Ten tricks for the balcony garden

In a recent interview on the many climate-friendly behaviors that we could adopt on an individual level, climatologist Luca Mercalli suggested to the writer to try planting vegetables instead of lawns and flowers. The reason, in extreme synthesis, is immediately clear: with the same resources required, in addition to their beauty, these plants give us something useful for the pantry. The season is perfect to start this adventure, because from the end of April we can transplant almost all summer vegetables outdoors. In practice, how to start a potted garden? We asked Matthew Ceredaeco-horticulturist and creator of the Ortodacoltivare.it portal that has just arrived in the bookstore with the new edition of the manual Put vegetable gardens on your balconies (Bur), updated with his reflections on climate change.

“On the one hand, intensive agriculture is responsible for the environmental disaster we are experiencing. On the other, global warming is overwhelming crops,” he says. “In recent years we have witnessed worrying phenomena including drought, mild winters, late frosts and extreme events. In the summer of 2022 we found ourselves shading the tomatoes to save them, who would have ever thought that before? Without bothering scientific studies, the point from the pragmatic point of view of the farmer it gives a concrete measure of what is happening and a responsible approach could reverse the course.Of course, the global problem is much bigger than our balcony and by planting vegetables on the terrace we will not change the fate of the world, but in this context cultivating is an important fact, because it allows us to have a relationship with nature and to develop a greater awareness”.

Let’s start with the choice of vases

To start, let’s remember that growing in containers is more fragile than growing in the field, because the plants have a limited volume of land and cannot develop their root system in depth. Global warming, therefore, has a greater impact on the balcony, which can also be oppressed by strong winds, capable of dehydrating the plants. “The larger the pots, the more autonomous the plants are; conversely, the soil in small containers dries out very quickly. A minimum depth of 40 centimeters allows us to grow any vegetable, even the largest and most demanding ones such as pumpkins, but we can also opt for windowsill boxes or vertical vegetable garden modules and focus on compact varieties. The most ecological containers are those made of terracotta and wood, or recycled. Whatever the material chosen, we avoid black pots, because the color dark heats up easily and accumulates more heat.At the bottom of the pool, we must always prepare a drainage layer with a few centimeters of gravel or expanded clay, to avoid water stagnation”, recommends Cereda.

Which land to choose?

“We can reuse the soil from previous crops, mixing it with 20-30% compost every year to restore nourishment and organic matter. However, let’s remember to apply crop rotation: we must never grow the same plant in the same pot, but it is it is preferable to alternate different botanical families, in order not to deplete the soil of a single element and to reduce the likelihood of diseases.Alternatively, we use the earth from our garden or we buy specific soil for vegetable garden plants without peat (which is extracted from peat bogs and it is not an easily renewable resource); I recommend mixing it with a few handfuls of country soil, which contains useful microorganisms to a greater extent than soils created with artificial mixes and stored in bags”, assures the expert.

The vegetables to be transplanted now

At this time of the year, even in the North, both short-cycle spring and summer vegetables can be transplanted in the open air. There is something for all tastes, therefore. In alphabetical order, watermelon, basil (alternating the purple one with the classic Genoese one and the Greek ball one), chard (among the most beautiful, the ornamental red or yellow ones), broccoli, cauliflower and cabbage (the curly kale), cucumbers, chicory and radicchio, beans and green beans, fennel, endive, lettuce, aubergines (the egg-shaped or finger-shaped ones are very nice), melon, peppers and chillies (they come in many colors and shapes) , tomatoes and cherry tomatoes (the yellow and black cherry tomatoes or the yellow date tomatoes look like jewels), leeks, parsley, celery, cabbage, pumpkins and courgettes. To grow healthy and bear fruit well, these vegetables need at least three to four hours of sunshine a day. Climbing varieties of beans, tomatoes, cucumbers and courgettes require supports, so we can place them in pots next to the balcony rail or put canes in them.

How to combine vegetables: the “winning combinations”

Combining different varieties, in addition to beautifying the terrace, can have beneficial effects for plants. Also in this case the rule “more biodiversity = less pesticides” applies. Going into specifics, some plants, if grown in the same pot, have reciprocal beneficial influences because they compensate from the point of view of nutritional elements, exchange precious elements, optimize space, shade each other and produce aromas and root exudates that repel insects of various kinds. “Among the most appropriate combinations, or the winning combinations capable of creating synergies between them: onions and carrots; cucumbers and corn; onions and fennel; strawberries and green beans, lettuce and strawberries; aubergine/pepper with beans/green beans; zucchini or pumpkins with runner beans and corn (for large planters).”

The beneficial effect of aromatic plants

Combining aromas with vegetables has further advantages. “Dill, next to beans, is unwelcome to aphids; basil and lemon balm are positive presences for tomatoes; chamomile helps onions and cabbage; rosemary repels insects that attack carrots, fennel and celery; sage attracts bees and other pollinators, but also insects that prey on parasites; chervil keeps caterpillars away from cabbages; savory keeps away aphids; thyme is loved by ladybugs, but keeps away caterpillars”, Cereda assures. But be careful: there are also pairings that are best avoided: “Among the plants that don’t always go well together we can mention cabbage and strawberries, or fennel with legumes and even peas with garlic and onions. Mint, on the other hand, is not a good close to none because it tends to colonize the whole vessel”.

Five ready-to-use recipes for vegetable gardening

For those who are beginners and want to start the adventure of the hanging garden by recycling, a fruit crate lined with non-woven fabric and filled with soil can become a small cultivation module. Below, five recipes for the garden in trays suggested by Matteo Cereda: “beans and chillies, because the former, being legumes, provide the nitrogen that fertilizes the latter; a fennel and two leeks, which go well in one box; parsley or celery with beets, one of the few combinations that can be satisfied even with a less sunny exposure; thyme and rosemary, or sage, which are perennial and compensate for each other for the shapes; blueberry and strawberries, because they both love an acidic soil and the bush shades the strawberries”. Let’s not forget to tuck in some beautiful and useful flowers here and there such as marigolds, nasturtiums, marigolds and lavender.

How to choose seedlings and transplant them

At this time of the year, the seedlings of all the varieties mentioned so far are on sale in nurseries in honeycomb containers. How to choose them? “We prefer very straight seedlings, with a robust stem and without yellowing of the leaves or spots. Too elongated plants indicate a long stay in the garden center, where they may have developed tangled roots due to the long time spent in the pot. Gently unthreading one of our seedlings moreover, from the container we will have to observe white roots (a sign that they are healthy) and not yellow or brownish. Once at home, we try to transplant as soon as possible, never in the hot hours. The ideal is to do it in the evening. We do not try to extract the vegetables by pulling them by the stem or by the leaves, but we press lightly on the sides and on the bottom of the jar in order to detach the earthen ball.Then we place the seedling in the hole at ground level (never too deep) and press with two fingers around, then we wet abundantly to make the earth adhere to the roots”. We can reuse the containers for autumn sowing or start separate collection.

Tips to wet less

To understand when to water, we insert a finger into the earth for two to three centimeters; if we “feel” that it is dry, it is time to intervene. “Wet the earth and not the plant and do it in the evening or early in the morning, using water at room temperature: this serves to avoid wasting liquid due to excessive evaporation, to prevent burns on the leaves and not to cause thermal shocks to the vegetables. Adopting large pots will allow us to water less, because larger volumes retain more humidity; let’s also remember to enrich the soil with amendments such as compost and humus, which absorb water and release it slowly. mulching, i.e. we spread a layer of straw on the surface around the plants to protect the soil from direct sunlight and reduce transpiration”, recommends Cereda.

What fertilizers to use

In general, vegetables are fast-growing plants, demanding in terms of nourishment, but the excesses of fertilization are as harmful as the deficiencies, not to mention that the surplus of fertilizer is wasted because it is washed away with irrigation. “The ideal is to plant in a substrate that is already well fertilized with organic products which, in addition to providing the necessary elements, improve the characteristics of the soil, for example a mixture of soil with a third of compost or floured manure. Among the organic fertilizers use in the cultivation phase, when the plants begin to bear fruit, the most common ones are pelleted manure and chicken droppings.Let’s distribute them in small doses because they are very concentrated, at the rate of a level spoon per plant, to be buried slightly on the surface, and then water abundantly. The absolute best fertilizer and soil conditioner is earthworm humus, which does not give any problem of overdose and also contains enzymes and microorganisms useful for the root system”, assures the expert.

The vegetable garden in one square metre

A practical, beautiful and sure success system to start with the garden is based on the method of square foot gardening conceived by the American Mel Bartholomew, which provides for a cultivation module consisting of a square box with one meter on each side and 50 or 60 centimeters deep. “To organize the crops we have to divide the area into smaller squares, for example by placing canes on them. Four squares of 50 cm each are suitable for bulky plants such as courgettes, cucumbers and climbing tomatoes. Nine squares of 33×33 cm are perfect for chillies and tomatoes dwarfs. Sixteen 25×25 cm squares are suitable for small crops such as salads, carrots and onions. Obviously, for each parcel we can also make associations between vegetables, herbs and flowers, following the combinations indicated above”.