The wonderful adventure of squash, and their secrets in the garden.

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Growing squash is easy and rewarding, and it makes vegetables that keep well in winter . So as these are great plants, we wanted to learn more about Cucurbita, and give you “tips” to succeed in cultivating long.

As we began researching this article, we thought it was fair to find some secrets about squash culture. But Cucurbita is a fascinating “family story” ! So if you want to make a little historical and genetic detour with us read on, but if you just want the culture tips, jump right to the second part of this article.

Our squash and pumpkins are the result of 11000 years of human domestication!

Hey yeah, it’s not a joke! The first traces of the species Cucurbita pepo date from … 8750 BC in the Oaxaca Valley in Mexico.

Several sources suggest that the species Cucurbita pepo was “invented” a second time around – 4000 BC. JC in Missouri … from the same wild spawners that are C. fraterna and C. texana. Imagine that the same species can be created twice 4000 years apart, it makes you dizzy …

Well, we must understand that the plants of the Cucurbitaceae family are champions of hybridization, so no need for complex techniques to create new varieties. Just leave seedlings of different species in the same garden and you get hybrid fruits. But after that, the chances of them becoming a stable species are much slimmer.

Cucurbita, a very diverse botanical genus.

Only 5 species of Cucurbita are cultivated, including:

  • Cucurbita pepo – zucchini and squash, which have a peduncle – the small tail to which the fruit attaches – with 5 hard ribs
  • Cucurbita maxima – pumpkin and pumpkin with tender peduncle
  • Cucurbita moschata – butternut squash and butternut

These species have about ten wild ancestors in common , because the Cucurbitaceae cross very easily together.

The parent species are separated into three levels of ”  genetic pools “. If you are not comfortable with the notions of “gene pool”, let’s just say that the primary pool has the natural parents of the species, and the other two are all the species that have brought genetic material into this pool, by methods of crossing more or less advanced – the brush stroke between two flowers to the fusion of protoplasts.

Modern varieties of the genus Cucurbita pepo have 9 wild species that have contributed to different degrees to their gene pool. This is quite striking, and it is undoubtedly one of the reasons for their exceptional vigor: an important genetic diversity limits notably the diffusion of the epidemics.

In addition, with so many parents, it was possible to obtain different varieties by selection: the composition of zucchini fruits full of water – and that of pumpkins – chestnut flavored, rich in sugars and beta-carotene – n have nothing to do.

A little history.

The squash arrived in Europe very early – in the middle of the sixteenth century – and zucchini – or Zucchini – was developed in Italy at the end of the nineteenth century.

The different varieties of squash are well acclimatized to European countries, they are present in France since the sixteenth century, where they were quickly adopted for their spectacular growth. The Cucurbita maxima – the pumpkins – are the most adapted to the cold, so they arrived faster than the Cucurbita pepo – squash and zucchini, which made a detour through the Mediterranean. 
It should be noted that pumpkins are varieties of Cucurbita maxima that were obtained in East Asia before returning to Europe.

A London publication of 1861, “Barr & Sugden’s spring seed catalog and guide to the flower and kitchen garden” already contained a considerable variety of Cucurbitaceae.

Good tips to know how to grow squash and pumpkins.

For contextualized culture tips: when to plant, transplant, water, use the groww application available for free here . The “tips” that we will develop in this section are intended to give you general notions about zucchini culture.

Rotate the zucchini!

“How do we turn towels? 
– But no Patrick, we’re talking about crop rotation there … “

If the Cucurbita are annuals, it is not by chance: they grow very fast and practice the scorched earth policy a little, after their passage, the soil is drained of its nutrients , it needs a little time to recover. The squash have nutrients needs quite unbalanced according to this document from the Chamber of Agriculture of Vaucluse – okay it’s traditional chemical culture, but it gives a good idea of ​​what squash consume. Squash consume more potassium and magnesium than nitrogen and phosphorus – in proportion to 10,10,20,15.

Suffice to say that compared to what brings a “normal” domestic compost, there is a big difference.

Here are the average contents observed in the domestic compost according to INRA.fr :

Nitrogen (N total) 0.3% – 0.4%
Phosphorus (P2O5) 0.15% – 0.4%
Potassium (K2O) 0.2% – 1.0%
Magnesium (MgO) 0.1% – 0 , 2%
Calcium (CaO) 0.4% – 1.2%

If we compare these values, it tells us that if we plant its squash in ordinary compost, they will make too many leaves and start to grow late, given the “excess” of nitrogen. At the end of cultivation, we will have a phosphorus and nitrogen residue, and probably a magnesium deficiency. Hence the fact that we advise against replanting the same thing the following year 😉. Because if we put back compost, we will have more and more nitrogen and phosphorus concentration in the soil, which forcibly causes very strong imbalances and can poison microorganisms. Hey yeah, it’s not because it’s organic that you can do anything 😉

So, make it turn!

Not too much water at the start!

This is advice for all plantations: never water too much at the beginning of cultivation, and do not provide too much nitrogen. Otherwise your squash will produce plenty of leaves that they can not feed. It is better to teach them from April to May what drought means: waiting for the soil to dry between two waterings will encourage root production. In this way, the seedlings will be rooted in proportion to their aerial system, and will be able to feed the fruit production.

If you see fruits that abort, do not worry.

When you see a young fruit that curls up, it is because the plant does not feel able to feed it. It usually happens in early summer, it just needs the foot to grow more and then it will make new fruits.

Cucurbita planted directly in the compost, the wrong good idea.

It depends of course on the exact composition of your compost, but the Cucurbita are so greedy that they will empty it of all its magnesium and its potassium, leaving you a completely unbalanced compost. So unless you only want to grow squash with this fertilizer, plant them in the garden instead and have them change locations every year.

Be careful if you want to recover the seeds.

Some will accuse us of being a little alarmist, but we must know that in the wild some Cucurbitaceae – like the colocynth – are very toxic. It can happen as a result of too many hybridizations – we talk about doing it over several generations – to end up with bitter fruits that contain a lot of cucurbitine. In this case you should not eat them, sometimes there are deaths after a dish of zucchini . Hybridizations are very easy between different Cucurbitaceae in the same garden, so be careful.

Dr. Kimberly Seltzer

Postdoctoral Scholar, UC Berkeley Research Assistant, MIT

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