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GREEN-Seeds.com
vegetables & herbs
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Zucchini and Summer Squash
Cucurbita pepo
 Summer squash is defined
as fruit of the Cucurbitaceae family that are consumed when immature, 100%
of the fruit of which is edible either cooked or raw, once picked is not
suited for long-term storage, has a soft rind which is easily penetrated,
and the seeds of which would not germinate at harvest maturity: e.g. Cucurbita
pepo (i.e. crookneck squash, straightneck squash, scallop squash, zucchini,
vegetable marrow).
Other genera in the
Cucurbitaceae family whose fruit may be consumed when immature include
Lagenaria spp. (i.e. hyotan, cucuzza); Luffa spp. (i.e. hechima,
Chinese okra); Memordica spp. (i.e. bitter melon, balsam pear, balsam
apple, Chinese cucumber); and other varieties and/or hybrids of these. Production
practices for all these species are similar to those described below for
summer squash.
VARIETIES (Days to harvest
are given for the Willamette Valley; warmer ares subtract 10-15 days).
Note: Only dark green
and yellow types are used for processing.
Advances in biotechnology
have resulted in genetically engineered squash with high levels of resistance
or immunity to some viruses for which no resistance has previously been
available. The first of these is a summer squash called Freedom II which
has been released by Asgrow Seed Co. after completion of extensive field
testing. This squash has shown resistance to zucchini yellow mosaic virus
and watermelon mosaic virus 2 in Oregon. For information on seed availability
contact Asgrow Seed Co. Genetically engineered zucchini lines are also available.
Zucchini
(approximately 60 days):
Dark Green: Ambassador,
Aristocrat, Black Jack, Dividend, Elite, Onyx, Raven, Revenue. For trial:
Black Magic, Green Magic, Seneca Milano, Zuchlong.
Medium Green: Ambassador,
Embassy (open plant, mostly spineless), Spineless Beauty (spineless stems).
For trial: Storr's Green, Senator, President.
Gray Green: Greyzini,
Caserta (bulbous - for specialty markets).
Yellow: Gold Rush, Golden
Dawn II and III. For trial: Aztec, Eldorado, Gold Finger, Goldbar, Rocky
Gold.
Other
Summer Squash (approximately 55 days):
Yellow Straightneck:
Sunbar, Superpik, Multipik, Enterprise, Golden Girl.
Yellow Crookneck: Goldie,
Sundance. For trial: Supersett, Cracker, Tara, Early Golden, Sunrise, Dixie
Hybrid. " Genetically transformed" yellow crookneck squash for trial: Freedom
series II and III.
Note: Jersey Golden,
Sunbar, Superpik, Multipik, and Supersett are squash varieties with a gene
for precocious yellow fruit. These start out yellow rather than green, and
may be used for yellow baby squash. This character also provides some degree
of tolerance to WMV II virus (watermelon mosaic virus II) by masking mosaic
symptoms for a short time allowing several harvests before fruit damage
becomes severe. Also, fruit stems are yellow instead of green.
Scallop: Peter Pan,
Scallopini, Sunburst (yellow scallop). For trial: Early White Bush Scallop.
Specialty
Oriental vine crops:
Vegetable Sponge, Dish-cloth
gourd, Sponge gourd (Luffa sp.). These may be used for cooking when immature
(approximately 75 days), or allowed to mature for the fiberous spongy tissue
(approximately 115 days): Angular types (Luffa acutangula): San-C, Ping-Ann.
Cylindrical types (Luffa aegyptica): Cylinder, Seven Star, Seven Beauty.
These produce higher quality sponge fiber.
Balsam pear, Bitter
melon (Momordica charantia; approximately 75 days): Green: Known-You Green.
White: Moon Shine, Known-You No.2
SEED AND SEED TREATMENT
Zucchini
and most summer squash seed numbers approximately 200-300 per ounce. Use
fungicide-treated seed. Summer squash seedlings are susceptible to damping
off and decay when soils are cool and wet.
SOIL TYPE AND TEMPERATURE
Zucchini grows best
on fertile, well-drained soil supplied with organic matter. The ideal pH
for zucchini growth is between 6.0 to 7.5, but it will grow on soils with
a pH of up to 8.0. Consult a soil test for fertilizer and liming recommendations.
The minimum soil temperature
required for germination of zucchini is 60 F, with the optimum range between
70 and 95 F.
SEEDING
Zucchini
are usually direct-seeded when all danger of frost has passed. In western
Oregon planting begins in early May and extends to mid-July. Stagger plantings
10 to 14 days apart to maintain a continuous supply of high quality product.
Use 36 to
40-inch spacing between rows with plants 18-36 inches apart within the
row.
FERTILIZER
A soil test
is the most accurate guide to fertilizer requirements. The following recommendations
are general guidelines:
The optimum
pH range is 5.8-7.0.
Apply 10
tons/acre of manure in the spring when available.
Western
Oregon - At time of seeding, band 2 inches to the side of the seed
and 3 inches deep the following:
Nitrogen:
50-70 (N) lb/acre. (Sidedress with an additional 30-60 lb N per acre when
plants begin to flower).
Phosphate: 115-125 (P2O5) lb/acre.
Potash: 50-100 lb K2O/acre (broadcast and disked-in prior to seeding).
Eastern
Oregon - At time of seeding, band the following:
Nitrogen:
40-60 (N) lb/acre
Phosphate: 115-125 (P2O5) lb/acre
Potash: 50-100 lb K2O/acre (broadcast and disked in prior to seeding).
Sidedress
with 25-50 lb N/acre, or where mulching and trickle irrigation are practiced,
N can be fed through the trickle irrigation system at 15-25 lb/acre when
the vines begin to spread. To prevent clogging or plugging from occurring
use soluble forms of nitrogen (urea or ammonium nitrate) and chlorinate
the system once a month with a l0-50 ppm chlorine solution. Chlorinate
more frequently if the flow rate decreases.
IRRIGATION
Summer squash roots
to a depth of 3-4 feet. Maintain soil moisture above 60% of the soil water
holding capacity. In western Oregon, 12-15 inches of irrigation may be necessary.
Approximate summer irrigation needs for the Hermiston area have been found
to be: 3.5 inches in May, 5.0 in June, 7.5 in July, and 7.0 in August. It
is important to regulate irrigations properly to avoid excessive moisture
or water stress. Research has shown that the use of drip irrigation under
black plastic mulch is superior to sprinkler irrigation with black plastic
mulch. Yields usually increase dramatically.
See also
the OSU
Irrigation Guide for this crop.
FLOWERING AND POLLINATION
Zucchini and summer
squash plants bear separate male and female flowers on the same plant (monoecious).
Only the female flowers set fruit. Bees transfer pollen from male flowers
to female flowers, making fruit set possible.
It is recommended that
one honey bee hive should be introduced for every 1 to 2 acres during the
blooming period since native bee populations may not be adequate, or may
not coincide properly with the blooming period. For more information on
beehive quality and pollination, see the OSU Publication PNW-245 Evaluating
Honey Bee Colonies for Pollination, A Guide for Growers and Beekeepers.
Questions come up about
cucumbers, melons, gourds, and summer and winter squash, crossing and affecting
the eating quality of one vine crop or another. This is NOT a problem. Intercrossing
is only a problem when seed is saved for replanting, in which case squashes
of the SAME species need to be isolated for crop purity. Cucurbits of different
species do not intercross sufficiently to create problems for seed producers.
For information regarding
cucurbit seed production, see the publication "Cucurbit Seed Production
in the Pacific Northwest," PNW 226, which can be obtained from the Cooperative
Extension Services of Oregon, Washington, and Idaho.
GROUND MULCHES AND ROW COVERS
Black plastic ground
mulch is sometimes used in the production of summer squash to enhance yield
and earliness. It controls weeds, may increase soil temperature, conserves
moisture, and protects fruit from ground rots. For black plastic mulch to
increase soil temperature, it is imperative that the soil surface be smooth
and that the plastic be in close contact with the soil. This can only be
achieved by laying the plastic with a machine designed and properly adjusted
for this task. Clear plastic mulch is very effective at transferring heat
to the soil, but does not control weeds.
A new generation of
plastic mulch films allows for good weed control together with soil warming
that is intermediate between black plastic and clear film. These films are
called IRT (infrared-transmitting) or wavelength-selective films. They are
more expensive than black or clear films, but appear to be cost-effective
where soil warming is important.
Plastic, spunbonded,
and non-woven materials have been developed as crop covers for use as windbreaks,
for frost protection, and to enhance yield and earliness. They complement
the use of plastic mulch and drip irrigation in many crops. Some sources
of these materials and information on their use are:
American AgriFabrics,
Alpharetta, GA. Phone 770-663-700, fax: 770-663-7690, email: dan@agrofabric.com.
Ken-Bar, Inc., Reading, MA. Phone: 800-336-8882, fax: 781-944-1055, email:
kenbarinc@msn.com.
Non-woven or spunbonded
polyester and perforated polyethylene row covers may be used for 4 to 8
weeks immediately after transplanting or seeding especially for summer squash
(such as zucchini) where the added cost could be recovered through increased
early season prices. Covers should be removed when plants begin to flower
to allow proper pollination. Row covers increase heat unit accumulation
by 2 to 3 times over ambient. Two to four degrees of frost protection may
also be obtained at night. Soil temperatures and root growth are also increased
under row covers as are early yields, and in many cases total yields.
A new insect exclusion
cover (Agryl P-10), is very light weight, offering season-long insect vector
exclusion without affecting canopy temperature very much. It is recommended
for trial in situations were conventional virus vector control procedures
are inadequate, and market economics justify. It must be frequently manipulated;
removed to allow bee pollination, and re-applied as necessary to exclude
aphid virus vectors.
HARVESTING, HANDLING, AND STORAGE
The University of California-Davis
has a file on Minimal
Processing of Fresh Vegetables that discusses film wrapping and other
topics.
In the Willamette Valley,
summer squash and zucchini is harvested for processing from July 7 to September
20. The prime harvest period is from July 25 to August 25. Fresh-market
plantings may be harvested up to two weeks earlier than this when transplanted
on mulch and rowcovers are used. Fields are normally harvested every 2 to
3 days in warm weather. Cut fruit from the vine, leaving a piece of stem
with the fruit.
Yields of zucchini for
processing of approximately 20-25 tons/acre can be obtained form multiple
harvests with zucchini planted at 24x36-inch spacings. Zucchini and summer
squash can be harvested anytime fruits reach the desired size but before
they forms hard seeds or rinds. For processing, zucchini is graded by diameter:
Grade #1: 1"-2"; #2: 2"-2.25"; #3: 2.25"-2.50"; anything over 2.5" is rejected.
Fresh market yields
are approximately 150 to 300 cwt/acre depending on the number of pickings.
When using appropriate plasticulture techniques, yields of 360 cwt/acre
have been reported. Crook-neck, straight-neck and zucchini should be 1.25
to 2 inches in diameter and zucchini and straight-neck squash 7 to 8 inches
long. Scallops should be 3 to 4 inches in diameter
STORAGE (quoted form USDA Ag. Handbook # 66):
Processsing squash is
not normally stored. For fresh market, store zucchini and summer squashes
at 40 to 50 F and 95% relative humidity. Summer squashes, such as Yellow
Crookneck, Yellow Straightneck, White Scallop, Zucchini, and other soft-skin
types are harvested at the immature stage for best quality. They are quite
perishable, as the skin is tender and easily wounded in handling. Small
fruits are more desirable than large ones because they have a more tender
flesh and a slightly sweet flavor.
Normally they should
not be stored except long enough to accommodate normal marketing delays
such as holidays and weekends. They can be held 1 or 2 days below 40 F with
no discernible damage, but such exposure should be avoided as summer squash
is chilling sensitive. Holding summer squash longer than 4 days at 32 F
will cause chilling damage and more rapid deterioration.
The recommended temperature
range is 41 to 50 F with 95% relative humidity. The storage life of summer
squash is only 1 to 2 weeks. If storage of yellow squash extends beyond
a week and distribution is involved after removal, storage at temperatures
of 45 to 50 F is best. The storage period at 45 to 50 should be limited
to 2 weeks or less. Recent research has shown that 41 F is best for Zucchini
squash stored up to 2 weeks. Storage in low-oxygen atmospheres was of little
or no value for Zucchini squash held at 41 F.
PACKAGING
Zucchini and summer
squash are usually packaged in 21-pound (5/9 bushel) crates and cartons;
24 to 28-pound cartons and L.A. lugs; 18 to 22- pound three-quarters lugs;
41-pound (1-1/9 bushel) crates; or 21-pound (l/2 bushel) baskets and cartons.
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Green - Seeds Co., Ltd.
81/10B Ho Van Hue Street, Phu Nhuan District, Ward 9, Ho Chi Minh City, Vietnam
Tel: +84 (8) 847 6901 - Fax: +84 (8) 844 1392 - Email: info@green-seeds.com
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