A
Fondness for Geophytes.
From the Davis Enterprise, October 25, 2007
Geophyte is the term for a plant with an
underground storage structure: bulb (tulip, daffodil), corm (freesia,
gladiolus), rhizome (iris), tuber (begonia, potato), and tuberous root (ranunculus,
dahlia).
It's not that
crucial to know which kind of root you are buying, but there are some
differences in how they grow. Bulbs and tubers can grow bigger and bigger,
blooming year after year, and often multiplying readily. Corms usually get used
up as the plant grows and blooms, so you need reasonably rich, well-drained
soil for them to produce new corms and continue for future years. Rhizomes grow
outward at ground level, so we don't plant them as deep as the others and we
give them room to spread. Rhizomes and tubers have multiple growing points,
making them very easy to propagate and share with your friends: just cut them
up.
For convenience,
we call all of these "bulbs" and fall is the time to plant the flower bulbs that bloom in spring. Summer-blooming
"bulbs" such as gladiolus and dahlias are planted in spring.
When we know where
a plant comes from we can surmise its cultural requirements. Although we
associate many bulbs with Holland (where 65% of the world's flower bulbs are
grown – 2002 figures), their ancestral geographic origins belie this
heritage.
Take tulips.
Hybrids such as the Darwin tulips prefer cold winters due to years of breeding
for that. But tulips originally came to the Dutch from the Ottoman empire in
the 16th century. Tulip species originated along the 40th
latitude from western China to Turkey, spreading out to Afghanistan, Iraq, and
Iran, and then west to the Mediterranean. So while the Dutch hybrids tend to
bloom only for a year or so in our gardens, species such as T. clusiana, from
warmer areas, will multiply and spread here.
Bulbs appear to be
primarily an adaptation to aridity, especially dry summers. In fact, some of
the largest bulb-like things in nature are from desert or chaparral areas. The
Manroot, a cucumber relative native to Southern California, develops
tubers that can reach 200 lbs! The
plant grows very rapidly with the sparse winter rain, then lies dormant for
months. Giant White Squill, a
native of Crete, has bulbs that average 5 – 6 lbs. each.
Protection from
winter cold is an added bonus of bulb formation, and a few require more winter
chilling than we get in order to break dormancy properly: lily-of-the-valley
and snowdrops are examples. But those are the exceptions. Most bulbs grow fine
here.
Geophyte geography: where is Asia
minor, anyway?
Researching the
origins of bulbs, I kept coming up with "Asia minor" for many species. Anemones
and Ranunculus. Hyacinths and some Tulips. What is this region that is the
source of so many of our favorites? I did well in high school geography, but
that was decades ago. Nobody I asked could place it ("isn't that, like, west of
China?").
Also known as
Anatolia, Asia Minor is basically the Asian portion of modern Turkey (about 4%
of Turkey is in Europe). Geographically it includes quite a range: the
Mediterranean coast, where subtropical fruits such as citrus and figs are
grown; high, dry plateaus, and east to even higher mountain ranges, including
Mt. Ararat (nearly 17,000 ft.) at the border with Iran at the furthest east end
of the region.
Mild-winter
coasts, high mountains, with fertile valleys in between? Sounds a lot like
Northern California. No wonder Ranunculus flourish for us! In fact, we are able
to grow most bulb species that originate from cold climates, as well as those
from mild-winter areas of both hemispheres. Two other major sources of bulbs
for California gardens are the mild-winter, dry-summer regions of the
Mediterranean and South Africa.
From the
Mediterranean we get Crocus
species, colchicums, cyclamen, grape hyacinths, several species of Narcissus, Scillas, and several more species of
tulips. Giant hybrid crocus prefer a colder-winter area, but the species types
do great here. Cyclamen hybrids are among our most popular winter-blooming flowers,
perfectly hardy outdoors even on frosty nights. Most people don't even know
they are a bulb, but you can save them from season to season. Just keep them
dry during the summer.
The powerfully
fragrant Narcissus papyraceus,
which we call Paperwhites, are
from the Mediterranean. They sprout early, often blooming before Christmas, and
spread rapidly in the garden – but in bulb catalogues from east-coast
firms you'll find them consigned to the back pages as "indoor bulbs". Ah, the
pleasure of living in balmy California: Mediterranean geophytes thrive here.
The Cape of South
Africa is another region of winter rains, dry summers, and mild temperatures
similar to California. The Cape boasts over 1500 species of geophytes, an
amazing diversity: our ubiquitous Agapanthus (Lily-of-the-Nile, a tuberous
root), old favorites such as freesia, gladiolus, and calla lily, and
lesser-known choices such as Crocosmia, Ixia, Sparaxis, and Watsonia. All of these latter bloom and multiply
freely here, yet are too tender for gardeners in colder areas.
Sorting them: Tulips and
Daffodils
Tulips
Tracing the
origins and relationships of these older bulb types and giving them proper
names is complicated. Why? Because gardeners had been growing, propagating, and
breeding them for a couple of hundred years before the whole science of plant
relationships (taxonomy) and system of naming (botanical nomenclature) was
invented. DNA research is revealing some interesting relationships, but many
are complex hybrids.
In this situation,
horticultural taxonomists will sort cultivars into groups based on similarity
of flower form or bloom period. In the case of tulips there are over 2000
cultivars, in 15 recognized categories such as Single Early, Darwin Hybrid,
Lily-flowered, etc. Hybrids known to be mostly from a particular species bear
that name: the Fosteriana tulips, also known as Emperors, have at least some T.
fosterana parentage (they
also happen to be good choices here).
By the way, we
can grow the
old-fashioned, long-stem tulips here. Just don't plant them too early. Wait
until the soil has cooled (Nov. – Jan.), and plan on planting new ones
each year. That said, I have seen tulips repeat, sometimes for years, when they
are planted where they get little or no summer watering. Follow the same
instructions for hyacinths: plant Nov. – Jan., and if you want them to
repeat put them where they will be dry in summer.
Tulips come in
nearly every color, including black, as well as striped, fringed, and freakish
forms. Hyacinths come in strong primary colors, including true blue.
Daffodils and narcissus come in yellow, white, and pink. Although some species of
Narcissus (the genus which
includes daffodils) grow wild in Europe, their great popularity as garden
plants came later: in the late 19th century and early 20th
century hundreds of hybrids were developed using species found in Asia and the
Mediterranean.
Today there are
over 3000 cultivars, sorted into groups called divisions. Because the parentage
is somewhat better known, the divisions other than the biggest-flowered types
reflect the species they resemble.
* If you want the familiar big-flowered ones,
plant Trumpet daffodils. They'll repeat year after year, but usually don't
increase.
* If you like novelty flowers, try the
Split-cup and Double forms. My experience is they don't return as well in
future years.
* If you want big, showy flowers on plants
that multiply, plant Large-cup and Small-cup types, and the dwarf Trumpets.
* If you want super-fragrant blooms on plants
that will multiply even more freely, plant from among the other divisions:
Cyclamineus, Tazetta, Triandrus. For elegant flowers, try the tall,
late-blooming Poeticus narcissus.
* For cute little plants that multiply
exuberantly, nearly all extra fragrant, plant some of the species types. N. canaliculatus (6" tall!) and N. jonquilla simplex (12") can be crowded in a pot and brought
indoors in bloom to perfume the whole house.
Whichever you
choose, all daffodils and narcissus are easy to grow and most will give years
of bloom.
I counted over 100
species of flowering bulbs that grow readily in our gardens in the Sacramento
Valley! Geophytophiliacs know that I've only scratched the surface here. The
bulb is truly the gardener's friend: easy to plant, and productive for many years.
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