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Snapdragon

Plant of the Week

Snapdragon
Latin: Antirrhinum majus

Picture of snapdragons, pink in color.
The dwarf, open-throated snapdragon is maintained as an inbred line

Continuing our discussion of how garden seeds are produced, we need to consider first the most basic type, the inbred line.  In February, when garden fever first begins to bubble up in our souls, display racks of inexpensive seeds magically appear in store isles. 

Almost all of these flowers and vegetables are produced as inbred lines.  For an example of how new characteristics can be introduced into a plant, I will tell you of Julie Snapdragon, a dwarf, open-faced inbred line.

Snapdragons are cool season annuals from the southern Mediterranean.  The Latin name, Antirrhinum majus tells us a lot about the plant.  The genus name is from Greek - anti (like) and rhin (nose or snout as in rhinoceros) - and tells us the flowers are like the nose of a dragon, complete with the ability for the mouth to open when the sides of the corolla tube are gently squeezed.  The species epitaph means "May," the season when the plant normally blooms. 

In its native habitat, snapdragons are winter annuals, with seeds germinating in the fall, growth through the winter and then blooms appearing in the springtime.  In central and south Arkansas, we are beginning to see snapdragons offered in the fall as a companion plant for pansies.  In northern areas snapdragons don’t usually overwinter.  It seems to me that they are only cold hardy to about 15 degrees.

The color range for this member of the Scrophulariaceae family is wide and includes bright reds, pinks, yellows, maroon and white, but not true blues or purples.  Architecturally it grows stiffly upright with straight stems and flowers along the ends of the branches in similar fashion to foxglove and penstemons, other members of the family. 

The flowers of the figwort family are designed for bee pollination, and snapdragons are specially fitted with a landing pad, a door for entry and a reward for the bee when the task is completed. 

But somewhere along the way, a breeder came across an open-faced snapdragon.  The flower was shaped more like a funnel than a nose; a snapless snapdragon.  This characteristic had the effect of making the flower appear more attractive from a distance because there was more display from each individual blossom.

Snapdragons have never been widely used as "bedding plants," their season of bloom being too short and their height not conforming to the foot tall size that seems to have crept into the notion of what a mass planted flower bed should be.  So, in the 1970s, a breeder set out to rectify this problem by developing a dwarf, open faced snapdragon.  This little tale illustrates how breeders can use the principles developed by Gregor Mendel and apply them to solve a specific problem.

The open-faced characteristic was found on a tall, cut flower type snapdragon.  The dwarf plant had a normal, snapable snapdragon flower.  The breeder, whose name I have lost, removed the anthers from the open faced flower and dabbed pollen from the dwarf plant onto the stigma of the open-faced form. 

Lacking the technique of a good bumblebee, he only got 30 seeds from this first cross.  These were planted out and the plants were remarkably uniform but with normal stature and closed flowers.  This told him that both the dwarf and open-faced flower characteristic were recessive traits.  Following Mendel’s mathematical approach, he knew that only one in 16 plants would contain both recessive characters. 

After the first manual cross, bees were allowed to do the heavy lifting for future pollination efforts.  These 30 plants were permitted to cross amongst themselves and the seeds from this population saved.  This generation, called the F2 generation, numbered 16,000 plants.  One-fourth were dwarf, and three-fourths were tall.  Of the 4000 dwarf plants, 1,000 had open flowers.  From these he selected 28 plants that had the color range and the strong garden characteristics he sought.

These 28 plants were grown in an isolated patch and seeds saved.  These seeds, the F3 generation, were  "rogued" for off-type plants and seeds saved from the best.  After six generations the line was "fixed" and Julie was ready for a coming-out party.  The six generations to fix a line is again a mathematical function.  With each generation, the variation is reduced by one-half; after six it has been reduced to the point it approaches zero.   

By growing these inbred lines in an isolated patch away from other plants of the same species, inexpensive seed is produced that tempts us the following spring.  Most line-produced flower seed is grown in the Central Valley of California around Lompoc. 

Snapdragons are easy to grow from seed, but as bedding plants it is best to transplant them as young plants to insure they root-in before they start flowering. 

If spring-planted, they should go in the ground while the soil is still a bit cool.  They tolerate light frost; so don’t worry about planting early.  Plant them in full sun in a well-drained soil.  Deadheading is necessary to keep the plants in bloom. 

The ever-lengthening raceme means that, at some point, you must simply cut it off and force it to send up new flower stems. 

By: Gerald Klingaman, retired
Extension Horticulturist - Ornamentals
Extension News - August 13, 2004

 

The University of Arkansas Division of Agriculture does not maintain lists of retail outlets where these plants can be purchased. Please check your local nursery or other retail outlets to ask about the availability of these plants for your growing area.