First published in
1976.
Propagation of the Primrose & Polyanthus from Seed
It is often said that the seed of the Primrose and Polyanthus should be
sown whilst it is fresh, that is within twelve months of gathering. This
however is not entirely true, for seed can be stored satisfactorily for at
least three years without any noticeable deterioration in the germination rate
or the quality of the subsequent plants. Seed must however be stored correctly,
the best way being to place the seed in an airtight container and either place
the container in a cool place, or better still in a refrigerator.
Polyanthus seed can be sown at almost any time of the year with the
exception of June. There are three recognised sowing periods, namely July to
September, December to February; and March to May. Despite the fact that in
nature seed is sown in July to September I have found that the best results
occur from an early Spring sowing. However I have also had no problems, or
difficulties, with seed sown at other periods. In fact the Primrose &
Polyanthus is a very easy plant to raise from seed, and seems to tolerate both
adverse conditions and mismanagement.
From a sowing of fresh seed -
that is a July, August and September sowing - a percentage of seeds will not
germinate until the following spring; this percentage seems to vary according
to strains, and colours. From a sowing at this time seedlings must be given
protection through the winter and a minimum temperature of minus 5ºC must
be maintained. The important factor under such conditions is to ensure that
should the temperature fall below freezing that a slow thaw to allowed. Any
attempt to thaw the soil or seedlings will result in disaster. A sowing between
December and February follows the natural sequence of germination. The best
method is to place the seed trays out of doors in a position protected from
rain, or dripping water - a Hessian sacking canopy is ideal. This sowing also
can be carried out directly into a frame, though this is the method used in
commerce I cannot see any sound reason for it's preference to the use of seed
boxes.
Sowings during March, April and May are identical to that
between December and February with the exception that great care must be taken
to protect the seed trays from direct sunlight or from drying out. The great
advantage of a December to February Sowing is that the seedlings have a full
twelve months vegetative growth before flowering, a later sowing reduces this
period of growth, and an earlier sowing often results in plants flowing only
months after sowing, thus producing inferior flowers, and adversely affecting
the plant size.
Many seed catalogues and articles in amateur papers
state that seed is best germinated at a temperature of I5-16ºC, and
advocate the use of propagators. Not only is this an unnecessary expense, but
if the temperature is too high it can seriously affect germination. It is
important to remember that the Primrose and Polyanthus are hardy plants, and
should be treated as such. The best results are obtained by following the
natural sequence, or reproducing them as accurately as possible. For fast and
full germination cool moist conditions are required.
Because seed is
small & round, and liable to roll into depressions the surface of the
compost on which the seeds are to be sown must be smooth and firm - any large
pores will result in the seeds being buried. The seed should be sown thinly,
evenly and MUST not be covered with compost. Great care must be taken when
sowing the seed, due to the spherical shape of the seed they are prone to roll
and bounce about, and this can result in seed collecting in pockets. Some
success can be achieved by applying a very light dressing of fine chippings to
the surface before sowing the seed.
To promote faster and even
germination some growers advocate watering the seed in with water at a
temperature of 49ºC, and repeating the treatment for two further days
using water at a temperature of 45ºC. This treatment should not be used on
Winter sowings, when freezing may destroy the germinating seed. In the Summer a
treatment of water at 45ºC should be given on one day only. This treatment
sounds at first to be somewhat drastic, but is highly effective.
It is
essential that the compost and seed is never allowed to dry out and accordingly
the trays should be checked regularity. Watering must be done with care, on a
large scale a very fine rose must be resorted to, but even with this there is a
great risk of washing the seed into a corner. Where the seed is sown in trays
the best method is to stand the trays in shallow water so that the compost is
moistened from beneath, and there is no risk of swamping the seed or tiny
seedlings. Whilst it is important to ensure that the compost is kept moist, it
is also imperative to ensure that there is adequate drainage, and that the
compost does not become water logged.
Once the seed is showing distinct
signs of germination it should be lightly covered with compost or vermiculite
to minimize the risk of drying out. Care must be taken however that the seed is
not buried, and a very fine sieve should be used.
The sowing medium for
Primroses and Polyanthus has been a subject of debate over the past few years,
and at the present time some growers advocate the use of a loamless compost
such as Vermipeat, though peat and sand based loamless composts are not
recommended. Growers who recommend loamless mediums in preference to loam based
composts do so because of the variability of loam.
Loamless advocates
have little worry with 'damping off', however provided seedlings in a loam
compost are given adequate ventilation and the seed sown thinly there is only a
slight risk, especially if the loam has been correctly sterilized. Should any
sign of damping off become visible an immediate treatment with Cheshunt
Compound, Captan, or Benlate will prove effective. As a precautionary measure
freshly sown seed can be watered with liquid Copper Fungicide at a rate of one
fluid ounce per five gallons of water.
Seedlings should be transplanted
at about the first true leaf stage, to leave longer may result in starved or
drawn seedlings. Undoubtedly the best results are obtained by transplanting
into boxes at a spacing of 5cm, into Jiffy pots, or best of all into plug
trays. Under these condition the young plants can be protected from the
elements, and their every need satisfied. In trays the young plants make rapid
headway and can be planted out into their flowering position as well developed
plants. Undoubtedly these plants will produce the best flowers. On a large
scale however, not only is this an expensive method in terms of labour, time
and space, but also quite impractical. Under these economic restraints
seedlings are planted out directly into open ground at a spacing of 20 cm.
Initially the seedlings will look lost, but once growth is well developed there
will be little or no soil showing between the plants.
An alternative
method is to space the seedlings 10cm and when the leaves touch every other
row, and alternate plants in the remaining rows are removed and planted in
another flowering bed, thus giving a 20cm final spacing. This later method
reduces the amount of weeding whilst the seedlings are small, and it always
seems that at a wide spacing the seedlings are slower in growth. On an economic
reasoning this method makes sense for only half the amount of land is planted
with unproductive seedlings, thus allowing a crop to be grown on the other
final flowering bed. Where cloches are used it is important to space the plants
so that the rows are at a suitable distance for covering with the maximum
effect, and without the necessity of moving rows which lie between cloche
placements.
© John S Harrison, 1976