If we leave seeds in the wild, the result can disappoint us. The living conditions outside are not always ideal. An indoor greenhouse, on the other hand, provides constant heat and humidity. Don’t be put off by the word house and build it yourself using readily available materials, some of which are free. We provide ideas including instructions and explain what to look out for.

When an indoor greenhouse makes sense

A greenhouse is not an equivalent alternative to the great outdoors. But there are situations in which it can usefully complement them. Because it offers:

  • weather-independent, “growth-promoting” temperatures
  • high, even humidity
  • constant living conditions
  • Protection of seeds/plants from harmful external influences
  • A head start for garden crops
  • “Replacement bed” for people without a garden
Tip: When it comes to exotic plants that are used to high temperatures in their homeland, or sensitive seeds, a greenhouse is usually the only way to propagate them.

Key data of a construction plan

Of course, there are numerous small and large indoor greenhouses to buy on the market. But with a self-made example you can create individual solutions. In terms of sustainability, materials that would otherwise end up in the garbage can can be used. Besides, it saves money. The following instructions are examples that you can build 1:1 or use as a suggestion. Because with a little imagination and skill, you can easily create your own indoor greenhouse. It just has to meet a few conditions:

  • provide sufficient space for planting
  • have enough depth for soil and seedlings
  • if possible have an underside provided with drainage holes
  • have a water drip tray to place underneath
  • have a sufficiently high, light and air-permeable cover
  • should be flexible to cover

The materials used must also be such that they can safely survive at least the period of time required for rearing.

Suitable location

First find a place to set it up, then build! This is the only way you can know what dimensions the greenhouse can have. The optimal location has these characteristics:

  • enough brightness
  • Close to the window is ideal
  • but without direct sunlight
  • warm air temperature
  • warm, insulating ground
  • adequate air circulation
  • good accessibility
Tip: If you measure the available space exactly, you can build the greenhouse to fit perfectly. Especially on windowsills it is important that it has a stable hold and cannot tip over with its contents.

“Ready” mini greenhouses

In theory, the smallest indoor greenhouse can be so small that it can only accommodate a single plant or seed. The advantage is that you can find a suitable place for it even in the smallest apartment.

Disused packaging from the trade is ideal as a mini greenhouse. Some are so perfect that nothing needs to be changed before planting. Here some examples:

  • rectangular plastic bowls with lids
  • e.g. B Sales packaging of grapes, tomatoes, etc.
  • common 1-kg cans of gummy bears
  • clear milkshake cups with lids
  • all containers must have holes in the bottom and lid
  • or get them afterwards
Note: Mini greenhouses from retail packaging still need to be supplemented with a waterproof tray that catches excess irrigation water.

Small indoor greenhouse

If you want to plant a larger area, you will reach your limits with “ready-to-use” mini greenhouses made from sales trays. In such cases we have to prove our handicraft skills and build a larger indoor greenhouse. You will need this material for the following instructions:

  • a standard box of mandarins
  • or an even bigger fruit box
  • stable plastic film for lining
  • translucent film for covering

Some plant species form long taproots. Others, on the other hand, the so-called flat roots, form richly branched roots to the side. If the seeds are sown closely, the roots of the individual plantlets can easily get tangled. When transplanting later, they must be separated, which often damages roots. This must be prevented. The small greenhouse is varied for these types of plants. You will then also need:

  • empty toilet paper rolls or kitchen rolls
  • some toilet paper or kitchen roll

instructions for construction

Steps 3 and 5 are only required when sowing shallow rooted plants.

  1. Lay out the fruit crate with the sturdy plastic film.
  2. Fold the ends of the foil outwards and staple them in place from the outside.
  3. Divide each toilet paper roll in two. Kitchen rolls are divided into four parts.
  4. Place the loo roll pieces in the box until the entire room is filled. One open end of each should be facing up.
  5. Insert 2-3 sheets of toilet paper into each opening and press them down. This is to prevent potting soil from trickling out later.
  6. Cut the foil for the cover. It should be slightly larger than the open area so that you can also attach it.
  7. Cut some ventilation holes in the cover foil.
Tip: If you have a suitable waterproof saucer for your indoor greenhouse, you should poke a few drainage holes in the foil lining.

A stable greenhouse

Building a stable indoor greenhouse is more work, but it also comes with a few benefits:

  • can be used for several years
  • can be used for sowing and cultivating some plants
  • can be made visually appealing

For the construction you need the following materials, the size of which must be based on your plans:

  • a large, untreated wooden board as a floor
  • four wooden boards cut to fit the side walls
  • brackets and screws
  • wax
  • cut Plexiglas as a cover
  • alternatively a foil stretched on a frame
  • two or more hinges
  • possibly paint for painting
Note: If you only need the greenhouse for sowing, side walls approx. 15 cm high are sufficient. If you want to plant lettuce, herbs or other plants, you should build it with correspondingly higher walls.

instructions for construction

  1. First wax all the boards to make them more water resistant.
  2. Screw the four wooden boards into a frame.
  3. Screw the frame to the floor board using angle brackets and screws.
  4. Drill holes for the hinges in the Plexiglas.
  5. Attach the hinges to the cover and frame.

Special equipment

If the site conditions for the indoor greenhouse are not optimal, you can help:

  • A heating mat provides more warmth in cold rooms
  • she comes under the greenhouse
  • Plant lamps bring more light

Ideal time for planting

Unlike outdoors, indoors can be warm all year round thanks to heating. If there is also enough natural daylight or, alternatively, special plant light, you can theoretically plant plants in your greenhouse whenever you want. However, if the young plants are only brought forward and later planted outside, they must be sown in good time so that they are the ideal size at the time of planting.

  • Germination time and growth rate depend on the plant
  • Note the information on the seed packet
Tip: If you sow different types of plants in a greenhouse, you should only combine those with similar requirements. In particular, it is crucial for success that they need a similar germination temperature.

suitable soil

Poor potting soil is usually recommended for sowing. You can buy it in stores. If you use a different type of soil for cultivation, you should first sterilize it in the oven or microwave to kill germs. Some plant varieties require special soil. You should give them this so that the seed germinates safely and the seedlings then develop optimally.

In addition, coarse drainage material such as gravel is useful. Especially for greenhouses without drainage holes and for plants that are extremely sensitive to waterlogging.

Instructions for planting

  1. Put the gravel in first. The height of the layer is determined by the size of the greenhouse. 2-3 cm is ideal.
  2. Cut a suitable piece of plant fleece and place it over it. It will prevent potting soil from mixing with gravel. This can be dispensed with in mini greenhouses.
  3. Now fill in the soil.
  4. Scatter the seeds evenly.
  5. You can label different seeds with a label.
  6. Scatter soil over again if and as much as is necessary. Light germs, for example, do not have to be covered or only slightly. E is enough if they are pressed. Corresponding information on sowing depth can be found on the seed packaging.
  7. Dampen the soil with a spray bottle.
  8. Close the greenhouse lid and, if necessary, optimize its location.

cultivate plants

An indoor greenhouse is usually only used for cultivation. But if you can build a sufficiently large greenhouse, you can continuously cultivate plants in it. Salads and various herbs are ideal due to their size. Her short cultivation time is also a plus. But in principle other plants can also live in it if the conditions are right.

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