Wednesday, December 9, 2020

Heuchera Species and Hybridizing History

Heuchera wasn't always the garden rock star we know today. For almost 100 years, selections were simple green foliage with variable amounts of silver veil, possibly with small but nicely colored flowers. The flowers tended to be on quite tall stems (a trait that I like, but isn't always what you want in a design!) and short-lived.

Heucheras these days come in a various shades of green, silver, burgundy, purple, red, orange, yellow, and nearly any combination of these colors. Flowers can be a range of colors including green, white, pink, and red. Flower stems now tend to be shorter, more in proportion to the foliage, and can be long lasting or even rebloom all season. Heuchera breeders have mostly concentrated on using just 5 species. Knowing which species are used in a variety's background will help you know it's tolerances.

H. americana 'Marvelous Marble'
H. americana is a hardy woodland species.  It likes a humus rich soil and some afternoon shade and is heat and cold tolerant. Foliage ranges solid green to green with silver veil and burgundy veins. I find that hybrids with a lot of influence from this species (and others in the same subsection) do best here in the upper midwest. Zones 3-9

It should be noted that we understand Heuchera very differently now compared to the 17th century when they were introduced to horticulture. Six species were lumped under the name H. americana at the time and are likely in the background of many early cultivars. These species consist of H. americana, H. caroliniana, H. pubescens, H. alba, H. longiflora, and 
H. longiflora
H. richardsonii
H. richardsonii

H. villosa 'Autumn Bride'

H. villosa is another woodland species, it also likes a rich soil.  It is very heat and humidity tolerant and seems to tolerate clay soils fairly well. Foliage tends to be somewhat fuzzy (villose) and is green. There is also a naturally occurring burgundy form, H. villosa f. purpurea Zones 4-9.

H. micrantha is a western species and prefers good drainage.  However it is also tolerant to moist soils during the growing season. Green foliage with somewhat ruffled margins. Zones 5-9, possibly colder.

H. cylindrica is a western species tolerant to harsh winds and temperature extremes, it tends to be a crevice dweller. Flowers are tightly packed on the stems.  Zones 3-8.
H. micrantha

H. cylindrica var. glabella

H. cylindrica var. glabella

H. sanguinea is a south-western species that is extremely heat and drought tolerant. Foliage ranges from green to green with silver veil. This is where great flower colors comes from as well.  Despite its southwestern heritage it is very hardy, but requires excellent drainage to grow successfully in wet climates. Zones 3-9.

H. 'Coral Cloud' from Alan Bloom
Hybridizing Heuchera first began in the very late 1800s. Victor and Emile Lemoine introduced the first hybrid, 'Brizoides' (H. sanguinea x H. americana var. hispida f. purpurea), in 1897 and then 'Gracillima' ('Brizoides' x H. micrantha) in 1900. Many more were introduced by Lemoine et Fils over the next 20 years. George Arends (known for Astilbe hybrids, the Arendsii group) introduced 'Rosamonde' ('Gracillima' x H. micrantha 'Rosea') in 1903. These 3 represent the oldest and most popular varieties of the time and can still be found in collections to this day. 

Alan Bloom started trialing and breeding Heuchera in the 1930s and continued this passion into the 1990s. He introduced many selections originating from 'Brizoides', 'Gracillima', and others that can still be found on the market today. 

H. 'Canyon Duet'

While most breeders concentrated on the five species I talk about above, Dara Emery of Santa Barbara Botanic Garden went a completely different direction. He used various California native species, such as H. elegans, H. meriamii, and H. hirsuitissima, crossed to H. sanguinea to create a group of lovely compact cultivars that are suitable for rock gardens. 'Canyon Duet' is the most readily available of them and has proven surprisingly hardy. 

Edgar Wherry collected seed that went on to become the selection 'Palace Purple'. This plant is largely sold as H. micrantha 'Palace Purple', but that is incorrect. Wherry never collected within the range of H.micrantha and no purple form of that species has ever been discovered. It's actually a superior form of H. villosa f. purpurea. Sadly, it has mostly been seed propagated and you can get inferior forms pretty easily. 

One of the most important hybrids to ever come about is 'Montrose Ruby' from Nancy Goodwin in 1990. It's a hybrid of H. americana 'Dale's Strain' and H. villosa f. purpurea 'Palace Purple'. 'Montrose Ruby' is the foundation plant for several modern hybridizing programs and most of today's cultivars can trace their lineage back to this plant! It's the basis of Charles Oliver's great selections, originally crossed to his 'White Marble' (which is H. pubescens x H. sanguinea 'White Cloud'). Oliver also worked with H. hallii and H. pulchella to produce garden worthy compact plants like 'Petite Pearl Fairy'. 

H. 'Georgia Peach' from Terra Nova
'Montrose Ruby' is also in the background of Terra Nova's program, crossed to H. sanguinea as well as backcrossed to H. americana. Later, they would use H. cylindrica, H. micrantha, and H. villosa; as well as recently using H. richardsonii. Terra Nova has been responsible for the bulk of modern Heuchera hybridizing and lots of innovation in the genus. I would say their most important variety is 'Amber Waves'. It was the first amber-colored Heuchera to be made available and its genes are responsible for broadening the color range to include orange, yellow, and true red. They've done really great work with plants for very colorful foliage as well as great flowers. One of the best varieties ever introduced for flowers is 'Paris', from their "city series". Maybe my favorite plant of theirs is 'Georgia Peach' which goes through seasonal color changes and has proven reliable across a wide range of the US. Some of their varieties can struggle in the upper midwest. This is most likely a result of the selection pressures in Oregon being very different from the climate here and may also involve some of the different genetics they've used. Making sure you have good drainage goes a long way to ensuring success; I find that most do well here provided drainage. 

H. 'Caramel'

Thierry Delabroye has done a lot of work with hybrids involving bringing H. villosa to the forefront of hybridization. 'Caramel' is his most popular cultivar and is a nice rich amber that is fairly reliable here in the upper midwest. He's also breeding a really nice line of larger cultivars, 'Mega-Caramel' being a larger version of 'Caramel'. 
H. 'Pink Panther' from Walter's Gardens Inc.

Walter's Gardens in Michigan has recently been breeding some real knockout cultivars that are performing well in the upper midwest. They've introduced several really nice purple varieties with improved vigor and size as well as some great plants with long-lasting flowers. Many of their varieties are part of the Proven Winners brand as well, as Walter's is the breeder and marketer of their perennial line. 

H. 'Carnival Watermelon' from Ball Hort.

Another series of plants I should mention is the Carnival series from Ball Horticulture. These are widely available mass market plants that can be found affordably at box stores. They seem to be performing fairly well in the midwest, which isn't surprising since they're bred and selected in Illinois. The standouts are 'Carnival Watermelon' and 'Carnival Peach Parfait'. Other than that, I'm not too excited by the series. Most of the varieties resemble plants that were released from hybridization efforts in the 90s and I don't find them to be improvements in any way. This isn't to say they are bad plants; I'd happily sub 'Carnival Peach Parfait' or 'Carnival Watermelon' for 'Georgia Peach' or 'Carnival Plum Crazy' for 'Plum Pudding' in design work if there was a significant price or availability difference. This applies to most of the series as well. If you're a landscaper or home gardener looking to do a mass planting without breaking the bank, this series is a good option. If you're a plant collector looking for novel plants, probably best to skip most of these as there are more unique plants out there. 

I'll go into more detail about specific varieties and how they've performed for me in an upcoming post, so stay tuned!

Friday, December 4, 2020

Growing Heuchera

It's been ten years since I originally wrote about Heuchera, and an update has been a long time coming. I'm scrapping my old posts and updating them with some slight revision for clarity. This post is going to be on just general culture and species, I'll post more about hybrids and history at a later time. 

Heuchera 'Caramel' with Hostas 'Stained Glass' and 'Fire Island' and Lamium 'Purple Dragon'

Nearly everyone (including me) mispronounces Heuchera; proper pronunciation is HOY-ker-uh. I've been pronouncing it WHO-ker-uh for 25 years, and it's hard to change! The genus is exclusively American in origin, with around 37 species in the United States and Canada and another 5 found exclusively in Mexico. 

Heuchera species fall into two basic categories. The mountain dwelling species are suitable for the rock garden and well drained soils. They tend to be heat tolerant and are more sun tolerant, but still appreciate some afternoon shade as they tend to grow in the shadows of boulders or scrub. The woodland dwellers are more suitable for shade gardens. They want soils that are consistently moist but well drained with adequate organic matter. They tend to be found on woodland edges, savannahs, or grasslands. Montane species are more heavily represented in the west and woodland species more so in the east; but both groups exist across their range. Regardless of montane or woodland, all species tend to be found in rocky, well-drained locations. 

In general, loose well-drained soil is important. Few varieties will last long in heavy or compacted soils.  Most varieties appreciate morning sun, with bright shade in the afternoon. Provided those 2 conditions, most varieties will do well. A little research will help determine which varieties will truly thrive in your location. Knowing where and when they were hybridized is also useful. Here in the Midwest, I find cultivars bred on the west coast are less likely to thrive compared to cultivars bred in the Midwest or Northeast.