Plant of the Month for July, 2020

Primula sieboldii

(PRIM-yew-la see-BOLD-ee-eye)

General Information:

Primula sieboldii, is a fun little primula with lots of variation in its flowers in both color and petal shape. It blooms after many other primulas and its flowers last for more than 4 weeks. It is a great addition to any shade garden.

Primula sieboldii: photo by Robert Pavlis

Primula sieboldii:photo by Robert Pavlis

The Japanese call it Sakurasou, the cherry blossom herb and they have been breeding and cultivating it since the sixteenth century. Other common names include Japanese primrose, Siebold’s primrose, cherry blossom primrose and Asiatic primrose.

I must have a dozen different flower clones and all of them are from seed mixtures, such as the one available from the Ontario Rock Garden & Hardy Plant Society Seedex. This primula cross breeds easily and it is quite common that a single pack of seeds will produce a variety of flower forms.

Primula sieboldii: photo by Robert Pavlis

Primula sieboldii:photo by Robert Pavlis

Some sources suggest planting seeds as soon as they are ripe, even in the green state. I have had no problem germinating dry seed in late winter.

They make excellent cut flowers and last more than a week in water. They spread into large colonies by shallow underground rhizomes, but they are easily controlled. If they get too dry they will become dormant and go underground in late summer.

Primula sieboldii: photo by Robert Pavlis

Primula sieboldii:photo by Robert Pavlis

Primula sieboldii: photo by Robert Pavlis

Primula sieboldii:photo by Robert Pavlis

Primula sieboldii: photo by Robert Pavlis

Primula sieboldii:photo by Robert Pavlis

Life Cycle: perennial

Height: 20cm (8in)

Bloom Time: late spring

Natural Range: East Asia

Habitat: damp meadows and light forests

Synonyms: Auganthus sieboldii, Primula cortudoides

Cultivation:

Light: part shade

Soil: well drained and moisture retentive

Water: average to wet, but does not like standing water

USDA Hardiness Zone: (3?) 4-8

Propagation: seed, division

Seedex availability (ORG&HPS annual Seed Exchange): common

Germination Tips:

Sow immediately. The viability of these seeds is short or the species propagates best with fresh seed. Stored seed might be coaxed into germination with temperature cycling and patience.

Requires darkness.

Germination is improved by using GA3. See http://botanicallyinclined.org/fridays-seeds-with-the-ga3-seeds-treatment

Use repeated cycles of 20°C, then 4°C for 3 months each. Germination is very prolonged.

Special Care:

germination unlikely after dry storage > 6 months

Contributions to this page were made by: Robert Pavlis

Plant of the Month for June, 2020

Disporum maculatum

(pro-SAR-teez mak-yuh-LAH-tuh)

General Information:

Prosartes maculata is a rare beauty for the shade garden. It’s flowers face down similar to hellebores, so you have to lift the flowers to really enjoy them but they do flower early in the year after most daffodils and before the big show of iris and peonies.

Prosartes maculata photo by Robert Pavlis

The common names for this plant include nodding mandarin, spotted disporum, and spotted fairybells. It used to be in the genus Disporum but was moved to Prosartes after DNA testing. So what is the difference between these two genuses? The Pacific Bulb Society says, “the differences are not readily visible to the naked eye. Without a DNA testing lab you can’t tell the difference.

Prosartes maculata has the unusual habit of developing two flowers on each forked flower stem. It produces straw coloured berries.

Prosartes maculata photo by Robert Pavlis

The nodding mandarin spreads by rhizomes, but this is one of the slowest spreading plants I’ve grown, especially compared to other disporum. It is part of the lily family, so it might get attacked by lily beetle, but so far I have not noticed them on the plant. It is persistent, provided it does not get too dry in summer.

Prosartes maculata photo by Robert Pavlis

Life Cycle: perennial

Height: 60cm (24in)

Bloom Time: mid spring

Natural Range: Eastern North America

Habitat: moist, shady woodlands

Synonyms: Disporum maculatum

Cultivation:

Light: part shade to full shade

Soil: well drained, high organic level

Water: moist

USDA Hardiness Zone: (4?) 5-8

Propagation: seed, division

Seedex availability (ORG&HPS annual Seed Exchange): rarely

Germination Tips:

Use repeated cycles of 20°C, then 4°C for 3 months each. Germination is very prolonged.

Contributions to this page were made by: Robert Pavlis

Plant of the Month for September, 2020

Clematis heracleifolia

(Klem-uh-tiss hair-uh-klee-ih-FOH-lee-uh)

General Information:

Clematis heracleifolia is an unusual clematis. It doesn’t vine and it’s semi-woody even though it is treated as a perennial. It also flowers late summer or early fall when most clematis are done for the season. If you see it in the garden for the first time you won’t believe it’s a clematis.

clematis heracleifolia China Purple main

Clematis heracleifolia:photo by Robert Pavlis

This plant belongs to a group of clematis called bush, or non-climbing or herbaceous; any of these terms seem valid. Treat them as perennials and cut them back to the ground in spring. They all bloom on new wood.

In colder climates the crown of the plant looks much like any other perennial but in warmer climates it becomes quite woody. Older plants can be divided with care.

clematis heracleifolia, photo by Robert Pavlis

Clematis heracleifolia:photo by Robert Pavlis

Clematis heracleifolia is also known by the common names, tube clematis and hyacinth-flower clematis. The flower color ranges from pale blue to quite dark purple-blue and several named cultivars are available. Many resources describe it as flopping and needing support, but I find that it has quite strong woody-like stems and never needs support. Other bush clematis do require some support.

This clematis prefer full sun with fairly moist soil, but not a wet condition. Plants that are grown too dry tend to be short lived. In my zone 5 garden, which is 40% clay, they get mulched but do not normally get watered. The ones pictured are grown from seed, except as noted. I find bush clematis a bit easier to grow from seed than the vine types.

clematis heracleifolia 'China purple', photo by Robert Pavlis

Clematis heracleifolia 'China Purple':photo by Robert Pavlis

The botanical name is pronounced “hair-uh-klee-ih-FOH-lee-uh”,which is a real tongue twister. I find it easier to remember the name by calling it “her-ass-is-a-leaf”.

This is not a spectacular plant compared to some of the showy clematis you are familiar with, but it is very low maintenance and flowers late in the season for a good fall display. Flowers are quickly followed by the classic clematis hairy seed heads.

clematis heracleifolia 'China purple', photo by Robert Pavlis

Clematis heracleifolia 'China Purple':photo by Robert Pavlis

Life Cycle: perennial

Height: 90cm (3 ft)

Bloom Time: late summer

Natural Range: China and Korea

Habitat: woodland margins

Synonyms: Clematis davidiana, Clematis hookeri, Clematis tubulosa

Cultivation:

Light: full sun to light shade

Soil: well drained

Water: moist

USDA Hardiness Zone: (3?)4-9

Propagation: seed, division, cuttings

Seedex availability (ORG&HPS annual Seed Exchange): common

Germination Tips:

Sow @ 20°C. Seed germinates within 3 months.

Contributions to this page were made by: Robert Pavlis

Plant of the Month for October, 2020

Caryopteris divaricata 'Snow Fairy'

(kar-ee-OP-ter-iss dy-vair-ih-KAY-tuh)

General Information:

Caryopteris divaricata ‘Snow Fairy’ is an elegant plant that requires almost no maintenance, has few if any pests and looks good most of the year. It should be in every garden that matches its hardiness zone.

Caryopteris divaricata ‘Snow Fairy’: photo by Robert Pavlis

Caryopteris divaricata ‘Snow Fairy’:photo by Robert Pavlis

You might know genus Caryopteris as shrubs, but this one is an herbaceous perennial. I have grown it for years and did not know this until I wrote this article. In my zone 5 garden it looks like a shrub that gets killed to the ground in winter, similar to the butterfly bush. It produces very stiff strong stems that keep their shape all year.

It is a bit slow to get going in spring, but by early summer you will have a nice clump of variegated foliage. It keeps growing all summer and never loses its color as so many variegated plants do. There is another cultivar called Caryopteris divaricata 'Blue Butterflies' which has green leaves but much larger flowers. Snow Fairy is a much better choice.

Caryopteris divaricata ‘Snow Fairy’: photo by Robert Pavlis

Caryopteris divaricata ‘Snow Fairy’:photo by Robert Pavlis

It does produce flowers in fall most years but due to their small size they really don’t add too much to the plant. You grow this one for foliage. Give it full sun or a bit of shade and don’t worry about watering it; it is quite drought tolerant once established. It will not tolerate a wet site.

The only maintenance I do is to cut it back to the ground in spring. Common names include blue spirea, blue mist shrub, and blue mist spirea.

Since I didn’t know it was a perennial, I took cuttings in midsummer just like my other shrubs and they rooted fairly easily. Spring tip cuttings are reported to work even better.

Caryopteris Snow Fairy flower

Caryopteris divaricata ‘Snow Fairy’:photo by Robert Pavlis

Life Cycle: perennial

Height: 100cm (3.5 ft)

Bloom Time: fall

Natural Range: Himalayas (for the species)

Habitat: sunny dry slopes

Synonyms: Tripora divaricata

Cultivation:

Light: full sunto part shade

Soil: well drained

Water: dry

USDA Hardiness Zone: 5- 9

Propagation: division, cuttings

Seedex availability (ORG&HPS annual Seed Exchange): never

Germination Tips:

Contributions to this page were made by: Robert Pavlis

Plant of the Month for April, 2020

Iris Katharine Hodgkin header

Iris histrioides x winogradowii

(EYE-ris hiss-TREE-ohy-deez)

General Information:

Iris ‘Katharine Hodgkin’, the orchid iris, is one of the best reticulata-type early spring flowering iris. It makes a great show every year and multiplies quickly to form a good sized clump. The flowers are short, but wider than other similar types. To be honest, I don’t like pale colors in the garden but I’ve fallen in love with this one.

Iris Katharine Hodgkin main

Iris ‘Katharine Hodgkin’:photo by Robert Pavlis

The naming of reticulata iris are a bit confusing. There is an iris group called reticulata which contains numerous species such as I. danfordiae, I. histrioides and I. winogradowii and there is a species, Iris reticulata, which is also part of this group.

Iris ‘Katharine Hodgkin’, sometimes spelled Katherine, is a cross between I. histrioides (pale blue flowers) and I. winogradowii (pale yellow flowers) but is usually called Iris reticulata ‘Katharine Hodgkin’. Some sources call it Iris x histroides ‘Katharine Hodgkin’, which is a more correct name.

Iris Katharine Hodgkin closeup

Iris ‘Katharine Hodgkin’:photo by Robert Pavlis

One of the great things about this group of iris is that snow, cold or even a cloudy day do not force the flowers to close. They are always open and even snow will do little danmage.

As the flowers open, the grass-like leaves start to grow and a few weeks after the flowers have faded, they will be about 30 cm tall. They are thin, but quite stiff. You hardly notice them unless they are planted right at the front of the border. By mid-summer the plant is back underground hoping for a dry spell.

Clumps can be divided after flowering but it might be best to leave them alone, unless flowering declines. Moved bulbs may sulk for a year or two.

If you would like to see more varieites of Iris reticulata, have a look at this video: https://youtu.be/QWI1NSZxzLY

Life Cycle: bulb

Height: 30 cm (12 in), flowers at 10 cm (4 in)

Bloom Time: early spring

Natural Range: Turkey, Caucasus, Lebanon, northern Iraq and Iran

Habitat: sunny dry slopes

Synonyms: n/a

Cultivation:

Light: part shade to full sun

Soil: well drained

Water: average to dry

USDA Hardiness Zone: 3 - 8 (9?)

Propagation: division of bulb offsets

Seedex availability (ORG&HPS annual Seed Exchange): uncommon

Germination Tips:

Give sown seeds several weeks @ 20°C to imbibe water (perhaps even germinate!), then expose to fluctuating outdoor winter temperatures including freezing for 3 months. Gradually increase light and temperature in spring. See https://www.youtube.com/watch?v=SO_KKbGYTEM

Special Care:

sow fresh or soak old seed; prechill 4 weeks or place outdoors over winter and bring indoors once germinated to avoid temperature shock; transplant at 4 leaves

Contributions to this page were made by: Robert Pavlis

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