Growing Giant Pumpkins


Basic Cultural Practices
by Joel

SOIL PREPARATION: Minimum space is
approx. 300 sq. ft. per plant. Doubling this space or even more would be an
advantage, and will generally result in a larger pumpkins. Prepare the soil by
cultivation. Rake out larger stones, clumps of sod, etc. Incorporate into the
soil an inch or more of organic matter in the form of compost, aged manure,
peat moss, leaf mold, or rotted straw. Adjust pH to 6.0 – 7.0. Prior to
planting, broadcast a balanced organic or commercial granular type fertilizer,
and work into the soil.

STARTING SEEDS: Start seeds in 4″ peat pots about May
1 – 10, depending on local conditions. The tendency is to start too early,
which generally works against the grower. The plants will need warm soil and
settled weather to grow well. Seeds germinate best at 80 – 95 degrees F.
Germination will be slow and may fail at cool room temperature of 65 – 70
degrees F. A commercial propagation mat may be used, or a warm micro-enviroramt
found. Some examples would be:

Over a hot water tank,
In the oven with just the
light on,
In a cooler chest with warm bottles of water inside,
On a
mantle near stove, etc.

Excess heat is to be avoided and moistened pots must be
covered to avoid drying. Fill moistened peat pots with a good light potting
soil.. Seeds may be pre-sprouted between moist towels to 1/4″ root protrusion
and then planted one to each 4″ pot, rooted side down and 1/2″ soil over the
rounded end.

TRANSPLANTING: After 2 – 5 days, transplant the potted
plant to prepared growing beds. Protect young seedlings with properly
ventilated cloches or mini-greenhouses. Water as necessary to avoid heat stress
or wilting. When well established cloches my be removed. Wind protection my be
needed until plant is well anchored with vines on the ground. Mound soil over
vines at several leaf axils to stabilize plant and to encourage secondary
rooting from the vines. Water as needed, adding balanced soluble fertilizer to
water once per week. Control weeds with mulching, shallow cultivation, and hand
weeding as necessary. Remember, shallow roots may extend 4 ft. or more out from
perimeter of the plant.

FRUIT SET: The plant should blossom and set fruit
between July 1 and 20. Male blossom will appear first. Males are on long stems
with a rod like structure inside the flower which is coated with pollen. The
first open male flowers will generally be towards the center of the plant.
Female flowers are on a short stem, and have a small round yellow pumpkin
behind the flower. ‘The first female flower to open will be out from the center
of the plant on one of the vigorously growing vines. In the absence of bee
activity or to get an earlier set, the grower my hand pollinate a newly opened
female blossom with several of the fresh male flowers. Pick several newly
opened male flowers and tear away the yellow flower portion, exposing the
pollen bearing stamen . Leave part of the stem to use as a handle and gently
roll the pollen from the males onto the stigma in the center of the newly
opened female blossom. Depending on temperature and weather, this is generally
done from early to mid morning. Males from the same plant as the female to be
pollinated, may be used, (self pollinated). However-,: for best seed quality,
it is best to use males from a separate and not closely related plant, (cross
pollinated). The plant must be large enough to support a fast growing pumpkin,
therefore setting a fruit too early can have a negative result. The plant
should have a minimum of 100 – 150 leaves before a pumpkin is set.

PRUNING: To avoid rampant crossing vine growth, it is
advisable to trim and prune. Generally 3 – 5 primary vines are allowed to grow
out from the center of the plant in different directions. Side vines will
develop on each of the primary vines, alternately at each leaf.. These side
vines are allowed to grow, but are trained away from one another or pinched
back before they cross. These side vines would in turn produce their own set of
vines alternating at each leaf.. The third set of vines (tertiary vines) are
removed from each secondary vine when they are small or in the bud stage. This
results in a more open plant with better air circulation, which can help
prevent disease problems. A pumpkin can be set on each of these primary vine
structures. After 2 – 3 weeks select down to the best 2 pumpkins.

STEAM STRESS: Stress or tightness can develop
where the stem of the pumpkin attaches to the vine. The vine must lift off the
ground as the pumpkin grows taller. The vine will be rooted to the ground on
the under side. These roots must be severed several feet each way from the
pumpkin. Also as the pumpkin grows the shoulders of the fruit on the stem end
my contact the vine and create stress. This usually happens on the side away
from the center of the plant. The pumpkin may be moved very slowly 1 inch per
day until it is at a 90 degree angle to the vine, ( both shoulders equal
distance from the vine on each side of the stem). Never move the pumpkin early
in the morning as the stem and vines are brittle when it is cool. Adjustments
should be made a little at a time in the afternoon, starting when the pumpkin
is approx. basketball size.

It is helpful to have the pumpkin growing on the outside
of a curved section of the vine. In this way the pumpkin will have more room to
develop without pushing on it’s vine. The vine can be manipulated at the
time of fruit set, so the female blossom is on the outside of a curved section
of the vine. Stem stress symptoms can develop very quickly with a fast growing
pumpkin. The vines near the pumpkin should be checked frequently for tightness.
As the pumpkin grows taller, several feet of vine will be supported by the stem
of the pumpkin in both directions. It is helpful to support the weight of the
vine with blocks of Styrofoam or other material in order to take the stress of
the stem.

Shading: When the pumpkin is small, it will be shaded by
the leave of the plant. When the pumpkin grow larger, shade should be provided.
Shading reduces the aging stress of direct sunlight on the tender skin of the
fruit, and allows the shell to expand and stay flexible longer. Shading also
reduces the internal temperature of the pumpkin, reducing the threat of rotting
or splitting

Splitting or cracking: Each year many large pumpkins
crack or split while growing at a rapid rate. We walk a fine line. The grower
wants his pumpkin to grow as fast as possible in order to reach a large size,
and as a result may step over the unmarked line ( Sustainable growth curve).
Some seed stocks are more at risk than others, especially those with genetic
potential to produce pumpkins over 700 lbs. Some factors which may help to
avoid splitting include:

-Try to grow your pumpkin at an even moderate pace over
the entire season.
-Avoid large doses of fertilizer and water at critical
phases of the pumpkin growth cycle.
– High level of soil organic matter
and an even concomitant moisture level can help moderate and buffer against
growth spurts and stops.

Multiple fruits on a risky cultivator, may act as shock
absorbers, spreading a surge in uptake over two or there pumpkins. Minor cracks
can be managed by applying a fungicide and reducing water and fertilizer to the
plant. Stem splits often appear much worse than they are. The stem is hollow
and may split all the way through and tear into the flesh of the pumpkin a
small amount. Sometimes this releases the stress allowing the pumpkin to
continue to develop. Treat all wounds sites with fungicide, allow for good air
circulation, and keep the area dry. Occasionally a stem split or a surface
crack will continue to expand and deepen until the seed cavity is breached.
Once the seed cavity is exposed to the outside atmosphere, the pumpkin is no
longer a viable candidate for competition. No effort should be taken in regards
to plugging or patching, as the pumpkin will rot from the inside out

PESTS AND DISEASE: Problems vary widely from region to
region. In the Northwest, Giant pumpkin plants are relatively free of pest and
disease problems. Sometimes black aphids appear o the undersides of the leaves
later in the season. Aphids can spread the mosaic virus, but this has not been
a major problem for Northwest growers. It is best to contact an experienced
local grower for specific problems regards to insect or disease problems
effecting pumpkins or squash in you area. Where vine borers and cucumber
beetles are present, plants my need preventative action before pests are


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