Growing petunias

 Sowing:
To sow seeds in the house, from February 8 to 10 weeks before the last frost. Petunias bloom in the morning and covered with flowers are stunning. They like the sun and often bloom within two months from seed and continue throughout the season until killed by the frost. They are easily cultivated, requiring rich soil and full sun. They grow best in high-moisture areas with well-drained soils, but can adapt to most soil types. For Established the plants need  less maintenance require dry weather than other plants.
Seed 6 mm (¼ inch) apart in rows 7 cm (3 inches) mm, that's for sure stand (especially the corners), so it is not eaten with irrigation. Do not cover the seed, as the seeds need light to germinate.
Provide light and constant warmth of 21 to 27°C (70 to 80°F)   respectively. In fact, the heat source from bottom to the use of the best results . F2 hybrids tend at the end of the previous germinate much better at about 27c (80f).  F2 hybrids tend to germinate better at the higher end, at around 27C (80F). The soil temp should not fluctuate and must not drop below 21°C (70°F). Finely mist and cover seed tray with plastic or paper to conserve moisture.

Need to check the compost for dryness regularly.  Add a little warm clean water from below, if this is the case, being careful not to over water. Don't use too much water ,can die seedlings, as it can spread "damping off fungi", and encourage other molds and diseases. 

Germination:
  Usually seed takes 10 to 21 days for germination and it depending on soil and temperature conditions. After sprout the seeds remove cover as soon as possible. Keep moist but do not use cold water as it lowers the soil temp and weakens tender seedlings.
  Transplant and grow on in cooler conditions, around 13 to 16°C (55 to 60°F) for stocky plants when seedlings are large enough to handle.  Acclimatize to outdoor conditions for 10 to 15 days before planting out after all risk of frost, 30cm (12in) apart in a sunny spot on light well drained soil. For pot plants, transplant the seedlings into 7.5cm (3in) pots, grow cool, well ventilated and give plenty of light, but shade from direct sun.

Cultivation:
When plants are 5 to 10cm (2 to 4in) tall, and ground is warm, transplant to their final positions in pots or into the garden, spacing 20 to 30cm (8 to12in) apart. Plant should be  a full sun location. They will tolerate light shade but blooming will be reduced. Use a low-nitrogen/high-phosphorus fertilizer sparingly. Do not over-water or over fertilize, Over-watering will  kill the plants.
After planting into baskets, when established give them a good spray from a watering can. The weight of the water flow will produce a perfect cascading habit.
Pinch or shear when 15cm (6in) tall and keep faded flowers picked, for denser plants and more flowers,
Petunias are sticky and will attract greenfly so keep an eye on them. Don't over water in the winter and keep them well ventilated.

Site and soil:

The most important requirement for growing petunias successfully is a location with plenty of light. Petunias need at least five or six hours of good sunlight; they'll perform even better when located in full sun all day. The more shade they receive, the fewer flowers they'll produce. Impatiens are a better choice for blooming in shady places.While soil needn't be terribly rich to grow good petunias, it must drain decently. It's always useful to improve garden soil by conditioning it with organic matter, such as baled peat moss, well-rotted leaf compost or manure.Spread the organic matter two to three inches thick. Then incorporate it into the soil to a depth of eight to ten inches, using a rototiller or garden fork. This helps open up heavy clay soil, which improves drainage, but can also increase the ability of light, sandy soil to hold moisture and nutrients.

Fertilizer and water:

Work a balanced fertilizer such as 8-8-8, 10-10-10, or 12-12-12 into garden soil at a rate of two pounds per hundred square feet. Later--early to mid-July--begin to use liquid fertilizer every three weeks (weekly for "spreading" petunias). Once the plants have begun to spread, it will be much easier to water this solution into the soil than to side dress with dry fertilizer.
Incorporate timed-release fertilizer into the soil when planting window boxes or other containers. Otherwise fertilize regularly every two weeks with a liquid fertilizer meant specially for flowering plants. ("Spreading" types require weekly fertilizing.)
For a fertilizer recommendation tailor made to your specific garden conditions, have an accurate soil test run. Contact your local County Extension office or the Soil Testing Lab at the University of Minnesota for information.
Petunias tolerate lots of heat, and are relatively undemanding when it comes to water. Except for "spreading" types, which require frequent watering, thorough watering once a week should be sufficient in all but the worst weather. Leave sprinklers on long enough to soak the soil to a depth of six to eight inches every time you water. Hanging baskets and other containers also need more frequent watering, perhaps as often as daily, depending on their size and the volume of soil they contain.


Plant Uses:
Window boxes, containers, tubs, hanging baskets and pot plants.
Origin:
The species was first sent from South America to Paris in 1823. It was discovered in South America by the explorer James Tweedie, (after whom the genus Tweedia is named), who sent specimens to the Glasgow Botanical Garden in 1831. Most of the varieties seen in gardens are hybrids (Petunia x hybrida), they were among the first ornamentals to be bred for the bedding plant market in the 1950s.

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