University of Vermont Extension
Department of Plant and Soil Science
Summer News
Article
GROWING
AND USING LAVENDER
Dr. Leonard Perry, Extension Professor
University of Vermont
Lavender flowers can be used in
cooking, although its flowers are most often used in potpourri and
as sachets,
and the leaves distilled for their oils.
Most are familiar with lavender through cosmetic products.
Herbalists consider its oil one of the most
important for therapeutic uses and healing, such as wounds and
burns. Lavender oil scent is used for calming, and
to induce sleep. Its first documented
use was by the Romans in 77 A.D. for insect bites and to repel
insects.
In the landscape, this low plant is used for
its gray-green to silvery leaves, or its flowers in July or August.
Generally in shades of blue or purple,
flowers of some selections are pink or white.
Flowers contain lots of nectar, so are attractive to bees.
Depending on the species and season, they may
bloom from 4 to 8 weeks. Lavender is a low-care, low maintenance
plant.
Although it is a Mediterranean small
shrub, termed “subshrub”, it can be grown in other climates as a
tender
perennial or even annual flower.
Lavender (Lavandula) can grow
year round in a hot and dry climate like southern California and the
arid
Southwest, or even arid West. Most of
the 15 or so species don’t grow as well, nor are long-lived, in hot
and humid
climates such as the Southeast or Midwest. Exceptions for hot and
humid climates are the
Spanish lavender (L. stoechas), and
the French or fringed lavender (L.
dentata), hardy in only warmer zones (7-9) where temperatures
stay above 10
degrees (F). These are often termed non-English types.
The English lavenders (L. angustifolia) generally are listed
as
hardy to USDA zone 5 (-10 to -20 degrees), although sometimes they
may grow
into a colder zone if sufficient reliable snow cover. Otherwise,
protect
these lavenders in these areas by straw or evergreen branches at
least 3 to 4
inches
deep. In warm climates with long seasons, such as
the West, these may rebloom the same year.
Some of
the best and most
popular English cultivars (cultivated varieties) include ‘Munstead’
(early, blue-purple
flowers, to about
2-feet high) and ‘Hidcote’ (dark blue flowers, to about 18-inches
high). ‘Jean Davis’ is an English lavender with
light pink flowers.
The third main group of lavender cultivars,
the “lavandins”, are a cross of the English species and the spike or
Portuguese
lavender (L. latifolia). The latter grow into zone 5, but
also are a
great choice for hot climates. The
lavandins (L. x intermedia) generally
are hardy, too, often into zone 5. They
are grown commercially for their increased vigor, size, and higher
oil
content. A couple of good ones to try
are ‘Grosso’ (dark purple flowers, to about 30-inches high) and
‘Provence’
(purple flowers, more rot resistant, to about 2-feet high).
‘Edelweiss’ is a lavandin with white flowers.
Lavender can be started from seeds,
but the cultivars often will not “come true” or have the same
desired traits if
grown from seeds, and seeds are difficult to germinate. Best is to
buy lavender plants already
started, and which your vendor knows are grown from cuttings. The
lavandins have sterile seeds, so only can
be grown from cuttings.
If moving a plant, do so in spring, and make
sure to get plenty of soil around the roots.
In the north, it’s best to plant in the spring so plants can
establish
during the summer. In hot climates, fall
planting may be best. Give plenty of
space, so air circulation can help reduce leaf disease. A spacing of
2- feet
apart is good for most cultivars, or slightly more space for the
larger
lavandins.
Lavender really needs full sun, and
although they will tolerate drought once established, they bloom
best if not
allowed to dry out. Plants do require a
well-drained soil, especially through winter, and grow well in rocky
or sandy soils. They prefer a neutral pH soil, so if somewhat
acidic you’ll need to add lime (an Extension soil test will tell you
how much
to add).
Don’t overfertilize, as they perform
best in lean soils. A side-dressing once
a year of some compost may be sufficient, but plants don’t like an
overly
organic soil either. You can fertilize a
couple times during summer with liquid
seaweed or fish emulsion.
While we appreciate the fragrant,
essential oils of lavender, pests, rabbits and deer don’t, so plants
are not
bothered by them. The main problem can
be fungal rots from too wet soil, or too humid a climate.
Plants will need some pruning, but
only in spring after you see new growth.
Only prune last year’s growth back, leaving about an inch of this
less
woody growth, unless plants have been left for a while and become
unsightly. In this case, prune stems
back by about one-third, or take out any dead or quite old stems.
You can cut them back lightly, shearing for
shaping, right after flowering.
Lavenders generally take 3 years to
reach mature size and peak yield. Harvest
lavender flowers just as they are beginning to open, in the morning,
as this is
when they have the highest oil content and scent. Cut the long
stems, spread on a screen or
trays, and let dry in the sun for several days.
If rainy, place in a warm, dry location with good air movement. Or,
you can hang bunches upside down. Bundle the dried stems for
sachets, or strip
flowers off stems to use in potpourri or even cooking. If
harvesting stems to use fresh in vases,
don’t put in water as this makes the small florets drop and stems
get mushy.
Lavender flowers make nice toppings
for desserts and ice cream, or mixed in with chocolate. Use them
with thyme on roasted chicken. Mix some in with a honey mustard
dressing for
salads. Steep flowers with tea, or mix
in with salt for flavor.
In landscapes, use lavender along
walks or near patios and stone walls where their scent can be
appreciated, and
where they can benefit from the reflected heat.
They are perfect in herb gardens, and formal herb knot gardens, or
sheared as a low hedge. Combine with
roses, irises, clumping perennial geraniums, salvia, low sedum, or
annual
flowers such as cockscomb or portulaca.
Make sure not to plant among perennials that will spread and
overwhelm
them. Keep your lavender weeded for the
same reason, as they don’t compete well with weeds.
In cold or humid climates, they may
best be grown as an annual in pots, or in pots that can be moved
indoors
overwinter in the North. This
particularly applies to Spanish lavender or less hardy selections.
Don’t let plants drop below 40 degrees
overnight if in pots under shelter over winter.
If growing indoors over winter, place in a south-facing window with
as
much light as possible.
Make sure pots have holes in the
bottom so water can drain. Use a potting
mix that drains well too. Some of the
heavy loam, or peat moss-based, bagged potting mixes may stay too
wet. One good potting mix for lavender contains
equal parts by volume of soil, sand, perlite, and compost. Some add
a few crushed egg
shells to help keep a higher pH (alkaline soil) as they decompose.
Fertilize sparingly.
Containers allow lavender to be
moved where it can most appreciated when in bloom. Since the roots
like tight quarters, plant
into a container only slight wider than the roots. If pots are too
large, they may remain too
wet. Clay pots will dry out quicker than
plastic ones, so lead to less chance of overwatering and root rots.
But as in the garden, don’t let plants dry
out too much. Repot yearly, and if
plants get too large you may need to plant them in the garden or
start over
with young plants.
Unless your climate is very humid or
cold, you should be able to find some lavender plants at local
nurseries that
will survive. Give them full sun, and
well-drained soils that aren’t too acidic nor fertile, and prune
lightly in
spring, and they should thrive. In fact, most states and regions of
North
America now have at least a few commercial lavender growers from
whom you can
buy a range of products.
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