Gardening: Give me a big splash of blue

A year or so ago a neighbour gave The Partner a few hydrangea cuttings. The Partner has a soft spot for old-fashioned things - hence the mound of annuals that is flourishing in the middle of our sub-tropical garden - so he planted them, as directed, in dappled shade behind a large vibernum.

They were completely hidden from view, which suited me, and anyway I never thought they'd grow, since he did nothing more than jam them into the soil and ignore them for the ensuing 12 months.

But this week, having spent three exhausting days repainting the kitchen and dining room white (including two sets of dark stained French doors and a big window - what was I thinking?) I went looking for something that would give the new look a bit of zing.

Searching the garden for anything that was colourful and not yellow, I noticed something a gorgeous shade of blue behind the vibernum.

I clambered over the rock wall and discovered the dead sticks had grown leaves and a whole heap of absolutely gorgeous, green-tinged, sky-blue flowers. I picked a bunch, jammed them in a vase (I'm known far and wide for my lack of talent at flower arranging) and they totally lit up the new room.

When The Partner wasn't looking, I did a bit of sneaky research on the internet to find out how to propagate them, and discovered that the ease with which we grew these ones wasn't just a lucky accident. You can plant them, preferably somewhere a little shady, ignore them apart from a bit of watering if it gets very dry, then just wait for the flowers, the arrival of which is almost guaranteed. Not only do they look great on the plant, but they're a fantastic cut flower even in my untalented hands, and they last in a vase of water for ages.

Better still, they don't come in yellow, but they do come in a zillion variations of blue and pink, and even white - the New Zealand-raised Trophy is a stunner. (See box for getting the colours you want.)

You can just stick a few hydrangea twigs in the ground and wait and hope, but if you want to be more scientific about it, put plants into well-worked soil with some compost and fertiliser to get them off to a good start.

They're not sun bunnies so the flowers will develop more vibrant colours and last longer in the shade.

In early autumn, give them more fertiliser and towards the end of autumn, prune them to about half their size. Hydrangeas flower on the branches from the previous year and do best if pruned every year, taking the second-year wood right down to the base of the plant. Usually, the second-year wood is lighter in colour, more branched out at the top and has old flowers on it. Taking this out lets more light into the plant so new shoots can develop from the base.

And now to that vexed question of how to get the colours you like. I'm totally enamoured of our sky-blue blooms, so the last thing I want is them turning the colour of the dog's gums or, heaven forbid, yellow, the second my back's turned.

So, the distillation of about 1000 pages of "expert" opinion and anecdotal information is this:

Pink

* For hydrangea blooms to be pink, the plants must not take up aluminum from the soil. If the soil naturally contains aluminum, try these tricks.

* Add dolomite lime several times a year to raise the pH to about 6.0 to 6.2.

* Use a fertiliser with high levels of phosphorus. That'll help to stop aluminum getting into the system.

Blue

* Obviously, you're going to need aluminium in the soil to make blue blooms. Aluminum sulfate is your baby - add it to the soil around the plants to lower the pH.

* Another method for lowering the pH is to add organic matter to the soil such as coffee grounds, fruit and vegetable peelings or grass clippings.

* Choose a fertiliser low in phosphorus and high in potassium to get good blues. Avoid superphosphates and bone meal.

If your soil is the opposite of what's needed to naturally produce your preferred colour, you can save yourself a lot of bother by growing hydrangeas in pots. In a pot, it will be much easier to control the requirements.

I consider myself lucky that something thrown in so carelessly could have produced exactly the colour I would have chosen. So I'm not going to push my luck - they can stay where they are and continue to be ignored, although I will snip off a few cuttings and stick them in somewhere else, just to see what happens.

It's probably the thin end of the wedge, and in no time I'll have a shedful of magic potions to see if I can make a black one. What will people think?

I'll just tell them something else I read on the internet - that the French adore them - they're evidently the top summer shrub in France. Well, the French are a stylish lot so perhaps it is OKAY to be harbouring a secret love of hydrangeas.

BOOK REVIEW

Salads year-round by Dennis Greville

Published by New Holland

I usually start to panic about this time of the year because I know there will come a time that I won't want to eat lettuce, and I won't have planned well enough ahead to keep us in home-grown veg for autumn, winter and spring.

So Dennis Greville's new book, Salads year-round, is most welcome, setting out numerous vegetables, herbs and fruit to grow throughout the year.

Dennis is keen to drag us kicking and screaming from our comfort-zone salads of lettuce, tomato and grated cheese and introduce us to a variety of new foods, along with very straightforward instructions on how to grow  and eat them. It's as simple as "what it is, when to plant it and what it needs", followed by culinary tips and recipes.

You can sit down with this book and plan your entire year's planting of fruit, herbs and vegetables. Couldn't be easier.