Re: Phormium tenax

I can say that Phormium tenax did not even last a year in the shaded lath house of our on-site nursery here in Riyadh.  The summer temps of just over 44 C or 120 F seemed to cook them, as they were perfectly healthy up until our hottest summer months of July, August and September.  These were not in full sun, but under 50 % shade cloth.  Other plants which could not take the sustained high temps here include Schinus molle, Ficus rubiginosa 'Florida', Hedera helix, Pelargonium peltatum, and P. hortorum.  These will all do quite nicely for at least a month into such heat, but will eventually fail.  It's interesting to note that other species of the same plant have much better performance in such high sustained heat loads, as Schinus terebinthifolius and some of the scented geraniums are widely grown here.

I wish there was a source of information one could turn to which listed cold and heat tolerances for many plants, but at least in Saudi Arabia the best indication seems to be the tried and true method: See if you can find it being grown in the area! 

Back to the general topic of heat tolerance of Phormiums, my experience with them back in California is that in hot summer climates they perform best with protection from mid day sun, especially the complex hybrids.  Being from New Zealand, I would expect that more moderate temperatures are what they are accustomed to, and they seem to thrive in coastal California with very little pampering.  I wouldn't suggest them for hot desert locations, though, unless you consider them as a replaceable annual!  Sometimes that may actually be a liberating concept from a designer's viewpoint, but it goes against the grain from a horticultural standpoint to plant things we know will ultimately die.

I think that my first reaction to the new Getty Museum gardens was one of horror at so may plants being used in the wrong climate, and treated as seasonally replaced plants. The idea of using large specimen sized (24/36 " box) shrubs and trees as annuals was not something I was used to.  I must say that after working on a palace landscape in Saudi Arabia, I've come around to the idea that if you really want to do it, try it.  (But I wouldn't suggest such follies for normal projects, just where the client has to have it, or has the means of a Getty or Bill Gates!)

I know that I have certainly been guilty of wanting to grow plants which are not adapted to where I garden, tropicals and xerophytic plants have been some of my weaknesses.  I try to justify it as research, and have many things survive, if not thrive, and have often been surprised at my successes.

What is it that drives so many of us to want to grow the exotic over the local indigenous plants?

Carol Moholt <moholt@gardens.com> wrote:

This is an interesting question. I see big stands of P. tenax in the
parking lot of my local Costco where they get full sun and radiated
heat from asphalt and cars all summer long. They seem to do OK and
there must be a drip system in place -- I've not really taken the
time to dig around (!).

But in my garden they seem to really have problems with the hot sun.
The more I look at this the more I think it is the cultivar and type
that is the variable. Those whose stems arch and drape rather than
stand stiff are more susceptible. And even the smaller cultivars of
the stiff stem types seem to burn on the tips in my garden. The only
way I can prevent this is rather more water than I'd prefer to give
-- the surrounding plants are euphorbias, lavenders, and the like.
Those in the Costco parking lot are the giants -- they would
overwhelm my s! ma! ! ll garden. I'm thinking of moving mine to areas that
get some afternoon shade.

What are other people's experiences?

I like in the southern portion of the greater San Francisco Bay Area,
sunset zone 15 which is quite warm in the summers.

Carol Moholt



>Phormium tenax has been in Israel for years. Heat hardiness should
>not be a problem
>as the weather here may be in the 35C+ range for more than six to
>eight weeks in
>several areas. In discussing plants hardiness to heat it should be
>noted that one of
>the primary factors is the sun radiation factor. In desert areas,
>with clear skies for
>over several months, it is probably the radiation which is more
>destructive than the
>heat itself. In addition, dessication factors and the additional;
>amounts of water also
>have to be taken in consideration. Unfortunately, the only book
>written on the subj! ec! ! t
>( to my knowledge ) is Heat-Zone Gardening by Dr. H. Marc Cathey. He gives
>Phormium the highest rating ( more than 210 days over 30C ).


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