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