Sunday, May 30, 2010


For beginning gardeners, the idea of planting roses in the depths of winter sounds a bit crazy, and for many of us older gardeners, the thought of mainly planting them in the flowering season seems like an equally insane idea! 
I can recall when container grown roses first appeared on the market, and the lack of enthusiasm that garden centre staff had for the idea, thinking it a silly fad that would not catch on.  We were wrong of course, and the rose planting season has long ago extended to cover most of the year.
I must be old fashioned but really believe it is better for most deciduous plants to be shifted during their dormant season, while they are at rest and can better cope with the surprise to the system that transplanting imposes on them.  Rose planting is easy at this time of the year, provided a few easy preparatory steps have been taken.
The first step is to decide where the roses are to be planted.    As a rule, they do best in new soil, so if you are planting into an area that has already had roses in it, it pays to remove the soil and replace it.  This is due to an insidious disease called “rose sickness” which, although it does not normally kill roses, makes them grow in such an unhealthy manner as to make them ungardenworthy.  If you are replacing soil in an existing bed you will need about a wheel barrowful of soil for each plant.
If you have the luxury of creating a new bed, make sure it is in full sun.  There are a few (very few) roses that will cope with semi-shade, but most will need the maximum amount of sunshine, to help keep them disease free if for no other reason.  Those that will do better in the slight shade are those whose flowers tend to get burnt in the full sun.
Soil type is important too.  The best soil for roses is undoubtedly a slightly stiff loam.  By that I mean a good garden soil that is not too light, as thin, sandy soils will dry out too much over summer, and the roses will fail to thrive.
If you have anything other than very rich loam, it pays to work in some compost or well-rotted farmyard manure.  Ideally, this should have been done about a month ago, but if you have not had a chance to do it, it is still fine to do it now as long as the manure is not green.  It is a good idea to try and keep the bed at the same level as the surrounding ground as elevating the bed will just make it drain more quickly, giving problems late in the dry summer period.

Sunday, May 23, 2010

Autumn foliage

This is surely one of the interesting times of the year, with a plethora of wonderfully coloured trees and shrubs to look for in the streetscape. I wonder how long this will last however, as the heyday of planting deciduous trees seems to have long gone, and as more and more gardeners plant almost only evergreens, we are going to miss out on such a grand autumn display.

One of the reasons for the diminished use of deciduous trees and shrubs is surely the more diminutive gardens we now have. We simple do not have the space for the same number of large specimens and are more reliant on smaller plants for the garden.

Some plants that will fit easily into most gardens, and can be reliably called upon for a spectacular display are the various members of the Cotinus family. These are the Smoke Bushes and feature some of the most amazingly lurid colours in the autumn palette.

There are three species of these in the wild, but there are only two that are commonly available. The first of these is the European smoke bush, C. coggygria which actually grows from Europe into central China, and is perhaps best known for the large panicles of fuzzy looking plumes in early summer that give the plant its common name, especially as they grey into the autumn.

The leaves are bright green during the bulk of the growing season, but as they autumn approaches they take on the most startling array of colours, from yellow to orange to fiery red. They appear to differ from plant to plant, suggesting the New Zealand forms have been seed raised, as overseas, varieties can be selected for a particular colour.

The exception to this rule is the strongly coloured ‘Royal Purple’ which has deep wine-purple leaves which have a conspicuous waxy surface that appears translucent in sunlight. The flowers are a slightly deeper colour through the growing season, and then turn bright orange and burning red in autumn. This is a great plant for associating with lighter coloured foliage. At slightly more than two metres high it is about two thirds the height of its plainer cousin.

The American species C. obovatus is a taller beast altogether, growing to perhaps five metres. It does not have the same floral display of its European kin, but makes up for that with a stunning foliage display in the autumn, when the leaves turn yellow, orange, red, purple – often all at the same time – to give an very impressive show.

In the very small garden, there is another little treasure that can be relied upon to give a great display in autumn – and it is not even deciduous. The dwarf heavenly bamboo (do not worry it is not actually a bamboo, so it will not go mad in the garden) Nandina domestica ‘Pygmaea’ was planted extensively during the 1970s craze for pebble gardens, and has perhaps not regained its proper place in the garden, but its fresh lime leaves during the summer always look attractive, and in autumn and winter it turns on a very impressive display of purple, orange and (more usually) bright red foliage. The colder the winter, and the poorer your soil, the better this will colour up. In fact, you could even do the old nurseryman’s trick of feeding it a bit of sulphate of potash at this time of the year – it will certainly colour up better then!

Saturday, May 15, 2010

Shining examples

When we select new plants for our garden we go through a sort of checklist.  We will include all sorts of different attributes for consideration as we think about our garden – flower colour, foliage colour, foliage shape, maybe even foliage texture – but we seldom think of how well the foliage reflects light. 
It might sound like a slightly daft thing to be weighing up when choosing plants, but it does have quite a bearing on how we perceive the plant in the garden, especially in winter when light levels are lower.  A plant that has a soft surface, covered with fine hairs for example, will absorb much of the light it receives, giving a soft reflection.  On the other hand, plants with highly glossy leaves will reflect back much of the light, giving them a brighter appearance.
Perhaps the greatest examples of the power of reflection –“shining examples” I call them – among native plants are the many Coprosma species and varieties.
There are over 100 species in the genus, distributed through the Pacific Rim but centred on New Zealand, where about half the species are found.  Many are dwarf shrubs with tiny leaves, but there are also some small trees to be found among the species.
Until recently the best known plant was undoubtedly, C. repens.  This is a soft-wooded shrub that will grow as a prostrate shrub in exposed conditions, but in sheltered and humus-rich sites can grow up to nearly ten metres.  It has dark green, very glossy leaves, earning it the common name of Looking Glass Bush, Mirror Plant, New Zealand Laurel or Shiny Leaf.  I am sure you get the idea!
What has made it very popular as a garden plant is the wide range of coloured sports it has given rise to, which has meant it has become a very popular garden plant in coastal areas in particular.  Unfortunately, its reliable performance in windy and exposed sites is matched by its tenacity at setting seed, and it has escaped from the garden in parts of Australia where it is now classed a weed. Perhaps that just our revenge for the magpie!
Over the past few years a lot of coloured hybrid coprosmas have been released onto the market, with so many options for the gardener that it is a little confusing.  A trip to the garden centre and a stroll down the “dwarf natives” section will certainly be a colourful experience, especially at this time of the year when so many of the cultivars colour up.
‘Lemon and Lime’ is a small leaved form with very interesting variegation of green and yellow.  As the cooler weather appears, the yellow deepens and hints of orange appear.  This is a tidy growing form, and like almost all of these hybrids, it is very disease resistant. It is the child of an even better variety – one that has become one of the best selling shrubs in New Zealand, the unremittingly cheerful ‘Evening Glow.’  This has golden foliage over the summer but as autumn arrives it takes on rich orange and deep red hues.  That is not a bad achievement for an evergreen shrub, and it has made it into one of the most popular natives.

Sunday, May 09, 2010

Autumn glories

The balmy autumn has continued, much to the consternation of many farmers and gardeners. Warm and sunny days, and near frost-free conditions might be nice of you are on holiday or looking to relax, but it is starting to be a nightmare again for those who need some rain. The summer was moist enough to keep most east coast farmers happy, but there will be a few out there scratching their heads, wondering what happened to the autumn rainfalls. The same applies to gardeners – a weekend in the garden has shown me it is much drier than I had thought, and as I finished each section of the garden, I dragged a hose behind me to try and get some moisture into the soil.

As always, we will be looking at the bright side, thinking that a relatively calm autumn might be good for autumn colour, but the warm conditions will militate against that too, as warmer temperature actually lead to less colour. Has anyone ever travelled to Auckland to see the autumn display?

I caught the start of the autumn colour season while in Dunedin recently. High on hills at the northern end of town, the Dunedin Botanic Garden is a treasure for garden lovers, filled with all sorts of exotic treasures, set in well-tended gardens that I wandered through on a number of occasions. Near the end of our stay, I took my camera with me for a concerted walk through as many of the different gardens as I could.

I was not expecting the Rhododendron garden to be as interesting as it was, bearing in mind it was so late in the season. There was very little in flower, although there were some R. yakushimanum varieties flowering out of season, but the effects of the coloured foliage, a mix of maples and azaleas mainly, was outstanding.

These plants are both relatively easy to grow, and can usually be called on to give a good year-round display.

The deciduous azaleas are probably best known for their wonderful display of flowers in late spring – October and November – when their delicious red, yellow and orange displays are so eye-catching. They flower on bare wood (usually see later) so the flowers are displayed very prominently, and being late flowering they are also safe from frost.

These very hardy plants are probably not as popular as they once were, but they give an unrivalled display, and they are very garden friendly. They are hardy, pest free, easy to look after, and very long lived – what more could you look for in a shrub?

Botanically, these plants are Rhododendrons, and as such need a relatively acid soil, preferably also moist. They are shallow rooting, and they do need to be kept moist over the summer, so thin limey soil is not for them.

There are many varieties on the market and it is pointless for me to suggest any particular ones, but the New Zealand raised Ilam hybrids seem as good as any to me. If you are in the Manawatu area in spring, a visit to the Rhododendron gardens at Kimbolton will be enough to make a convert of you.

Sunday, May 02, 2010

Edges and hedges

One of the difficult areas of the garden is the border lands – those awkward areas where the garden finishes and other elements of the environment start.  It can be the line between the garden and the lawn that is the problem, or perhaps the delineation between physical boundaries, such as neighbouring properties or a driveway or roadway.
In some situations an informal edging between the two environments works well.  In a woodland garden, for example, it looks great of the understory of planting gradually give way to a soft bark pathway, or even on the edge of quite hard planting, the effect can be softened by having sprawling plants that help blur the edge.  We have a wooden wall retaining an elevated lawn area, and have planted some trailing plants to help soften the boundaries.  Sometimes, though, you actually want a clear delineation between two different areas, and that is when formal hedging some into it own.
 I was recently in the extensive gardens of Larnach Castle, high on the Otago Peninsular, overlooking Otago Harbour and Port Chalmers – I was supposed to be visiting the castle itself, but the gardens held my attention for much longer than the building.  Even though it was late autumn and the garden was long past its summer splendour, there was still plenty of interest.
The formal gardens in front of the house have been cleverly designed to reflect and augment the severe Scottish Baronial architectural style employed in the castle, with very formal edgings in somewhat informally shaped beds.  The beds are extensively edged in box, with corner highlights of totara topiary.
There are a number of varieties if box hedging, all forms of Buxus.  The most commonly grown is English box, a relatively slow growing form.  This sounds like a less desirable trait, but you have basic conflict between the desire to have your edging looking as mature as possible, as quickly as possible, and the need to keep the growth under control once the plant has reached its desired height and width.
I would plump for English box, perhaps buying the more expensive advanced grade plants, which can be found easily enough in the trade. They will be four years old and perhaps 40 cm high.  Pop some fertiliser in the soil once the plants are well established, and continue to fertilise about twice a year.  It is essential to water the fertiliser in well as it will burn the foliage is just left sprinkled on the surface.