Alstroemerias as pests or not

Jane McGary
Tue, 06 May 2008 22:52:08 PDT
Recently Diane mentioned Alstroemeria aurea (formerly known as A. 
aurantiaca) as an invasive geophyte. The "Ligtu Hybrids" are also noted for 
invasiveness. I wouldn't let this stop me from planting alstros, though, 
because I love them very much. I think you just have to designate a place 
where they can romp away.

In nature A. aurea can be seen carpeting light woodland (mostly Nothofagus 
or Southern Beech) and also on open hillsides. I have forms from the latter 
habitat and they're not obnoxious here; they're also shorter-growing. The 
Archibalds sell seed of this population from Termas de Chillan, Chile. 
Populations from farther south seem to be taller, more shade-tolerant, and 
less brilliantly colored.

In my rock garden is a very large berm of sand and gravel over a mound of 
soil, given over to two subspecies of A. ligtu: ssp. incarnata and ssp. 
simsii. They're just making their major growth now, but sharing the berm 
with them are some Juno irises and quite a number of "extra" bulbs that 
flower earlier, and some species tulips. By the time the alstros elongate, 
the early bulbs are withering and aren't harmed. Flowering about the same 
time as the alstros is Hastingsia alba, a big plant from northern 
California that coexists well. The alstros don't escape because the berm is 
surrounded by a packed gravel path that is sprayed with Round-up a couple 
of times a year. If you have room for a feature like this, it is rewarding 
and provides masses of cut flowers in midsummer.

There are also plenty of small Alstroemeria species, some of which should 
be hardy outdoors in temperate regions. I expect A. revoluta would be, and 
perhaps A. diluta. A. hookeri did not survive in the open for me (it's 
coastal). I'll eventually experiment with quite a few on raised scree beds.

Jane McGary
Northwestern Oregon, USA

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