Androsace Group

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Listing
of Alpine Plants and how to use
::

The Androsace Group issues four Newsletters
each year and two Androsace Notebooks. It aims to circulate
information on the cultivation and naming of these plants
and on their ecology and conservation status in the
wild. It also aims to investigate the problems of preserving
species and hybrids in cultivation and to take what
steps it can to ensure such preservation.

Androsace is a genus of a true alpine,
annual or pernennial plants of the Primrose Family,
known as Rock-jasmines. They grow naturally in the rocky
stretches above timber-line, and many of them require
special treatment in the alpine or rock garden. Their
leaves, which are often very woolly, are usually tufted
or in rosettes. The small flowers-pink, red, or lavender
– are usually borne in rather flattened rounded clusters.
They are grown from seeds, division or cuttings, and
require a dry, gritty soil and good drainage, through
they must never suffer from drought.

The offical Androsace Group homepage

Cultivation of Himalayan Androsaces in pots in the
south-east of England by John T Lonsdale

This contribution deals only with the
cultivation of Himalayan androsaces in pots, I have
very little experience of growing them in the open ground
or raised beds.

Seed Sowing

All seed is sown on a single compost,
ie., 60% very sharp 2-4mm grit, 30% fine grade Cambark
& 10% John Innes 3, surfaced with a gently firmed
1mm layer of sieved peat. Sown seed is covered only
with a 5mm layer of grade 2 Flintag (100% silicaceous
grit, nominal size 2-3mm); pots are then soaked from
below, gently watered from above using a fine rose and
placed outside, fully exposed to the elements. Seed,
regardless of the date of receipt, is sown around the
New Year, or as soon as received if after this time.

In my experience, seed of most Himalayan
androsaces does not have any particular requirements
to trigger germination other than a general rise in
temperature such as is generally experienced in southern
England in late February & early March. Seed received
from the Kunming-Goteborg expedition (KGB) in late February
1994 & sown immediately started to germinate in
late March 1994, whereas AGS China expedition (ACE)
seed sown at Christmas 1994 started to germinate in
mid-February 1995 with germination continuing into early
April. Interestingly, seed of Androsace bulleyana was
the last to germinate from both collections. One exception
to this general observation is seed of two collections
of Androsace delavayi made by the KGB expedition; no
germination was experienced in the first season following
sowing but several seedlings germinated the following
spring.

Treatment of Seedlings

As soon as any germination is apparent
the pots are brought under cover. When the cotyledons
are fully developed, and there is an indication of formation
of the first true leaves, the seedlings are pricked
out into 2.5″ pots using a compost consisting of 70%
sharp grit, 15% John Innes 3 & 15% sieved ericaceous
compost. Seedlings are kept shaded for a week then in
the greenhouse for a further 3-4 weeks before being
grown on in an Access frame with some protection from
heavy rain until well established, & shading at
all times from the hottest sun. Copious amounts of water
are given.

Mature Seedlings and Established Plants

All of the above are grown in Access frames,
no Himalayan species are kept in the alpine house at
any stage other than as immature seedlings. Roof glass
is kept in the frames from early October until after
flowering (mid-April), side glass is only used in the
winter during prolonged heavy rain or when temperatures
fall below -3oC. Watering in the pots commences after
Christmas and is increased throughout the early spring
until, following flowering, water provided by rainfall
is supplemented where necessary with overhead watering
using a fine rose on a hose-pipe. Androsace muscoidea
var. longiscapa seems particularly susceptible to crown
rot in late summer, this may be a reflection of the
drier conditions experienced by this species at this
time in it’s native habitat. Consequently, overhead
protection is provided from early August. Androsace
spinulifera (KGB seedlings) was lost completely to crown
rot following the onset of dormancy in late September
even though no water had been given in the pots for
several weeks. This species has a reputation for difficulty
in this respect & ACE seedlings have been moved
into an extremely gritty compost with pure grit from
the point of emergence of the roots to the crown of
the plant.

In a normal summer very little shading
is provided, plants are grown with full exposure to
the sun from mid-morning until late afternoon. For example,
during the relatively hot summer of 1994, shading in
the form of a single layer of 30% shade netting was
provided only for 5 weeks during mid-July to late August.
Androsace rigida, rigida var. minor & spinulifera
(KGB seedlings) were particularly affected, the foliage
becoming lime-green, although I suspect that the major
cause of the plants distress was prolonged temperatures
over 75oC rather than excessively high light levels.
Healthy growth resumed as soon as the temperatures dropped.
Saxifraga georgii & S. lowndesii and Solmslaubachia
spp. are ideal indicator plants for heat stress, the
foliage being among the first to show the adverse effects
of high temperatures.

As soon as good root growth is seen to
emerge from the bottom of 2.5″ pots they are moved into
3.5″ clay pots in the same compost as above; all clay
pots are plunged in sand. Henceforth, they are potted
on every year, no nutrient is given other than that
contained in the compost. Root aphids, green fly &
red spider mite are the major pests with which I have
experienced problems but damage can largely be avoided
by suitable prophylactic treatments. Root aphid is prevented
by drenching the compost in early spring and late summer
with spray-strength dimethoate (commercially available
as Murphy’s Bio Long-Last in combination with permethrin),
green fly and red spider mite are fully controlled by
over-head spraying with dimethoate or bifenthrin (available
as Polysect) at regular intervals. Species which, in
my experience, are particularly susceptible to red spider
mite include Androsace tapete & A. villosa var.
arachnoidea.

The major fungal disease is botrytis,
which is mainly a problem on senescent foliage. Very
effective control can be achieved by overhead spraying
monthly from September to late December with Rovral
(Iprodione), a specific antifungal agent. This is, however,
no substitute for regular observation and the rapid
removal of any diseased growth. It is interesting to
note that botrytis on any plant is always far worse
in the alpine house than in a well-ventilated outside
frame. I would go so far as to suggest that the alpine
house is totally unsuitable as a home for any Himalayan
androsace (or saxifrage) other than small seedlings.

Propagation

Propagation is an absolute requirement
for the successful maintenance and distribution of any
species. Germination of wild-collected seed (or home-saved
seed in a few cases) is usually very good & should
result in a high percentage of flowering-sized plants.
Androsace rigida, for example, flowered well the first
spring after germination. Unless large populations of
mature fertile plants can be maintained it is likely
that future propagation will rely on vegetative means.
Every effort must, however, be made to cross-pollinate
different plants as this is the sole means to ensure
the survival of healthy, genetically diverse, individuals
of a given species. Vegetative propagation is via the
rooting of single rosette cuttings; this is relatively
straightforward as long as cuttings are taken at the
correct stage of growth. A common mistake is to take
cuttings too late in the season when the runners have
started to become woody – young, soft daughter rosettes
with 0.5″ stems will give better than 90% success if
taken into silver sand in a propagator. The optimum
time to take cuttings varies greatly; Androsace mucronifolia
is generally propagated in early April, immediately
after flowering, at a time when Androsace muscoidea
var. longiscapa, for example, is still dormant. Rooting
will usually occur within 4 weeks and plants can be
potted up immediately to make strong plants which will
over-winter without difficulty.

The cultivation of androsaces in the south-east
of England should, with sensible attention to their
basic requirements and regular propagation, be no more
of a problem than anywhere else in the country. There
is absolutely no substitute for continuous observation
of your plants – they alone will tell you whether they
are happy – although it is up to you to decide what
they are saying !

The offical Androsace Group homepage

MEMBERSHIP

Don Peace
8, St. Martins Way,
Kirklevington,
Yarm,
Cleveland TS15 9NR
United Kingdom
e-mail: don.peace@iname.com
Fees: GBP 4 in the UK, GBP 5 elsewhere
Seed exchange: Only Androsace and Douglasia

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