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Original Post-We've got weed issues in our winter squash and are
considering harvesting the squash early to make it easier to take care of
the weeds. This would be 3-4 weeks earlier than normal.  We have space to
spread them out in a greenhouse.  Does anyone have experience with
harvesting a crop this early?  Will they all still ripen fully? How does it
affect the taste and texture?

Responses
1. Depends on what you mean by "early" - if butternut has not started to
turn tan, I wouldn't do it.  There is a fairly defined tipping point for
each type, but any pronounced green in any of the major squashes is a
strong indicator that the plant has not accumulated all the sugars it
needs, and won't have the capacity to heal any harvest wounds inasmuch as
the skin is still immature.  You could always mow it post-harvest and bare
fallow that field next summer.

​
2.​ I
n a word, don't! Only pumpkins will do that, unless the squash is so close
to ripening they may rot instead

​3.
I have never tried it, but I think unfortunately it is important for them
to ripen on the vine. Here is an article that I found helpful:
http://us6.campaign-archive1.com/?u=5b78824b88&id=62bb673b16&e=b52011428c

​4.
Read the following article from Brent Loy’s work.  It all comes down to
variety and when fruit set occurred.  Some varieties will be fine with
harvesting early, other’s should definitely NOT be harvested early.

--
​Brent Loy, Plant Biology, University of New Hampshire, Durham, NH

There are three major species of squash that are grown worldwide –Cucurbita
pepo, C. maxima, and C. moschata. The species C. moschata includes calabaza
or tropical squash, round to oval pumpkins grown in the Midwest for pie
processing, and the popular butternut varieties, highly regarded for
excellent shelf life. The species C. maximaincludes the large show
pumpkins, Golden Delicious type processing squash, Hubbard varieties, and
buttercup/kabocha varieties, the latter esteemed for their exceptional
eating quality. Lastly, C. pepo is the species having the greatest
variation in type, including hard-shelled gourds, summer squash, ornamental
pumpkins, and squash. In North America, acorn is the most popular C.
pepo squash,
but striped Delicata and Sweet Dumpling varieties are known for having good
eating quality. Cultural methods for the above species of squash are
similar; however, harvesting schedules and post-harvest handling may vary
considerably.

Components of eating quality:

People differ in their preference for flavor components and degree of
moisture in squash. Nonetheless, connoisseurs of squash usually prefer a
relatively dry squash that has a pasty, slightly moist texture after
cooking and a high level of sweetness. High sugars not only contribute to a
desirable sweet taste, but also mask undesirable flavor components
associated with certain varieties and that may be acquired during cooking.
Sugar levels can be estimated easily by freezing small tissue samples and
then pressing a drop of clear juice from the thawed samples, and measuring
soluble solids in the juice with a hand-held refractometer. Relative sugar
content is given in units of percent soluble solids (or oBrix). Soluble
solids levels of 10% are passable, but generally levels of 11% or greater
are considered necessary for good eating quality in squash. The pasty
texture of squash is attributable to starch. At harvest starch comprises
about 45 to 55% and sugars about 10 to 15% of the dry matter of squash, so
a squash with high dry matter also has high starch content. Other minor
constituents of the dry matter (dried flesh) are proteins, fats, cell wall
constituents (crude fiber), and minerals (called ash). Starch provides
substrate for conversion to sugars during the latter stages of squash
maturation and during subsequent storage. Squash with low dry matter,
generally less than 16%, lack sufficient starch levels to produce a
combination of pasty texture and degree of sweetness for acceptable eating
quality. In varieties with low dry matter, starch is depleted during
storage by conversion to sugars, and the texture of the squash becomes
excessively moist and fibrous.

Stages of squash development:

To understand how harvest period, storage and variety selection can affect
eating quality, it is necessary to understand basics of squash development
and maturation. This process includes not only the development of flesh
quality, but also the effect of seed development on maintaining flesh
quality. A general outline of development is shown in Figure 1.
Small-fruited varieties of squash, such as acorn, reach close to full size
within 15 to 20 days after pollination (DAP).
Dry matter and starch accumulation begins shortly after fruit set, but is
most rapid between 10 and 20 DAP and reaches a maximum content at 30 to 35
DAP. In acorn and other related squash​ in Cucurbita pepo, sugar levels
begin to increase rapidly between 25 to 30 DAP, and usually reach a maximum
between 50 to 60 DAP (Figure 2). Increases in sugar content and maximum
sugar content will vary among varieties. In varieties with low dry matter,
sugar levels usually accumulate slowly and maximum levels are lower than in
varieties with high dry matter and therefore higher starch content. In
kabocha and buttercup squash (Cucurbita maxima) sugars will usually reach
acceptable levels (11% soluble solids) between 60 and 70 DAP. In butternut
squash, the situation is more extreme. Soluble solids levels are often only
8 to 9% at 60 DAP, and storage at room temperature for 25 to 40 days may be
necessary to elevate sugar levels.

Even though the dry matter of the flesh (mesocarp tissue) peaks at about 30
days after pollination, seed development takes much longer. If a squash is
cut open at 20 DAP, the seeds appear to be full size. This is because the
seed coat, the leathery covering over the embryo, reaches full size by this
time. But if the seed is cut in half, the embryo is actually barely visible
at this time, being about an eighth to a quarter of an inch in length. The
embryo expands rapidly and largely fills the seed coat cavity by 35 days
after pollination. However, dry seed biomass (seed fill) continues almost
linearly until about 55 DAP. Thus, a squash fruit can be considered to
reach full maturation when seed development is complete at about 55 days
after pollination.

Post maturation changes occur in stored fruit. There is a progressive
moisture loss during storage, so fruit fresh weight decreases. Respiration
consumes carbon in the form of sugars, and starch conversion to sugar
continues to replace the sugar consumed by respiration. The eating quality
of squash varieties with low sugar at harvest will initially be enhanced in
storage because sugar levels increase. Eventually, however, long storage
time will deplete starch levels to a point where the texture of the squash
is compromised.

Harvest period and eating quality:

Because seed maturation is not complete until 7 to 8 weeks after fruit set,
it is important to maintain a healthy plant until at least the earliest
harvest date or about 50 days after fruit set. This insures a continuous
supply of photosynthates (organic carbon source produced from
photosynthesis) to the developing fruit. Seeds are the primary sink for
assimilates such as sugars and nitrogen compounds, so if photosynthesis is
impaired by disease or insect feeding, nutrients required for the
developing seed are withdrawn from the flesh, depleting starch levels and
lowering eating quality. If fruit are picked immature, seed development
continues in stored fruit at about the same rate as in fruit left on the
plant. Seed development in an immature, detached fruit occurs at the
expense of depletion of nutrient reserves in the fleshy tissue, thereby
reducing dry matter (mostly starch) and lowering eating quality.

Because fruit and seed development are similar in all three species of
squash, their recommended harvest periods are somewhat similar. However,
with kabocha or buttercup varieties, it is actually desirable to harvest
them before complete seed maturation, about 40 to 45 days after fruit set
when the fruit are still bright green. New Zealand studies indicate that
rind hardness is maximum around 40 DAP, so fruit harvested at 40 days
suffer less damage to the fruit surface, and in turn, less chance for
disease entry during subsequent storage, than fruit picked during later
stages. Kabocha squash are also susceptible to sunburn damage as leaf
canopies senesce (die back), resulting in changes in rind color from green
to brownish and bronze colorations. Extreme sunburn and heat damage can
cause the rind to turn white. Therefore, it is best to harvest the squash
before fruit are exposed to direct sun as the vines die down. Kabocha
squash have a high dry matter content, usually 20 to 30%, and a small seed
cavity, so that any seed maturation following harvest has a minimal effect
on depleting starch
[image: page3image30848]

reserves in the flesh. If kabocha squash are harvested between 40 and 50
DAP, they will need to be stored for 10 to 20 days at room temperature to
allow for elevation of sugars to acceptable levels for good eating quality.

Acorn squash present the most difficult problem with respect to determining
harvest time. Most modern acorn varieties not only reach near full size within
two weeks after fruit set, but also develop a dark green to black mature
color. For this reason, acorn squash harvested for the large wholesale
markets are often picked immature. Immaturity can be easily recognized by
observing rind color on the ground side of the squash. Immaturity is
indicated if the ground color is light green or light yellow rather than
having the dark orange coloration of mature fruit. If these immature squash
are sampled, they are found to have low sugar levels and may have low
starch levels as well. If such immature squash are left in storage, sugar
content will increase, but starch will be depleted both by respiration and
remobilization of sugars from the flesh to the developing seed. This has a
negative impact on eating quality. The problem of poor quality in
prematurely harvested squash is further exacerbated because many commercial
acorn varieties and many of the newer striped varieties have inherently
(genetically determined) low dry matter and starch levels.

In contrast to acorn squash, butternut squash do not reach their
characteristic tan color until relatively late in development (35 or more
days after fruit set), so premature harvest before starch accumulation and
seed fill are complete is generally not a serious problem. The biggest
problem in butternut squash is that sugar levels are usually not sufficient
for good eating quality when squash are harvested, especially in parts of
New England where the growing season is marginally short for butternut
squash. This year, for example, we harvested fruit from six breeding lines
and three open pollinated cultivars, Ponca, Puritan and Waltham butternut,
at 60 to 62 days after pollination. Levels of soluble solids were mostly 8
to 9%, with a few as low as 7%. In an adjacent trial, experimental hybrids
and some standard varieties were harvested and sampled between 67 to 78
days after fruit set. Other than one sample at 10.6% soluble solids, the
levels ranged from 7.4 to 9.8%, well below the 11% or higher preferred for
good eating quality. To increase sugar levels sufficiently for satisfactory
consumption, butternut squash harvested at 55 to 60 DAP may have to be
stored at room temperature for another 30 or more days. Can this process by
accelerated? Studies with kabocha squash have shown that storing squash for
short periods at high temperatures (ca. 80-85 oF) can accelerate
post-harvest increases in sugar levels. In preliminary studies at UNH, we
harvested butternut squash at about 55 to 60 days after pollination and
stored squash for three weeks in a greenhouse where daytime temperatures
ranged from 75 to 85 oF. Out of 28 fruit sampled, 20% had soluble solids
between 10 to 11% and 80% had soluble solids between 11 and 14%. Eating
quality ranged from good to excellent for most samples. It would have been
preferable to store the squash under shaded conditions, because some light
discoloration of the rind was observed on some fruit.

For long term storage, temperatures between 50 and 60 oF and relative
humidity (RH) between 50 to 70% are recommended. Higher temperature and
lower humidity result in more weight loss of fruit and can accelerate the
development of hollow neck in butternut squash. The higher temperature also
increases respiration rate and loss of dry matter. Even though some squash,
particularly butternut varieties, may store reasonably well beyond three
months without

disease problems, the texture and overall eating quality of the squash will
be compromised after long storage.

How do you determine when to harvest?

Most acorn varieties are semi-bush and set most of the crown fruit within
about a week period. Modern hybrids tend to produce some female flowers
before male flowers appear and these usually abort unless there are other
varieties of C. pepo nearby supplying pollen. But this is shortly followed
by a period of both male and female flowering and fruit set. Some later
fruit sets will occur on runners, but these fruit are usually undersized
and lack quality, and so should not be harvested and sold. These late set
fruit are a drain on photosynthates, and pruning these fruit off of the
plant can actually increase quality of the crown set fruit.

By noting the initial flush of male and female flowers on a semi-bush
squash cultivar, a grower can estimate the approximate time when most fruit
set occurs, and delay harvest until about 50 days or more from the fruit
set period. Another approach is to check the ground spot on the fruit, and
not harvest fruit until the spots turns orange. Some of the newer striped
varieties of C. pepo will show some color changes with maturation, but the
color change, say from white to tan between the stripes or stripes changing
from green to orange, may occur well after the fruit are ripe enough to
harvest. In addition, some varieties may have a dark yellow rather than
dark orange ground spot at maturity. So with these, I think that it is
better to keep track of the approximate date of fruit set. However, if you
observe a color change that correlates with maturity in a particular
variety, then you can use that as a harvest indicator.

How about variety selection? That is a tough call. I have found that most
modern hybrids being commercially sold lack the eating quality of a good
Sweet Dumpling or Delicata squash. UNH has developed some high quality
acorn and sweet dumpling type varieties that are being released to the seed
industry. High Mowing Organic Seeds offers a UNH-developed, sweet dumpling
hybrid, Sugar Dumpling, which also has intermediate resistance to powdery
mildew. Johnny’s Selected Seeds is in the process of producing seed of one
of my PMR mini-acorns, and currently sells an acorn hybrid, Tip Top, that
has good eating quality. Cornell Bush Delicata is another variety in this
class with good eating quality and powdery mildew resistance. There are
several other varieties available that have reasonably good eating quality,
so growers will just have to evaluate them to determine if they fit into
their particular farm and marketing situation. ​

​