This is their advantage and a slight disadvantage: grow bags drain water quickly. So expect to water your plants more often.
That said… “Watering is the Achilles heel of gardeners. Regardless of the container or whether the plants are in the ground, it is necessary to make an almost daily round to assess the humidity of the soil, “says the horticultural manager of Urbainculteurs, Marie-Andrée Asselin.
Mulching is one way to reduce evaporation. In the vegetable garden, except for onions, shallots and garlic which do not need a cover, bet on untreated mulch (straw, cut grass or dead leaves), leaving a small space at the base of each planting . Also note that the smaller the bag, the faster its contents will dry.
Most grow bags are black, which has a knack for trapping heat. This particularity is an advantage for certain plants such as eggplants, tomatoes or hot peppers which only ask to be warm, but will put off the less chilly in the heart of summer. By surrounding the bag with a structure, for example a wooden crate, it is protected from the sun and the wind, while improving its water retention capacity.
“As plants grow and wind and rain put pressure on the bags, the soil naturally compacts,” warns Kevin Espiritu in his new book, Create a Bag Garden. Use a pointed object to gently aerate the soil on the surface, without touching the roots.
Since water loss is greater in bags, the substrate must ensure good water retention. Kevin Espiritu suggests this mix of one part compost, one part peat or coir, to one part perlite, pumice or pozzolan (volcanic stone). If your plants are particularly water-intensive, increase potting soil efficiency by using the same elements in a 2-1-2 ratio.
Some whitish dark circles and traces of mold inevitably end up appearing on the textile. These inconveniences can be limited by raising the bags to promote better air circulation. If the damage is done, brush the walls with a solution of water and baking soda.
Exposed to the elements, the bags end up being damaged, warns Kevin Espiritu. The horticulturist advises storing them sheltered from bad weather during the winter after having emptied them and cleaned them by hand or in the washing machine, cold, in a solution of vinegar and baking soda or a chlorine-free detergent. .
For her part, Marie-Andrée Asselin advocates simplicity. “I put myself in the shoes of a person who lives in an apartment and who gardens on his balcony. It is not said that she has space to store her land. One of the advantages of these containers is that they can withstand bad weather. At Urbainculteurs, some pots have been in place for seven to ten years and have not yet needed to be renewed. Choosing a quality bag with UV protection is a guarantee of longevity. “If we don’t empty the bags at the end of each season, we will have to think about amending the soil to improve its quality before replanting,” recalls Marie-Andrée Asselin.
Logically, small bags move more easily than large ones. Plan ahead before buying. However, the 95 liter bags are suitable for trees and shrubs, as well as root vegetables such as potatoes.
Many grow bags are made from plastic materials. Avoid those that contain PVC and those that are stamped with the number 7, which contain phthalates or bisphenol A that are harmful to your health, advises Kevin Espiritu.
Most fruits and vegetables can be grown in bags. Choosing the right cultivar, however, increases the chances of success. Prefer compact varieties and bushy habit rather than climbing ones.
The Urbainculteurs develop urban agriculture projects. Grow bags are among the containers they favor in their layouts. “The advantage is that they are super versatile and easily adaptable to the space. Bags are much easier to carry than jars. It’s a great asset when you’re gardening on a roof, for example,” points out Marie-Andrée Asselin. In addition, when they are light, they can also be moved to follow the sunshine or according to the needs of the layout.
One of the big differences between the pot and the bag, however, remains its permeability. The bag “breathes” and therefore allows air and water to pass through. Rather than twisting and sticking together on contact with the walls, the roots tend to atrophy when they reach the edges of the bag, which are exposed to the air and poor in water. The tips of the roots die off, but the process promotes the emergence of new branches, the rootlets, which capture more water and nutrients than the large roots.