Hamburg - Orchids, cyclamen and cacti - put them next to one another on a windowsill, add a little fantasy and together they become more than just a few plants positioned where the sun shines in.

They become a lovingly-arranged, potted garden assembled with the help of a huge selection of house plants now available in shops.

"Thirty years ago you had more or less the same 10 plants, but today there are about 250 green candidates to choose from," said John Langley, a master florist from Hamburg.

However, not all the plants on this list are appropriate for every apartment. Temperature, humidity and available light set parameters. House plants generally do best in a room that is kept at 18 to 20 degrees centigrade with a humidity level of 40 to 60 per cent. South-facing windows can be problematic.

"Very few plants can tolerate long-lasting direct sun," warns Marcus Klemke, a manager at a plant shop in Werl, Germany. "Among them are cacti and succulent plants with thick fleshy leaves. Almost all other houseplants need at least temporary shade when the sun is strong.

To make the windowsill look uniform and harmonious, the plants need a binding element.

"A common colour, for example, can be used to tie the plants together," said Langley. This could be a combination of plants with green and white leaves or plants that bloom in orange.

The pots can also play a role when they are all made of the same material or have a unifying shape.

"Baskets are still trendy. In addition high quality material that has a glossy finish is coming on strong," said Julia Bockheim, manager of buying in the indoor plant and accessories division of a garden centre in Heilbronn. To ensure that the pot is still large enough when it's time to repot, use a larger size right from the beginning.

"Small pebbles or florists clay can be placed in the bottom of the pot and the plant can be placed on that," said Langley. This props it up and lets water run out through the holes in the bottom of the inner pot.

The way the plants are arranged can underscore their relationship to one another. Instead of placing them all in a row, consider grouping them. Variation in height creates a lively look, said Klemke. Grouping a plant that grows upright with a low one and a hanging plant works well.

Putting plants close together in the same pot is another way of displaying houseplants.

"They can, however, be planted right beside each other only when their water need is the same," Klemke warned. The alternative is to combine a number of planting pots inside a larger one. Covering the spaces in between with sand, gravel or decorative pebbles makes it look a bit like a miniature landscape. (dpa)