Monday, December 13, 2010

Growing Heuchera

I've been putting off talking about Heuchera for a quite awhile now.  There is a huge number of fantastic cultivars, it's been hard deciding where to start.  I'm going to leave out a lot of the older varieties, as there's already a great book out by Dan Heims and Graham Ware that covers them.  I'm told the book by Charles and Martha Oliver is also good, but I have yet to read it.  This post is going to be on just general culture, I will post about various color groups later.

Heucheras come in a various shades of green, silver, burgundy, purple, orange, yellow, and nearly any combination of these colors.  Nearly everyone (including me) mispronounces Heuchera.  Proper pronunciation is HOY-ker-uh.  I've been pronouncing it WHO-ker-uh for 15 years, and it's hard to change.

The common name coral bells comes from the pink to red flowers of H. sanguinea.  Nearly every other species goes by the name alumroot.  The genus is exclusively American in origin, with around 37 species and naturally occuring hybrids in N. America and another 4 found exclusively in Mexico.  Heuchera breeders have mostly concentrated on H. micrantha, H. americana, H. sanguinea, H. cylindrica, H. pubescens, and H. villosa. 

Heuchera species fall into two basic categories.  The western species (micrantha, sanguinea, & cylindrica) tend to be crevice dwellers, suitable for the rock garden and well drained soils.  They tend to be heat tolerant and are more sun tolerant.  The eastern species (villosa, pubescens & americana) tend to be woodland dwellers suitable for shade gardens.  They want soils that are consistently moist but well drained with adequate organic matter.  Each species will impart certain characteristics.  Knowing which species are used in a variety's background will help you know it's tolerances. 

H. americana is a hardy woodland species.  It likes a humus rich soil and some afternoon shade.  It is however heat and cold tolerant.  Zones 4-9
H. villosa is another woodland species, it also likes a rich soil.  It is very heat and humidity tolerant.  Zones 3-8.
H. pubescens is a woodland variety, but it's found on rock ledges and shale barrens so good drainage is important.  It's similar to H. americana but smaller and with nice flowers that are often tinged with pink.  It tends to be a robust and sun tolerant species.  Highly used by Charles Oliver in breeding.
H. micrantha is a western species and prefers good drainage.  However it is probably the most tolerant to heavy soils and moisture.  Zones 6-9.
H. cylindrica is tolerant to harsh winds and temperature extremes.  Zones 3-8.
H. sanguinea is extremely heat and drought tolerant.  This is where great flower colors comes from as well.  Zones 3-9.

In general, loose well drained soil is important.  Few varieties will last long in heavy or compacted soils.  Most varieties appreciate morning sun, with shade in the afternoon.  Provided those 2 conditions, most varieties will do well.  However a little research will help determine which varieties will truly thrive in your location.  In future posts, I will give which species are in the background if possible.  Some time in the next week I'll post about the green varieties.

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