Have you ever considered growing grapes in a greenhouse?
Growing vitis vinifera grapes for some of you guys in the colder climates is something you can only dream of. Vitis vinifera, as you probably know by now, is susceptible to cold damage when the temperatures drop below 0 *F or -15*C. Now this is really cold, but even at higher temperatures, most vinifera grapes will not do well in your area.
However, there are a few grape growing techniques used by viticulturists that can prevent the grape vines from getting hurt by these extreme temperatures, like covering the vines, late pruning and even in some cases removing the vines from the trellis and burying it!
There is another way, not so well known to people in the USA. The people from Europe and especially the UK use greenhouse gardening quite often in their backyards and successfully grow grapes in cold conditions.
Why grow grapes in a greenhouse?
First of all, let’s take a look at what a greenhouse really is. Greenhouses come in all shapes, sizes and materials. They range from conventional types that have vertical sides and include a traditional span, to those with one side against a wall (a sunny one is best, and the wall provides extra warmth.) A lean-to is ideal for limited space and excellent where a decorative show is required. Mini, low cost greenhouses are good for beginners new to gardening and greenhouse keeping, and also small gardens.
During the Victorian times, greenhouse grape growing was used to produce crops out of season, or to make the grape crops much earlier than the natural ripening season, by heating up the greenhouse. Today, greenhouse fruit and veg growing is done a lot more sophisticated with the introduction of hydroponics, alternate sources of energy like solar heat panels, airflow controllers and even mist control to regulate heat in the greenhouse. Over the years, the art of growing veggies in a different medium than soil, has been fine-tuned to such extend, that it is used commercially to grow out-of-season products.
Now, it is important to know that not ALL grapes are suitable for greenhouse grape growing. Varieties like Thompson, that is known as a unfruitful variety, will probably need some extra source of light in order to grow it in a greenhouse. Too vigorous growing varieties are also not suitable for greenhouse grape growing, because of the extra work that needs to be done to keep the vine’s growth under control.
Many greenhouse owners grow their vines directly in the ground, and will open up the greenhouse during winter to satisfy the grape vine’s cold units for dormancy and then close the greenhouse just before spring. During this time, they heat up the greenhouse and force the grape vines out of dormancy, without the danger of cold damage to the vines. When the danger of cold damage is over, they will open up the greenhouse to let the heat from the sun into the greenhouse and the grapes will normally ripen. One very big advantage of growing grapes in a greenhouse, is that you can close the greenhouse when rain or bad weather is expected and therefore lower the chances of getting botrytis rot (grey rot) and downy mildew.
Growing grapes in pots is not ideal, as the root system of a grape vine is enormous, but there are greenhouse grape growers that prefer to grow their grapes in pot, and successfully do this as well. The reason for growing grapes in pots is the fact that the grape vine can be moved in and out of the greenhouse as they please.
For sure there are some obstacles when growing grapes in a greenhouse. For one, if the airflow, temperature and humidity in the greenhouse is not regulated, then diseases could become a headache. Even pollination will be a problem, as most grapes are pollinated by wind. Insects that penetrate a greenhouse, normally thrives on the plants because of the lack of predators in this controlled atmosphere. In other words, you will have to have a strict disease and insect control plan.
A greenhouse increases the productivity of your garden but making that decisions about the type of greenhouse you want to add to your garden, even if it’s some way off in the future, needs special planning. There is lots of help available out there, but make sure you do your homework before you start growing grapes in a greenhouse.
For a detailed and proven system for greenhouse veg and fruit growing, I do recommend the following website
A clear plastic tube that is filled with grape juice. The sugar content of the juice is measured in brix, and is determined by the hydrometer that is placed into the tube and floats in the grape juice. Take several bunches of grapes from different parts of a row and squeeze them in a plastic bag. 17 brix to 23 brix is what you are looking for, but some winemaker prefer to harvest no later than 17 brix – it is believed that this ensures a better wine flavour. It is up to you to experiment witn different brix levels, to be sure at what brix your grapes should be picked.