Growing Campanulas

Mar 1

Written By En

Taxonomy

Latin name: Campanula medium (Canterbury bells)

Kingdom: Plantae; Order: Asterales; Family: Campanulaceae (Bellflower family); Genus: Campanula

It is a classic biennial prized for its tall spikes of bell-shaped blooms in shades of blue, purple, pink and white. They are easy to grow and can tolerate short dry periods, especially in partial shade. Non-toxic to animals.

Growing in Zone 9b

Seasonal behavior: Annual
Height: 30-40”
Sow indoors 6-8 weeks in July/August (6-8 weeks before September/October), cover with vermiculite. Sowing in January is ok
Germinates at 65-70F in 14 days, requires light
Plant out in September/October, 4”-6” apart (for Jan-sown, plant out in Mar).
Soil: Well-draining, 6.0-7.5 pH. Avoid heavy, soggy soils
Light requirement: Sun, tolerates part shade
Watering: Moderate watering, about 1 inch per week, more during hot/dry spells. Deep watering not essential
Support: Yes, netting

Pests/diseases

Generally healthy, I never had any issues with them

Organic Fertilizer

Organic Chicken manure pelleted to prep garden but test your soil for pH to be sure
Fish fertilizer every week, helps produce blooms

Harvesting

Blooms in 120-150 days from germination
Harvest when top flower is open or buds are showing color
Where to cut: At the very base

Lessons Learned

When I sow, I only put one seed per hole but 2 helps, just in case the other one doesn’t survive.
Provide support netting, stem tends to flop as it grows.
Store upright to keep the flower from bending although curved stems add some whimsy to your arrangement!
Start sowing early to ensure plants are ready for fall transplanting. Last year, I sowed on March 1, and they bloomed in June without any issues—but starting earlier would have been more productive. The earlier you sow, the longer your stems will grow.
I planted them in part shade, and they survived, yay! The ones in full sun grew taller but flopped, with their flowers curving—just like snapdragons do when unsupported—because they became top-heavy. So, some kind of netting or support is definitely needed. They flopped because the stems were longer under full sun.
Frequent shallow watering encourages weak root development, increasing the risk of plants toppling over—so aim for 1 inch, infrequent watering instead.
When you buy seeds, note that they may be pelleted. Pelleted seeds are coated with a thin layer of inert material—usually clay, limestone, or a polymer—to form a smooth, round shape. Campanula seeds, for example, are pelleted because they are extremely tiny (almost dust-like), making them difficult to handle and sow evenly without the coating.
Test your soil to understand pH but since I use and replenish my garden beds with organic compost from Napa Recycling, my soil is always in the appropriate pH condition - 5.5 to 7.0 pH.

Regenerative gardening notes:

Healthy Soil: Composting, mulching, and minimal tilling to nourish life underground. I want to grow with the land, not just on it. It’s not just about beauty above ground, but life below it - soil that breathes, supports, and keeps giving.
Biodiversity: Flower taxonomy is one thing that I check all the time to ensure I am growing a variety of plants to support pollinators - bees, butterflies and good bugs and visiting birds and other animals.
No Chemicals: I grow my flowers organically, avoiding synthetic fertilizers and pesticides, and focus on applying sound cultural practices. I have plastic pots from the garden store, I try to avoid using plastic but to minimize waste, I reuse them or send them to places that recycle them - Home Depot, etc.
Closed-loop Thinking: Reusing garden waste and feeding it back into the system. I have not space to compost on my own so I send my compost-worthy trimmings in the composting bin.
Water-Wise Practices: I plant seasonal flowers that align with the weather, which helps with water management. My plan is to build drums to collect and store rainwater and to install an irrigation system.
Working with the seasons - I work with the seasons, planting flowers that suit the current weather conditions. No rushing nature.

Resources:

These are my go-to, trusted resources—everything I use in my own organic flower garden.

Seeds: Johnny’s Seeds
Organic Compost, Mulch: Napa Recycling
Medium to start/sow seeds: Use any organic soil starter
Fertilizer to start garden bed/soil: Espoma Organic Chicken Manure, I get mine from the Tractor
Support: Hortonova - I get them from Johnny’s Seeds or Amazon
Pest management: UC ANR IPM
Organic Fish & Seaweed Fertilizer - Neptune’s Harvest