Growing Hydrangeas Outdoors

October 25, 2013 in Flowers and Bulbs by Christine

Growing Hydrangeas in your garden 

Growing hydrangeas outdoors brings welcome colour to the shadier parts of the garden grown for their domed or flat flower heads which have masses of inconspicuous flowers. The name hydrangea comes from the Greek “hydra” meaning water, and “angeon” meaning vessel. Hydrangeas belong to the family known as the Hydrangeaceae.

Hydrangea Identification – 5 species of Hydrangea widely grown around the world

 growing hydrangeasGrowing Hydrangeas Marcrophylla 

Hydrangea Macrophylla, commonly known as bigleaf Hydrangeas, most popular species of the hydrangea is native to the Japanese that produce thick individual canes coming from the base of the plants with big flat round toothed edged leaves that measure around 4″-6″ long and 3″-5″ wide they are toped with a big showy 8 inch diameter flowers called mopheads of white, red, blue or pink round shaped flowers, which look fabulous when in full bloom. Hydrangea plants do flower in Australia late January early February but mainly have sterile flowers and more importantly these are the type of hydrangeas that you can manipulate the flower colours.

Growing Hydrangeas Oakleaf 

Hydrangea Oakleaf, this species is native to the United States and has a similar shaped leaves as acer macrophyllum the big leaf maple tree unlike the other cultivars of hydrangeas these leaves turn to deep mahogany red colour in autumn this species has a taller cone shaped flower known as long panicles and not round like the popular bigleaf known as hydrangeas macrophylla. The oakleaf hydrangea can tolerate sunnier conditions and dryer soils, not to much water being left in soggy soil otherwise this plant will get root rot.

Growing Hydrangeas Pianicle

Hydrangea Panicle is very cold hardy but tolerates a bit more sun than the others on this list with large creamy flowers similar to the lacecaps, these plants have a deciduous habit often used as a deciduous hedge, but regain their new foliage in early spring.

Growing Hydrangeas Petiolaris 

There is a new climbing hydrangea called Hydrangea Petiolaris you have to be very patient as it is very slow to grow eventually growing to 80 feet and can take 10 years to bloom providing a spectacular floral display of white lacecap type blooms in early to mid summer on established plants, it loves to grow in filtered light like other hydrangeas. It is not best to climb this plant on the side of your house or where you don’t want a mark left as it leaves a residue that is very hard to remove.

Growing Hydrangeas Lacecap

The hydrangea lacecap variety has a unique style of bloom then the increasingly popular variety of hydrangea that has cropped up in recent years is the lacecap hydrangea. Almost identical in every way to other species the lacecap produces a unique style of bloom. The lacecap blooms produce a large bunch of buds in the centre of the bloom and is surrounded by gorgeous open flowers that can range from pink and blue, to white.

General Care of Hydrangeas

The majority of hydrangeas love morning sun till 11am. If you experience extremely hot summers like some parts of Australia hydrangeas need to be planted on the east side of the house where they receive morning sun and afternoon shade. If the soil is poor you can improve the quality of your soil by adding some good organic compost. Hydrangeas require a good soaking on a weekly basis but if the weather gets hot and dry, like it does regularly in Australia, then water more frequently as it is not a good look when the huge flowers and leaves have already wilted besides they like a dose of blood and bone and a small scattering of super phosphate annually after they have been pruned, but these fertilisers should be avoided if you are trying to get blue hydrangea flowers, I would just use compost or a balanced fertiliser not to much otherwise the fertilisers will burn the roots when the soil has dried out, this has been known to kill the plant.

Pests and Diseases while Growing Hydrangeas

While growing hydrangeas they are usually pest fee, they do get some diseases.
Here are some of the diseases to look out for.
You do have to be on the lookout for powdery mildew this is caused through warm wet weather as well as too much shade and the plant not being watered enough. Powdery mildew is described as a light grey powdery substance on the leaves, usually starting at the bottom leaves, it won’t kill the plants but can be unattractive, powdery mildew is more severe on the bigleaf hydrangea Marcrophylla you can PREVENT this by spraying the plant with 2 cups of milk in a bucket of water.

Oakleaf hydrangea are susceptible to root rot, the symptoms are that the whole bush is wilted but not though lack of water, when this happens it is usually too late as the plant will die, the usual fault of this happening is being planted in poorly drain soil.
Hydrangea Marcrophylla are susceptible to Iron Chlorosis, this is caused when the pH of the soil increases and the iron in the soil becomes less available for the plant, the best way to fix iron chlorosis is to use a chelated iron fertiliser.

How to Change the Colour of your Hydrangeas Flowers

Growers and gardeners cannot change the white hydrangea Annabelle it stays white no matter what soil pH it is planted in. Hydrangea Macrophylla the most popular hydrangea grown in home gardens and landscapes, they have huge flowers and are the hydrangeas that you can change the colours of the blossoms, the pink hydrangeas can be changed to blue and blue hydrangeas can be changed to pink and colours in-between aside from this the colour is determined by the amount of aluminium available to the plant. So how is this done? First of all, to control the colour of your hydrangeas macrophylla you should first take a sample of your soil and test the soil pH to see if the soil is alkaline or acidic if you don’t know the colour of the hydrangea plant already, this is a guide below what pH gives you whatever colour.

pH between 5.0 to 5.5 would be already blue flower
PH between     6.0      would be already purple flower
pH between 6.5 to 7.0 would be already pink flower

How to change the hydrangeas colour from blue to pink you would need to add lime, by mixing a cup full of lime to a gallon of water and pouring this around your hydrangeas this will change the colour of your hydrangea flowers to pink, you would also use a fertiliser with high levels of phosphorus being the middle number of the NPK on the packet of your fertiliser.

How to change the hydrangeas colour from pink to blue you would have to use aluminium sulphate or powdered alum a tablespoon into a gallon of water and poor this around your hydrangea plants and this will change your hydrangea flowers to blue. Coffee grounds, grass clippings organic matter will help to lower the pH too. I know my grandmother use to put heaps of nails or tin around her hydrangeas and hers were blue whether this helps or is just a myth I don’t know, but it is worth a try, a fertiliser low in phosphorus and high in potassium can work too.

Only do this when the hydrangea plant is dormant usually but I personally think that it doesn’t matter, it just means you will have to wait till next year to see the outcome if the hydrangeas that are already flowering. From the change of the flowers pink to blue and blue to pink in hydrangeas this can take at least two or three years for the final colour to take place depending how dark pink or dark blue you want the end result to be. It is not easy to get the right colour you want, it would be much easier if the hydrangea was planted in a pot or a container, as there is less soil to deal with. Personally I wouldn’t go any lower than a pH of 5.0 you may run into trouble with the leaves turning yellow.

When and How to Prune Hydrangeas 

Without pruning your hydrangeas they are likely to become leggy with lots of dead branches and leaves and more likely to not flower. It is advisable to give your hydrangeas a regular cutting back every year so they will flower. Hydrangeas produce their flowers primarily on the second year growth therefore this is where you should prune them by starting at the top of the hydrangea bush and following the stems down till you see the plump buds that are on both sides of the main cane or stem, you may see two or even three sets of these buds along the stem but pick the double bud closest to the ground because it will be the strongest and thickest and make a cut a quarter of an inch higher than the double buds, if you cut shorter than this to a single bud your hydrangeas will not bloom till the following season, you should also get rid of dead branches by cutting these out down to the ground and also cut two or three of the really old stems down to the ground as well this will make new stems emerge from the base of the plant  these new canes will take two years to flower so you are constantly replacing the old branches with new ones over time. The best time to prune hydrangeas is in the winter months of July and August around the same time as roses. Hydrangea cuttings can be taken in the summer you will need the soft wood cuttings to propagate with. The white flowering ‘Annabelle’ hydrangea is easier to prune as you just prune it close to the ground a quarter of an inch above a node and it will flourish with a new lot of flowers on new wood.

Drying Hydrangeas Flowers

The best way to dry the flowers of hydrangeas is to leave them dry on the plant until they are almost completely dry and they have a papery feel they are best collected off the bush when the weather temperature is low in humidity this is at night, you can then cut the stems at your desired length to make a floral arrangement aside from this you need to strip off the leaves, down the stem then place the flowers in a dry place indoors where they can finish drying without water, it is best that the big blossoms are kept separated while they finish drying so they don’t get squashed.

These are some of the tips and tricks of growing hydrangeas by being able to get them to flower through pruning them the correct way, changing the flowers to your desired colour and knowing how to make a dried floral arrangement with hydrangeas.


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