These are more compact and also flower better, if they are more hardy is a question, but it will depend on the conditions where they grow.    As stated a shaded spot is great for Hydrangeas, this means that they will grow and flower where few other plants will.   So, if you have a shaded side of your house where nothing else will grow you many think of using a Hydrangea shrubs.   Hydrangea plants look great mass planted and particularly suit cottage style gardens.     In regard to soils it is important to pick a soil which maintains moisture well but does not become sodden (there is a difference).    They will grow in almost any soil however, if moisture is available.   In fact this is what makes them so great for shaded spots as soils tends to stay moist in shaded spot.    We feel Hydrangeas grow best in acid soils, where the leaves tend to stay a darker green and the plant more vigorous.   However soil pH can affect flower colour as we will talk about next.

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How to change flower colour of Hydrangea plants

The secret to changing flower colour of macrophylla Hydrangeas (old varieties) is all in the soil and the fertilisers you use.    In acid soils, flowers start to go blue, in neutral pH, around 7 plus, flowers start to go pink and get darker the more alkaline the soil gets.     So, if you have an acid soil and you wish to have Pink hydrangeas you will need to use garden lime to increase pH.    We find that using a pH test kit is the best way to test your soils pH properly, and it is a bit of fun also.    If you have a neutral or alkaline soil, then you can use almost any fertiliser that has a sulphate base to lower pH, and so change the flower colour to blue.    This includes using azalea/camellia fertiliser.     The best way to change your Hydrangea flower colour to blue is to purchase some Hydrangea bluing treatment/tonic from your local nursery.   It is already made up, mostly of sulphate base fertilisers.    This is designed for turning the soil acid, so follow the instructions and don't apply too much at once.   It needs to be done now and then over a few months.   The whole process of changing soil pH (and Hydrangea flower colour) is slow and can take a number of months to start taking affect.  Just a note on Hydrangea flower colours, most of the new varieties have been bread to a single colour, so you can not change the colour of these.    Only the older varieties will change colour, also white hydrangeas will also not change colour, white Hydrangeas always stay white. 

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Pruning, fertilising & care of Hydrangea plants

Generally speaking Hydrangeas do not have many pests, they do get the odd caterpillar in spring and summer, which don't always do much damage.    Hydrangeas can get mildews which will tend to create spots on the leaves and sometimes the whole leaf will be covered in a fury fluff, with the leave eventually wilting.    This is generally created by unusual climatic conditions, usually warm, wet weather.    But, if you have this constantly then look at moving the plant to a better spot (it could be too shaded).    You can also use Mancozeb fungicide which tends to fix most mildews.

In regard to fertilising your Hydrangeas you can just use a general purpose garden fertiliser to increase plant vigour.     We prefer to use a liquid fertiliser with a seaweed tonic, like Seasol.   You can also purchase seaweed based fertilisers which are ready made, these are excellent and tend not to be very powerful, so you can use them regularly during the growing season.

Pruning is an important issue with Hydrangea plants to keep them flowering well.    There are just a few simple rules to use when pruning: 1. Once flowering has finished prune off old flower stems, the trick is not to prune too hard at this point, just enough stem to make a good flower arrangement. (Imagine you are going to use the flowers for a vase in the house, take about enough stem to do this) you can prune in this way after each flowering.   The plant will then produce another flush of flowers a few weeks later.

2. Major pruning in the cooler months - In most temperate climates it is best to prune some weeks after plants have stopped flowering, this is usually sometime in autumn.    You can prune Hydrangeas pretty hard if required, but in temperate climates it is better to take the plant back to around one third of its size.   In cooler climates with frosts or snow you may like to take the stems back even harder, this reduces the risk of the stem freezing. 

The great thing to know is that Hydrangeas can take a good prune, and even if you don't think you have done it 100% perfectly they will still flower in summer. 

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