Petunias

(Question)

Can someone tell me the variety of Petunias we see in planters around the city they are usually pink and cascade all the way to the ground and flower all summer and if one can purchase seed some where

(Answer)

Thank you for your question to Toronto Master Gardeners. I share your admiration of the abundant flowering containers of annual plants that the city sets out all over town. Part of the city’s extensive urban beautification plan, I understand that the petunias are grown, with lots of other plants, in the greenhouses in High Park. One way to see them may be the annual Doors Open event that may, with much luck, be held again in 2021.

The question is, how can an urban gardener get the same effect at home?

Petunias are a hardy, showy, and very reliable annual plant that are understandably popular as tried-and-true for containers. They come in many colours from white to almost black. They come in solid colours and variegations—petals with white spots on purple, coloured petals with white edging (called “picotee”), and other bi-colours. Bloom sizes ranging from small to large are classified as Grandiflora, Multiflora, Milliflora, and Spreading (or ‘Wave’). New varieties of petunias have been cultivated for non-stop flowering. These annuals have no serious insect or disease problems.

Easy to grow, petunias need full sun for at least six hours a day. Use a potting soil if you intend to plant them in a container, and if you prefer to plant them in a garden bed, they aren’t fussy about soil quality. Weekly watering should suffice. Like most plants, they do need good drainage so make sure that containers have a sufficient number of holes, adding more with an awl or drill if necessary. Plant seedlings densely together to create that eye-catching appearance. The city often plants a few species together. Petunias look good planted with other trailing plants like periwinkle (aka Vinca; with dark green foliage), Dichondra (with silver or green foliage), or Lamium (with variegated foliage). You might consider the rule for container design—Thrill–Fill–Spill. Petunias are both fillers and spillers. For “thrill,” consider a tall plant in the centre such as a small variety of canna lilly or an ornamental grass.

Toronto Master Gardeners are unable to recommend sources for buying products like seeds, but you should have no trouble finding reputable sources. If you are determined to start petunias from seed, you will need to start 10 to 12 weeks before it’s safe to set them outside, so early March. The University of Minnesota site below provides excellent instructions for starting petunias from seed but it warns gardeners to expect a challenge. Petunia afficionados may use seeds when there is no other way of obtaining a particular cultivar. Instead, consider buying petunia seedlings in the spring. You can find many varieties and colours at large and small garden centres, home centres, and even at supermarkets.

The secret to the size of the city’s street containers is fertilizer! The city regularly feeds its hanging baskets with a fertilizer applied with a long hose and nozzle attached to large vats transported in city maintenance trucks. Petunias respond very well to being fed. At home, use a balanced fertilizer like 8–8–8 or 10–10–10 that you can buy at any hardware or garden centre. There are many kinds available from organic to inorganic, pellets to powders to liquids. Perhaps the most popular for petunias is an inorganic fertilizer that needs to be diluted in water and applied about every 2–3 weeks. Large spreading petunias may enjoy weekly feeding. Follow the package instructions.

Another essential practice to ensure ongoing bloom is deadheading. As soon as you notice a bloom drooping, pinch it at its base and pull upwards until it snaps off. Deadheading stimulates the growth of new blooms by preventing seed formation. It also ensures that your containers always look full, fresh, and tidy. You may want to wear garden gloves for deadheading petunias because the blooms and stems are quite sticky to the touch.

For more information, please see:

https://extension.umn.edu/flowers/growing-petunias

https://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?kempercode=a601

Dec 1, 2020)