A friend with a garden maintenance business rang recently to discuss buxus blight. This is a fungal ailment which attacks box plants. It was first found in New Zealand in 1998 and has been a problem in Auckland for some time. Buxus being an infinitely useful but deathly dull plant, we made contingency plans early, in case the fungus ever struck our modest metreage.

I have just paced out our box hedging and we only have around 25 metres of it plus one established topiary, so it does not exactly feature large in our garden. From the start, we figured that buxus did not warrant spraying to keep it healthy so we have always been ready to rip the plants out and burn them if necessary. We have alternatives out the back, so to speak, so taking out the buxus hedges was only ever going to be a minor inconvenience.

But Garden Maintenance Friend was horrified when I suggested he advise his clients to rip out their box hedging and replace it with something which does not get blight. Most of them have a great deal more than 25 metres and do not have the advantage of alternative plants for instant replacement. He suggested he would far rather I write a column on the topic and that his clients may take the advice better from the newspaper than from him.

The bottom line is that if you have buxus blight (or fungus cylindrocladium) in your garden, you have a problem and if you don’t do something about it, it will spread rapidly. Doing something about it is easier said than done in this day and age when a severely restricted range of chemicals is available to the home gardener. There are no heavy duty fungicides that can be bought over the counter unless you have a spray certificate. Which means that if you want to go the spraying way, you will have to employ a certificated operator. But we are also strongly of the view that gardeners should take more responsibility for their actions and that spraying a utility plant like buxus is simply unjustifiable. It is time we asked many more questions about the spraying practices which have become the norm in this country over the last four decades.

There appear to be three main ailments that hit buxus and if you have plants which are looking poorly, it may not be the dreaded blight. A dead patch in one area just above the ground is most likely to be animal urine – territory marking by dogs or a tom cat. I am not at all sure how you stop the offending animals, but it is no reason to rip out your plant.

Zephyr the dog treats the buxus hedge with some contempt. (Photograph: Abbie Jury)

There is a pinky mildew (called volutella buxi) which has been around a long time. It disfigures the plant but is not usually fatal. It takes hold in wounds so if you clip your hedge hard, it is likely to be more apparent soon after. Healthy plants can outgrow volutella so a bit of effort may retain your hedges.

The dreaded buxus blight has cut a swathe through the United Kingdom’s millions of box plants since the mid nineties, through Auckland’s since the late nineties and is likely to be the cause of dying buxus reported in Taranaki. It is the problematic one. It starts as dirty dark spots on the leaves and black streaks on the stems and spreads rapidly, causing the plant to lose all its leaves and usually die. It often shows up initially as dead patches along the top whereas the sides will appear to be fine. Research has shown it takes only five hours to start multiplying so if you ignore it, it may well surprise you by how fast it takes hold. It is impervious to cold (most fungi prefer warm, moist conditions) which is why it has taken hold in the UK. This means it does not slow down in winter. It is only very dry conditions which it dislikes and as most of Taranaki is humid most of the year, we have splendid conditions for it. Being a fungus, it increases from spores so it can be airborne which means that if you live in town and your neighbours have it, sure as eggs you will get it too. And as the spores survive in decomposing leaves for a year, it is nigh on impossible to eradicate. You may burn the offending plant (avoid the compost heap for this one) but you are not going to be able to pick up every dead leaf. You also need to disinfect all tools which have been in contact with it – household bleach apparently works.

Prevention is better than a cure. There is a tendency for owners of buxus hedges to cut them hard twice a year and, ever obliging as they are, they sprout afresh. But over a period of years, the hedges get increasingly dense as well as being filled with dead leaves which sit in the middle. I was a bit surprised when I overheard a buxus expert holding forth recently on the need to thin out buxus hedging and topiary shapes and to vacuum out the accumulation of dead leaves. Really, I thought. But she is right. And if you want to reduce the chances of getting a terminal case of buxus blight, you may like to head out now with the nippers, the clippers, the secateurs and the blower vac. Some good hygiene, housekeeping and air movement will reduce the chance of blight getting hold. But it is not a cure and personally I am not so enamoured of buxus that I think it justifies that sort of effort.

I am told that two sprays of copper a week apart with a wetting agent added can help, even cure it, so if you have affected plants you may like to try this approach. Mark is surprised that copper, which is anti bacterial and not a fungicide, could be so effective. And the information from the UK where buxus blight has been extensively researched, certainly does not bear out the copper theory. If copper is working here, it is unlikely that we have found a wonderfully simple solution and are therefore cleverer than our overseas colleagues. It is far more likely that the cause is not in fact fungus cylindrocladium. That said, it is worth a try if the alternative is the drastic step of total replacement.

If you have to rip out your buxus, burn it all. And don’t replace with more buxus. You will need to be looking to some of the alternatives that clip – coprosma, camellia, teucrium, corokia or the like. There are no species of buxus that are resistant to cylindrocladium. The fungus does not reside in the soil so treating the soil or replacing it is a waste of effort. It is the plants that are the host.

Sadly, for owners of buxus hedging, there does not appear to be any good news as far as fungus cylindrocladium goes. The only good news overall is that it may curtail the slavish use of buxus as hedging and edging in every second garden.

I recall some years ago having two conversations in a short space of time where people regaled me with tales of coming to buy plants from Mark in the early days of our nursery. Both shared a similar experience. “It was at least 20 minutes,” said one, “before I was confident that I was going to be allowed to buy a plant.” Readers who know and like my Mark will be smiling at this point, recognising the likely truth in these accounts. He, himself, sees humour in the retelling but retorts slightly defensively that of course he was right. There is no point in selling elite and difficult plants to people who will fail with them. It will only backfire all around. It is a philosophy of retailing to which I am forward to returning.

I have one plant here which I insist on an interview before allowing anybody to buy it. It is very slow to grow, scarce as hens’ teeth and likely not available anywhere else, expensive and I don’t want to waste precious plants on unsuitable people. It is a tiny vireya species, saxafragoides. After about five years, you get a little bun of a plant measuring around 7cm across. It is reported to be the most cold hardy of the vireyas (it is in fact the mother of hybrids Jiminy Cricket, Saxon Glow and Saxon Blush) and also the most tolerant of damp conditions. But not only is it very slow to grow, I have also not had great success with it in the garden, despite, I thought, giving it optimum conditions.

A decade or more ago, vireya rhododendrons were all the rage. A fashion plant of the day, it was predicted by some that these sub tropical rhododendrons would supplant the hardier, traditional rhododendrons in areas where they could be grown. Mark even heard one self proclaimed expert claim that vireyas were as hardy as maddenii rhododendrons. They are not. Nor are they as easy to grow well in the garden as many of us hoped. In fact as we go through the process of winding down the nursery, vireyas are the crop that we most often agree we will not be sorry to farewell out of commercial production.

Don’t get me wrong. We are vireya aficionados. They are a wonderful family of plants and we would not be without them. Our association with vireyas goes back to the mid 1950s when Mark’s father collected a form of R.macgregoriae in New Guinea and brought it back here to Tikorangi. In those days border control was considerably more lax. That plant still survives in the garden here and mass flowers every year without fail. It was the start of a father and son plant breeding dynasty which has seen more than twenty five different hybrids named and released on the market over the years and is still continuing.

Vireyas are deceptive because they are very easy to put roots on, as we say. In other words, even home gardeners with no special facilities can have success with cuttings (although the aforementioned saxafragoides may be a challenge). They grow quickly (except for saxafragoides). Because they come from the equatorial areas where day length is pretty standard all year round and seasons are not defined by temperature change, they don’t have the set growing season that other plants show. So if plants are relatively warm, they will put on growth spurts most of the year. They also have the endearing habit of flowering randomly and often over many months. Indeed some are almost never without a flower and if you have enough plants in your garden, you can pretty well guarantee something in flower for twelve months of the year.

The down side is that they have pathetically little root systems and even well established plants can up and die on you when your back is turned. Being sub tropical, they are frost tender (any touch of frost will burn them and more than about three or four degrees of frost will kill them). With such small root systems, they are also extremely vulnerable to wet conditions and many soil fungi can take them out.

Readers who have lost vireya plants will be heartened to hear that it may not be their gardening skills at fault. In nursery production, we have always had a better cuttings take on vireyas than any other production line. But from then on, it is mostly an up hill battle. We always have a much higher death rate in the finished crop of vireyas than any other plant line we have grown over the past twenty five years. It can be very disheartening going through and pulling out the deaths. And we work harder to get bushy, well shaped plants than any other plant line. I figured this year that they are easily the most under priced crop we grow and were we staying in production, I would want a much higher wholesale price to justify the effort.

Compounding all this is that, of course, it is the highly desirable varieties which are the hardest to keep alive. Many if not most of the fascinating species are difficult. The named hybrids with big, luscious, scented trumpets are also more vulnerable whereas the utility toughies are more reliable but less coveted. Ain’t that always the way?

If you want to try taking vireya cuttings, select a stem of new growth which has hardened sufficiently to be firm. Make a clean cut across the base and then take a sliver off the outer green stem layer for about 2.5 centimetres from the base on two sides. It is very important to take it on both sides because this is where the roots are formed on vireyas. Reduce the cutting to two leaves only. If you have rooting hormone, it will increase success but you can manage without it. Stick the cutting in potting mix and place it somewhere warm but not in direct sun. You can cover it with a loose, clear plastic bag or a cut-off plastic PET bottle if you want to keep it warmer. Keep the potting mix damp but not saturated. You may see roots forming in about six weeks or so but they are best left undisturbed for three or four months.

Well grown vireyas are a delight and a great addition to the garden. But as a plant family, they are just not quite as easy and bullet proof as some of us hoped back in their hey day. They are great container plants and excellent for people who like to make a fuss of their plants but are certainly not an easy care option for the garden in the way that their hardier cousins are.

Autumn is a time to look at trees even if we can’t compete with the seemingly endless blazing colour of countries like Canada. A friend from Te Popo Garden, inland from Stratford, commented in passing that it didn’t get much better than last weekend with the sun streaming through the autumn leaves on the trees. We have had remarkably little wind recently and a sharp drop in temperatures from the Indian summer straight into winter chill, so it is shaping up to be a splendid display.

It should not be necessary to point out that you only get spectacular autumn colour on deciduous trees which shed all their leaves each year. I thought everybody knew that, just as I thought that everybody knew that our native flora is pretty well all evergreen. Ergo, we do not get autumn colour from our native plants. This did not stop an enquiry a couple of months ago about whether we have places noted for autumn colour in Taranaki and (wait for it) were any of these native trees, for example a grove of kauris. I could accept that the enquirer did not know that kauris do not occur naturally this far south, but I did wonder what had happened to general knowledge that nobody in the chain of this particular organisation had picked up on the fact that our native plants do not colour up in the way that some deciduous plants do. There are subtle seasonal colour changes at best in our native flora but for the golden leaves or the fiery reds and oranges of autumn, you must look to imported deciduous trees and shrubs such as maples, poplars, parrotias, gleditsias and cornus.

It is the sharp drop in temperatures which triggers the plant to stop feeding its leaves and let them die and drop. Inland areas are colder at night so they get significantly more impressive autumn colour than those of us closer to the coast who just gradually drift from one season into another. And coastal points northwards (Auckland and Northland) get even less autumn colour. Travellers in the tropics will know that you don’t get autumn colour at all in hot climates.

That said, Prunus Awanui has been a vision of golden leaf this past week. The wisterias and rugosa roses always surprise me with their autumn colour and the grape vine which covers the large verandah out from my office is a delight every year. It looks as if the sun is shining on even the greyest of autumn days.

But while admiring the trees in autumn, gardeners may also like to do some critical analysis on the merits of the different trees in their garden. We have been talking recently about the failure to differentiate between short term nurse trees and long term trees.

In our windy country, we need nurse trees. They are a quick and cheap option to grow in order to provide some protection so that longer term, quality trees (which by their very nature tend to be slow growing) can get established. And because nurse trees grow quickly, they can give height and impact in a garden in a surprisingly short space of time. But few nurse trees in our climate age gracefully and there comes a time when decisions need to made about which are worth keeping and which have frankly passed their use-by date. Not all trees are equal and not all trees improve with age.

Many gardeners make one of two mistakes. They either overplant badly and then fail to discriminate a few years down the track as to which are the good long term trees worth looking after, even if it means cutting out the filler trees. Or they plant specimen trees out in exposed areas in solitary confinement.
In using nurse trees, you are learning from nature. When bush regenerates, the nurse plants are the first to get established and to create some cover. In that protected environment, the longer term trees come through and are forced up in search of light. In due course they supersede those nurse plants. Without the protection and microclimate of nurse trees, they can be too exposed, stunted and often multi trunked because they do not need to shoot up in search of light.

Trees are going to become a great deal more important in the immediate future. The talk about carbon footprints, climate change and sustainability is not just a fad which will fade away in a few months. We are in a time of radical change and long term trees will be part of our future and quite possibly part of the survival of our planet. The day may not be far away when we are shamed by our outdoor furniture made from Indonesian hardwoods.

While tiny town sections are not going to accommodate forest giants, neither is an espaliered apple tree going to save the planet (though it might help feed the family and taste better than cool store apples). But gardeners with a bit of space (or non gardeners for that matter) could and should be thinking about planting long term trees and treasuring existing trees which have the potential to outlive most of us. By long term trees, I mean those with a lifespan which will be fifty years at least, maybe a hundred and some have the potential to live many hundreds of years if they are planted in the right position. In New Zealand we have a tendency to think in terms of ten or twenty years and far too few trees are allowed to ever reach maturity.

So by all means plant pretty flowering cherries, albizzias (though I think I have seen those on a banned list somewhere), gleditsias, paulownias and birches. But see these for what they are, which are short term trees and look to using them as cover to get some good trees of potential longevity established. It doesn’t have to be a mighty kauri, rimu or totara though goodness knows, we plant too few of our majestic native trees. There are some magnificent members of the conifer family which are not native – the sciadopitys or Japanese umbrella pine is a gem and the somewhat maligned Norfolk Island pine is a great statement of form on the landscape. Magnolias can live a very long time and are unparalleled for splendour in flower. Liriodendrons give brilliant autumn colour, as do scarlet oaks, ginkgo biloba and even plane trees. All get more impressive with age.

If you are unsure what you are doing, seek out advice and never plant any tree anywhere near power lines. It will come off second best in a tangle with the lines companies. The challenge is to make sure that you plant some good, long term trees in your lifetime. What better legacy to leave?