Roots 'n' Shoots: November 2012

Friday, 30 November 2012

Squash & Pumpkin: How To Grow − Fruit(s) of the Month

Squash stats/requirements at a glance


Ease of Raising:
2/5       - Weekly check up
Water:
4/5       - Daily
Sun:
5/5       - Full sun, no shade
Training:
2-4/5    – Minimal (Zucchini) to Moderate (Squash), dead or damages leaves to trellis training
Fertilise/Feeding:
3/5       – Moderate (monthly)
Time to Harvest:
2-5/5    – Soon (Zucchini) to end of summer (winter squash), 1-4 months
Frost Hardiness:
1/4       – Very Tender (can’t take light frost)


Uses
Culinary, Pollinator attractor
Most Problematic Nemesis:
Powdery Mildew
Container Plant:
Rather not

Squash Vine
Cucurbita moschata
 Quick intro

The terms squash, pumpkin and marrow are often confusing and applied indiscriminately. From what I could decipher, squash are applied to both summer and winter varieties. This again can be misleading, summer and winter squash are both grown during the summer months, the only distinction is that summer squash cannot keep for too long (zucchini, patty pans AKA soft skin varieties ect.) and winter squashes after preparation can be stored throughout the winter (hubbard, butternut, pumpkins AKA hard skin varieties). Squash are a pleasure to grow and are likely favourites at the table whether it is as soup, steamed, roasted or served with syrup. The only problem is that they take up a lot of space in the garden and are hounded by powdery mildew - grrr!...

Cucurbita pepo
Marrow
History

The oldest archaeological remains of squash cultivation are from Mexico (7000-5500BC) and formed part of the important pre-Columbian ‘Three-sister’ diet complex. This consisted of maize, beans and squash, where the maize stalk provides support for the beans and shade for the squash. The squash limited provided ground cover to limit weeds and water loss from the soil, whereas beans (being legumes) provide nitrogen to the maize and squash. These ancient cultivars are now distributed around the world as they are hardier than other squash species and are cultivated in cooler climates, such as the United Kingdom and northern Europe.



Science Stuff

Squash belongs to the Cucurbitaceae family, which contains approximately 25 species, although only a few are cultivated plants. These belong to several species, Cucurbita (the genus, abbreviated with the first letter), C. pepo, C. maxima, C. moschata, C. mixta and C. ficifolia – and then you get several varieties under each species, such as C. pepo var. pepo and C. pepo var. melopepo. Now on with the naming game… Pumpkins are sometimes classified as winter squash or food used for animal fodder. So to solve all the confusion my very informative “The complete guide to Saving Seeds” book has provided both illustrations and comprehensive table. Here is a remade image and table of the species differences:

 Fruit stems help to identify the species in question.
Cucurbita maxima has a soft and rounded fruit stem that seems to be inserted into the fruit.
Cucurbita pepo have hard and prickly fruit stems that are enlarged at the point of attachment.
Cucurbita moschata are flattened at the point of attachment.


C. maxima (Cmax)
C. pepo (Cpep)
C. moschata (Cmos)
Can cross-pollinate with Cmax & Cmos
Can cross-pollinate with Cmos and Cpep
Can cross-pollinate with Cmax, Cmos and Cpep
Arikara
Acorn
Butternut
Banana
Cocozzelle
Dickson Field
Boston marrow
Crookneck
Kentuchy
Buttercup
‘Pumpkin’ cultivar
Long Island Cheese
Hubbard
Scallop/Patty Pan
Calabaza
Jarrahdale
Straighneck
Trombocino
Kaboscha
Zucchini/Marrow
Seminole
Lakota
Gourds
Neck
Turbans
Gem/Rolet
Long of Naples
Flat white boer
Spaghetti
Giromon

I hope this will clarify some issues surrounding the naming problem. An additional terminology issue is that of Zucchini, Courgette and Marrow. Zucchini and courgette refer to the smaller C. pepo summer squash (I usually stick to the ones that look like fingers and patties), whereas marrow refers to the mature fruit of a C. pepo plant (25-30cm long!).

I think that pretty much covers it.



Growing Squash

Squash are delightful, especially the zucchinis as they are prolific and start to produce fruits within two months of planting. Their seeds germinate within 5 days given the soil is warm enough (21-35oC, 70-95oF), which is usually after the first frost. If you live in an area with a short summer, start seedlings indoors 2-3 weeks before it should be warm enough and plant out once the seedlings have 3-4 leaves.

Cucurbita species
Squash seedlings

Now I have never concerned myself with spacing, as these plants do what they will. The bush varieties (patties and zucchinis) remain in a roughly 60cm circumference area, but later on they do have longer stems, as the zucchinis are produced on the new stem and so they start to move outside this area. Bush varieties have large leaves that take up a lot of space, but provide shelter to vegetables below and they retain soil moisture (carrots particularly like this arrangement J). Trailing varieties (these are hubbards, butternut, crooknecks, larger pumpkins) creep along as they please. Hubbard and pumpkins have large leaves but they are spread along the creeping vine and so do not take up much space in that sense, but the vine can creep through the entire garden soon enough – and that takes up more space that your bush varieties.

I do not restrict zucchinis on the amount of fruits they carry, since they develop and set within a week making a constant rotation of crops. The larger trailing varieties I limit to 8 fruits (for smaller fruits, such as gems, butternuts, crooknecks) and 3-5 fruits (for medium to large fruits, hubbard and pumpkins). This ensures that the fruit sets properly and the seed cavity develops (important for seed saving). One must also remember that the trailing varieties have to ‘pump’ nutrients all the way along the vine to the developing fruit, so ones further away will get the most nutrients. The amount of nutrients the closer fruits will get is less, due to the gradient in which the plant supplies nutrients, so more nutrients at the tip of the growing shoot (and fruits) to less nutrients closer to the base of the plant where the root are located. This is why the amount of fruits needs to be limited, since the plant continues producing fruit at the tip, these will steal nutrients and the others will not get enough to develop properly. So to prevent more fruit from forming simply pinch off the growing tip, this will ‘force’ nutrients to the other fruits. Be vigilant of new shoots developing and pinch these off as well, it can be quite a battle to keep a plant restricted as they want to produce as many fruits as possible, so new shoots will spring up all along the length of the vine.

Hubbard
Cucurbita maxima
The some squash varieties, such as butternut, large crooknecks, hubbard and pumpkin, require support for fruits. Since fruits are in contact with the soil and may rot. Fruits are supported in a variety of ways, I am still trying to find the best for me, such as straw, black plastic bags and carton. Also the side in contact with the ground will become yellow and might be a bit harder than the rest of the fruit, this is a natural process of fruit development and the fruit is safe to eat J.

I have tried planting the squash in containers, but it did not work out so great, since the plants were fairly small and did not carry fruits well. One of my reference books "Pot it Grow it Eat it" manages to get it right, so give it a try! J

Other Squash Tips

There are no squash varieties resistant to powdery mildew. This fungus grows on the top of the leaves and can soon cover an entire squash plant. Some books say that this doesn’t impact on fruit production, but I do not believe this as the fungus will sap nutrients from the plant, which will decrease fruit and growth potential. To limit the onset of powdery mildew always water squash at the base of the plant on the ground, do not water on the leaves as this increases the growth and spread of mildew. Once mildew starts, remove badly infected leaves. You can spray the mildew with an environmentally friendly spray I developed, under Pest Control.

Cucurbita species
Powdery Mildew
On that note, me and a friend were discussing that it would be awesome if you could breed squash with waxy cuticles (layer surrounding the outside of the leaf) similar to that of Brassicas (the cabbage family) so that water simply trickles off the leaf and mildew will have a harder time growing on the squash J. But this has other physiological implications, especially when concerned with energy required to grow the wax layer, hence fruit production is decreased J...


Harvesting & Storing

OK it is quite a process for harvesting and storing squash. Zucchinis are harvested when the fruit is 10-15cm, they can keep for about 5 days in the fridge (in a closed container that doesn’t let the fridge dehydrate the fruit). Fruits are cut from squash and 5cm of the stem is left on the fruit. This prevents the fruit from dehydrating and prevents infection of the fruit by fungi or bacteria. Marrows are 25-20cm long and can be store for longer periods of time as the fruit has matured. The rule for marrow harvesting is that if your thumbnail goes into the skin easily they are ready. Marrows can be stored for a few months in an airy frost free location. We are investigating whether marrows will still be edible after freezing, we grill them in a little oil before they go into the freezer.

Winter squash (hard rinds) are harvested and stored differently and include all squash except zucchini and patty pans. So these are ripe when the fruit skin is pale, dry, uniform in colour and the rind cannot be puncture by thumbnails (brown and dry stems for gourds – bicoloured squash, a more decorative ornamental squash). Then cut the fruit from the stem, leaving 3-6 inches (8-16cm) of the stem for pumpkins and no more than 1 inch (3cm) for hubbard to prevent damage to other squash during storage. Wash the fruit with soapy water and rinse with bleach to remove pathogens (1 part of bleach to 10 part water, so 1ml bleach to 10ml water). Make sure the fruits are dried properly before curing. So most pumpkins, except butternut, hubbard and acron varieties do not need to be cured. Pumpkins require curing. Curing pumpkins involved leaving them in the sun for a week (7-10 days) after harvesting. This allows the skin to harden and the fruit to fully ripen. Cured pumpkins can be stored cool dry place for 2-3 months. Store fruits on wooden pallets and do not let them touch one another, this prevents rot. For more info check out: http://urbanext.illinois.edu/hortihints/0410c.html

NB: Remember to check on stored fruit regularly and remove any rotten fruits.


Seed Collection & Storage

Squash have unisexual flowers, meaning male and female reproductive organs are borne in separate flowers. Female flowers carry small immature fruit at the back of the flower and need to be pollinated to set fruit. Male flowers do not carry fruits. Squash are pollinated by insects and this can be problematic if you pollinators are more interested in the basil plant and ignores everything else! But luckily squash are easy to pollinate J. I do this with a soft (horse-hair) brush that is similar to a bees’ body. You can use a feather as well or simply rub the anther (male part) over the stigma (female part). I find you get better pollination, pollen use and distribution when using a brush. Simply pick a male flower, strip the petals and get some pollen (yellow) onto your brush. Strip the petals from the female flower (careful not to remove the flower completely) and make sure you brush all the stigmas (3-4 lobed shaped structures). Technically you only need to get one pollen grain on one stigma, so brushing the all the stigmas with pollen will ensure pollination.

Squash male and female flowers
Cucurbita pepo

Squash male flower (anther)
Cucurbita pepo

Squash female flower (stigma)
Cucurbita pepo

Now, squash are sometimes selfish to produce male flowers when females are around. So, when the squash just start growing, they produce mostly male flowers – this is less energy expensive than producing female flower as they can disperse pollen (and genes J) by male flowers hoping that there are already plants with female flowers around. But if the male flowers aren’t used (not sure how the plant will detect this stimuli) they will start making lots of female flowers and fewer male flowers (since one male flower can pollinate multiple female flowers). So then you get lots of females waiting to be pollinated with insufficient or no males at the same time. But do not fear! As squash are promiscuous and can easily accept pollen from different species in the same family. This goes with the table I showed earlier. So you can use zucchini (Caserta or patty pan, as they have lots of male flowers with lots of pollen) to pollinate (and fertilise) pumpkin or butternut or hubbard… female flowers. The only thing is that you cannot harvest seeds from these fruits as the fruit will either be parthenocarpic (meaning the fruit does not contain seeds) or the seeds will be sterile (this is not the case for tomatoes! J). So to save seeds; select a fruit to pollinate with the correct pollen and close the female flower with twine (tie up the petals) to indicate that this is the one meant for seeds. You can also use cucumber pollen to pollinate squash (although, cucumbers do not produce lots of male flowers).

To harvest seeds pollinate the female flowers and leave the fruit to become botanically ripe (the fruit goes past its consumption point). This is necessary to allow the seeds to develop fully and become viable. Fruits are left to rot down or become calabash. Seeds can be removed and washed. Viable seeds will sink. Seeds stored in glass will last for up to 5 years.

Botanically ripe gem squash (rolet squash)
Cucurbita pepo

My Squash

I have three varieties of zucchini, a long green one, long striped one and a patty pan (scallop).
The striped one is a Mayford variety and other two are Starke Ayres. The Mayford becomes quite larger than the Starke. All others are Starke varieties which include, Butternut, gem squash and Boer Pumpkin (Afrikaaner variety of South Africa J, basically translates to Farmer’s Pumpkin).

Pumpkin Patch

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