102 | Pruning Petunias

Today I’ll be pinching back petunias that are in hanging baskets, deadheading fading flowers, removing developing seed pods and giving a general trim to rid the plants of any leggy growth so that they maintain their bushy appearance and continue to flower profusely.

Planting out petunia plug plants grown from seed

I grew the petunias from seed at the end of February and slowing began planting them out from May onwards. My plug plants were quite leggy because they were grown in a south facing window as opposed to being grown under grow lights and were in their little cups for far too long so my hanging baskets and containers weren’t very attractive to start with.

March 22 | Petunia seedlings three weeks post sowing

March 25 | Four days after petunias transplanted from seed trays to 4oz cups

May 28 | Petunias have outgrown their 4oz cups

May 29 | Petunia plug plants potted up in hanging basket three months after being sown

This wasn’t discouraging because I knew that once they became established in their final containers and got trimmed, they would become fuller and compact over time.

Soil Mix for petunias in hanging baskets and containers

I used my general home made soil mix to plant out the petunias which consists of:

• Peat moss
• Compost 
• Vermiculite 
• Perlite
• Bone meal
• Lime
• Granular all purpose slow release fertiliser

Some gardeners like using water retaining gel capsules to help retain moisture but I opted not to add this to the mix because I was prepared to water them daily.

Cutting back petunias hard for the first time

Once there was some significant growth, I gave the plants an aggressive cut back to encourage side shoot growth. They looked super unattractive but in just a few weeks time, they began to really fill in.

June 12 | Blooms appearing for the first time

June 20 | Slowly filling in

June 20 | Slowly filling in

June 29 | Ready for the first hard cut back

July 1 | Trimmed

I decided to cut each main stem separately as opposed to randomly trimming away at the entire group of plants simultaneously. I did this so that I ended up with a neater appearance by cutting right above a leaf nodule - not in the middle of a stem which would have given it a twiggy look.

Cutting back petunias hard for the second time

After inspecting the petunias more closely, I realised that just dead heading faded flowers and removing seed pods would not be enough. The plants were beginning to become leggy and they were slowly loosing their compact, round shape. Gaps were beginning to appear due to leggy growth and the weight of the flowers were weighing the branches down, revealing the black hanging basket frame underneath. 

The best approach would be to cut as much as I could off (about 1/3 of each plant or two to three inches from the base). This would mean that I would loose just about all of the flowers but it will make for a more attractive hanging basket in the long run.

Tools I use for pruning petunias 

Not much is needed other than:

• a pair of gloves (petunias are very sticky), 
• sanitised cutting tool (sanitised to prevent cross contamination from previous cuttings) and 
• a container to put the cuttings in.

How I approach trimming leggy petunias

I decide on a general cutting height for the entire basket by looking for the shortest branch. I use that as a rough guide for the height I’ll cut the remaining branches to.

Looking for a leaf node, I snip directly above it being sure not to cut any new side shoot growth.

Once I’ve finished cutting everything back, I look for any developing seed pods and cut them off. If the plants are allowed to set seed, they would stop producing blooms because they’ve completed their one objective - reproduction.

Petunia seed pod which will ripen in two weeks time

In about two weeks time blooms will start to appear and at the three week mark, it will be smothered in blooms.

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Q&A

I started this project with a few questions in mind and have since found answers to them either through my own experience or via the internet: