Monday, January 29, 2007

Sweet pea bushes

As summer moves on, and the raspberries finally stop fruiting it is time to clean out the bed they grow in, to remove the old spent canes and to tie up the new canes. Most raspberries, of course, fruit on wood they made the previous year, so it is important to remember to keep the supply of new wood replenished, and to remove the old wood.
I do try to keep an eye on the canes during the earlier part of the growing season as the job of training the new stems is a lot easier while they are still pliable.
While I was down in the raspberry patch, I had a wander along the back of the shrubbery that I wrote of last week. It is about three meters wide, with a number of large natives, and a few deciduous shrubs, including a couple of the more unusual Hydrangea species and a giant mock-orange, Philadelphus. I have been cogitating about how I am going to change this garden, more or less deciding on replacing the under storey with some native ferns, so I was taking a mental stock take of the existing planting when I came across a Polygala growing against the fence. I was a bit puzzled at first as I did not recall planting it, then I remembered that it was already here when we arrived, planted by the previous owners. I have not noticed it for a while, as it is so shaded that it does not flower very well now.
I had a chuckle because a work mate, Paul, was talking about Polygalas the other day, saying how valuable they were as a no-fuss shrub – and he is absolutely right, they are very useful shrubs. I told him I did not have any in my garden.
There are many, many species of Polygala, found scattered over most of the earth except our little corner of the world. The only one commonly grown in gardens is the South African species, P. myrtifolia. This has bright green leaves, and has tidy growth habits meaning it has become deservedly popular in New Zealand gardens. The usual form you will find is “Grandiflora”, which has larger flowers that the type species.
These flowers are reddish-purple and pea shaped, although the plant is not actually a legume. The flowers are held in clusters at the end of the branches, with a pronounced flush in the late winter/early spring, but also intermittently throughout the year.
There are other forms around too, with “Dazzler” being perhaps the best known. It has more compact growth and slightly more glaucous leaves. There is a smaller form again, “Liddle Dwarf,” grown by Liddle Wonder nurseries in Waikanae. It is said to only grow to 80 cm so it should be a great addition to the very small flowering shrubs available, especially with its extended flowering season.
There is a bit of a drawback to these plants – the colour of the flowers. The purple shade is strident and it is hard to find flowers that will tone in with them. Perhaps the best bet is plants that flower in a similar colour range, or perhaps in very light shades.
Plants do not get as popular as these have without a reason, and the main reason is the ease with which these shrubs grow. They will flourish in any good soil in full sun, and will even do well in poor soils, provided they are well-drained.
They benefit from as light pruning when planted and an annual trimming will keep them looking nicely shaped.
Most of you will have probably grown one or another of these, but few will realise that some forms of this species have become a pest in the north, in yet another example of a foreign plant succeeding altogether too well in its new environment. It seems that the problem stems from seedlings establishing themselves sin coastal areas of western Auckland. The forms that most nurseries offer are sterile and, as such, will not cause a problem out in the wild.
This plant is often known as the sweet pea shrub – Paul calls it that – but to my mind that name belongs to another shrub Podalyria calyptara. This is another South African shrub but this one has altogether different growth habits. To start with, it has the most amazing silky grey foliage. The leaves themselves are greyish green but they are covered with tiny white hairs, giving a silvery sheen.
The flowers are equally surprising – pale pinkish mauve flowers about the size of sweet peas, very nicely scented and carried with abundance in the spring and summer. These are very useful cut flowers, lasting for weeks if properly cared for. They probably need slightly warmer conditions than the Polygala varieties, and I suspect that they cannot cope with such strong frosts.
This is also a lot easier to mix in the garden as the subtle shades can be more easily accommodated. It grows to about two metres when happy.
Another Podalyria, the satin bush P. sericea, is also available in New Zealand. This also has silver leaves but is a lot smaller than the sweet pea bush, only reaching about 80 cm. the flowers are correspondingly smaller. The flowers are lilac rose and carried in large numbers in spring. They are followed by silvery seedpods.
And yes, they have escaped from the garden and are on watch lists in the north, so plant with caution, especially in coastal areas.
Another plant is sometimes called the sweet pea bush – the bright blue Psoralea pinnata, more commonly called blue broom. This has needle-like foliage and mainly flowers in spring. Commonly found in coastal areas, it is not so usually found inland as it will only cope with moderate frosts.
And, as I am sure you will have guessed, it has become a weed, this time on Great Barrier Island! Not so sweet after all.

Monday, January 22, 2007

That big bad bed in my backyard

Cosmos in flower among the Pervoskia
We have been in our “new” garden for nearly ten years now. In some ways it is barely recognizable from the property we bought. Over the years, we have added many garden beds and extended others –some of the changes have worked well while others have been less successful.
I think that the biggest disappointment has been the large island bed I dug in the rear of our section. This part of the garden has a sleep out and a pool, and it is an area we spend a lot of time in summer. When we arrived there was a tiny strip alongside the perimeter fence so I greatly widened that (from about 30 cm to over three metres) and completely barked the whole area. There were a few native trees in the area - a lemonwood, a golden akeake and a silver matipo – but there was adequate light for most plants to thrive.
That has changed over the years. The natives are now tall and cast a deep shade over the bed and to I need to shift many of the perennials I planted when I first made the bed.
One idea in particular had been a bit of a flop.
I wanted a summery feel to the edge of the border so I planted a row of day lilies, Hemerocallis varieties. I bought ten different varieties from one of New Zealand’s top nurseries, but the garden was, even at the time of planting, marginal for such sun lovers, and as the shade has increased, they have done worse and worse each year. It is time for me to shift them to a sunnier place.
I made the large island bed to give us somewhere to grow the sun-loving perennials and bulbs we both love so much. I took all the turn of a large area then put trailer load after trailer load of chicken manure and compost onto the soil before digging it all in. At the time, I made the bed I remember thinking that the soil felt dry but I thought the addition of all the humus would do the trick and I would have great soil. We garden in thin, well-drained soil, and it usually gobbles up humus, but does give wonderful soils if treated properly.
The new bed soon proved to be a sticky mess. It seems most likely that the spoil from the pool was spread into this area, and the soil we have worked on have proven to be far from the free-draining humus rich soil I had envisioned. Bearded irises, an important flower for us, have proven to be hopeless in this bed – they sulk and they do not flower. We even have a devil of a job getting Montbretias to flower!
Most of us are aware of the weedy Montbretias that often line stream-sides and damp places in New Zealand gardens, but few know or grow some of the vastly better Crocosmia varieties. These have flowers that are three of four times the size of the weedy species and have a fabulous colour range from soft apricot, through the usual oranges, to almost red. I grow ‘Star of the East’, which has large flowers of soft apricot-yellow – only I hardly ever see any flowers. It has grown well enough and has formed a respectable clump, but just does not flower very well at all.
Other plants have flourished in the soil. The Hellebores that are a feature of one end of the bed do fine and provide lovely flowers in late winter, and some Dahlias have done very well too. One has even seeded, the white cactus-flowered form, giving rise to a lovely pink decorative.
Another surprising success has been the sun-loving Perovskia atriplicifolia ‘Blue Spire – and no, it does not seem to have a common name. This is a Himalayan shrub with the amazing combination of grey leaves, white stems and lavender-blue flowers. The form usually grown in New Zealand, “Blue Spire’ is an award-winning variety raised in Britain. The flowers are larger and bluer than the type species. It is not a tidy grower – it tends to sprawl and flip about a bit so make sure it has a little bit of room. The books all say it needs great drainage to succeed, so quite why it is doing so well in this garden I do not know.
The plants that have done well tend to be those derived from meadow-growing species. A couple of Siberican irises have flourished, as have some self-seeded Delphiniums. At the moment the highlight of the garden is the bergamot, Monarda ‘Raspberry Wine.’
The bergamots have hooded tubular flowers atop strong stems – this variety grows about 1.2 metres high- and this bright raspberry-wine coloured form is lovely. There are other varieties in the purple-red-pink range.
The other plants that I am sure will flourish in this bed are the “queens of the summer border”, the Penstemons. These are brilliant value as they flower for months on end and are very hardy. The colour range is great too, and it would be possible to find Penstemon varieties to suit most garden situations.
We have a number of varieties in different beds but I have decided that I will plant up a number of these into this problem bed. I have already purchased a couple of forms that are happily bedded in. ‘Purple Passion’ has tiers of deep grape purple flowers that fit in perfectly with the other colours in this range in the bed, as does ‘Sour Grapes.’ I think I will plant the relatively new ‘Alice Hindley’ around the Perovskia, as her large pale bluish-lilac flowers will combine beautifully with ‘Blue Spires’.
It is surely one of the delights of gardening that gardens change with time and as they change, they allow different spaces for new plants. Meanwhile, I am looking for another new bed to plant those sun-lovers.

Monday, January 15, 2007

The lily of the Nile

Over the past year one of the noble institutions of the great New Zealand horticultural summer has come under attack, a plant that, although not a native, is almost as much an iconic plant of our summer as the pohutukawa. I am referring, of course, to the bluest of blue summer flowers, the ubiquitous agapanthus.
Last year BioSecurity New Zealand announced that they wanted to add agapanthus to the list of plants on the National Pest Plant Accord, saying that the free-seeding habits of some of the larger forms of this popular garden plant poses a threat to the environment, especially in more northern areas. It seems to have been fired up by a group at the Auckland Regional Council who were saying that up to 287,000ha of their region could potentially be infested with agapanthus.
Such claims were fought vigorously by the nursery industry and agapanthus is now registered as being of concern only in the Auckland area, and even then only for research purposes – there are no restrictions on the sale and distribution of agapanthus plants.
That hasn’t sopped a lot of people from forming the view that the plants are banned and sales have plummeted. One of New Zealand’s largest propagation nurseries reports that their s sales have dropped from 30,000 to 5,000 – and they are not happy.
It seems the very things that gardeners love about agapanthus make it a nuisance in the environment. The larger forms especially, have strong fleshy roots that will let the plant grab hold of any ground they find themselves in - the drier the better – and will soon establish themselves, even under evergreen trees or out in the hottest sun on a Napier beachside.
They can cope with the strongest north-easterlies straight off the sea, the harshest southerly whipping off Cook Strait, or the driest, hottest north-westerly. They will even bounce back from being walked over or driven over. They will find spots in nooks and crannies of banks and cliffs, and will reliably flower each summer, bright blue flowers shimmering over pest-free leaves.
They will not want cosseting. You will not have to water these plants each second day, and you will not have to get the organic insect spray out either- they seem immune to attack from any creepy crawlies, and their dark green leaves always seem to be nice-looking.
These are all good things for the gardener wanting a reliable plant that will thrive in the poorest of conditions, but they are also why agapanthus can be a problem in areas where they are not wanted. Thos beautiful blue (and sometimes white) flower heads are followed by attractive seed heads, and then by light seeds that readily disperse in the wind.
These seeds germinate readily. I recall they we grew some in the nursery, saving some seed from a plant down the road. I think every one of them came up. Similarly, I have some new seedlings in a garden along the side of our driveway, a garden made of large bark sitting atop compacted fill – about the worst kind of growing conditions you could imagine. It is narrow and difficult to water, so anything that can grow in it is allowed to, including a cluster of seedlings from my neighbour’s agapanthus plants, which sent their flowers sunwards over our drive, and drop their seeds into the bark.
The resulting seedlings show a great range of colour, from very pale blue through to much deeper shades of purple.
It is easy enough to remove unwanted agapanthus seedlings if you find them when they are young, but once they are established their strong root system makes them very difficult to eradicate. Many weed killers do not work either. You can spray Roundup over the foliage of these persistent growers and they will lap it up and keep on their merry way - useful for weeding between agapanthus and a problem if they are growing in an unwanted area.
I think agapanthus are very useful plants, and do not think they need banning from our gardens. The usual reason given for banning them is that they will invade the bush. It is true that they will grow in shady areas, and very nice the dark green foliage looks too, but they are very reluctant to flower under those conditions – they seem to need light to initiate flowering.
The biggest varieties are a bit of a handful in small gardens, though and I wouldn’t plant them in any garden of mine unless I had a large area I wanted to blank out. They look fabulous in country gardens and along the beachfront where they can be allowed to grow naturally.
There is a wonderful range of dwarf varieties though, and these are fabulous for the smaller garden. They do not seem to be quite so tenacious and do not seed with the same vigour so they present less of a threat to the environment too.
Which variety to choose, when there are so many to pick from?‘Peter Pan’ is an older variety but it is still one of the most popular of all the dwarf forms. It is sterile, so sets no seed, and is light blue highlighted with dark blue contrast. This is popular for bulk plantings or edgings.
‘Kinston Blue’ is a very dark blue form – probably the darkest among the dwarf blues – and is a very compact growing plant. It is deciduous.
‘Gayes Lilac’ is a New Zealand-bred form, with flowers that tend toward lilac, although they are not true lilac buy any stretch of the imagination. It is very nice though, especially among similarly lighter-toned flowers.
‘Streamline’ is another very popular sky blue form, while ‘Snowstorm’ and ‘Snowball’ are probably the best of the dwarf white forms.
‘Tinkerbell’ is a variegated sport of ‘Peter Pan,’ with deep green foliage banded white. It is a shy flowerer, but always looks tidy in the garden.

Monday, January 08, 2007

Genetics and Fuchsias

This weekend has been an interesting one, as it usually is when my geneticist son David is home. His level of learning is now far in excess of my own, and his PhD research has touched on areas of New Zealand plant and animal life, so a chance to talk plants is always welcome.

We took advantage of his being home to go for a walk through the forest at Pukaha Mouth Bruce, timing our walk to coincide with the kaka feedings. I guess the purists will be a bit upset at the concept of feeding these wild parrots but to amateur naturalists is a great chance to see native parrots up close - and by up close, I mean up very close. As the kakas descend from the surrounding forests to take up their station in the trees they take little notice of the humans gathered to watch, roosting a metre or less from the spectators’ heads. It is an amazing experience to be able to stand that close to a wild bird, and for a photographer it is a dream come true.
One of the things David has been explaining to me is the latest scientific thought on the influence of Gondwanaland on our plants. Gondwanaland is the name scientists have given the giant supercontinent that held all the Southern Hemisphere lands including the land we now call New Zealand. We parted company with Gondwanaland about 80 million years ago.
The theory I was taught was that many of our ancestral plants came with us at that time, and evolved in the interim. It now seems that this is very unlikely. Much of what is now New Zealand was submerged during the Oligocene, about 30 million years ago, and most of our ancient plants seem to have arrived in the period following that. Many of them arrived from Australia, and we have many plants in common with our western neighbour, including tree ferns, manuka and southern beech trees.
But we also have a lot in common with South America, where relatives of many of our plants and trees are also to be found, along with a great many of the most popular flowers, trees, shrubs and vegetables for the garden.
Among the plants that first appeared in New Zealand 30 million years ago, as dated from fossil pollen, is the Fuchsia genus, New Zealand being the extreme edge of its range across the Pacific from South and Central America where it is centred.
The New Zealand species have a number of peculiarities that separate them from their pan-Pacific kin. For a start one species, the ground-covering F. procumbens, has yellow flowers (well partly yellow at least) and they face upwards. This is a coastal species and is not reliably hardy but is well worth making an effort to grow as it is very pretty. The light green leaves are charming, and the flowers, although on the small side, are also very pleasant. The main reason for bringing it into the garden though is the wonderful display of berries once the flowering season is over. The berries are relatively large and are bright red.
I grow species this in hanging baskets on the patio where we can see the flowers at eye level and appreciate them more, and where they will be out of the frosts in winter.

Fuchsia procumbens

The other Fuchsia that New Zealanders should be familiar with is the kotukutuku, the tree Fuchsia that is such a feature of the forest margins. This is a semi-deciduous small tree which bears a large number of small flowers, which again are followed by attractive deeply coloured berries. The berries are called ‘konini’ by Maori and are said to be very useful for jam making – something I have no experience at. Old Maori friends tell me that kereru, wood pigeons, taste lovely when they have been eating konini berries, but again I cannot comment – I’ve never eaten illegal Tegel.
The garden fuchsias we grow are not derived from New Zealand species, although there would be potential for some interesting hybrids if they could be persuaded to produce viable seed.
Our garden plants, with their wide range of flower colours, forms and growth habits, are descendants of early introductions of some of the nearly 100 species to be found in South and Central America. They were extensively hybridized during the first half of the nineteenth century and reached their peak of popularity in Europe in the second half of that century, when they were among the plants cultivated extensively under glass.
In New Zealand, we can grow our fuschias outside, even in frost prone areas such as the Wairarapa. I grow some in pots on the patio, others on a south-facing wall of the house, and still others along an east-facing wall of the glasshouse. These plants get cut back by the winter frosts but I just prune out the ugly dead pieces in the spring and they soon shoot away again. Those in more sheltered areas would hardly even need to do that.

I like mine to grow in a natural fashion, but these plants are very easy to train. If you are looking for a stylish standard just keep one strong central lead growing, removing any side growths as they appear. Weeping varieties can easily be trained to grow in a basket by applying the opposite technique – just remove any leaders, encouraging side growth. This is, of course, easier on the varieties that have natural pendant growth – just keep an eye out when you are in your local garden centre.
These are no-fuss plants, but it does pay to keep an eye for thrips, which can attack the undersides of hanging baskets in particular. Just make sure you water the bottom of the leaves occasionally and they will be fine.
And just think. You’re growing plants that have been in New Zealand for 30 million years!