1) If you have a plant with silver leaves, it has nasty sucking insects called thrips. You can’t turn silver leaves to green again and the new foliage will get affected unless you do something to alter conditions. You can spray with an insecticide, though we prefer to advise alternatives. Open up around the plant to increase air movement (thrips don’t like drafts) and feed and mulch the plant to encourage increased vigour. If it keeps getting infected, take it out and replace it with a healthier option. There are rhododendrons which are better suited to warmer climates and are more resistant to silver leaves.
2) If you have a plant which has not set flower buds, the most common cause is too much shade. Because they set flower buds on their new growth (which is coming now), open up and let more light in as soon as you can. The other cause may be incorrect pruning.
3) Rhododendrons are surface rooting – in other words they go outwards not downwards. A healthy plant has a big mass of fine, fibrous roots which resembles old fashioned carpet underfelt. Mulching is good practice to keep these roots cool and nourished. Never plant them in wet spots where water can pond. They will die very quickly.
4) Deadheading is to stop the plant putting all its energy into setting seed. You don’t actually have to deadhead unless the plant is a seed setter, though it does make them look better.
5) Feed now as the plant goes into growth, if you feel it needs it. Rhododendrons prefer soils on the acid side (which our volcanic soils are here).
6) Moving plants around your garden needs to take place in autumn and winter, not now. Hard pruning of rhodos takes place in late winter or very early spring, not now.
Category Archives: Abbie’s column
Sculpture in the garden
The large chicken netting peacocks in the meadow at Hilliers were both whimsical and charming
Would we consider having an exhibition in our garden during Rhododendron Festival, the sculptor asked. It is pretty last minute but we replied in the affirmative, though rather regretting the missed opportunities in the official programme which had long since been printed.
We have tended to be a bit iffy and sniffy about sculpture in gardens and it wasn’t until we saw it at Hilliers and at Wisley in England that we found a perspective we could live with.
The key issue is quite simple. In our eyes, gardens are about plants and they should be the stars. Even garden design is primarily a vehicle to carry the plants and to enhance the viewing experience. Drop a sculpture into a garden and in most cases the created object made by a human becomes the dominant feature. The plants and garden become the backdrop. That is fine if sculpture is your interest and you merely want a pleasing outdoor venue to display a collection. As long as the piece is placed well, the garden setting can enhance it considerably. But the reverse is rarely true and takes a great deal more skill.
Gardens are more usually dominated or taken over by the sculptural statement. If you doubt this claim, walk around a garden which has a significant sculptural installation. Do you look at the sculpture or the garden? I bet your bottom dollar that you look at the sculpture first (and longest) and the garden setting second but the detail of the garden slips into the background.
- Sputnik shapes in a bed of vinca at Hilliers
When we visited Hilliers famed gardens and arboretum near Winchester earlier this year, there was a sculpture exhibition in place. And even we, pretty dedicated as we are to the plants and gardening side, looked in the first instance at the sculptures. Don’t get me wrong. We really liked some of them and it was here that we figured that our personal tastes lean more to the organic forms which represent shapes in nature. This was a large exhibition with many artists involved so it lacked the cohesion and vision which are part of a solo display. It was also temporary and that was when we decided that there is a world of difference between permanent installations and short term exhibitions. The latter can add a great deal of interest to the experience of the visitor (which is why we said yes to the sculptor who approached us) without the commitment of permanence.
- Ephemeral whimsy in willow at Wisley
The RHS Wisley gardens just outside London had some charming, large, woven willow creations placed strategically in parts of the garden which were otherwise a little empty, almost barren. There is something about the ephemeral nature of woven willow which ages gently and will in time disappear entirely, making it fit easily to the surroundings. The whimsical nature of these works added appeal. But these were hardly Serious Sculpture or High Art – large woven toadstools and pieces of fruit don’t quite rank up alongside massive Henry Moore pieces.
In the end, garden sculpture is about personal taste and our personal tastes lean more to smaller scale, environmentally sympathetic whimsy which can gently blend in to our garden, rather than dominate. Others prefer much bolder pieces which shout out a statement and where the garden and environment curtsey to the power of the piece.
From what I can see from his list, Rangitikei artist Steuart Welch from Cannock Forge is bringing to us pieces from both ends of the spectrum – big bold statement pieces which require a truck to move and some which represent the whimsical aspect of his nature. We are really looking forward to seeing the effect of placing such strong pieces in our garden and learning first hand how to tread that line between enhancing a vision and dominating it. The works will remain in place throughout our Rhododendron Festival until the second week of November.
Plants to impress in English early summer gardens.
It does appear to us at this stage as if the seasons are early this year. Mind you, winter struck early and with a vengeance so it is only fair that spring should similarly make an early appearance. With that comes a sense of panic. Should Rhododendron Rubicon be flowering in mid September and will we have any rhodos left to flower during Festival? We have enough experience to know that these things tend to even out over time and if the flowering remains early, at least our nuttalliis and maddeniis will see us through. But it has had our thoughts turning to the plants that really impressed us in an early English summer. We may need to draw on these for future festivals.
- Frilly large and pink – we can’t grow herbaceous peonies here
Herbaceous peonies (or paeonia). Big frilly, fluffy, pink herbaceous peonies. They look fantastic, they need staking to stop them falling over and they don’t grow in Taranaki. Apparently they do extremely well in Central Otago and they are happy in a continental climate (dry, cold winters and hot, dry summers – rather the antithesis of here). We just have to admire them when we travel. And they are another short term wonder where they look just fantastic but then have a rather long time “passing over” as we say.
Philadelphus, aka mock orange blossom. These we can and do grow though we don’t feature them as much as we saw in England. There are a wider range on the market there, including larger flowered forms and double forms. Facetiously, I would add they probably have forms with variegated leaves too. The Brits do love their variegated foliage and their yellow foliage. These affectations add colour and texture in their climate with its diffuse light whereas we shun them here where our unfiltered sunlight burns them. The philadelphus is known as the mock orange blossom, I assume, because of its wonderful fragrance. It makes a large deciduous shrub – most forms get to 3 metres if you don’t trim them.
Cornus kousa was great all round the country. It is the dogwood from China and Japan – a small tree with flat flowers favouring pink but can also come in shades of white, cream and green tinged. We have a nice pink flowered one in our garden though it is a little poorly these days. There were a whole range of different selections in the UK, including some very large flowered ones and some top pink forms. We need to have a closer look at kousa. The American dogwood species don’t do as well for us here (they get decimated by the puriri moth) but kousa is a different story.
In the perennials, the stand out plants were alliums, verbascums, astilbes and eryngiums. Alliums are onions, though ornamental onions in this case. Some forms put up wonderfully decorative large spheres of purple and I wanted them instantly. Alas these archetypical inclusions of the English summer border are not really any easier there than here and the bulbs are often bought in annually. What a wonderful feature plant they are, though. The famous Beth Chatto Gardens list no fewer than 21 different ornamental alliums in their 2009 mailorder list.
Tulbaghia are onion relatives. English gardeners love to amass what are called National Collections of each and every plant genus, often in private gardens. We visited one garden which proudly proclaimed itself as the holder of a number of national collections, including tulbaghia. Hah, declared Mark, commenting that he thought there were only a very few different tulbaghia species. He was right. They are a small plant family, modest in number and modest in appearance. And indeed the National Collection of tulbaghia was considerably more impressive on paper than in reality. But it did give Mark a new claim to add to his repertoire. He has since been heard to proclaim: “Ah. But I have seen the national tulbaghia collection.” We do grow tulbahia violacea here but truly it looks a little chive-like.
Verbascums put up tall spires of flowers, typically yellow or white, with a rosette of leaves at the base. Great Dixter used self seeded verbascum spires as a repeated flower motif throughout the garden so we felt we were in good company as we too have a large flowered yellow form which is a biennial through our rockery. But we only have two forms and there are more than that which we will be tracking down for summer displays. We have tried and lost the most impressive verbascum, a splendid grey felted rosette with an impressive flower spire. Time to try it again.
- Miss Willmott achieves immortality – eryngium giganteum
Eryngiums are sometimes called sea holly and are mostly somewhat prickly. We have a lovely blue form in our rockery and it was because one was planted too close to the pathway that I discovered they have phenomenally deep and sturdy taproots. It makes them difficult to move. Eryngiums were used widely in English gardens, being tolerant of dry. There is a large form of the plant, eryngium giganteum, now called Miss Willmott’s Ghost. Said Miss W was a fine gardener but possibly a cantankerous old biddy who was a law unto herself. Allegedly, she made a practice of secretly scattering seed of eryngium giganteum in gardens that she visited so that the large, silvery plants would rise, ghost-like, long after her visit. Apparently eryngiums will seed down and many are biennial so only last two years. All I can say is the one I have in our rockery is a deciduous perennial and it has never yet self seeded, though I would be pleased if it did.
Astilbes. I fell in love with astilbes and the national collection of these at Marwood Hill in Devon was worth looking at. Big fluffy plumes in shades of white, cream, pink and rusty reds, all happy in damp areas but also preferring some shade with our harsh sun here. We visited Hollards Garden in South Taranaki last weekend and noticed their dell held the promise of a good display of astilbes later in the season. We can grow them here in the north, but they just don’t like being built up in nursery conditions (weevils seem to sniff the pots out from afar and move in) so we need to be more organised and build them up in the garden, not the nursery.
We were greatly taken with aruncus as soon as we saw it. Aruncus is a rather like a giant creamy astilbe on Eastern European steroids, ideal for wild or natural gardens. It needs space, at least a metre and a half across. We fell out of love with it equally quickly when we realised it had a short season and its beautiful creamy plumes of flowers turned brown and hung on, so it just looked burned. We noticed Persicaria polymorpha filled the same niche and a skilled gardener confirmed that this plant passed over more gracefully.
The stand out beautiful garden plant was a grass at Beth Chattos. I have now lost the piece of paper where I wrote its name down but I am sure it was a stipa. It is rather academic anyway because if there is one plant group that we will never be allowed to import new family members into this country, it will be ornamental grasses. Oh, and the ornamental thistles which looked great. The most truly awful plant we saw was widely grown, though goodness knows why. It was a thoroughly nasty spirea. Clumping yellow leaves (may even have had some sort of variegation to make it worse) contrasting with a yukky mauve pink flower. It was a good argument for glyphosate.
More a murky khaki than clean and green
Our geographic isolation works to our advantage environmentally. But our clean and green tag has more to do with a very small population than with a high level of environmental awareness. Many of us have a long way to go before we can claim to be green and clean at a personal level and some have even further to go than others. It would be good if the gardening norm here embraced sustainability and sound environmental practice. I think it is described as gardening with the environment, not in spite of it.
A feature last week on the gardening pages of our regional newspaper highlighted an increasing awareness of environmental issues in public sector gardening. Followers of organics have also embraced sound practice at a personal level. But sitting in the middle is the vast majority of the population, including, alas, a fair proportion of gardeners.
Most of us accept clean and green as a statement of fact for New Zealand. A clean atmosphere, yes. Overall, we enjoy what must be some of the cleanest and freshest air in the world. But once you hit ground level, it is a different story. Yes, some people are extremely clean and green, but others, and they are large in number, could not care less.
Living where we do in the country, I can tell you that all that litter, almost without exception, is thrown out of car windows. It is nothing for us to collect over a supermarket bag full of inorganic rubbish just from our own stretch of road verge. An entirely unscientific study a little farther down the road suggests to me that on average, there would be a visible piece of plastic, glass, tin or similar every three metres on both sides of the road. Added to that is a whole lot of rubbish that has been cut to pieces whenever the verges are mowed. That is a lot of rubbish.
The weekend rubbish accumulation at the corner
Down at the crossroads, there is a district council-sanctioned horror that is nothing short of bizarre. Founded on a belief that the vast majority of people will play the game, there is a rubbish collection point. The rules are that rubbish must be in approved bags with appropriate stickers and recycling will be collected free. No rubbish is meant to be left there before Sunday. The reality is that there are far too many people who couldn’t give a toss as long as the rubbish is not outside their house. From Saturday morning onwards, a veritable tsunami of assorted rubbish bags builds up, often ripped and with the contents falling out. Get a wind and it blows around the area. On Monday morning, the rubbish contractors come along and pick up the rubbish that meets regulations. What remains does not seem to be anybody’s responsibility, although from time to time, somebody will do a clean-up. Would I want to own one of the four properties around that corner? No. I can’t think windblown plastic and polystyrene are great for cows, and the recyclable light plastic bottles are also scattered widely. We open our garden to the public and get a fair number of overseas visitors. If they come at the weekend, they get to pass the unedifying sight of a small rubbish tip beside the road that would give anywhere in Asia a run for its money. Frankly, it is disgusting.
Straight after the rubbish collection on Monday morning - the pink stickers say why these bags were not collected.
The current row over the use of 1080 also belongs to this environmental discussion. Yes, there are pros and cons on both sides, but what its use indicates is a high tolerance level and official sanctioning of the mass application of poison as the lesser of two evils. 1080 enters the food chain, as we well know, but at least it kills quickly. There are various over-the-counter poisons that are uncontrolled and readily available in this country. Cholecalciferol is one we learned about last year to our grief. Our little dog Wilfred took two weeks to die from slow poisoning and while final results were inconclusive, we are sure in our minds that we were dealing with secondary poisoning. The widespread use of rat poisons is questionable. Selling slow-acting poisons for vermin over the counter with no controls and no monitoring is no longer acceptable in large parts of the developed world. Not only do we use a scary amount of it here, but even many environmentalists will argue in favour of unleashing such toxins into the environment.
Home gardeners have seen a sharp reduction in the availability of many chemicals in recent years and given the often cavalier attitude to handling them in our gung-ho pioneer country, that is a jolly good thing. But our gardeners still have access to many sprays that are now tightly controlled overseas or simply no longer available. It could be that at least one reason for the increasing attention to organics in the developed world is that government regulation has removed most of the alternatives. If you can no longer buy fungicides or insecticides and the only available herbicide is glyphosate, then you have to look to other ways of managing garden pests.
The spray we have been talking about here most recently is copper. Now, in the scheme of things, copper is useful and the occasional seasonal application is unlikely to do any harm to the wider environment. What is disturbing is to see frequent and regular applications of copper every two or three weeks in the mistaken belief that it is safe. While copper is a natural trace element, it accumulates rather too well in soils and can reach toxic levels quite quickly. One useful measure for a home gardener is earthworms. If you are a regular user of copper and you don’t have many worms, that is an indicator of toxic levels. I would advise all gardeners to err on the side of caution and minimise its use. If you want to know more, try doing a search on http://www.sciencedirect.com. There is quite a bit of international research being done on the build up of copper residues in the soil as a result of repeated spraying.
Routine spraying used to be advised as a preventative measure, even for home gardeners. In this day and age, the much more advisable philosophy is to avoid application of chemicals where possible and, if you are going to use sprays, even simple copper, only use when needed, not according to some sort of timetable. In this case prevention is not better than a cure.
We can not continue to rely on this country’s geographic isolation to keep our environment clean. Gardeners espouse nature and beauty and celebrate the growing of plants so it seems a real contradiction when we employ practices which are suspect and dodgy. I am not sure that there is a whole lot of difference to throwing your rubbish out of the car window. I would rather our country was clean and green than murky khaki.
The appropriately named buxus blight
Buxus blight, fortunately not in our garden
One of the frequently searched articles on our website is a piece I wrote a while ago on buxus blight (aka: why is my box hedging turning brown and looking as if it is dead and what can I do to resurrect it?) Given that we are a bit sniffy about box hedging here, it seems ironic that we are apparently seen as a source of information on the matter. Mind you, in deference to the level of interest and concern from others about both the short term look and the long term viability of their box hedging, I have been taking a slightly more than desultory interest in the whole matter.
You too can google it if you have some level of computer literacy and it is likely that you will come to the same conclusions from the international research and the anecdotes that I have. There are certain incontrovertible facts: it is a fungus called cylindrocladium and its rate of multiplication does not appear to be temperature related – in other words, it will multiply quickly in cold temperatures too. Most fungi thrive in warm, moist conditions but nasty buxus blight appears to be quite well adapted to cool and even dry conditions. The fungi spores are long-lived and can survive for years on dead leaves.
There are around 30 different species of buxus originating from Europe, Asia, the Americas and even North Africa. I have been told by individuals that the Asian forms from Japan and Korea (Buxus microphylla and microphylla var. koreana or Buxus sinica) don’t get it but the scientific evidence does not back this up. It is likely that the personal anecdote is based on the fact that in one particular location, this type of buxus is not showing signs of infection. That does not mean it won’t be affected in another location and the research says none are immune. The bottom line is that I wouldn’t be ripping out affected sempervirens (and suffruticosa, the very low and slow form used as an edger is still a sempervirens variation and is particularly susceptible) and replacing it with a different species of buxus, be it from Japan, Korea or anywhere else. I would be wanting to use a totally different plant family altogether.
You will know if you have buxus blight. Small dead patches are more likely to be dog urine or an accidental whiff of glyphosate. Buxus blight is simply devastating. The dead patches spread rapidly and do not show any willingness to regrow.
The first bit of bad news is that if you have buxus blight already, you will have to spray endlessly, for the rest of the buxus life, to keep the blight at bay because you won’t ever eliminate all the fungal spores. You can manage some level of control but the days when all your handy little hedge needed was clipping twice a year are over.
The second bit of bad news is that if you live in an urban area and do not yet have buxus blight, it is probably only a matter of time before you will get it because the fungal spores are easily dispersed by wind, so will gently spread throughout built up areas where there are host plants at regular intervals. You can reduce your chances of getting it but you are doing a King Canute number.
The good news is that if you live in the country and none of your neighbours have buxus blight, you may be able to keep it out because the spore don’t seem to be travelling quite as far as, say, camellia petal blight spore which have been tracked up to 5km. But quarantine your garden. Don’t bring in buxus plants or cuttings from other places unless you are 100% sure that the source is isolated and free of blight. Propagate your own additional plants at home. The international advice is that you should routinely quarantine all buxus plants brought in from other sites until you are sure they are free from blight. The problem is that quarantining plants at home is difficult. They need to be confined to a shed, glasshouse or nova house for an extended period of time and few people have the facilities to quarantine effectively which means that if by any chance the plants or cuttings you have brought in are harbouring the fungi, even if you try and keep them separate the spore will spread. Easier by far to seal your garden borders and not admit any foreign buxus. They are dead easy to propagate at home for even the most amateur gardener.
If you have masses of box hedging or topiary in your garden that you want to try and keep, you probably have to accept that it is going to take more work. Don’t let the hedge get too dense – there appears to be a connection between the ability of the plant to shed water quickly and slowing the fungal spread. Avoid overhead irrigation. Keep thinning the plants so they are not too dense and get as much of the build up of dry leaves and sticks out of the centre as possible to allow more air movement. There is some evidence that copper sprays will at least slow down the fungal spores and copper may be kinder to the environment than most anti-fungal sprays. It may be worth trying sulphur sprays too because sulphur has anti fungal properties. An all round rose spray may be effective if you are willing to treat your buxus hedge like your hybrid tea roses.
The big problem is what you can use instead of the infinitely useful buxus. There are three stand out characteristics of buxus. Number one is that you can keep it looking tidy on two clips a year and it does not grow too fast. Number two is that if you hard prune back to bare wood, it will resprout so you don’t end up with woody legs. Number three is that it roots so easily it is a doddle for the home gardener to produce and correspondingly cheap(ish) to buy. And we could add numbers four and five– that it is long lived and a good dark green. We are of the general opinion that hedges should be green. The problem is finding a substitute which meets all the above characteristics. Lonicera and teucrium are cheap and clip well but grow so rampantly that you have to clip frequently to keep them looking sharp. Small leafed camellias and totara clip really well and resprout from bare wood but are not easy to propagate so are much dearer to buy . Some of the small leafed hebes may clip well (but some don’t so you have to get your variety right) and root easily but are not always long lived. Pittosporums grow too well and get too tall too fast and tend to be a pale green in colour, not the desired dark shading. And they have larger leaves. Corokia can get a bit bare over time. Griselinia tend to have large leaves. Taxus (yew trees) are notoriously short lived in our climate because the roots get phytopthera. The biggest gap of all is the lack of a clear replacement for the dwarf suffriticosa which is used where a low edger is desired.
There is no like for like swap for box hedging. In the end, if box hedging features large in your garden and you have to cut your losses on it because of buxus blight, you may be wiser to go back to the drawing board and look at garden plans which don’t depend on clipped and well behaved little hedges for structure. We are mulling around the role filled by buxus hedging and will return with more thoughts on this in the future.
