Thursday 23 August 2012

rose, thou art sick

Two large branches of the Grevillea rosmarinifolia were completely dead, and I sawed them out.  Quite a large portion of the rest of the plant doesn't look too good, and if that dies too I shall be left with something very oddly shaped, and will be faced with a hard decision.  I am really not sure why it has started ailing in the past few months.  My records show that it was planted in March 2003, and according to Plant Database it can take eleven to fifteen years to reach its ultimate height, suggesting it isn't normally short lived.  It is an evergreen shrub, with leaves that look very like those of rosemary, though the resemblance is superficial: the grevillea leaves are sharp to the touch, whereas rosemary is soft.  It has unusual, long red flowers through much of the year (when it is doing well) that are attractive to insects.  Until it began to look poorly it was growing vigorously, and was a good couple of metres tall and wide, if not larger, and densely bushy and leafy.

It comes originally from Australia, and is a member of the protea family.  It is supposed to love sunshine and to be drought tolerant, and so it has proved with me.  Its cold hardiness must have been tested in the nine years I've had it, but it has come through until now.  Knowing that many proteas are unable to cope with  high levels of some nutrients I have always been nervous of feeding it.  The question now is what is wrong?  Were those two very cold nights in February too much for it?  The previous two winters were long, but probably didn't go down that low, and certainly the thermometer didn't drop that quickly.  Does it need feeding, even though it is in the family Proteacae?  Is Plant Database over optimistic about its normal lifespan?  I don't know Plant Database.  Hunting around the web for cultural advice (and a description so that I could post a link) I found that the RHS didn't have much to say on the subject, mainly featuring some of the named varieties.

The Magnolia grandiflora in the back garden doesn't look too good either.  Most of the leaves went bronze and then dropped, and now there is a dark oozing patch at the base of the trunk.  I spent some time last night leafing through my copy of Diagnosis of ill health in trees, and I am pretty sure that it has sat too wet over the summer, and that phytophthora has now taken hold.  The book tells you what environmental problems and diseases each plant species is especially liable to, as well as listing diseases with symptoms, and the signs I've observed exactly fit the bill, while it has been exceptionally wet.  Phytophthora covers a group of plant pathogens, similar to fungi but technically Oomycetes, whose spread is facilitated by water.  M. grandiflora has fleshy roots, prone to rot and die if they sit in constantly wet soil.  Odd branches have died back in the prostrate juniper in the same bed, which is likewise consistent with a diagnosis of water logging followed by infection.  Indeed, my conifer looks depressingly like the photograph in the book.

I love the episode in Three Men in a Boat when the author looks up his symptoms in a medical dictionary and discovers that he has everything, except housemaid's knee.  I feel rather like that about looking up plant diseases, which is why normally I try not to do it, and just blame the bad soil and drought, or the wildlife.  Plants dying is a mixed blessing.  If it was a good specimen that gave great pleasure one is sorry to see it go. If it was large it can leave an inconveniently large gap in the view, that has to be filled.  If it still had a solid root system it can take days of one's life and great physical effort to dig out the remains.  On the other hand, if the plant was always a bit poorly, or you'd got bored of it, then having the decision made for you that it's got to go can be a good thing, as the resulting space gives you the chance to plant something nicer.



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