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Campus Crops is a student run urban gardening initiative at McGill University's downtown campus. We want to grow food on campus, by students, for students. We have been running garden behind the School of Environment building at 3534 University since 2007. In 2009 we started a terrace garden behind the James Administration building. We're really excited to keep improving these two spaces, and need lots of helping hands for the summer ahead! Get in touch and get gardening!

Saturday, June 14, 2014

Pruning and trellising more stuff: cucumbers, summer squash, and winter squash

Cucumbers, summer squash, and winter squash are all cucurbits. They share similarities and differences. Cucumbers are a short-season crop, and produce continually before dying. Succession planting every 2-3 weeks ensures a continuous harvest throughout the season. They grow rambling vines, all starting from one main vine. Summer squash are mostly similar to cucumbers, although most varieties grow as a bush from which rambling vines may emerge. They are also a short-season planting and succession planting works well for a continuous harvest of summer squash. Winter squash, unlike summer squash, are harvested when mature, that is when the rind of the fruit is thick. For this reason they are long-season crops that will produce successfully only a limited amount of fruits per plant, which will have to mature throughout the season. Like cucumbers, they grow a main rambling vine, from which secondary rambling vines extend. Bush winter squash varieties also exist for gardeners with limited space.

Pruning and trellising can be helpful for the management of cucumbers, summer squash and winter squash, but are in no way necessary; all of these crops can be allowed to spread directly on the ground and all over the place. There are, though, some advantages to pruning and trellising.

Like for most crops, pruning cucurbits may be for reasons of plant health and management. Pruning is also necessary if growing cucumbers or summer squash vertically. When pruning, follow the general rules of hygiene, and cut vines either at a leaf joint (leaving the joint itself on the living plant) or as close as possible to the main vine or bush, depending on the type of cucurbit.

Removing excess anther-bearing flowers (flowers that produce pollen)
All squash produce both anther-bearing and ovary-bearing flowers. The pollen from the anthers must be carried to the ovaries in order to get fruit production; otherwise the ovaries die. Pollinators can do that just well, but hand pollinating can be helpful (see below). Especially if hand-pollinating squash or cucumber, there will be many more anther-bearing flowers than are necessary to pollinate all the ovary-bearing flowers you need. It is usually safe to remove up to half or even 2/3 of the anther-bearing flowers if you want to eat them.

Left: anther-bearing flower; right: ovary-bearing flower
Via forum.earthbox.com

Pruning excess vines
If the vines of your cucurbits are starting to take all over the place, they can be gently picked up (be careful, as they may have grown roots under leaf nodes) and moves somewhere else, like outside the garden and over a useless lawn. If space really is an issue, it is also possible to prune summer squash to 2-4 rambling vines, by cutting part of the vines or whole vines. In winter squash, non-producing secondary vines can be removed, but pruning should wait until there are already a few fruits going. For all cucurbits, removing vines will result in less production. An alternative can be to remove the growing tip of the vines a few leaves after a fruit, so the plant stops expanding in that direction.

Removing excess foliage
Not recommended for winter squash, as they need quite a lot of energy to mature the fruits, but will probably become necessary for disease management. Indeed, squash and cucumber are, most years, plagued by a fungal disease called powdery mildew, which is brought up North in Canada by strong weather systems such as hurricane tails from the United States. The disease attacks the leaves of some plants, mostly cucurbits, and is noticeable by the white powder that develops on leaves, which then yellow, wilt, and die. It spreads like crazy, carried by wind or water, and is hard to prevent and to control. Removing leaves as soon as infected can slow down the spread of the disease and give some time to the plants. Hygiene is the rule in order to prevent spreading the fungus to other plants; the gardener is a vector of diseases, after all. Infected leaves should be disposed of far away or burned. Do not compost them.

Aside from diseases, foliage can be removed from summer squash that produce rambling vines, like zucchini. Make sure to leave 5-6 leaves on each side of fruits to shade them well. Some gardeners remove leaves for reasons of management, as it is easier this way to notice when fruits are ready to harvest. It is not usual for summer squash fruits to go unnoticed for a while, hidden by a dense foliage, only to be found later in the season, too big to be eaten. Removing foliage before powdery mildew kicks in is also a better way to prevent the disease, or at least major damages to the crop.

Via paulandangelasfamily.blogspot.ca

Removing excess fruits
There is rarely such thing as excess fruits for most gardeners, and this practice is indeed controversial, but some gardeners like to remove smaller fruits from winter or summer squash in order to allow others to mature more rapidly. It sounds reasonable for winter squash, especially when the end of the season is a few weeks away and the fruits have yet to mature fully. For summer squash, though, it usually results in more loss of production than anything else. There is usually no reason to remove fruits in cucumbers.

For all cucurbits, though, removing weird-looking and diseased fruits is recommended, so as to make sure that the energy of the plant doesn’t go to waste, if the fruit ends up rotting or being inedible for some reason.

Pruning suckers and secondary vines for trellising
Like tomatoes, cucumbers have a sucker growing at each leaf joint, between the leaf itself and the main stem. Those suckers, if allowed to grow, will become stems that will produce more cucumbers. In addition to a sucker, though, each leaf joint on a cucumber plant also produces a pollen-producing flower, an ovary-bearing flower, as well as a fragile tendril that wraps around nearby objects for support and achoring.

When trellising, the first 4-6 suckers need to be removed to allow the main stem to get on the trellis. Once the plant is on the trellis, the suckers can be allowed to grow into secondary vines on the trellis. The main vine and secondary vines should be pruned near a leaf joint when growing out of the trellis. It’s also possible to try to train the vines back on the trellis, in which case pruning some leaves would be recommended if the trellis becomes too crowded.


Vertical trellis via forums.gardenweb.com
Cucumbers and summer squash with rambling vines can be trained on an upright trellis, a sloping trellis, or simply on a horizontal trellis to provide shade to another crop. Winter squash, producing heavy fruits, can’t be trained on a too steep sloping trellis, as the weight of the fruits would probably result in damage to the stem. In any case, although trellising helps for disease management, easier harvest (the fruits are easier to monitor), and results in straighter and better-looking fruits for cucumbers, the additional air flow around the plant means that the plants will need more water.
Leaning trellis via floridavegetablegarden.com

To train a cucurbit plant on a trellis, the gardener must gently direct the vine on the trellis to allow the tendrils to attach to the support. On most sloping trellises, the support provided by the tendrils will be enough for the plant to climb on its own. On vertical trellises, though, which are usually used for cucumbers, the vines will need to be attached to the trellis every foot or so with a special clip, or any type of garden twine. As is the case for tomatoes, thin twine should be avoided, as it will damage the stem.
Horizontal trellis via buildavictorygarden.com

Trellis clips

Hand pollination
The idea here is basically for the gardener to become the pollinator in order to ensure pollination of ovary-bearing flowers. Anther-bearing flowers usually have a thin and long stem, compared to that of ovary-bearing flowers, which is short and fat and may look like a tiny fruit (which it is).

To hand pollinate, simply pick a pollen-producing flower while ovary flowers are open (from 10am to noonish), remove the petals from the anther flower, and use it like a brush to rub the anthers on the central part of the ovary flowers. One anther flower can pollinize 2-3 ovary flowers. For a more detailed explanation, see this very helpful, step-by-step illustrated how-to.

More resources
All the information you need to grow cucumbers : http://www.gardening.cornell.edu/homegardening/scenef65b.html

A neat YouTube video to show you how to prune cucumbers for trellising : http://www.youtube.com/watch?v=A9YQ2WsubpI


Tree Service Queens said...

This is such a helpful post! I love squash

Herry Johnson said...

La coltivazione di cucurbitacee ha bisogno di una buona ventilazione per prevenire malattie micotiche, cucumber trellis vertical, e la rete per cetrioli come spalliera lo permette.

Unknown said...
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Roynok said...

Nice post! Currently we are preparing our garden for growing potatoes.