Lilacs and
Redbuds for the Sacramento Valley
Watch out for
sentences that begin with “in my day.” It's a sign that some old guy is about
to tell you a story about the way things used to be.
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| Syringa 'Sensation' -- lilac |
Well,
in my day, people planted fruit trees in the winter, bulbs
in the fall, tomatoes in April or May. And some flowering shrubs (including
roses) and shade trees were also planted in the winter, when they're dormant.
But as each new cohort of beginning gardeners comes along, I realize that these
seasonal gardening cycles haven't been passed down from the previous
generations. Nowadays lots of people look for daffodils in spring, fruit trees
in summer. Industry terms like “bare-root” are no longer common knowledge.
Most deciduous
fruit trees, most roses, many shade trees, and a lot of flowering trees,
shrubs, and vines are grown in fields like agricultural crops. They're planted
very close together, pruned and trained minimally, and then dug up by machines
in December. That's when the whole supply for the season becomes available. All
the soil is washed off the roots, and they are stacked and bundled and shipped
off to nurseries all over the world.
The roots are
bare, so they are called bare-root. They're dormant, and stay that way for
several weeks. So garden centers can stick them in shavings or sand, keep them
moist, and (hopefully) sell them to you before they leaf out. Or they can pot
them up when they have time. If sales are strong, selection tends to dwindle by
late spring. This applies to certain popular flowering shrubs. I want to
highlight two of these that have best availability in the winter and spring.
Lilacs
“I didn't know
we could grow those here!” is the most common thing I hear about this old
favorite garden plant. This is reinforced by many online resources which
inexplicably list lilacs for “zones 3 through 7.” We're in USDA zone 9. They
don't bloom reliably in Southern California or coastal climates due to a lack
of winter chilling. But we get sufficient chilling here, and they sure do
bloom.
Those online
references are usually from the East coast or Midwest, and California is
different. The zones they are referring to are USDA zones. West-coast gardeners
do better to use the Sunset Western Garden Book. We're Sunset Zone 14, and
Sunset lists the Common lilac (Syringa vulgaris) for zones 1
- 11 and 14.
When we bought
our rural property it came with lilacs that had been planted decades prior by
the original owner. They've always grown and bloomed well for us with very
little care; in fact, the original shrubs have reseeded. And I've planted more.
Lilacs tolerate nearly any soil type, prefer alkalinity (something that likes
Davis water!), and accept drought. Full sun is best. They will grow in some
shade, but mildew on the leaves can be a problem. You can prune them, or not,
as you prefer. Just wait to do it until after they bloom. The only caveat as to
location is that they should not be in a cold-sheltered location. Lilacs want
winter chill, so don't plant them against your house. Out in the open is best.
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| Cercis 'Don Egolf' -- Chinese redbud |
There are
hundreds of varieties; dozens of species, with many hybrids within and between
those species. Best-known and loved are the varieties of Common lilac
(Syringa vulgaris), as they have the largest flowers and
most fragrance. They bloom at the end of the branch in the
spring, and the bushes have an upright habit. Others bloom all
along the branches, with clusters of smaller flowers, often
also very fragrant. A good example is the Arboretum AllStar, the laceleaf
Persian lilac (Syringa x persica laciniata). These tend to
have a more informal, arching growth habit.
Climate
change indicators?
My lilacs bloom
from early to late April, varying slightly by year and by variety. Lilacs have
long been noted as plants that mark the season: their leaf emergence and bloom
is a sure sign of spring. In fact, they hold a special place in the study of
phenology, which is the science that connects seasonal biological phenomena to
variations in climate. Gardeners and botanical gardens have been recording the
dates of flowering of lilacs for generations.
Phenology is
just a fancy term for what old gardeners have done for years. “Plant corn when
oak leaves are the size of a squirrel's ear,” is an example. Handy if you have
an oak tree and a squirrel nearby. Or this: “Plant bean, cucumber, and squash
seeds when lilac is in full bloom.”
In the 1950's a
more systematic approach to using phenology was developed. In order to provide
consistency, and avoid planting an invasive species, a naturally sterile
variety of Syringa chinensis called Red Rothomagensis was
distributed to hundreds of sites around the country, and a reporting network
was created. The results? “Regional differences were detected, as well as an
average 5-6 day advance toward earlier springs, over a 35-year period from
1959-1993… spring warming is strongest regionally in the northwest and
northeast…” So when grampa says, “sure seems like the lilacs are bloomin'
earlier than they used to,” he is right.
Want to
participate? Check out the USA National Phenology Network at www.usapn.org.
Red
Rothomagensis is sometimes available in garden centers.
Redbuds
Every March
when the redbuds in the Arboretum come into bloom, we get lots of inquiries.
Compared to lilacs, these get a little dicier. Do they grow here? The answer is
more complicated.
Western redbud
(Cercis occidentalis) is our native species, represented
locally in the Warren G. Roberts Redbud Collection in the UC Davis Arboretum.
It grows fine here so long as you don't water it very often after it is
established (usually by the second summer). Western redbud is very prone to
crown rot if it gets watered too frequently. It is a multi-stemmed shrub,
rarely grown as a tree.
Eastern redbud
(Cercis canadensis), very common in nurseries, doesn't like
our dry heat. During hot spells the leaves get badly spotted and burnt. That
goes for the regular species as well as the red-leaved variety called Forest
Pansy. You can try planting them in the shade of a taller tree, but expect
unsightly foliage by mid-summer. This species is not at all drought
tolerant.
Just to confuse
things, a variant or hybrid of the Eastern redbud called the Oklahoma redbud is
quite heat tolerant. Usually classed as Cercis canadensis
texensis, it has a thicker, glossier leaf that resists sun scorch. A
smaller tree than the Eastern redbud, but larger than our Western redbud, it
can tolerate some drought, and also can take regular watering, so it is one of
our best choices for the garden.
Yet another
good garden variety is a variety of Chinese redbud (Cercis
chinensis) called Don Egolf. This seedling was discovered in the U.S.
Arboretum in Washington. Very slow-growing, it also happens to be naturally
sterile. If the seed pods of the other types bother you, this one is cleaner.
The flowers are a more intense dark magenta purple than the other varieties.
Tolerant of watering as well as some drought, it has an upright form but only
appears to get to about ten feet tall.
Redbuds can
tolerate nearly any soil type, and don't mind alkaline water. No pruning
needed.
Lilacs and
redbuds both fit in a low-water landscape. They have spectacular blooms, and
are carefree.
