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Platycodon grandiflorus

Commonly known as “balloon flower”, the Platycodon has lovely small flowers with unique paper like texture and visible veins. The common variety in my area (Tokyo, Japan) has purple and white flowers. A notable feature of the plant is the flower bud, which swells like a balloon before fully opening.

At the supermarket or home centre it’s not hard to find them on sale in planters. As soon as I saw them the first time I decided I want to have them in my balcony garden.

I bought the seeds from Amazon and used a spare planter that I was planning to grow some vegetables. It turns out the planter wasn’t the best choice for Platycodons because the drainage is not good. More on that later.

There is plenty information about Platycodon online but their pictures at various growing stages and caring tips are hard to come by. I hope my experience will be useful if you also want to grow some balloon flowers!

Platycodon grows slowly in the beginning

For reference, the Köppen climate classification for Tokyo is “Cfa”, meaning humid subtropical climate. In summer the hottest day can go above 34 degrees Celsius. In winter it sometimes can go below zero degrees Celsius and perhaps snow a few days. The variety I have is a dwarf variety Samidare-murasaki native of Hokkaido, so extreme climates shouldn’t be a problem. In theory it will enter dormancy in winter and come back in spring. According to the back of the seeds package, the best starting time is either April or September.

I started my first attempt in growing them in September, 2019. Their germination needs light so it’s better to keep them in partial sun light or under shade. What I didn’t know is the seedling grows really slowly in the beginning. It took about 20 days for the seeds to germinate. Then it just seemed it’s going to take forever to grow their true leaves.

At this stage I faced another problem - watering the seedlings. Platycodon loves soil with good drainage, even a bit sandy quality. I needed to keep the soil moist but not wet. The problem was they grew so slowly they didn’t really use much water. The planter I used made the situation worse becase it’s designed to preserve water. So it’s kind of hard to gauge how frequently and how much water was needed.

Another problem for me was the growing season was too short. In order for the Platycodons to survive the dormancy I think they need certain mass in their fleshy root. I suspect they were focusing on growing the root system so their foliage grew slower in the beginning. In the end the time wasn’t enough for them to grow into the size to survive the cold spell.

During winter the plant parts above the ground died down. Be patient and keep the soil moist; they will eventually come back around April. Yes, around the time I lost my hope and started my second attempt.

Starting in earlier spring is much easier

It turns out if I only started in April, the result is still the same. Although they still grow slowly in the beginning, eventually they start to grow the foliage vigorously after they are more established.

This time I kept the seedlings in an egg container box because it was easier to control the watering. I recommend using the bottom watering method because water from top might move the seedlings and prevent their root system from settling down.

The relative warm weather in spring seemed to help the growing of the seedlings. However comparing to the basils next to them, they are still in totally different leagues.

Their roots started to emerge from the bottom of the container, so it was time to transfer them to the bigger planter. They don’t like their roots being disturbed, so re-potting needs to be done carefully and before grow too large.

Another two weeks after re-potting the Platycodons, they started to show visible foliage growth. The original two sets of true leaves grew larger and all of them started to grow the third set of true leaves.

The other side of the planter was empty because I was thinking to plant another four Platycodon plants there. Why? I thought I need more of them to have more flowers. Look at them; they look like they will only grow one shoot and one flower bud. A lot of pictures I found showing them growing in clusters. I was wrong!

Platycodon is capable of growing multiple side shoots

One month after transfer them to the planter, they started to show their tendency of their decumbent stems. Initially the stems grew upwards but then some of them started to lying along the surface and then turning upwards again.

They grew towards all directions. If one only look at the end of the stems, they would not be able to guess from where was the base.

As they grew larger they also started to grow new shoots from nodes on the stem and the base of the stem. It became clear that a lot of “cluster” picture I saw may actually be from only one or two plants.

If you look carefully you might find some white spots on the leaves in above images. I suspect it’s a kind of fungal disease. Luckily they didn’t seem to have material impact on the plants.

Platycodon may produce flower in first year

I was worried that I may not get any flowers this year because they grew so slowly. However, around end of July some flower buds started to appear on the top of the stems. I was so excited to see the “balloons” growing bigger and bigger.

One day the biggest balloon suddenly got some shade of purple. I knew it was going to pop but when? By the way, the balloon flower is typically associated with autumn by Japanese so the timing is right on the spot.

The next day, the flower opened while I was watering other plants in the morning.

There are more flower buds and new shoots growing. Hopefully this autumn I'll have a lot of new balloon flowers!

Do you grow balloon flowers? Do you have tips you want to share? Drop an email or leave some comments :)