One thing a hybridizer must be is flexible.
About thirty years ago, when starting my delphinium breeding, my idea was to follow the English method of selecting individual seedlings, which would then be propagated by cuttings and sold as named varieties.
However, I had to revise my thinking as this method seemed to apply only to localities with ideal climatic conditions such as we have in the Pacific Northwest.
In addition, propagation of individual varieties is slow and costly and does not lend itself to large-scale distribution.
Editor’s Note: Increasing delphiniums from cuttings is feasible for the home gardener, though, and can be done successfully in most parts of the country. Cuttings must be taken in early spring before shoot growth is much over 5″ inches. The end of the cutting, which will form roots, must not be hollow but should be solid.
Delphinium Strains
The only alternative was to create a delphinium strain that would come reasonably true to color from seed so that anyone could grow show delphiniums in his garden without resorting to expensive named varieties.
Instead of naming individual plants, we named series, each representing a different color and each being produced new every year from seed, always selecting the most outstanding plants as the progenitors of the next generation.
This proved eventually so successful that it became a standard for delphiniums in America and since has been applied to other flowers by other plant breeders.
In this way, the public immediately receives the latest advancement in breeding at a fraction of the cost that it would take to produce the same varieties by vegetative propagation.
It also enables people with little gardens to grow as fine delphiniums as the favored few with unlimited resources.
The original species back of the English strains came from the mountains of Asia.
Eminent Delphinium Breeders
Years of crossbreeding and selection by eminent breeders such as Kelway, C. F. Langdon, and Watkin Samuels transformed them into towers of beauty.
In America, N. F. Vanderbilt pioneered a strain. He combined the English hybrids with our native Delphinium scopulorum found in the high Sierra Nevada Mountains and produced a strain of graceful plants with thin, hard woody stems.
These were first exhibited at the Panama Pacific Exposition in San Francisco in 1915 and caused great excitement in gardening circles.
Another outstanding American breeder was Dr. L. H. Leonian, who combined the Vanderbilt strain with some of the English hybrids to produce the first pure self colors that have become the standard for delphiniums today.
To Charles Barber of Oregon, the honor of producing the first good white garden hybrids.
Breeding Delphinium Colors
Thirty years ago, being a pretty green beginner in the hybridizing fraternity, I envisioned producing red garden hybrids by crossing the California native D. Cardinale with the garden hybrids.
A professor of genetics at the University of California told me that this was impossible to accomplish, but I had to try it just the same!
Breeding is much like mixing colors on an artist’s palette. There are three primary colors:
- Yellow
- Red
- Blue
All others are mixtures of these. It is a simple matter to make combinations, but it is impossible to create a basic color.
You must have this to start with. No plant possesses all three basic colors in pure form.
In the delphinium, the basic color is blue. However, even the purest blues have a slight admixture of magenta noticeable on the reverse of the petals.
This gives us the variation down the ladder to the pale lavenders and deep purples.
White is an albino which appears in every plant and acts as a diluting factor.
However, the base of the white stems from the basic color of the plant, which in delphinium is blue.
When the white is successfully crossed with the red Delphinium Cardinale, it does not produce pink flowers but gives magentas or purples.
It is the same as when you mix scarlet and blue paint—the end product can never be anything but purple.
Magenta can be diluted to appear pink, but it is actually simply a diluted magenta.
The scarlet in delphiniums seems to be associated entirely with Delphinium Cardinale—a tuberous rooted species requiring a long dry resting period during the summer months.
Red Hybrids
To A. A. Samuelson of Pullman. Washington goes to the credit for bringing out the most advanced strain of red hybrids that will grow under varying climatic conditions and have much larger flowers than the California species.
However, they retain their tuberous roots and the habits of growth of the original species and are definitely not garden hybrids, although they are fascinating rock garden subjects with exquisite shades ranging from palest pinks to deepest scarlets, some in yellow tones with red eyes.
For years I tried hard and raised great numbers of seedlings from the Cardinale parentage but finally gave it up as hopeless.
While I did not get a red garden hybrid, some of the derivatives of cardinals, when combined further with the garden hybrids, gave such luminosity to the colors that the by-products proved far more valuable than the original quest.
Blue And Purple Hybrids
Blues and purples were comparatively dull 25 years ago. Then, the Cardinale blood brought both the life and brilliancy to them that became the individuality of our strain.
Another by-product of the cardinales heritage was a series of whites with pinkish-lavender edges, comparatively new then.
From there, we gradually developed our Astolat series, which range now in tone from pale diluted lilac, the nearest approach to pink, to brilliant rosy magenta, which in the orange light of the late afternoon gives the impression of red.
Under overcast conditions or artificial light, these colors become warm and glowing.
The fact that blue is the rarest color in our gardens accounts for the great popularity of delphiniums.
Our various blue series are also the most difficult to improve as any admixture of other colors takes the purity away.
Time and time again, I have produced much larger blues by such combinations, only to discard them because of losing the true blue color.
Yellowish-Cream Garden Hybrid
A yellowish-cream garden hybrid with a peculiar shiny, sickly foliage occasionally appears in our plantings.
I have traced it back to Kelway in the last century, who used some Asiatic species from which it must have come.
In every generation, someone breeds these, intensively hoping to get a yellow delphinium. Every year, I get at least one query from some amateur who “discovers” it in his planting.
Like the others, I bred these creams until they came about 75% percent true to color but finally discarded them as hopeless because of their scraggly growth and weak constitution.
Delphinium Sulphureum “Pure Yellow”
There is a pure yellow species, Delphinium sulphureum, coming from the Asiatic region similar to the California species in the habit of growth.
The dry roots may be stored for as many as 3 years and still remain alive.
Although I have tried many times to cross this yellow species with the garden hybrids, I have never been successful and have not heard of anyone who has been.
Successfully Grow Delphiniums In Localities
Successful growing of delphiniums largely depends upon locality. Generally speaking, if you could draw a line from San Francisco to Washington, D.C., you would find that your chances for fine delphiniums would be better than south of it in the area north of this line.
However, there are exceptions to every rule, and you may find a finer locality at higher altitudes south of the line than you would at low ones farther north.
In warm localities, plants are forced to bloom rapidly, not reaching the size they can attain under cool, moist conditions.
Their lives in a warm climate will be considerably shorter than in a cool one.
Plants that are comparatively perennial at the Canadian border will become more or less biennial in the middle of the United States and practically annuals in the Deep South.
Propagation Of Delphinium
The simplest means of propagation is from seed.
The seed can be sown in early spring in February or March, possibly under glass depending on locality, so that strong young plants can be fielded out in permanent positions during May or June.
These will bring good flowers during August and September and leave well-established plants for the following spring.
In climates with hot summers, it is preferable to sow the seed in July and August so that strong plants fielded out in October keep enlarging their root systems all through winter and bring magnificent spikes in spring.
The draw-back of spring sowing in such localities is that the young plants are forced by heat to bloom before they can develop an adequate root system, and one seldom gets much of a spike on them.
The hotter your conditions during the early stage, the quicker the plants will bloom and the smaller they will be.
Here along the Pacific Coast near the shore, we sow our commercial plantings in November, transplant the little plants in beds in greenhouses during January, and field them out in March.
Our springs are usually cool, and the plants develop beautiful spikes by July when the field is in full bloom.
We could not follow this method in the interior valleys where the temperature is too high, and autumn planting is far more preferable.
The bulk of the delphinium industry, both for seed and cut flowers, is located in a narrow belt along the Pacific Coast, where summer fogs moderate the temperature.
Ideal Soil Conditions
Sandy loam is an ideal soil for delphiniums, but they will tolerate various mediums.
For sowing, we mix approximately 1/3 peat or well-decayed leaf mold with 2/3 of very sandy loam.
If the soil contains too much fresh decaying material, the chances for damping off are greater, especially under warm, humid conditions.
One-third peat and two-thirds sand are other mixtures that some Easterners prefer, and vermiculite is still another material that can be used for germination.
When the first true leaves develop, we transplant them into nursery beds of sandy loam, which have been enriched previously with well-decayed manure.
In this medium, they develop a healthy root system and are transplanted directly into the field in rows 2’ feet apart and a foot apart in the row.
This is simply because we expect to go rogue and discard almost 50% percent of the plants to maintain our high breeding standards.
A 2-foot distance between plants each way is necessary for the perfect development of specimen plants in your own garden.
Proper Growing Conditions
Soil deeply prepared and enriched with bonemeal and well-decayed manure and combined with perfect drainage is a must if you wish to grow show delphiniums.
A sunny location with wind protection is another must. In semi-shade, the plants grow spindly.
When the shoots reach 2′ feet, they should be staked with bamboo and tied securely.
In the second year, the plants will produce a great number of shoots which should be thinned out, leaving 2 or 3 of the strongest by simply breaking out the weaker ones.
In this manner, the strength of the plant will be conserved for the remaining shoots, which will give far finer spikes.
During the growing season, delphiniums require a constant supply of moisture.
In localities with warm, dry summers, some top dressing will be necessary to keep the soil from severe drying out.
Peat is perhaps the most accessible available mulch, but other materials could be used successfully, such as glass wool, straw, buckwheat hulls, or what we have been using here for the last few years, red wood sawdust.
Pine or fir sawdust is not recommended due to its toxic properties. Well-decayed manure is an excellent mulch, but care should be taken not to bring it close to the plant’s crown.
Sharp sand or wood ashes around the crown will keep the decaying material away from the stem.
When the first flowers have begun to fade, the flower spikes can be cut off, leaving the stems with foliage standing to protect the plant until the new growth from the bottom is well under way.
When this new growth reaches about a foot in height, the old stock, which has begun withering, can be cut off about 6″ inches from the ground.
This is to mature the stem and prevent an open wound close to the root system, which fungi could easily invade.
The second growth will require additional feeding to produce a good crop of flowers.
Quick action fertilizers such as ammonium phosphate or sulphate of ammonia can be sprinkled on the ground around the plant at a teaspoonful per plant, repeating this dose if necessary at two- to three-week intervals.
Washed into the soil will give the quick boost that the plants require.
Safer is even liquid fertilizers with a ratio of about 5-10-10 applied bi-weekly in light doses. These give the plants complete food, lower in nitrogen and higher in phosphorous and potash.
High nitrogen fertilizers tend to produce very lush and soft growth, which does not stand any wind.
Potash will significantly strengthen the stems and make them quite woody. This is why wood ashes are very desirable to incorporate into the soil or even sprinkle on top of the ground.
Pests And Diseases
The greatest enemy of delphinium is the bacterial crown rot which is prevalent in the hot, humid summer conditions of the Eastern United States.
So far, there has been no specific cure for it, and once the soil is infected, avoid planting delphiniums in that area for several years.
Green flower or aster yellows is a virus disease that crops up more in the West. This is transmitted chiefly by leaf hoppers from the adjoining weed lots where the disease winters.
Affected plants will form creamy transparent growth from the ground.
The plants should be destroyed as there is no cure for it. Mildew has been largely eliminated through selective breeding.
The cyclamen mite, a tiny pest invisible to the naked eye, causes deforming and blackening of foliage and flower shoots. It, too, can now be controlled by many sprays.
The main change in delphinium in the last twenty years, as I see it, is that where we had only a limited range in mixture with comparatively dull colors, today we can paint garden pictures with luminous colors that come true from seed in a far wider range.
46531 by Frank Reinelt