By Jim Hole
If floral beauty is judged by popularity then petunias would surely wear the crown. When I look around the yards and streets of Canadian cities, petunias dominate. Today, they are grown in everything from hanging baskets to patio pots to flowerbeds, with some varieties are even used as annual, quasi-hedges.
There is little doubt that the ascent of petunias to the top of the bedding plant world has much to do with their beauty and diversity. But it’s the depth and richness of their genes that has allowed them to reach that lofty height.
Most of the garden petunias that we enjoy today are, primarily, the result of extensive plant breeding of two South American species: Petunia integrifolia (violet petunia) and Petunia axillaris (white moon petunia). The result was Petunia x hybrida, also known as the hybrid petunia. Plant breeders latched on to this hybrid petunia and developed a serious addiction to creating as many new and beautiful varieties as cross breeding would allow.
Part of the reason that petunias and their kin are able to display such a richness - and sometimes weirdness - of floral colours and patterns is because they possess what are known as “jumping genes”. Jumping genes are little ‘packets’ of genetic material that can jump within the plant’s DNA, resulting in some truly fascinating blotch-patterned and stripped flowers. I like to think of these genes as ‘cut and paste’ bits of genetic information that are ‘snipped’ from one variety and ‘glued’ onto another. If you’ve ever seen a flower that looks like it has been splashed with paint, you can be pretty sure that jumping genes were responsible.
Clever plant breeders have not only exploited the use of jumping genes but they soon discovered that they could cross-breed petunias with a closely related species called ‘calibracoa’ also known as million bells. So, today not only is there is a plethora of new petunia and calibracoa varieties, there are also many hybrids resulting from crossing petunias with calibracoas. The name for the resulting cross is ‘petchoa’ – rather unimaginative but at least it’s simple to remember.
The toughest job might just be selecting your favourites from the vast number of choices.
There are four broad flower categories: grandifloras (big flowers), mutlifloras (lots of good-sized flowers), millifloras (lots and lots of smaller flowers), minifloras (lots a and lots of tiny flowers). They are all great with each category containing some terrific varieties.
Once you’ve nailed down the flowers, it’s critical to choose only healthy plants whose growth habit is best for your yard. For example, a great series called ‘Littletunias’ have a fabulous display of small flowers and a nice, short mounding growth habit making them ideal for smaller yards. At the other end of the spectrum is the ‘supertunias’ series that have lots of big flowers and a very aggressive growth and are great for large flowerbeds.
Whether in containers or beds - and without exception – petunias and their relatives grow best with a wet/dry water schedule. In other words, saturating the plants with water, followed by a ‘dry-down’ period, keeps the foliage tight and tough while stimulating the production of blooms. I like to let the petunias dry to the point that there is just a bit of leaf wilt before soaking them once again.
All of the varieties are ‘heavy feeders’ so weekly feedings of a water soluble fertilizer like 10-4-3, or a controlled-release granular fertilizer will keep the plants flowering beautifully all season long. Hanging baskets, in particular, need to be fertilized at least once per week. Adding some SeaSoil (compost comprised of fish waste and bark) to the containers keeps the plants in great shape throughout the growing season. And keep in mind that the best floral displays are found in spots where the plants receive six hours or more of direct sunlight per day.
Now, if you are still somewhat confused by all of the permutations and combinations of species, categories, series, and crosses, don’t worry. I share your anxiety. For me, it begins the moment that I flip to the petunia section of our stack of seed catalogues and continues as I desperately try to memorize all of the bloody names of the new varieties!
If I can remember half of all the new introductions each year, I consider that to be a huge personal victory.