Now, it varies by type of plant, but most of the plants we have in our homes, and above all those we like to surround ourselves with in pots, urns and hanging baskets during the summer half of the year, cope poorly without supplementary lighting.
Many of the annuals we have outdoors can happily be overwintered and become even nicer next season as long as they get access to the right lighting.
When the sun is shining in it is easy to think ‘it’s quite bright in this window’, but no, it isn’t particularly bright for a plant, and the time it is light during the late autumn months, winter and early spring falls far short of what plants need to thrive and feel well.
Overwintering without light
For some types of plants there are well-proven ways of getting them through winter without extra light. These are the plants that can basically go dormant during the cold, dark part of the year. They include, for example, pelargoniums, fuchsias, angel’s trumpets and most tuberous and bulbous plants. The condition for them to survive without light is that they are kept cool but frost-free. It is also important that it isn’t too damp, to avoid attacks by mould spores. When it is cool and dark, growth stops, the roots partly dry in and the plant rests. It is therefore also very important to water only very little, very seldom.
Supplementary lighting
With the right lighting you can in principle grow anything at any time of year. The biggest problem is usually space!
An ordinary, old-fashioned incandescent bulb doesn’t make any plant happier. At too great a distance it gives too little light, and if it is ‘close enough’ the plant gets burnt.
Today there are different types of lighting designed especially for plants. Which you choose depends on the placement and what it is to be used for.
Fluorescent tubes and compact fluorescent lamps
For a single plant, a small fitting with an ordinary low-energy bulb or a special grow lamp gives a good result. If you have several plants to light there are different types of fluorescent fittings designed especially for plants to choose from. They can be used both for lighting adult plants and for raising cuttings and young plants. Fluorescent tubes should be placed relatively close to the plants, so it is practical if you can easily adjust the height, e.g. if it is used for raising new plants.
When you choose a fluorescent fitting, find out what area it covers, the weight (for the suspension) and the type of fixings. The look can also matter, as not all of them are attractive enough to put in the living room or kitchen. Imagine having constant access to fresh, lush herbs in the kitchen window or on the worktop without having to buy new ones every other week.
T5 fluorescent tubes
There are now several new developments in plant lighting that are really worth mentioning.
One is the so-called T5 fluorescent tubes, which give a very broad light spectrum that is optimal for plants, and the other is the new LED technology, which has gradually begun to find its role in plant growing.
LED lamps
LED lamps are very energy-efficient relative to the output they give the plants. The drawback is the slightly odd blue and red colour, for us humans, which you might not prefer in a living space, but which is fine in a plant room, a cellar or a greenhouse.
High-pressure sodium and metal halide lamps
For anyone with access to a somewhat larger space for overwintering and raising plants, a high-pressure sodium lamp or a metal halide lamp may be the solution. These are the type of lamps that most professional growers have in their greenhouses. The advantage is that they give a really good light that covers up to 10 square metres. The drawback is that it is quite heavy, uses a fair amount of electricity (the lamp is often 400 W) and gives off a great deal of heat. The heat can, however, be an advantage in cool spaces such as a glazed balcony or terrace, where it can help with heating. In a smaller, well-insulated space it quickly gets quite warm. A lamp of this type should hang two metres above the plants and no closer than 1.3 metres, as the plants are then easily burnt.
The choice of lamp type depends on whether the space to be lit also has some daylight, as in a greenhouse, or not.
With a metal halide lamp a garage or an otherwise completely dark space can be turned into a jungle. On a glazed terrace, balcony or in a greenhouse a high-pressure sodium lamp is good. The difference between the two types is the colour spectrum they give off. The metal halide lamp has a spectrum that gives sturdy, fine plants even without added daylight, which is not needed in, for example, a greenhouse with plenty of daylight.
Lighting time
Use a timer to regulate the lighting time.
How long the lighting should be on each day depends on the use and the temperature. At lower temperatures plants manage with a shorter lighting time. At room temperature plants do not rest at all, but need lighting for at least 12 hours. When overwintering plants that are not to go dormant, 8–10 hours may be enough. They then grow a little and flower now and then. When spring comes and you want to kick them properly back into life, you gradually increase to 16 hours a day. 12–16 hours is also right for sowings and cuttings.
During parts of the season natural light may be sufficient for a couple of hours in the middle of the day, and you can then set the timer so the lamp has two lighting periods and thereby save a couple of hours of electricity.[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column]