The
following is written based on my experience with growing butternut
squash in the high deserts of southern Arizona, latitude 31.5 N,
elevation 4600 ft. where we have about 6” of rain July 1-September
15 and an alkaline mineral soil initially of pH 8.5 . If you grow them elsewhere you will
need 90 to 100 frost free days.
Butternut
squash prefer a slightly acid soil (pH 6.0-6.8) are heavy feeders
that require multiple applications of fertilizer through the growing
season. There is no need to plow an entire field to prepare for
butternut squash as you will be growing them in relatively small
mounds and the vines will spread out to a diameter of eight feet from
the mound over unimproved soil. If you have a good loam soil (40%
sand, 40% silt, 20% clay) all you need to add is a lot of organic
matter and a bit of fertilizer. If you have a clay soil, add fine
sand/silt. In the fall prepare the soil by marking out where you will
plant. Dig into the soil when it is moist, not wet, to a depth of 18”
and 18” diameter(2.6 cubic feet) one-half cubic foot (about five
gallons) of uncomposted manure, 8 tablespoons of fertilizer
(16-16-16) and five tablespoons of soil sulfur (to reduce pH to 6.5
from 8.5 like mine). Elsewise, use 1 tablespoon of sulfur per cubic
foot of soil to reduce the pH by one unit. Soak with water to allow
the fertilizer to dissolve and organic matter to rot over winter. Add
more water every few weeks if you live in a dry climate. If you
failed to prepare in the fall you can still plant in the spring but
you will need to use composted manure and the fertilizer (16-20-0)
may burn the roots unless you add it at a depth of 3” below the
seeds. To make the digging to 18” and mixing the amendments easier,
place half the soil in a wheelbarrow with half the amendments and mix
those there while adding the other half of the amendments to the hole
as you dig to 18”. My soil stops at 12” when I hit caliche but I
still get a good crop.
In
the late spring (May 15 here) form mounds and a bury a water pail
(see last page for description) to 1” depth in the center of the
mound. Plant three seeds at 5” radius from the center of the mound
at a depth of 1/2” to 1”. To locate the seeds, mark a circle of
12” diameter by using the open end of a five gallon pail or use the
suggested screened shelter (see last page for description) and place
the seeds 1” to the inside of that mark and evenly spaced around
the perimeter. Add water to the pan and over the entire mound and
keep the ground moist until the seeds sprout. Cover the seeds with
the screened shelter to protect from birds and rodents. To speed
germination cover the shelter with translucent plastic. Remove the
plastic after the seeds have risen. If all the seeds have not risen
in two weeks replant those not risen. Replace the wire shelter. Once
the plants are too large for the shelter remove it.
After
the plants are developed with foot long runners, allow the first two
inches of soil to dry before adding a total of 1” to 2” of water
per week. This is enough so the soil will be moist at one foot (one
gallon of water spread over 18” diameter is 0.9” of water). The
water amount and frequency will depend on the temperature. During the
hottest days you may need to apply one quart of water every day to
reduce wilting. Allowing a plant to wilt will damage the fruits or
they will not set fruit at all. If you can provide shade in the
afternoon during the hottest time of the year do so. If you have many
mounds, watering is easiest with a simple irrigation system. If you
use such a system, water at a cool time of day so the water coming
out onto the plant roots is cool. If you water during the brightest
time of the day the water may exit at a temperature such that it
scalds the roots even if the air temperature is moderate. If you
scoop the common soil away from the outside of the mound to a
distance of three to four feet you will form water harvesting swales
that capture rainwater. This should be done before the vines
interfere. Continue to water if there is not sufficient rain. As the
vines spread outward it is possible to encourage additional roots to
develop along the runners by pinning down the vines at the joint
points. A light sprinkle of fertilizer in the swale area will improve
its fertility. Add one-quarter tablespoon of fertilizer to the water
pail every two weeks after the first blossoms appear. Each fall add
more organic material and if you use uncomposted organic matter use
triple-sixteen fertilizer.
When
the vines reach four feet in length pinch off the ends to encourage
lateral vines to develop. If you want many fruits harvested gradually
over several months you can plant seeds every other week, in
additional mounds up to mid July (mid August assuming warm weather to
November 15). Space mounds at eight feet. Once a vine has three to
five fruits (depends on the variety), pinch out any new blossoms or
fruits to force food into the remaining fruit.
If
you do not have good soil you can grow a single squash vine in a five
gallon pail with drain holes in the bottom. The bucket sides need to
be sheltered from the sun otherwise the soil may overheat. Use a high
quality potting soil that has a slow release fertilizer.
Harvest
the fruits at 90 to 100 days when a fingernail will not indent the
skin or the stem begins to turn brown. Harvest the fruit by cutting
the stem, don't break off the stem from the fruit. Remove all fruits
before a frost as it will damage them and the shelf life will be nil.
Separate all damaged fruits from the others. It is ideal to cure the
fruit in the field by storing at 80-85 Fahrenheit and 80% relative
humidity for 10-14 days in a plastic shelter to retain the moisture.
Long term storage should be at 50-55 F and 50-70% humidity and will
keep at least three months. If not cured, let the fruits stand on the
shelf for at least two weeks to come to full sweetness before
cooking.
Vine
borer worms are the greatest pest. Look for damage to the vine
indicated by a tan color sawdust where the worm has entered. Look for
damage every couple of days starting in late June. The only thing I
can recommend to kill the worm is to use a needle to pierce the worm
hidden within the vine. Pierce along the length multiple times one
inch on other side of the damage area. I am not sure what type of
insecticide to recommend but if you use one apply it in the evening
when the blossoms are closed and the bees are in their hives. It is
recommended to dig new mounds every year as the vine borer worms will
lay their eggs in the soil and that pest problem will increase. You
can reuse the old soil if you pour into each mound one gallon of
non-sudsy ammonia and cover with a patch of plastic to slow its
evaporation. The ammonia will fertilize the soil and sterilize it of
parasites.
Powdery
mildew fungus will attack the vine leaves in August. Spraying with
fungicide is only slightly effective and very difficult to do as both
the tops and undersides of leaves need to be sprayed. As the old
leaves are attacked and die, new leaves will begin to sprout and the
additional roots along the length of the vine will help to sustain
the plant. Hopefully the fruits will be well along in development
before the fungus destroys the vines.
If
you have rabbits (and you will) surround the squash patch with at
least 18” tall 1” mesh chicken wire with at least 4” draped on
the ground outside the enclosure. A small enclosure needs only half
inch rebar to support it and bailing wire to attach the screen to the
rebar. If you have havalina or steers you will need to use T-posts
and stands of barbed wire. If you use 24” wide chicken wire, run
one strand near the ground, another strand at 20” from the ground
to support the top of the chicken wire, a third strand at 29” (for
havalina) another strand at 38” and at least one more strand at 48”
(0”, 20”, 29”, 38”, 48”). If you use 18” chicken wire set
the strands a 0”, 14”, 22”, 34”, 48”. Attach the chicken
wire to the strands with bailing wire every foot. Otherwise, use
field fencing with chicken wire at the bottom.
Weeds
can be partly controlled by watering the area where you will plant in
the early spring to encourage the seeds to sprout which can then be
sprayed with glyphosate herbicide (typical brand name Roundup). You
can continue to spray until the vines seeds have sprouted. If you
spray beyond that time take great care to keep the spray from
drifting onto the young plants. After that you will need to pull or
use a hoe to control weeds.
A
12” diameter shelter can be made with 37 ½” of plastic
edging overlapped by 1” and held together with three short gold
screws. Cover with window screen 14” x 14” (consider using
aluminum for durability as creatures can eat their way through
fiberglass screen) and hold in place with heavy 3/8“ staples at
four places around the perimeter. Bend the staples over. I suggest
using the solid plastic edging 4 ¾” X 1/8”.
Plastic
water pails can be made from the bottoms of one gallon milk or
bleach containers to help maintain a good water well and distribute
the water. Cut the bottom off the container so the sides are 1 1/2”
tall. Puncture the bottom with a nail or thumbtack in a dozen or more places so the water will drain into the soil. Set the
pail at the center of the mound and sink 1” deep into the ground. A
6” x 6” x 1 1/2” pail will hold about one pint.
