I decided to plant some marrow seeds this year. I planted 5 pairs of
seeds and sacrificed the rubbish ones for the greater cause. I now
have 2 plants, one is small but has a lovely marrow growing out of it,
the other is massive but every time I think it's going to sprout a
marrow they just shrivel up and die.

My questions a

1 The marrow that is growing is a bit of a funny shape and doesn't seem
to be filling out to a proper marrow shape (it's really narrow at the
top). Is there anything I need to do (other than plenty of water) to
help him along?

2 Is it possible that the massive plant is taking up all the water and
the good bits from the soil? Is it worth considering culling it to
give my smaller plant with a marrow a better chance of full marrow
shapeness (Ok so I might have made up a word there but you get the
idea).

If in doubt just snip off the big marrow and let it grow another.
I always end up planting too many "courgette" plants, and they produce too
many courgettes for us to eat, so some grow into big marrows (a couple of
feet long), It breaks my heart to waste food, and there is only so much
marrow soup a person can eat, so I end up just chopping most of these off
and putting them into the compost bin to encourage the plants to produce
more courgettes.
Provided the plants have plenty of sun, water and nutrient in the form of
well rotted manure or fertiliser (I use Miracle Grow) they just keep on
producing an endless supply of courgettes and marrows all season long.
Some do grow a bit misshaped, but they are usually OK for cooking with.
There are occasionally some with end rot - I think this is something to do
with getting water into the flower so try to avoid wetting the flowers
during watering. Just pull any like this off.
Some varieties seem prone to disease, I think it is some form of cucumber
mosaic virus. Courgette plants should be vigorous growers, if you get one
that isn't then it may be diseased, in which case pull it up and destroy
it - do not compost it or the virus may be re-introduced next year.
--
David
.... Email address on website http://www.avisoft.co.uk
.... Blog at http://dlts-french-adventures.blogspot.com/