Physoplexis-Phyteuma

Phyteuma scheuchzeri

Phyteuma scheuchzeri, photo by Jeremy

Do you like blue unusually-shaped flowers? If so you will like Phyteuma scheuchzeri. This plant has spiky ball-shaped, sputnik like clusters of deep-blue flowers. It is a relative of campanulas but looks nothing like a bell. It grows in full sun, in rich soil with good drainage. Some say it is hardy to –10 degrees F since it is a European mountain native. Since it is an alpine I decided to grow it in a trough. I have had it for two years in Zone 4 but I do put the trough on the north side of the house in the winter. If grown in the rock Garden make sure in Zone 5 or colder that you give it protection if there is no snow cover. As for watering, leave the soil dry for a few days between watering. Like most alpines, fertilize in the spring and not in the fall, but some recommend the use of a slow-release fertilizer. (Chuck, Minnesota)

Additional comments on hardiness:
I've grown this species in northern zone 3 for a number of years now, in a dry climate that does not have reliable snow cover (Calgary, Alberta) and have found it to be completely hardy without protection. More cold-climate gardeners should try it! Mine are also in relatively rich garden soil, which seems to lead to it being quite a floppy plant; I suspect its form might be much improved if grown in very lean conditions. (L. Skulski)

Physoplexis comosa, photo by Mike Ireland

GROWING FROM SEED
NARGS members: for background, see "Patience without Risk: Propagating Difficult Small Seeds" in the Summer 2007 Quarterly, and "Gentianopsis and Gentianella from Seed" in the Summer 2008 Quarterly. For Physoplexis, I follow the procedure in the Gentianopsis article nearly step-by-step. Note that I do not sterilize the seed mix or the growing-on mix. I can't guarantee that this will work for you, since your soil may have troublesome critters in it.

I have found that Gibberellic acid (GA-3) improves germination in both Gentianopsis and Physoplexis. I make a 1000ppm solution, as per the instructions from J.L. Hudson (where I buy my GA-3). I then surface-sow the seed and moisten the mix with a fine spray of water. I then drip the GA-3 solution onto the surface of the potting mix, enough for thorough coverage. This is probably a much weaker treatment than is usually recommended, but it seems to do the trick and does not cause stem elongation. Both Gentianopsis and Physoplexis will also germinate without GA-3, but the percentage will be lower.

Physoplexis comosa, photo by Mike Ireland

Next the container is placed in a sealable plastic food bag, which is placed about 5 inches under fluorescent fixtures in an air temperature of 60 degrees F. The lights are on for 10 hours per day. The seeds germinate in two to three weeks. It is helpful for these tiny seedlings to start photosynthesizing as soon as they germinate. This is a great advantage of germinating them under the lights. Once a good stand of seedlings has emerged, I give them a sprinkling of pulverized dolomite lime (to make them feel at home) and an application of dilute liquid fertilizer. The Physoplexis seedlings start out very small, but grow much more quickly than the Gentianopsis, and will develop several true leaves within six weeks of sowing (see the photo). I take them out of the plastic bag at this stage, and grow them on under the lights.

Seedlings at six weeks from sowing of seed

In another month or so, they will be ready for transplanting. For the growing-on mix, I use a mix of equal parts loam, half-rotted bark, pumice, perlite, and peat, with a little vermiculite, lime and bone meal thrown in (see step 13 in the Gentianopsis article). I place the transplants under fluorescents for a couple of weeks to get them established before exposing them to outdoor conditions. For small numbers of plants, I place them in sealed plastic bags for this step. For larger numbers, I place a clear plastic propagation dome over the plants (see photo), to provide a humid environment while they rebuild their root system. This also greatly reduces the amount of watering that needs to be done.

Use of propagation domes for fresh transplants. Fluorescents are raised for picture taking.

Now they are ready for the greenhouse or a shaded area outdoors. They do not like full sun and high temperatures. But too much shade will result in weak growth and few if any flowers. Also, keep in mind that slugs are the mortal enemy of these plants. So far, I have not tried them in the garden. I grow them in a cool greenhouse with 50% shade cloth. Make sure to plunge the pots to keep the roots cool and moist. If the plants go dormant in midsummer, don't panic; cut back on watering until late fall. In winter, I do not allow the containers to freeze hard. I start heating the greenhouse when it gets down to 30 degrees F.

My plants usually flower in two years from seed (see the photo). It will take several more years to develop a "show" specimen with dozens of flower clusters.

First bloom at two years from sowing

Hand pollination
To assure good seed set, I hand-pollinate these plants. There is nothing complex about this, once you know where the pollen is located. The flowers are ready for pollination when the stigma is reflexed into a spiral shape (see photo). The pollen is scattered like dust all along the style below the stigma. The pollen needs to be transferred to the stigma. Since all of my plants are in pots, I simply lift one and rub the stigma along the style of another plant. You may be able to achieve the same result by removing a flower and using it to pollinate another plant, or by using an artist's paintbrush or some other means. To assure that the pollen is ripe, this process should be repeated over the course of several days. Make sure that the pollen is not washed off the stigma by rain for the next week or so. It is generally preferable to cross-pollinate genetically distinct plants; that is, plants grown from two seeds. Plants which have been vegetatively propagated, such as by cuttings, are genetically identical.

Physoplexis flowers ready for pollination

The seed pods are similar to the ones on Campanulas, except much smaller. They look like a slightly thickened stem. When they turn brown, carefully remove them from the stem, let them dry indoors for a few days, then roll them between your fingers, over a receptacle for catching the seeds. The seeds are very tiny, but if your eyes are good, you will be able to see them falling. I let them dry at room temperature for about two weeks, then either sow them or place them in an airtight container and freeze them for later use.

So why on earth is the pollen distributed along the style? Where are the pollen sacs? I got this answer from Mr. Pierce Simon and Bruno Cerabolini, associate Professor of botany at the University of Insubria, Varese, Italy, close to where these plants are native. They believe that the pollen originates "from the anthers that are enclosed within the base of the corolla. As the style develops it grows along inside the tube of the corolla, pushing everything in front of it, until it finally sticks out from the end of the corolla, and at this point the stigma reflexes. So, as the style elongates it also pushes outwards against the anthers and the corolla, and at this point some pollen can become "pasted" onto the style and is transported out of the corolla with the developing and elongating style. For the plant to avoid self-pollination it is only important that the stigma does not come into contact with the pollen, but at that point it is still immature, and losing some pollen in this way does not appear to be a problem for the plant.
 
If you wanted to get larger quantities of pollen I would suggest removing part of the corolla, and the anthers can be found inside. They look just like the anthers of other flowering plants, so they should be fairly obvious once exposed, but they are very short in relation to the style and corolla." End of quote.

My best guess is that this plant shares habitat with a highly specialized pollinating insect. I wouldn't be surprised if that insect is not found in the US. If you are serious about collecting seed, hand-pollination is probably in order.