Carlina acaulis Seed Germination

[CG100]

One thing I can say is that Carlina is an extremely tough plant forming a big and very deep tap root. So for sure it will not be happy in a pot

Some years ago, we visited a local plant nursery on their open day, when visitors could walk around the whole nursery.

Growing on their huge compost heap were dozens of flowering milk/St. Mary's thistle (Silybum marianum). I have always liked the plant but these were trully spectacular and they were covered in bees.

We got back to the nursery proper, to pay, and complimented them upon their spectacular display and were told that they agreed, and had tried growing it in pots, for sale, but with no root room, they grew to no real size and then flowered.

If anyone has the room, it is certainly well worth growing - here it normally reaches 1-1.5m, maybe a little more if happy. It is a solitary biennial, so should never outlive its welcome.

Sometimes restricted root room has beneficial effects though - out walking in local meadows we found a mullein around 45cm tall growing in minimal soil amongst rocks, in flower with the most intense, deepest pure yellow flowers imagineable. It looked a lot like Aaron's rod (Verbascum thapsus), which I also really like as a garden plant, but way too small and with amazing flowers, and it had a few ripe seeds, so I took the seeds home.
It is/was very standard Aaron's rod.

[Bern]

Success!!! Here is a photo of my Carlina acaulis seedlings. The cold stratification apparently was the key to success. I planted about 10 seeds and 6 germinated. After a particularly cold and rainy night, 3 perished and 3 survived. When these guys get a bit bigger, I will repot them into larger and deeper containers. I'll then get to see if they will grow in the heat and humidity here in the summer.  I will protect them from torrential summer rain by moving them under the patio. The good thing is that I learned how to get them to germinate and it only took 2 seasons. 

[Bern]

But if you have hot summers, expect the seedlings to die soon, unless it cools down in the night to 15 degrees or less. At least, that's what happens in the Pyrenees, where I have seen it wild.

One thing I can say is that Carlina is an extremely tough plant forming a big and very deep tap root. So for sure it will not be happy in a pot and therefore I recommend planting seedlings into their permanent position as soon as possible.

Here's an update on my Carlina acaulis plants. I transplanted my seedlings into larger pots around June 1st. They did not like this. One of them perished and the other two pouted for several weeks. I live in USDA Zone 8a in a humid, subtropical climate. During July, there have been many very hot days, some as high as 99F (37C). Most nights have seen a low temp around 74F (23C) or above. There was an unusual amount of rain in July with more than 12 inches (30.5cm). It's been brutally hot and humid, to put it mildly.

In spite of this, C. acaulis is alive and growing in pots. I keep them on a covered patio where they get a few hours of morning sunlight and then bright, indirect light the rest of the day. I protect them from the rain and I hand water them. I was surprised how much water they like.  Next season, I will plant seeds in 3 gallon nursery pots so they don't have to be transplanted.  I will give them more sun, but I will still protect them from excessive rain. There's a good possibility that they would be able to grow in a raised bed with well draining soil. And all of this work is because this plant has an interesting and pretty flower.  I encourage anyone who is interested in growing this plant, but was hesitant to do so because they thought it was an "obligate" alpine plant, to reconsider growing it in pots.  Ill post photos if I get flowers. (Yes, they look a bit ragged, but they are a work in progress!)

 

[Bern]

Here is a photo of my plants on September 10, 2024. They have exceeded my expectations and have thrived in the hot and humid summer weather in Tidewater Virginia, as well as growing splendidly in pots.  The plant on the left is in a black nursery pot that is about 7 inches (18 cm) tall.  The plant on the right is in a clay pot that is about 5 inches (13cm) tall. I suspect that these plants would remain evergreen under the right conditions and not subjected to freezing temps. I intend to bring them inside this winter and keep them under lights to see how they will fare. My only regret is that they did not flower for me yet this season. Perhaps these plants might even be able to be grown in pots in south Florida if protected from excessive rainfall.

(If you see a thumbnail photo of the plants on your screen, you can click your mouse cursor on the photo and it will expand for you.)