University of Vermont Extension
Department of Plant and Soil Science
FOR ST. PATRICK'S DAY
Dr. Leonard Perry, Extension Professor
University of Vermont
don't have to be Irish to wear green on St. Patrick's Day, nor do
you need a
green thumb to grow shamrocks indoors. This plant, which is
this March 17 holiday, is quite easy to grow.
are a member of the Oxalis (wood sorrel) family, which contains more
species. Most of these grow from small bulbs although some have
The distinguishing characteristic is the three rounded or
leaves at the end of delicate stems. Most oxalis plants fold up
their leaves at
night, hugging them tight to the stems until daylight "wakes them
again—described botanically as “nyctinastic movement.” Due to
oxylates in plants, they may be toxic
to cats, dogs, and horses if ingested in large quantities.
familiar St. Patrick's Day species (Oxalis acetosella) is
florist shops and many grocery stores this time of year. It has
green, triangular leaves and grows to a height of about six inches.
hails from Europe, Iceland, and Asia. It is not the official Irish
dubium)-- a yellow-flowered clover or trefoil-- which is what
feel is the authentic species. That clover is difficult to grow
nurseries and florists sell Oxalis plants instead.
you are wondering how the shamrock became part of Irish history,
there are many
explanations going back to the significance placed by the ancient
peoples in the number three. The most popular story is that St.
Patrick, who is
credited with bringing Christianity to Ireland in the second half of
century, once plucked a shamrock from the grass at his feet to
illustrate the doctrine of the Holy
Trinity to his congregation. St.
Patrick's Day, which is celebrated on the anniversary of his death,
heralds the arrival of spring. The shamrock was adopted as a symbol
this patron saint and the "season of rebirth," and can be seen on
coins and medieval tombs.
like cool air, moist soil (except in their dormant period), and
bright light. Ideal
temperatures are between 50 and 65 degrees (F), and over 75 degrees
plants to become dormant. Soils should
not be kept too wet or waterlogged. If
the plant yellows, it may be getting too much water and roots may
rot. Too little water and it obviously wilts. Too
little light, or too much warmth, and plants may get tall and
not have an extensive root system, so unlike many plants, actually
prefer to be
crowded in a pot. However, if the plant dries out too quickly, you
may need to
move it into a larger pot. Fertilize every two to three weeks while
is actively growing or flowering, using regular houseplant
application rate, follow directions on the container.
aware that no matter how much care you give this plant, at times it
sick and lose its leaves. This dormant period, which often occurs
is part of the growing process common to all plants grown from
bulbs. During dormancy, stop watering. Let the
leaves die back naturally, then remove dead, brown leaves. Place the
plant in a
cool, dark place while it goes through its dormancy period. Plants
"sleep" for about three months. New green shoots signal that the
plant is waking up and needs to be moved back into the light.
divide your shamrocks, wait until the bulbs reach the end of a
Take them out of the pot, and remove small side bulbs. Then replant,
the surface, in a mix of potting soil and sand. Place in a
non-south facing window. Water, keeping the surface just
moist to the touch, until plants become
Oxalis varieties have similar growth requirements though many go
shorter, or no, dormancy period. Depending on the variety, the plant
yellow, white, pink, purple, or red flowers and grow as tall as 10
color ranges from dark green to deep red.
Those with dark red or purplish leaves only need about a month of
you are giving or getting shamrocks this St. Patrick's Day, there's
thing to keep in mind. Because these plants go dormant, shamrocks
suitable for growing with other houseplants in mixed pots or
planters. If you get
a mixed basket of plants, after the holiday, separate the shamrock
rest and replant in its own container. Don't wait until the plant
or sickly looking. By then, its roots will be deeply intertwined
with the roots
of other plants and will be difficult to transplant.
giving your Shamrock plant bright light, even moisture, and cool
and letting it go dormant during summer, it should provide years of