About us

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 vertical growing: some general guidelines

Pruning is the removal of vegetative parts (stems, leaves) of a plant. It is usually done to increase productivity, improve appearance, ensure plant health, and/or facilitate harvesting.

General guidelines
-                Tools (scissors, knives, etc.) must be cleaned and sprayed with a 70% alcohol solution (rubbing alcohol) before being used. Hands must also be washed if a diseased plant has been touched.
-                If cutting can be done near a budding region or a leaf joint, make sure you cut close to the bud while leaving it intact on the plant, as plants tend to heal rapidly there.
-                For better healing, pruning should be done at a 45° angle through the stem (a beveled cut).
-                When trying to limit the expansion of the plant, cut only the top third of a stalk (the third of the length starting from the tip) or of the plant, in the case of naturally dense plants like chives.

Plants to prune, and why
-               All crops : You definitely want to remove any yellowing or diseases leaves or fruits from any plant.
-               Tomatoes : We’ve covered that elsewhere in great details.
-               Cucumbers and squash : We’ve covered that somewhere else.
-               Tomatillo and ground cherry : Both crops are of the same genus (Physalis) and can get very bushy. Prune to limit expansion of the plants if desired. Cutting out branches will reduce the harvest, which is rarely limited if the plants are growing in proper conditions.
-               Eggplant : For large-fruit varieties, some people suggest keeping 5-6 fruits per plant to avoid breaking the stem.
-               Sunflower : Some varieties produce many flower heads, which can become too heavy and break the stem. You may want to remove some flower heads in that case.
-               Herbs & flowers : Topping some herbs and flowering plants can result in a bushier and more productive plant, or in more flowers.
-               Fruit bushes, trees, etc. : Most woody plants will need pruning at some point or another. Raspberries and blackberries, as a notable example, grow new canes every year, which bear fruits the second year, and then die the third year. For this reason, canes that have borne fruits during the summer should be cut back in late fall or early spring, when the plant is dormant. More information on pruning woody plants can be found here.

Staking and trellising
While not all crops need support to grow vertically, some do benefit from it. Different methods exist, such as staking, trellising, twining, and caging. Plants can be grown vertically to save on horizontal space, for plant health management, for aesthetic reasons, or for general plant management such as facilitating harvest. Vertically grown plants should always be installed on the north side of a garden, where they won’t shade other sun-loving plants.

Plants to grow vertically and why
-       Tomatoes : Covered in another article on this blog.
-       Cucumbers and squash : Covered in greater details right here.
-       Peas : To facilitate harvest and for health management, peas are usually grown vertically. They are, after all, climbing plants. Install a trellis of at least 4 feet high next to the peas. Training them to grow on the trellis might be necessary at first, after which the plants may climb their way up on their own.
-       Pole beans : Beans exist in two varieties, bush beans and pole beans. Bush beans do not need support and can be grown anywhere that is very sunny. Pole beans are usually grown up a piece of twine, a trellis, a pole, or a teepee of poles (see image below). Note that some varieties can grow up to 10 feet during a single season.

Via kiddiegardens.com

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

Wednesday, June 11, 2014

The one and most important article on this blog: how to prune and support tomato plants

So this is it. We're doing that thing, where we're helping you with your tomato plants, THE most common garden crop in North America, and Europe, and probably somewhere else too. We assume here that you know the basics of growing tomatoes, such as full sun, full water, full nutrients, etc. A long read, but hopefully worth it. Enjoy!

The tomato being the most popular garden crop, its maintenance is very well documented. Before going further into the topic, readers should know that there exist indeterminate and determinate tomato varieties. Determinate varieties first grow vegetatively (roots, stems and leaves), then stop and produce fruits, giving a single early-season harvest. Indeterminate varieties grow and grow and grow. Determinate varieties usually do not need to be supported or pruned, while indeterminate plants absolutely need to be supported, and most people like to prune them for reasons that will be explored further below.

There are different varieties of tomatoes with different advantages and disadvantages. Without going into great details about that, let’s just say that there are tomatoes of different sizes (cherry, small, medium, and big), different colors (green, black, brown, purple, yellow, red, pink, green zebra, red zebra, etc.), and different shapes (round, beefsteak, pear-shaped, oblong, etc.). There are also varieties that are resistant to certain diseases and conditions, and other varieties that are susceptible to certain diseases and conditions (e.g. drought). There are also varieties that stay very short, which are denominated by the qualification of ‘patio’ tomatoes, and are especially well-suited for growing in containers or limited space.

When choosing a tomato seedling, make sure to choose one that is not yellowing, and that isn’t too elongated. Elongated seedlings are characterized by having a long internode (the length of stem between leaves), and thus have less leaves than a healthy seedling of a similar height. This usually happens because of improper lighting or crowding in the greenhouse, forcing the seedlings to reach out for light, and can result in more fragile stems. Contrary to the common belief, do not pick seedlings that already have flowers or fruits on them, unless it’s a patio variety. The first thing that a tomato plant should be doing upon transplanting is growing an extensive root system and a sufficient foliage to harvest all the nutrients and energy it needs to grow lots of tomatoes (and hell do they need a lot!). Once a tomato plant has started producing fruits, most of its energy goes into maturing these fruits. For this reason, such seedlings often stall growth when transplanted and get caught up, and even surpassed, by smaller fruit-less or flower-less seedlings, which then proceed to grow an earlier and more bountiful harvest later in the season (i.e. at the time when they should be). If seedlings with flowers is all you have, because of, say, cold temperatures that are extending too late into the growing season, the fruits and flowers can be removed upon or before transplantation, so the plant can focus on what matters (mainly roots). It may hurt to do so, but it’s for your own good!

As a last piece of advice, make sure not to transplant tomato seedlings too early, that is when the weather is still too cold (even if it shouldn’t be!). A lot of problems of stalled growth, root diseases, lower productivity, and bad pollination leading to catfacing can result from planting tomatoes too early. When transplanting, plant the seedling a few inches deeper than in its original pot, so as to bury the base of the stem. Tomato plants grow roots from there, which help for support and nutrient catching.

All those hairs there: future roots, I tell ya.

Once the plant is a bit more than a foot tall (30 cm), some sort of support should be provided, or else it will slump and will be hard to get back up properly. There are four methods for supporting tomatoes : staking, which consists of driving a pole into the ground next to the tomato plant and attaching the latter to the pole as it grows; trellising, with a trellis net; caging, with a tomato cage, cone, or tower; and using a twine attached to a hook or a horizontal bar over the plant. In general, providing support the earlier is the better, as big tomato plants are much harder to train and could be damaged in doing so. Staking and twining are good methods to add at the last minute, when the plants are starting to slouch over. Trellising and caging are basically impossible to do unless the plants are small enough (under one foot tall).

Staking can be done with bamboo poles, concrete rebar, T-posts, wood posts, or any other solid support. Drive the pole at least one foot into the ground to make sure it will not fall over under the weight of a 6-foot tall tomato plant full of fruits. It is better to put the post at or before the time of transplant, so as not to damage the roots of the plant. If pruning to one, two, or three stems (see below), put one post per stem. Attach the stem to the post using pieces of soft fabric to avoid damaging the stem by friction. If using twine, make sure it is thick, otherise it could cut the stem. Attach every 8-12 inches using a figure 8, with the stem in one of the loop and the pole in the other loop. This leaves enough room for the stem to grow bigger, offers a steady support, and avoids having the stem rub against the pole on windy days. For tomato varieties producing big fruits, the stem can also be attached loosely over each flower cluster using a simple loop, or ‘O’ loop. Pass the ‘sling’ right over where the cluster meets the stem, and attach it 6 inches higher on the stake (see image below). This removes some weight from the stem, which could otherwise bend and crease from the weight of all the fruits.

Via taunton.com

Trellising is usually done with a big hole mesh netting (around 6-inch-wide holes is optimal). Nylon trellis netting can be found in hardware stores or garden centers, and is usually the favorite of gardeners. The trellis should be 6 feet tall or more, and should almost reach to the ground. Tomatoes can be trained in the trellis by passing the main stem(s) alternatively behind and in front of the net, or around a vertical twine in the mesh. This should be done as the stem grows, otherwise the stem or leaves could be damaged from bending or twisting the stem too much. It is thus not a good support method to add at the last minute.

Via howlerband.com

Caging is done with the short tomato cages or cones most people put around their tomato plants. These are usually not well suited for indeterminate varieties that can reach at least 5 feet in height. There also exist tomato towers or ladders, which are similar to tomato cages but with a square or triangular frame, and are much taller. If put around the plant while it is still small enough, these provide a good method for lazy gardening, as the plant usually needs little to no training, the leaves and fruit clusters resting naturally on the horizontal bars of the tower as they get heavier.

Via forums.gardenweb.com

Finally, twining is done by attaching a twine to a stake planted near the base of the plant, or by attaching the twine directly but loosely to the base of the plant, and attaching the other end to a support over the tomato plant. The plant then needs to be trained around the twine, clockise or counter-clockwise, the friction with the twine being what supports the plant. Unlike other methods, it offers no additional support to fruit clusters, and may thus be inappropriate for varieties producing heavy fruits. The twine can be attached over the plant to a hook, a vertical post (this way you can have many plants growing at an angle toward a single post), or a horizontal post (such as with an A-frame). It is a good method for tomato plants that have gotten quite big and need a last minute support method.

Via Campus Crops

The main reasons to prune tomatoes are plant health, ease to harvest, and sometimes to save on horizontal space. But first, let’s look at a tomato seedling :

As we can see, the tomato plant usually grows one main stem, from which grow leaves (composite leaves, each of which being one leaf starting from the stem, and not many leaves on one "branch"). It’s possible to keep the tomato plant with only one stem, but it’s also possible to prune for two, three, or four main stems, or not prune at all, for reasons we’ll explore below. What’s important to know is that each stem starts by producing leaves, and then starts producing flowers clusters at a somewhat regular interval.

Now if we look at the plant where the main stem meets a leaf, we can see another stem branching out at a 45° angle between both:

That’s a sucker (that’s really what it’s called). If left on its own, it will become a stem, producing leaves and flowers, but relying on the same root network than the main stem. It is common for suckers to grow again where one has been previously removed, so check your whole tomato plants regularly! Just like the head of the main stem, suckers have a zone of continuous growth at their top. Be sure not to remove the head of the plant while pruning! If that happens, a sucker can be allowed to grow and become the "new" main stem.

A few things can be concluded from this :
1) The more stems, the more leaves, and thus the less aeration.
2) The more stems, the more tomatoes.
3) The more fruits produced, the more nutrient and water needed.
3.1) The more nutrient and water needed, the more intensive the culture is and/or the more extensive the root network has to be.

1) Health
More leaves means less aeration, which means greater chances of developing fungal diseases, especially in a relatively humid climate like Québec. It also makes it easier for diseases and pests to spread from stem to stem, and from plant to plant. This is why most people remove suckers from their tomato plants, allowing a few to grow near the base to obtain two, three, or four stems.

A lot of diseases, and especially fungal diseases, can stay dormant in the soil as spores. When watering your garden, it is possible that some soil may splash on the lowest leaves of your tomato plants, allowing fungal diseases to develop. A first solution is to put mulch under tomato plants, whether black plastic mulch (not any black plastic, though) or woodchips, making sure the mulch doesn’t touch the stem of the plant. Another easy thing to do is to prune the lowest leaves at the bottom 6-8 inches of the plant, once it’s comfortably tall (you don’t want to remove half the leaves from a plant by pruning it).

It is also possible to remove leaves (especially recommended for diseased leaves), but one thing to keep in mind is to try, as much as possible, not to prune the leaf right above a fruit cluster. The leaves will provide shade to the fruits and avoid problems such as sunscald, which is similar to a sunburn for tomatoes. Sunscald mostly happens when tomatoes are exposed to intense direct sunlight under hot conditions, and although the fruit is still edible, it is also more susceptible to black mold.

2) Productivity
As has been said, the more stems are allowed to grow, the more tomatoes are produced. For health reasons, as seen above, most people keep up to four main stems and prune all other suckers, although it can be totally ok to let an indeterminate tomato plant go crazy. Apparently, pruning to less stems allows for an earlier harvest, with bigger but less numerous fruits.

3) Nutrients and water
More growth and more production are only possible if water and nutrients are present in sufficient conditions. For this reason, it is usually preferable to prune container-grown tomato plants to one main stem, because of the limited amount of water that is available in a container. Nutrients can also be limiting in containers, unless the plants are fertilized properly. Water is crucial for good growth, and most importantly for the production of good fruits, which may crack or develop other problems under limited water conditions.

For tomatoes that are grown in the soil, nutrients can also be limiting, but water rarely is. Managing the plants, preventing diseases, and facilitating harvest will be the main reasons why tomatoes grown in soil will be pruned.

For all indeterminate varieties, and even more so for bigger tomatoes, the head should be removed about 4 weeks before the first frost date. When headless, the plant can no longer grow, and spends its energy to the maturing of tomatoes. The head is pinched to make sure that all tomatoes and flowers produced by the plant so far will have enough time to turn into mature tomatoes. Otherwise, green tomatoes that were still expanding in size, and were thus not technically ripening, will never turn red; there’s just no way they’ll ever ripen. Small tomatoes will need less time to ripen, so 2-3 weeks before the first frost date may suffice, but huge tomatoes will need 4 weeks or more.

Simple vs Missouri pruning
Before we let you rush back to your garden, we’ll detail the two different ways of pruning suckers: simple pruning and missouri pruning.

Simple pruning is used for suckers up to 4 inches long. The method is to take the sucker between thumb and forefinger, and to rock it back and forth in order to snap it off clear from the stem. No breakage, no mess, just a clear break. If it doesn’t work, it is because the sucker is too big. Switch to missouri pruning.

Missouri pruning is used to control those larger suckers that escaped your attention and are now becoming a life-sucking stem. The method here is simply to pinch the head of the sucker, or in other words to remove the zone of continuous growth, Simply pinch it off with your fingernails, or use clean pruners.

To remove leaves, cut them near the stem using clean pruners.

More info on growing tomatoes