Germinating Aroid Seeds

17 Pages·2009·1.08 MB·English

p. C. BOYCE, 2007 145
Germinating Aroid Seeds - Some Observations
Peter C. Boyce
Malesiana Tropicals
Suite 4, Level 9, Tun Jugah Tower
No. 18 Jalan Abdul Rahman
93000 Kuching, Sarawak, Malaysia
[email protected]
INTRODUCTION quickly once the seed is cleaned of the
berry pulp and so the seed should remain
The following notes are based on more
in the berry until ready to sow. If seed must
than 20 years growing aroids from seed in
be removed from the berry then it is vital
Europe and a further four years doing the
that it remains damp but not wet. Placing
same in the everwet equatorial tropics of
the seed in a folded, moistened kitchen
East Malaysia. These notes reflect personal
paper towel (not toilet paper, which breaks
experience gained from trial and error -
down when wet) inside a plastic bag kept
mostly the latter - but with records made all
in a cool room is a good temporary storage
the while on what failed and what, very
medium.
occasionally, worked but are in no way
intended to be neither comprehensive nor
Cleaning
equivocal.
The cleaning methods will VaIY depend
General ing on whether the seed is medium to large,
or small. For medium or large seeds
Whether sowing seeds in a pot on the
(e.g., Alocasia, Aglaonema, Amorphophal
windowsill in the temperate parts of the
world or in trays in the tropics, the crucial Ius, etc.) that are easy to handle they first
need be removed and cleaned of any
starting point is fresh seed. Aroid seed is for
surrounding beny. The simplest method is
the greater part recalcitrant (does not
withstand storage) and stored seed (that is to squash the berries gently onto kitchen
to say commercially bought) very soon paper towel and then separate the seeds
loses viability. from the pulp and any seed membrane. The
seed membrane tightly adheres to the seed.
Buying seed Its presence is detectable by the seed feeling
slippery. Gently working the seed between
Seed from commercial seed houses thumb and index finger will remove the
generally gives poor to non-existent ger
membrane, after which the seed will often
mination, especially seed of species with
feel very slightly rough. It is vital that this
little or no endosperm, which includes
cleaning is done wearing latex gloves - the
Aglaonema. All seed should be purchased
fruit pulp of almost all aroids ranges from
inside the still-fleshy berry. Dried seed (in
mildly to highly irritant. Gently rinse the seed
or out of the berry) will have a low to non
in a nylon sieve and dry on kitchen paper
existent viability rate due to the problems
towel for a minute or two to ease handling.
of storing aroid seed.
Small seeds, aside from being fiddly to
handle, have the additional problem that
Storage
inside each berry the numerous seeds are
Aroid seed stores poorly and dried seed embedded in very viscous gel which is
will have a very low viability rate. For best water insoluble and thus difficult to re
results seed must be sown as fresh as move. The easiest method is to put the
possible. Seed viability falls extremely berries into a plastic beaker full of water,
146 AROIDEANA, Vol. 30
Fig. 1. Tray suitable for seed sowing in the everwet tropics.
macerate them with the fingers anel then large seeds require to be just covered with
leave the beaker and its contents in a warm, planting media and then well watered.
shaded place for a few days to ferment (it Thereafter keep damp and moderately
will smell pretty bad at the end of the time shaded. Small and very small seed are best
but the seed will come to no harm). After surface sown and then settled in by water
fermentation it will be found that the gel is ing but not covered.
very easily washed off by placing the entire Almost any organically rich, moisture
beaker contents into a fine nylon sieve retentive yet well-drained medium will
under gently running water and working produce good germination results. A suit
the seed/gel/pulp mass with the fingers. able selection is:
The decomposed gel will dissolve and the
larger pieces of berry, etc., may be re 1:1 ground sphagnum: Perlite/coarse Ver
moved by hand. miculite, or
1: 1 sieved coconut peat (coir): washed
Planting containers and coarse (2-3 111m) river sand, or
planting media 1: 1 sieved coconut peat (coir): Perlite/
coarse Vermiculite, or
Plastic pots or trays are better then clay
1:1 propriety soil-less compost: Perlite/
(terracotta). Tn very wet tropical habitats
coarse Vermiculite
plastic mesh trays of the type used to drain
kitchen dishes (crockery) are excellent From experience for tropical species 1: 1
(Fig. 1). ground sphagnum: Perlite works best in the
Aroid seed requires light to germinate so everwet tropics while the 1: 1 propriety soil
do not bury too deeply, if at all. Medium to less compost: Perlite mix is ideal for
P. C. BOYCE. 2007 147
Fig. 3. Alocasia chaN with mature fruits;
note that the lower spathe while still fresh
has split segments that have recurved to
reveal the fruit.
be underway loosen the bag but do not
remove immediately. Allow the plants
Fig. 2. A/ocasia XPortodora at onset of inside to acclimatize to the drop in humid
fruit maturity; note the persistent lower ity that the loosened bag provides. After
spathe beginning to split longitudinally to two or three days remove the bag at night
reveal ripe orange-red berries. to allow a period of cooler temperatures
before the first full day without a covering.
Temperate genera are best germinated in
a frost-free greenhouse.
temperate regions. If using coconut pear
(coir) ensure that the source is free of salt
NOTES FOR SPECIFIC GENERA
contamination; most coconut peat origi
nates from coastal areas of the tropics and if
not properly matured often contains signif AWCASIA (including XENOPI-IYA)
icant salt contamination.
Size
Temperate genera listed belO\v (Arul11,
Arisarum, Siarum & Dracunculus, El17i
Alocasia seed is medium to moderately
nium and Helicodiceros) benefit from
large (on average black peppercorn size)
a small quantity of mineral soil (c. 0.25) to
and easy to handle.
whichever mbc is used. The seed of these
genera should be covered limestone grit to
Home collection
the depth of the seed, rather than sowing
media. In most species the seed is mature once
the persistent lower spathe splits into
Germination recurved strips to reveal the orange-red
berries (Figs. 2 & 3) although in the A.
Ideal conditions for germination of trop
longiloba complex the lower spathe \vith
ical genera are a heated greenhouse or in
ers and falls before fruit maturity (Fig. 4).
warm climates a shade house. If germinat
ing indoors then choose a brightly lit but
Cleaning
not sunny windowsill and put the entire
pot inside a polythene bag secured by an Squash onto kitchen paper to\vel; re
elastic band. Once germination is seen to move pulp and seed membrane and rinse.
148 AROIDE A, Vol. 30
Fig. 4. Aloeasia longiloba "",ith the fruit displayed and the lower spathe withered
and fallen.
Sowing leads to either fungal or bacterial rotting.
Thereafter, pot-on with minimal root dis
Cover to own depth.
turbance.
Germination
Notes
2-3 weeks at a minimum of 21°C (70°F)
As Aloeasia grow and enter maturity they
and a maximum of 29°C (84°F). Medium
become very intolerant of root disturbance.
shade.
It is important that after initial pricking OLit
plants are potted on in such a way as to
Post germination
minimize root damage.
AIIO\N the seedlings to continue growing Species (and their hybrids) originatina
until a second leaf has fully developed from limestone habitats benefit frol11 a scant
topdressing of small (Y2-1 cm) limestone
before transplanting.
chips. Species and hybrids concerned are:
Transplantation A. x Amazonica, A.longiloba 'Iowii' (syn. A.
lowii), A. jJ/.I/.eri, A. jJangeran, A. jJrineijJi
At the start of third leaf emergence eulus, A. reginula, A. reginae, A. reuersa &
transplant into individual pots taking care A. ridleyi. In addition, although their
not to bury the stem base as this invariably habitat is not recorded the following
P. C. BOYCE, 2007 149
species also benefit from a limestone Transplantation
dressing: A. c!ypeolata, A. nebula & A.
At the initial potting from germination it
sinuata.
will be seen that there will already we an
extensive root system and great care should
AGLAONEMA, AGLAODORUM & NEPHTHYrIS
be taken to prevent root damage. Once
Size potted, grow on until the pot is full of roots
and then pot on successively into the final
Aglaonema, Aglaodorum and Nephthytis
container or ready for planting put, avoid
seed is large (hazelnut to date stone size)
ing root disturbance at each potting.
and easy to handle.
Notes
Home collection
Aglaonema brevispathum, A. costatum
For Aglaonema and Nephthytis the seed
and A. chermsiriwattanae benefit from
is mature once the fruits turn red (Aglao
a scant topdressing of small 0/2-1 cm)
nemcr Fig. 5) or orange (Nephthytis). By
limestone chips.
contrast, ripe fruits of Aglaodorum remain
As an adult plant Aglaodorum requires
green (Fig. 6). Ripeness is indicated by the
a heavy mineral rich soil but germinates
fully formed fruits falling easily from the
best in a loose medium such as 1: 1 ground
peduncle.
sphagnum: Perlite/coarse Vermiculite.
Cleaning
AMORPHOPHALLUS
Unlike many other aroid seed there is no
Size
endosperm; instead the seed consists of
a massive green cotyledon that is easily Amorphophallus seed is usually medium
damaged, so the squash onto kitchen paper to large (small peanut to date stone size)
towel and subsequent removal of pulp and and easy to handle.
seed membrane must be carefully done.
While the red or orange pulp of Aglaonema Home collection
and Nephthytis is very soft when ripe and
Seed is mature once the fruits turn red or,
readily removed, the spongy fruit tissue of
rarely, blue or green. Whatever the colour
Aglaodorum is very difficult to remove
of the ripe fruit at this stage the pulp will be
(undoubtedly because in nature these
soft and squash easily.
entire fruit functions as a floating dispersal
unit) and these fruits are best sown whole
Cleaning
into individual pots.
Squash onto kitchen paper towel; re
Sowing move pulp and seed membrane and rinse.
Cover to own depth.
Sowing
Germination Cover to own depth.
4-6 or more weeks at a minimum of 21°C
Germination
C70°F) and a max. of 29°C (84°F), Light
(Aglaodorum) to medium (Aglaonema & 3-5 weeks at a minimum of 21°C (70°F)
Nephthytis) shade. and a max. of 29°C (84°F), Light to medium
shade.
Post germination
Post germination
As soon as the first green shoot emerges
the seedlings should be individually pot Once the first leaf has expanded trans
ted. plant into individual pots.
150 AHOrDEANA, Vol. 30
Fig. 5. Ripe fruits of Aglaonema simplex. Note that the epidermis is beginning to split.
P. C BOYCE. 2007 151
Fig. 6. Fruits of Aglaodon/.Jn grifflthi! at the onset of maturity. The berries remain green
to full ripeness at which point fully formed fruits detach easily from the peduncle.
Transplantation a scant topdressing of small (Y2-1 cm)
limestone chips.
It will be seen that there will already be
an extensive root system and great care
AMYDRIUM, ANADENDRUM, PEDICELLARUM,
should be taken to prevent root damage.
POTJ-JOIDlUM & POTHOS
Once potted, grow on until the pot is full
of roots and then pot on successively Size
i.nto the final container or ready for planting
Seed is medium sized (black peppercorn
put, avoiding root disturbance at each
to small peanut sized) and easy to handle.
potting.
Home collection
Notes
Amydrium hu.mile, A. medium and A.
These notes are based on the germina
sinense fruit ripen white (Fig. 7); the other
tion and aftercare of the Bornean species.
genera ripen red (Fig. 8).
These generally do not have a fixed nor
long dormant period. I have no experience
Cleaning
with germination and aftercare of species
from monsoonal habitats. Squash onto kitchen paper towel; re
The limestone species (e.g., A. hrachy move pulp and seed membrane and
jJhyllus, A. ehurneus, etc.) benefit from rinse.
152 AROIDEANA, Vol. 30
Sowing
Cover to own depth,
Germination
3-5 weeks at a minimum of 21°C (7O°F)
and a max, of 29°C (84°F), Light shade,
Post germination
As soon as the first green shoot emerges
the seedlings should be potted individualJy,
Transplantation
It will be seen that there will already be
an extensive root system and great care
should be taken to prevent root damage,
Once potted, grow on until the pot is full of
roots and then pot on successively into
the final container or ready for planting
put, aVOiding root disturbance at each
Fig, 7, Ripe infructescence of Amyd1"ium potting,
medium,
Fig, 8, Ripe infructescences of an unidentified Anadendrum,
P. C. BOYCE, 2007 153
Notes caustic; prolonged handling of the pulp
will result in skin loss. Latex gloves
Many climbing aroids genninate as
essential. Seeds of Biamm and Eminium
a shade-seeking leafless (minute cataphylls
have a large fatty structure on one end -
present) thread-like, creeper ('eocaul') ca
a strophiole or elaiosome that functions as
pable of extending for a considerable dis
a dispersal agent (ants) attractant. Experi
tance along the forest floor and, although
ence has shown that this is prone to fungal
the green stem is presumably capable of
attack that can spread to the seedling and is
photosynthesis, at least in the initial stages it
best removed prior to sowing - in habitat
appears to depend partly on food reselVes
this fatty body is eaten by the ants and the
in the large seeds. Field obselVations
seed discarded.
suggest that the function of the eocaul is to
locate a climbing host on which to establish
Sowing
juvenile shoots. It is apparent that once this
function is satisfied the eocaul soon withers. Cover to own depth.
Once a suitable vertical surface is encoun
tered, the shoot alters its mode of growth Gennination
and attaches itself to the substrate by means
3-5 weeks at a minimum of 15°C (59°F)
of short clasping roots and begins to pro
and a max. of 22°C (c. nOF). Bright light
duce foliage leaves. If no such climbing
but not full sun.
surface is found the plant will continue to
exist as a thread-like stem but will eventually
Post gennination
exhaust itself and perish.
It is important that seedlings are not
ANADENDRUM-SEE AMYDRIUM grown too shady, especially the steppe
dwelling species of Biamm and Eminium.
Too-shady conditions will lead to soft,
ARlDARUM - SEE COLOCASIA etiolated growth that aside from being
susceptible to fungal pathogens will also
ARISARUM - SEE ARuM produce a weak tuber.
Transplantation
ARUM, AMBROSINA , ARISARUM, BIARUM,
DRACUNCULUS, EMIN/uM & HELICODlCEROS Plants should be kept growing as long as
possible during the first year and the pots
Size
should not be allowed to dry out as this
encourages the plants to become dormant.
Seed of these European and Mediterra
When the leaves start to yellow the water
nean genera is medium sized (black
ing should be cut back but not stopped.
peppercorn sized) and easy to handle.
When dormant, the tubers should be
treated in the same way as mature plants.
Home collection
It is best to repot the tubers, about three to
Amm, Dracunculus, Eminium and He a 10 cm pot, into fresh compost at the time
licodiceros fruits ripen red; Ambrosina dull when the rest of the collection is repotted.
green; Arisamm pale green; Biamm white The seedlings should now be treated as
to lilac. mature plants.
Cleaning Notes
Squash onto kitchen paper towel; re Sow in pots rather than trays since on
move pulp and seed membrane and rinse. genninating seedlings immediately begin
The berry pulp of Amm, Dracunculus, to fonn a tuber and the shallow nature of
Eminium and Helicodiceros is especially seed-trays can inhibit this severely. The
154 AROlDEANA, Vol. 30
pots should be filled with compost to
within 3 cm of the top, the seed sown on
the surface and then covered to its own
depth with limestone grit.
The seed will germinate at the same time
that the mature plants begin grO\vth. If the
seed is fresh it should germinate at the start
of the next growth season, but if old or dry
it may take up to a year longer. Seedlings of
those species subjected to wimer cold will
spend their first growing season as un
derground tubers, showing no signs of
aerial growth. They will not produce leaves
until the start of the second grO\ving
season. It is most important that pots are
not discarded for at least two years.
BIARUM - SEE ARUM
BUCEPHALANDRA - SEE COLOCASIA
Fig. 9. Sebismatoglottis cf. l1iahensis at
COLOCASIA, FURTADOA, HOMALOMENA &
ripe fruiting.
SCHISMATOGLOTTIS (including ARIDARUM,
BUCEPI1ALANDRA, PHYMATARUM
& PIJYIOSPATI-IA)
Size
Cleaning
Seed is small (average 1 mm X l.5 mm)
and tricky to handle. The main problem with cleaning is that
inside each berry there are numerous seeds
Home collection embedded in very viscous gel which is
difficult to remove. The easiest method is to
Ripe fruits of Coloeasia are pale yellow to put the berries into a plastic beaker full of
brown and strongly fruit-scented; before water, macerate them with the fingers and
maturity they are contained in the persis then leave the beaker and its contents in
tent lower spathe; at fruit maturity the
a warm, shaded place for a week to ferment
lower spathe splits irregularly and peels
(it will smell pretty bad at the end of the
to reveal the fruits. The lower spathe of
time but the seed will come to no harm).
most Sehismatoglottis and Pbymataru111
After fermentation it will be found that the
behaves in a similar manner but the ripe
gel is very easily washed off by placing the
fruit are white to pale green (Fig. 9) and
entire beaker contents into a fine nylon
odourless. In Homalomena and the allied
sieve under gently running water and
Furtadoa the whole spathe persists into
working the seed/gel/pulp mass with the
fruit ripeness and then splits from the base
fingers. The gel will dissolve and the larger
into long strips that curl upwards to reveal
pieces of berry, etc., may be removed by
the pale green or white, weakly perfumed
hand.
fruits (Fig. 10). Aridarum, Bueepbalandra
and most Piptospatha carry the fruits in
Sowing
a splash-cup formed by the persistent
lower spathe. At maturity fruits are green The cleaned seed is most easily sown by
(Fig. 11) filling the beaker of seed with fresh water,