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
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 areas
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 that 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
Scallop: Peter Pan, Scallopini, Sunburst (yellow scallop). For trial: Early White Bush Scallop.
Specialty Oriental vine crops:
Vegetable Sponge, Dishcloth gourd, Sponge gourd (Luffa sp.). These may
be used for cooking when immature (approximately 75 days), or allowed to mature for the fibrous
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 number 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.
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.
A soil test is the most accurate guide to fertilizer requirements. The
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
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
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
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
ammonium nitrate) and chlorinate the system once a month with a l0-50 ppm
Chlorinate more frequently if the flow rate decreases.
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
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 irrigation
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
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
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
American AgriFabrics, Alpharetta, GA. Phone 770-663-700, fax: 770-663-7690, email: firstname.lastname@example.org.
Ken-Bar, Inc., Reading, MA. Phone: 800-336-8882, fax: 781-944-1055, email: email@example.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
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 spacing. 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
STORAGE (Quoted or modified from USDA Ag. Handbook 66 and other sources)
Processing 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
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
damage, but such exposure should be avoided as summer squash is chilling
summer squash longer than 4 days at 32 F will cause chilling damage and more
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.
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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