"Summer garden blues"

We have endured one of the hottest weeks on record in our gardens, but plants have still provided solace.
Sunday, 06 February 2011     

Clerodendrum ugandense, the blue butterfly bush

I hope that when this blog is being read that the ghastly heatwave - the longest of its kind on record here, apparently - will be over. This past week has given us the sort of conditions that would be enough to drive a gardener to give up their hobby and take up something less weather dependent - mah-jong, anyone? I for one cannot stand to be outdoors when the temperature soars above 30C, so with many consecutive days here of close to or over 40C, my only contact with my garden has been to try to keep the water up to it as best I can.

It's hard to find much solace in a wilting garden but some flowers provide us with the illusion of coolness even on the most desperate days. These are the summer flowers in hues of blue, and many have bloomed on despite the most ferocious heat this past week. Perhaps it is the evocation of refreshing blue water that these flowers give, but they instantly make me feel a little better when I see them. The effect is most pronounced when the flowers are in a shady border. Blue is a very calm, agreeable colour that associates well with every other hue in the garden; pure blue in flowers is not often found, however, with many so-called blue blooms being closer to mauve or purple. Along with white flowers, blue flowers remain visible at dusk for longer than those of any other hue: a bonus for us when the evening is the only time that it is bearable out of doors after a scorching day.

The bobbing heads of Agapanthus have all but faded, but they provided an impressive swathe of pastel blue all along our driveway and in garden beds for six weeks or more in midsummer. The most intensely blue cultivars I grow are 'Guilfoyle' and 'Electric Blue'. The groundcover Evolvulus pilosus has startlingly blue, rounded flowers on a groundcovering plant and is a trouper for hot, dry positions. Like many blue blooms, it looks particularly striking nearby lime-coloured leaves, such as those of Sedum mexicanum or Lysimachia nummularia 'Aurea'. Another bright splash of true blue comes from the self-seeding annual Browallia americana (ht 30-60cm), which has a mass of starry bloom with a white centre in summer and autumn. It is rarely seen for sale: if you are able to obtain even a single seedling from the garden of someone who grows it, you will have it forever. I started with one such lone plant and now have literally hundreds of them coming up each spring. They obligingly fill in any spare spaces in the garden, without swamping surrounding plants.

Blue-flowered shrubs provide the bulk of the cooling hues in my garden. The mophead and lacecap Hydrangea macrophylla provide a mass of bloom earlier in summer, and there are still a few fresh heads forming even now. The so-called evergreen hydrangea (Dichroa febrifuga, ht 2-3 m) has an amazingly long flowering period and its large frizzy flower heads of denim blue have been a welcome sight on these hot days. It seems a very tough shrub and will grow well in sun or shade. Nearby I have the blue butterfly bush, Clerodendrum ugandense (ht 2-3 m, pictured at the start of the blog), in flower at the moment, with its pretty whiskered blooms of two shades of blue. It is a heat-loving shrub from East Africa that thrives in our climate and will grow in sun or part shade. Tibouchina multiflora (ht 1.5-2 m) is another blue-flowered shrub looking good at the moment: it has sprays of bright blue rounded flowers, similar to the purple-bloomed Tibouchina but on a smaller scale. Small shrubby Ceratostigma species (ht 50 cm - 1 m) - sometimes known as Chinese plumbago - are also starting to flower, with their dainty flowers of amazing blue. They have to be kept an eye on, though, for their tendency to self-seed.

Another semi-tropical shrub is Brillantaisia subulurgica (ht 3 m), which I have mentioned previously in a blog as often being thought of as being some type of giant Salvia - however, it belongs to the Acanthaceae family of plants, which contains so many robust shrubs suitable for our Sydney climate. This one blooms from late spring until autumn, with a procession of tall spikes of hooded blue-purple flowers. Salvia do offer some of the bluest flowers in the plant words and at the moment I am enjoying brilliant blue Salvia guaranitica Large Form (ht 1.3 m), and powder blue Salvia 'African Sky' (ht 1-2 m), both being among my favourite salvias. In my experience, the so-called 'Large Form' of Salvia guarantica is not an invasive plant like the original species - which developed enormous tubers and took over whole garden beds - and its vibrant colour goes well with any other hue in the garden: though I particularly like it with yellow and orange, or with silver and pinks.

I am sure that we will soon forget the unpleasantness of the heatwave and will be back in our gardens again once the temperature cools. But meanwhile, cool blue flowers provide some solace ...

 Reader Comments

1/6  Norm - 2046 (Zone:10 - Warm Temperate) Monday, 07 February 2011

Great blog. Also, one of the best true blue flowering shrubs is the Ceonothus. its a pity it only flowers in spring!!!

It is a lovely shrub - I have seen some specimens of it doing well in Sydney but it does probably prefer a cooler climate than ours. Deirdre

2/6  Rae - 2119 (Zone:10 - Warm Temperate) Monday, 07 February 2011

Hi Deidre - thank goodness the cool change has come! Thanks for all the blue theme ideas. My duranta repens is flowering mauve at the moment along with plumbago and a small amount of wisteria in flower. I also have some small margeurite daisies and very blue hydrangea Macrophylla 'Endless summer'.

Thanks, Rae. The little blue Felicia daisy has pretty blue flowers and that hydrangea sounds a good one! Deirdre

3/6  Margaret - 3777 (Zone:10 - Mediteranean) Monday, 07 February 2011

Thanks Diedre, I always enjoy your blog. We have had an exceptionally cool and wet summer here in Melbourne - only 2 days over 40. It was about 16 yesterday! Chinese plumbago was my toughest bloomer in the heat of February 2009 - never watered, but still flowering and surviving.

Thanks, Margaret. The weather has been extraordinary everywhere this year. The Chinese plumabgo is definitely a good tough plant. Deirdre

4/6  Peta - 2758 (Zone:9 - Cool Temperate) Monday, 07 February 2011

I've made a fairly big blue garden in memory of my little Italian Greyhound. Great therapy for me.Ill put in blues for the whole year. The native Scaevola has been tough in the heat and a beautiful blue. Annuals have helped give colour and I look forward to my bulb order - crocus,Iris reticulata!

I was given a Scaevola at Christmastime and it has flowered all through that awful heat so thanks for reminding me of that one! You are lucky to be able to grow those cooler climate bulbs for spring - I will have to be content with bluebells and starflowers for my spring blues!Deirdre

5/6  Margaret - 2122 (Zone:10 - Warm Temperate) Monday, 07 February 2011

thank goodness for the cool change! Love blue flowers in the garden, but at the moment only Browallia americana flowering. My Dichroa had mainly pink flowers, but at the top, three blue. Would love to buy Brillantaisia and a Clerodendrum - have cleared a couple of plants and now have room for them.

6/6  Jill - 3941 (Zone:10 - Mediteranean) Saturday, 12 February 2011

Thank you for publishing the blue flowers in the extreme heat you have suffered. We are also enjoying the 'blues' - here it is salvia azurea and the Russian sage - petrovskiana? and of course the feral salva patens, which the birds love regardless. Hope you have some cool weather. Best wishes.

Thanks, Jill. We are enjoying some welcome rain now. Your blue flowers sound lovely - not ones that grow so well in Sydney, alas! Deirdre

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