Plant of the Month for November, 2011
Clematis columbiana v. tenuiloba
(KLEM-uh-tiss man-SHEU-ree-ka)
In his talk on the flowers of the Western United States, Barrie Porteous highlighted Clematis columbiana var. tenuiloba. Just 15 to 28 cm (6 to 10") in height, with a sprawling growth habit, and native to areas of limestone rubble and cold winters, it is a highly desirable species for Ontario rock gardens. Like other alpine plants, it thrives under high ultraviolet radiation and drying winds. ORG&HPS member, Barry Parker observed that the one he planted outdoors in a trough was superior to his greenhouse specimen. Former member Rodney Shaver had success growing this plant at the base of a crevice garden.
Clematis columbiana var. tenuiloba photo courtesy of Barrie Porteous
While the species flower is mauve, the selection 'Ylva'™ is darker and bluer. Henrik Zetterland of the Botanic Garden in Gothenburg named the latter after his daughter.
'Ylva' outside in trough
'
Ylva' in bud in greenhouse
'Ylva' photos courtesy of Barry Parker
Because it is challenging to get Clematis columbiana var. tenuiloba to bloom in cultivation and obtaining viable seed is even more difficult, you will rarely find seed offered through our Seedex. Propagation from seed will produce plants identical to the parent species. Seed should be sown while it is still fresh in a very well-drained medium, then placed outdoors over the winter. For those who like to tend their seed pots indoors, this species is one that will also germinate at room temperature without prechilling. Growth of the seedling is slow. Flowering can be expected in the spring of its second year and may continue into August.
Sources: Larry Davidson, member of ORG&HPS, carried the plant last season http://losthorizons.ca. Kristl Walek carried the seeds of this species last year at www.gardensnorth.com. She hasn't indicated whether it will be available this year.
Sow @ 20°C. Seed germinates within 3 months.
Requires light or the small seeds should be surface sown. See https://www.youtube.com/watch?v=RgkXUSI1GWo&index=1&list=UUJfYCNSWCIuOB2...
Clematis alpina
(Klem –uh-tiss AL-pine-a)
General Information:
Clematis alpina is a very hardy, early flowering vine that adds a great splash of color in your spring garden and then goes on to make interesting seed heads in late summer. As seen in the picture below, I grow it in a planter, in zone 5 and leave it outside all year. You can also plant it in the garden and just about forget about it. It doesn't need to be pruned, and it will not take over most trees and shrubs the way some larger clematis do.
Clematis alpina:photo by Robert Pavlis
Its main color is a blue/mauve but a variety called C. alpine var. sibirica (Siberian clematis) is white. If these colors are not to your liking cultivars of Clematis alpina are available in a variety of other colors including pinks and pale blues.
It is a Group 1 clematis so pruning should be done after it flowers in spring. If you want a taller plant, don’t prune it for a few years. After that, prune just for shape or size. In my planter I cut it to soil level after flowering so that it never gets taller than 3 to 4 feet.
C. alpina can be grown from seed fairly easily, but it does take some time. For more information on this see Growing Clematis From Seed.
Clematis alpina:photo by Robert Pavlis
This clematis is not prone to clematis wilt, but it is still a good idea to plant it a few inches lower than in the original pot.
Alpine clematis is a close relative of anemone and hepatica which have similar leaves and flowers. It belongs to the Atragene Group which also includes species such as C. chiisanensis, C. fauriei, C. koreana, C. macropetala, C. ochotensis, C. sibirica, C. turkestanica.
Clematis alpina:photo by Robert Pavlis
Life Cycle: woody vine
Height: 3 m (10 ft)
Bloom Time: spring
Natural Range: European Alps
Habitat: rocky and wooded sub-alpine areas
Synonyms: Atragene alpine
Cultivation:
Light: full sun to part shade, especially in warmer climates
Soil: well drained, humusy
Water: drought tolerant once established
USDA Hardiness Zone: 3 - 9
Propagation: seed, layering, softwood or semi-hardwood cuttings
Seedex availability (ORG&HPS annual Seed Exchange): usually
At one time, we advised "Tails may inhibit germination. Remove them." The advice applied primarily to pulsatillas and clematises. Our most recent data indicates that leaving the tails on has no effect on germination.
Use repeated cycles of 20°C, then 4°C for 3 months each. Germination is very prolonged.
Robert Pavlis
Plant of the Month for July, 2018
Chrysogonum virginianum ‘Norman Singer’
(kris-OG-oh-num vir-jin-eeAN-um)
General Information:
Chrysogonum virginianum ‘Norman Singer’ adds great color to an early summer garden and is easy to grow. It forms a mat that is thick enough to keep out most weeds, it does not need deadheading and it is semi-evergreen, making it almost no-maintenance. The only thing you need to do is reduce the size of the clump every 2-3 years.
The Norman Singer clone was selected for its larger flowers and the fact that the flower stem is shorter than the species which makes for a nicer display. It was originally called Norman Singer’s clone, after the North American Rock Garden Society member who found it. More recently, it can also be found under the name Chrysogonum virginianum ‘Superstar’.
The species grows in part shade conditions along the edge of woodlands in moist conditions. It can take quite a bit of shade and is deer resistant. I did not know that when I got my Norman Singer cultivar, so I planted it in a zone 5 rock garden, in full sun. It does quite well there in clay soil and without extra water. This seems like a very adaptable species, but it is possible that Norman Singer is more tolerant of full sun than the species.
It is a great ground cover even when not flowering, forming very tight mats of green. The clump spreads using rhizomes which are easily pulled out to keep it in control. The dazzling flowers appear in late spring and early summer and reappear in fall for a subdued display. Every garden should have this plant.
Common names for the species include green-and-gold, gold cup and golden star.
Life Cycle: perennial
Height: 5cm (2in)
Bloom Time: late spring
Natural Range: Eastern North America, from Pennsylvania to Florida
Habitat: edge of deciduous forests, mesic to dry woodlands and open rocky woodlands
Synonyms: Chrysogonum australe
Cultivation:
Light: full sun to full shade
Soil: prefers moist rich soil, but is very tolerant
Water: consistent moisture
USDA Hardiness Zone: 5 – 9
Propagation: division
Seedex availability (ORG&HPS annual Seed Exchange): never
Robert Pavlis
Plant of the Month for August, 2014
Cephalanthus occidentalis
(sef-uh-LAN-thus ok-sih-den-TAY-liss)
General Information:
Cephalanthus occidentalis, the buttonbush, is a very interesting shrub that is rarely seen in gardens. It’s flowers are so unique that it always attracts attention when in flower. Even the seed heads make a statement in the garden.
Cephalanthus occidentalis; photo by Robert Pavlis
The buttonbush is native to most of North America and Mexico and is found in wet swampy areas. It’s fondness for water is one reason it is not found in many gardens, but it is an ideal plant for a wet location, bog garden or a rain garden.
The flowers are white and almost the size of a ping pong ball. Each flower lasts about a week, but they are produced in succession. The left picture below shows the current flower as well as several developing buds. The flower head is actually made up of many small individual flowers, shown in the right photo, which together form a ball, much like an Allium flower. Long projecting styles stick out past the petals giving the ball a starburst appearance.
Cephalanthus occidentalis; photo by Robert Pavlis
Individual flowers, photo by University of Texas
Individual flowers photo was kindly provided by Plant Resources Center and Bio406d at the University of Texas at Austin.
The flower is fragrant, and produces a lot of nectar making it very popular with bees and butterflies. In Ontario they open late July around the same time as daylilies. They mature to ball-like fruits with a slight reddish colour, and persist into winter.
Buttonbush normally grows to form a 3-8 foot shrub, which occasionally develops into a taller tree. It is slow growing and can be trimmed to stay smaller. If this is too large for your garden a new cultivar is now available with the trademark name of Sugar Shack, which has redder fruit, and grows to about 4 feet tall.
Life Cycle: small tree or shrub
Height: 150-360 cm (5 – 12 ft)
Bloom Time: July
Natural Range: Eastern Canada, USA (mostly in the east), Mexico and Cuba
Habitat: swampy wet areas in full sun
Synonyms: Cephalanthus occidentalis var. californicus, Cephalanthus occidentalis var. pubescens
Cultivation:
Light: full sun to part-shade
Soil: any type of soil
Water: even moisture, even standing water
USDA Hardiness Zone: 5-10
Propagation: seed, soft or hardwood cuttings, division
Seedex availability (ORG&HPS annual Seed Exchange): occasionally
Requires light or the small seeds should be surface sown. See https://www.youtube.com/watch?v=RgkXUSI1GWo&index=1&list=UUJfYCNSWCIuOB2...
Sow @ 20°C. Seed germinates within 3 months.
Robert Pavlis
Campanula betulifolia
(kam-PAN-yoo-luh bet-yoo-lee-FOH-lee-uh)
General Information:
A lovely campanula for the rock garden, Campanula betulifolia has large flowers in white or light pink. The white form is more readily available. The flowers tend to point down so it is a good idea to locate the plant higher up so that it is easy to see inside the bells.
Campanula betulifolia:photo by Robert Pavlis
The leaves on this campanula are quite unique and look like birch leaves, hence the species name, betulifolia and the common name, the birch-leaved bellflower.
The plant in the pictures was grown from seed obtained from the annual Ontario Rock Garden & Hardy Plant Society seed exchange. This is a great way to obtain some real gems for the garden.
Campanula betulifolia:photo by Robert Pavlis
The birch-leaved bellflower grows low to the ground and looks its best if it is sited so that it can cascade over rocks, as shown in these pictures. The plant forms a tap root making it very difficult to divide. It can be propagated easily from seed or from cuttings taken before the plant flowers.
Life Cycle: perennial
Height: 12 cm (5in)
Bloom Time: early summer
Natural Range: Turkey, Caucasus
Habitat: Crevices in igneous and limestone rock, up to 2,300 m
Synonyms: Campanula denticulata, Campanula betulifolia var.exappendiculata, Campanula finitima, Symphyandra finitima
Cultivation:
Light: part shade to full sun
Soil: well drained, scree
Water: drought tolerant once established
USDA Hardiness Zone: 5 – 8
Propagation: seed, cuttings
Seedex availability (ORG&HPS annual Seed Exchange): occasionally
Sow @ 20°C. Seed germinates within 3 months.
Robert Pavlis
