Origin and history
the plant-type of the Petunie (Petunia) belongs to the nightshade-grounds (Solanaceae) and is relative with the tobacco-plants (Nicotiana), to whom it owes its name, means “petun” in the language of the Brazilian natives “tobacco. Their original home is tropical South America. Petunias are among the garden flowers with the longest garden tradition, because the magnificent summer flowers bloom tirelessly from May until the first frosts with large, brightly coloured flowers. The garden petunia (Petunia x hybrida) is in the 19th century from a crossing of the white petunia (Petunia axillaris) with the purple petunia (Petunia integrifolia). Most of the varieties currently on the market are garden petunias.
Botanically speaking, the petunia is not a flower, but a fast-growing, shrub-like herb. Its appearance, with funnel-shaped flowers on dark foliage, is typical of the plant genus and easy to recognise. The classic garden petunias are divided into four main groups: Grandilflora petunias, which score with their oversized flowers, Multiflora petunias with compact growth and countless smaller flowers on short stems, the NanaCompacta petunias, which grow rather small at 15 centimetres, and the elegantly hanging Pendula petunias.
Petunia’s leaves are dark green, with entire margins and slightly hairy. Typically they are slightly sticky. They form a contrasting background to the fresh flower colours. Attention: Since the Petunia belongs to the nightshade family, its foliage is poisonous!
Petunias are characterised by their trumpet-shaped flowers in the summer colours white, pink, violet, red or blue, with spotty, starry or striped patterns that appear tirelessly and in large numbers from May to October. Grandiflora petunias and multiflora petunias differ in flower size. Representatives of the Grandiflora breeds are characterized by a very large, flat flower, which sits individually on the stem. Multiflora petunias, on the other hand, carry their somewhat smaller flowers close together and appear rather compact due to their shorter shoots. Filled specimens with their round heads are reminiscent of rose petals and are therefore also sold under the name Rosen-Petunien.
Garden petunias are not always monochrome. In the meantime, dotted, speckled and striped varieties are also available.
Location and substrate
Petunias are typical summer-flowering balcony flowers, so they need a lot of light. The plants also thrive in semi-shade, but then fewer flowers form. Hot summers and blazing sun do not harm the sun worshippers. However, their delicate flowers suffer strongly from wet and cold weather influences, so a location sheltered from the wind is recommended. Grandiflora petunias should be protected from rain in any case, as the large flowers quickly wash out. The smaller the flower, the more robust the variety is. For flower pots and boxes, special ferrous petunia earth with a low pH value (about 5.5) is available on the market, the composition of which is well adapted to the needs of the plants. Alternatively, normal potting soil can be mixed half with bog bedding as substrate.
Planting and care
Petunias can be sown in seed boxes in the greenhouse or on the windowsill from mid-February at 20 to 21 degrees Celsius. The seedlings may then be slowly accustomed to the fresh air after the ice saints. Usually, however, summer flowers are sold as young plants in pots, which are then simply planted in the early summer directly in the desired place.
To stimulate the beautiful growth of the petunia, it is necessary to regularly clean the plants. In the process, flowered, wilted shoots and damaged areas are removed. An occasional pruning also has a stimulating effect on flower formation. Water is poured abundantly with water low in lime (rainwater), on hot days in the morning and evening. Always water the soil directly, don’t overdo the leaves or flowers! The colourful summer bloomers grow very quickly, so they have a high nutrient requirement. The Starkzehrer need a well-permeable, fertile soil. Fertilizer should be applied every 14 days with phosphorus-based flowering plant fertilizer.
Garden petunias are annual and not frost hardy. If you would like to overwinter the plants, you can do so in a bright, cool room (five to ten degrees). To do this, prune the plant back strongly. Before the night temperatures go below zero, the plants should be cleared. In the winter quarters a little water must be poured regularly.
Use in the garden
Because of their luxuriant growth and abundance of flowers, petunias are very popular as plants for pots, flower boxes and hanging baskets. Whether as solitaires or as underplanting for tall stems such as roses or Wandelröschen – the colourful flowering wonders cut a good figure everywhere as long as they get enough sun. Garden petunias also feel at home in the bed in company with other annual summer bloomers. But do not put the fast growing petunias together with weak-growing partners. Suitable plant neighbours for petunias are for example snowflake flower, marigold, verbena, pelargonium, ipomoea, lobelie, dahlia, fuchsia or coneflower. The Petunia belongs to the classic farmer garden plants, therefore it can also be used decoratively with vegetable plants or herbs in boxes, tubs, barrels or troughs. Ornamental grasses form a delicate contrast and loosen up the sometimes somewhat gaudy petunia floral pattern. Leaf ornamental plants such as Gundermann or Buntnessel also bring optical calm into the planting.
Plant neighbours in the our store-Shop
At the moment there is a trend towards small flowered varieties such as the magic bells (Calibrachoe), which are available in all colours. These resemble the gardenpetunias optically strongly, however, belong botanically seen to another type. Filled varieties from the Bonanza range are also in great demand. Cascade petunias (also known as magic petunias) such as ‘Giants of California’, whose long shoots pour over boxes and railings like a waterfall of blossoms, belong to the permanent burners of balcony and traffic light planting. The Plum Petunia displays veined flowers. Who loves it discreetly, reaches best for the Celebrity series. This variety specializes in flowers in fine pastel shades with a light throat. A Japanese new breed is the very robust Surfinia Petunia. Its large flowers withstand even prolonged downpours.
If you want to propagate a particularly beloved variety, you can collect seeds from the flowering plant in autumn. Do not clean out the petunia, but wait until seed capsules have formed. These are then harvested and allowed to mature in a warm room. If the seed capsules pop open by themselves, the seeds can be collected and kept cool and dry. In February the seeds are sown under glass. If seedlings have formed, the small petunias are pricked and isolated into pots. Watch your step! Many modern breeds are disposable and therefore do not carry germinable seeds. Find out in advance from your specialist dealer whether pulling seeds is worth the effort at all.
Diseases and pests
Petunias are susceptible to tomato wilt and powdery mildew. Also the mosaic disease sometimes seeks the summer flowers at home. Therefore, you should already pay attention to withered leaves or white spots on the plants when buying. In addition, balcony flowers should be regularly checked for aphids and white fly infestation. In the garden, petunias often suffer from snail-eating. If the summer flowers suddenly get yellow leaves in the pot and tub, it is probably an iron deficiency (chlorosis). This can be seen in the young, regrowing leaves. An ammonium-containing fertilizer application provides remedy.
In an interview with our store editor Dieke van Dieken, plant doctor René Wadas reveals his tips against aphids.Credits: Production: Folkert Siemens; Camera and Editing: Fabian Primsch
I am Don Burke, one of the authors at My Garden Guide. I am a horticulturist that cultivates, grows, and cares for plants, ranging from shrubs and fruits to flowers. I do it in my own garden and in my nursery. I show you how to take care of your garden and how to perform garden landscaping in an easy way, step by step.I am originally from Sydney and I wrote in local magazines. Later on, I have decided, more than two decades ago, to create my own blog. My area of specialization is related to orchid care, succulent care, and the study of the substrate and the soil. Therefore, you will see many articles dedicated to these disciplines. I also provide advice about how to improve the landscape design of your garden.