Tips For Growing Amazing Petunias You Likely Didn't Know

Growing petunias isn't difficult gardening but there are a few tricks that will make your plants grow even better. The first is understanding there are several different kinds of petunias on the market (not just different colors)

Kinds of Petunias

One of the interesting things happening is the breakdown of some of these traditional "types" of petunias as the breeders work their magic - either increasing flower size or decreasing the amount of care needed to deadhead.


These have the largest flowers with 4-inch (10cm) flowers. They require constant deadheading to remove spent flowers or the flowers rot on the stems. These are the large flowering forms most often found in the plastic cell packs.

Growth spread from 18-24 inches across on average.


Are small flowering types 1 to 1.5 inches (2.5-3cm) plants and are most often found in hanging baskets or massed beds of flowers.


These are the blowsy double forms and they are appearing in all classes of petunias now with flower size based on the specific breeding - from small to quite large and it depends on the variety. So check the tag.


These have the smallest flowers - usually in the 2-inch (5 cm) range - but they are usually "self cleaning" meaning you don't have to pull the spent flowers off the plant. The flowers roll up, die and fall off the plant themselves. So yes, they will litter under any hanging basket. But they are the largest spreaders - a well fed Multiflora will easily reach 3-feet across. These plants respond the best to excellent feeding - every two weeks with an organic liquid plant food will give you a huge swath of color


Many of the modern varieties are sold under trade names such as Wave or Supertunia.

wave petunia

'Wave' Petunias on our front entrance.

How To Start Your Own Petunia Seed

When to sow: The first thing to understand is the timing of when to sow. This is what we call a 12-week crop so you sow the seed 12 weeks before you want to plant it outside in your garden. Count backwards from your planting date (third week of May) and you should sow seed the last week of February to first week of March.

Germinate seed at 80F (27C) soil temperatures for best germination. Lower temperatures will reduce germination rates but anything over 72F (20C) should give you decent germination indoors.

Growing On Temperature. Once the seed is germinated, night temperatures of 60F are the best.

Full sunlight with grow lights right above the leaves is needed to keep the seedlings short and bushy.

The seeds are quite small and when sowing, gently press the soil down so there are few cracks left in it and spread the seed on the surface. Then water with warm water. The watering will lift a bit of the soil and that's all the covering the seeds require. If you put them a quarter-inch down as many guidelines suggest, you'll be killing a great many of them.

Transplanting seedlings. When the seedlings have 4 true leaves (not the small first two leaves) transplant them into larger pots for growing in until it is time to plant them outdoors (after all frost)

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How To Pinch For Superior Growth

Not Many Folks Know This

The thing to understand about growing petunias is they are greedy feeders once they go into the garden.

And if you want to see superb growth - particularly on the multiflora types, you do have to feed at least weekly. These types are the greediest but also the fastest growing and heaviest flowering.

Full sunshine is best although they will flower and grow with a very light shade.

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