There are a number of alpine or miniature plants that will self-sow in the rock garden. Some are dangerously invasive. I would never have planted so many thymes if I had known they would spread so well by seed! Others, however, seed for a few years and then disappear or have seedlings that are easily removed. One that falls into the second camp is Globularia trichosantha. It forms a small clump of shiny green leaves and the grey-blue flowers nod on short, wiry stalks. It's easy to snip off the dead flowers before they go to seed, but if you forget, you will soon see Globularias in other parts of the rock garden.

June, when do you sow the Globularia trichosantha seed, and what is the bloom period for it? It is such a lovely blue.

I've never been able to keep a Linaria alive over winter, but I did find one that came back from seed: Linaria aeruginia var. nevadense. I'm not sure if that's a valid name, but the grower assured me that's what was written on the seed packet. This Linaria is an airy sort of plant, with thin stems and gray leaves, and is hard to see until it produces little snapdragon-shaped flowers, which it does from early summer to late fall. The grower had plants flowering in various shades of red, from which I chose a dark purple-red, and most of the seedlings retained this color. I planted it in 2006, and seedlings flowered every summer for the next 5 years. I suspect its failure to appear after that was due to lack of open gravel for it to seed into, as creeping thymes and other plants had grown over all the open spaces.

Hi Lynn, we cross-posted! I haven't purposely grown Globularia from seed, but I'd guess that either sowing outdoors in gravel or sand in fall, or in periodically-chilled pots of well-drained mix in early spring would work. In my Zone, Globularia blooms from early to mid-May to late June or early July. I'm not sure how well it would grow in your Zone, but it would probably flower a lot earlier.

Thank you for the information June.
I also love your above photo of Linaria aeruginia var. nevadense, even the foliage is interesting.

One of my favorite self-sowers is Pulsatilla vulgaris, sometimes called Anemone pulsatilla, and commonly known as Pasque Flower. It is not in the least invasive, so you can enjoy the silky seed-heads that persist for some time after the lovely flowers are over. In my Zone it flowers from mid-April, which is before the last frost, to late May. The seeds will travel quite some distance in the wind, and I occasionally need to transplant seedlings that pop up in the gravel driveway on the other side of the house.

I planted a couple of mat-forming Scutellarias. S. alpina, the prettier of the two, with dark violet snapdragon-like flowers with pale violet lower lips, self-sowed for 5 years and then died out. Scutellaria pontica, however, has kept going for 7 years and can even cohabit with creeping thyme. S. pontica has clusters of small, pale purple flowers in summer (mid-June to mid-July in my Zone) and sometimes reblooms in fall.

This next plant is moderately invasive. It has a long flowering period (midsummer to early fall) and the first flowers are setting seed before the last flowers have opened, so it is impossible to dead-head it without cutting off open flowers and flowers in bud. My advice is to be ruthless and give it a late-summer haircut, but I often don't follow my own advice and spend time pulling up seedlings next spring. The plant is Scabiosa columbaria 'Alpina', and the original plant I bought in 2004 is still going strong.

JuneOntario said:... I occasionally need to transplant seedlings that pop up in the gravel driveway on the other side of the house.

Great observation there! Gravel and sand beds are amazingly good at trapping every seed that blows into them. Weeding the alpine beds themselves is pretty well a nonissue for me, but I do spend time weeding the edges, where vast numbers of seeds from every plant in the yard collect and start to grow!
Yes, all the Pulsatilla species are excellent plants for the rock garden, or the regular garden if you're in an area where conditions allow it (like here). Pulsatilla vulgaris is the easiest to grow and self seeds very well here too.

I grow a cultivar of Scabiosa columbaria but not in the rock garden - it's extremely vigorous in regular soil.

I see that the butterflies are enjoying your Scabiosa... We need more butterflies!

JuneOntario said: I would never have planted so many thymes if I had known they would spread so well...

It depends entirely on what your image of a rock garden is, and on what plants you want to grow and how... My own perspective is that if my whole yard was rock garden, I might have thymes in it but they are generally rather overly vigorous for the small rock garden, if you want to maintain space for a variety of less-dominating plants. (Fortunately, they do very well here outside the rock garden.)

Lori, I totally agree. Thymes are just too vigorous for alpine treasures to cope with, but they have their uses. I have encouraged thymes to colonize a wide gravel walkway on the south side of my house. There they form a multicolored carpet (pink and white flowers, dark and light green leaves), bees love the blooms, and the plants can withstand being walked on occasionally.

Absolutely. I have lots of thymes and enjoy them a lot - love watching the bees and butterflies in them!

This is one of my favorite rock garden plants. I have it in full sun and it seems to be very happy. I noticed that it may be self sowing, or sending new plants out from underground roots.

Wonderful, valleylynn! I couldn't tell you how many Polygala I've killed - too dry here, I think (unless I create a really special little area for them).

It is very dry here in the summer months, so not sure why it does so well for me in full sun. It has grown since the above photo taken last year
I also have another one that I got this last February, so not sure how it will do for me this coming year.

Those polygalas look yummy! Would they be hardy in my Zone? I planted Polygala sibirica, thinking that if it came from Siberia it ought to cope well with cold, but it didn't overwinter for me - maybe due to unreliable snow cover.

We have almost no snow cover. Not sure how they did the last 2 weeks. The temps went as low as 6 degrees F. For part of it they did have snow, so maybe they are okay. I will try to check on them before I leave for work tomorrow morning.
I read that they can be hardy down to minus 5 degrees F.
http://www.paghat.com/polygala...

And this site says down to zone 4a
http://plantlust.com/plants/po...

Pulsatilla vulgaris is very vigorous here and quite adaptable, and many do consider its self seeding invasive in the rock garden, but it doesn't reach into the wild lands. Still nearly all of us rock gardeners up here grow them, but usually keep a watch on the seed production.
A red selection growing in fairly rich soil:

That is lovely Rick. I wouldn't mind that one self sowing in my garden.

I got my first Pulsatilla this summer. Can't wait for it to come out of dormancy and bloom. And hopefully set seed.