Page 16 - Simply Vegetables Spring 2025

Watermelon Karobi prick one out, pots take up valuable space,
initially. Prick out the seedlings when
true leaves are barely visible in between
the cotyledons, I prick out into 3”x3” (7.5
*7.5cm) pots, this is when I go over to my
own mix, which is as previously mentioned
for 10/15 litre pots, the addition of perlite is
optional. It is important when watering to
use tepid water, this means taking a kettle
of water down to the greenhouse to warm
up the contents of the watering can, I tend
to get nagged for this, ‘where’s the kettle
gone?’ False prophets tell us that leaving a
watering can full of butt or tap water in the
greenhouse will warm up, my experience
is, it may take days, possibly a week or
more to get to around 70 degrees F (21
˚C), depending on the amount of sunshine.
The pots require to be left on the heated
propagator until the great day arrives; this
is best done during a forecasted prolonged
sunny spell - difficult, the longer the better.
In the past I have the 10/15L pots filled up
and in position with twine buried in the
bottom of the pots or trapped underneath.
I have scrapped the binder twine because
it disintegrates into fibres, I now use some
lime green coloured twine from B&Q. If
you are growing a small number of plants
and the weather plunges back to Winter,
put the pots back on the propagator. If you
over water them, you will have to provide
some urgent care anyway – bottom heat is
everything in our climate if things start to
go pear shaped – well not melon shaped.
Once planted out, tie up the twine to the
Watermelon, Moon and Stars
16 Simply Vegetables
roof of the greenhouse / polytunnel and
as the leader grows away wrap it around
the twine, normally the plant produces side
shoots that also require wrapping around
the twine. It is mostly these side shoots
that produce female flowers. You can nip
the leader to accelerate the side shoots,
but all this uses up ‘seasonal time’.2024
was notable for a dearth of female
flowers, it was also notable for a dearth of
bumble bees which I rely on to pollinate
the female flowers, plants produce both
male and female flowers, so pollinating
insects require to crawl over both sexes
to get a fruit set. Unlike cucumbers where
we don’t want fertilized female flowers
as this produces bitter fruit, melons and
watermelons will not set fruit unless the
female flowers are fertilized. I normally
leave pollination to the bees, last year
it was some time before the realisation
struck that the female flowers were dying
off because they were unfertilized. It then
became a daily ritual around mid day or
when the temperature shot up to nip off
a male flower, pull off the petals and rub
against the sexual parts of the female
flower. If you want to save your own seed,
bear this in mind, most modern varieties
of melon and watermelon are F1, so saving
seeds will not produce another fruit like the
parent. Watermelons will not cross fertilize
melons and the other way round. So,
one open pollinated melon will not cross
pollinate an open pollinated watermelon,
simply meaning non F1 melons will not
Watermelon tasting at Medwyn
William's Masterclass Weekend,
Royal Victoria Hotel, Llanberis
Watermelon, Blacktail Mountain
cross pollinate a non F1 watermelon
and the other way around. You can take
advantage of this and grow one variety
of each in the same’ house’ and save the
seed. The female flowers have mini fruitlets
behind the flower, this starts to swell once
fertilization has taken place. When the fruit
reaches the size of a golf ball it is time to tie
in the growth that the fruit is on. When the
size of a grapefruit, support it with a melon
net, hammock fashion. If you want to show
it, try and leave the dead flower attached.
Handmade melon nets can be bought off
the ‘net’, net to net you might say, these
look very professional.
THE VARIETIES
The readily available varieties of
watermelon from seed suppliers are dark
green and generally F1s, most melons are
F1s also. If you want something more exotic
and exciting, then American firms like
Baker’s Creek have a reasonable choice.
Three interesting varieties of watermelon
that I grew in 2021/2 were, Moon and Stars,
Cream of Saskatchewan and Kurobe. I
grew several varieties of melon that year
only one, Petite Gris de Rennes had any
real sweetness; I assume that the seeds I
bought were a result of cross pollination
with other varieties that is they were not
grown in isolation. The grafted melon plants
I grew last year were also not very sweet
either, (bring back the variety Sweetheart),
grafted plants tend to be more vigorous
and less prone to the effects of over-
Somewhat advanced melon
and watermelon seedlings