The Secret of Success in Dahlia Breeding

Originally published as The Evolution of the Dahlia: Chapter Five (1922)

Original text by J. J. Broomall is in the public domain.

Compilation, editorial notes, introduction, biography, and revised text copyright © 2026 by Steve K. Lloyd. All rights reserved.

In The Secret of Success, Broomall asks how a grower can make practical use of the variation examined in the preceding chapter. His answer begins broadly: success depends upon determination, close observation, and attention to detail. He then applies that principle to dahlia breeding, arguing that a parent should not be judged simply by the quality of its own flowers, but by the quality of its offspring.

That leads him directly into heredity. Broomall describes ancestral traits as capable of reappearing unexpectedly and uses his black Toggenberg goat, Topsy, as an analogy for the same phenomenon in plants. The historical genetic explanation is imperfect, but the practical rule he extracts from it becomes persistent in his later work: breeding value must be demonstrated through progeny rather than assumed from appearance alone.

The second half applies the same investigative habit to cultivation. Apparent “running out,” Broomall argues, should not be accepted as an explanation. The grower should look for causes in climate, soil, moisture, cultivation, or other conditions. Breeding and cultivation are therefore joined by a common method: observe results, investigate causes, and judge from repeated evidence rather than appearances.

Chapter Five also fulfills Chapter Four’s contemporary pre-announcement of another factor in variation, giving this particular transition unusually strong support in the surviving serial record.

The text printed here is from J. J. Broomall’s 1922 Dahlia Guide.

The 1921 “Dahlia Guide” had not been mailed many days before I received the following from a correspondent in New Jersey, “Send me the secret of success.”

Well, my friend, I am going to give you one secret of success which will apply not only to the development of the Dahlia, but to every undertaking in life, “start in with the determination to succeed;” and do not overlook the smallest detail; it is by careful attention to every small detail that success is attained.

In a conversation with the late John Lewis Childs I was surprised at the intimate knowledge he possessed of every branch of Dahlia growing; if he had the same minute knowledge of the other plants he dealt in it is no wonder that he succeeded in building up a great business from a humble beginning.

It should be understood in my talks on the Dahlia that I am not speaking as a botanist (I know very little of botany), but from the standpoint of a practical gardener; and what I say and believe is based on experience and observation; and whether my conclusions are right or wrong I think my critics must admit that I have been fairly successful in my efforts to improve the Dahlia; and now I will attempt to tell you about—

Probably no flower from the time it was first cultivated until the present has shown a greater tendency to vary in color and form than the Dahlia. The introduction of D. Juarezi (the original cactus Dahlia) and the subsequent crossing of this with the other species, and later crossing and recrossing of the different varieties, has resulted in a variety of shapes, colors and combination of colors and tints that is endless.

To English growers is due the credit for having developed the Cactus Dahlia to a high state of excellence; giving to the world some of the most magnificently formed flowers ever seen.

It is to be regretted that the majority of the English Cactus Dahlias, with few exceptions are inclined to have weak stems, and some are such weak growers that it requires all the skill of professional gardeners to grow them to perfection; such flowers could never be very popular with amateur growers.

The cause of their weakness I believe to be the selection of seed, and pollen parents too close to type; excessive inbreeding is as certain to result in weakness in plants as in animals. I have found that almost invariably the greater the difference between the parent plants, the more robust the seedlings would be.

The giant decorative, hybrid decorative, hybrid cactus, and peony flowered dahlias introduced by American growers in the last few years are rapidly becoming more and more popular; not only because of their immense size and gorgeous coloring, but also on account of their robust habit of growth, and the ease with which they can be grown.

While the development of the dahlia has been wonderful, I look for still greater improvement in the future, for I believe the only limit to the improvement not only of the dahlia but of every plant of ornamental or economic value that we cultivate is our knowledge of the plant; therefore, it behooves us to learn all we can of such plants.

In improving the dahlia at the present time, hybridists are contending with a force as unfathomable as it is uncontrollable, and which I believe is as yet but little understood, and this is its inheritability.

To make my meaning more thoroughly understood I will refer to this trait as seen in domestic animals. I have a black Toggenberg goat. Topsy’s arrival at the dahlia farm was a surprise, for all of her ancestors, so far as I knew, were either chocolate brown or some lighter color; so whence came the black?

From a man familiar with Toggenbergs I learned that there is a strain of black in that breed; so away back several generations, one of Topsy’s ancestors had been black, and it appears the time had arrived for this strain of color to reappear.

Now this trait in animals is nothing new. It is common knowledge among all well posted stock men, and has been for generations; but I believe it is not so well known that this same inheritability exists in plants, and in the dahlia perhaps to a greater extent than any other flower because of the innumerable crossings between the ancestors of the varieties we now cultivate.

Thus it may occur that a hybridist using parents with perfect stems finds among the seedlings some that have very poor stems and which are much inferior to either of the parents; now whence came the poor stems?

Why, away back no man knows how many generations, one of the ancestors had poor stems and this trait being in the “blood,” figuratively spreading, was certain to reappear in the cycle of plant life.

This inheritability which might appear to be a barrier to the improvement of the dahlia I believe to be of the greatest advantage because I have found by experiments that in some flowers the good strains of blood predominate, and the seedlings from such will show a high percentage of good flowers, while there are others, including some of our very best dahlias, that are very poor parents, nearly all of their progeny being retrogrades.

And here is the secret of success in dahlia breeding: the selection for breeding of those parent plants in which the desirable traits predominate; in other words, those whose progeny have shown the greatest percentage of improvement.

This rule, if followed in conjunction with intelligent culture and a favorable environment, can hardly fail to give satisfactory results.

It seems to me of the greatest importance that we should more thoroughly understand the habits and characters of the varieties we already have, in order that we may give them more intelligent treatment, and thereby obtain the best possible results from growing them; for this reason I am going to reiterate and repeat with emphasis some things I have previously written in regard to their culture.

First of all, I consider this talk about Dahlias “running out” a fallacy; DAHLIAS DO NOT RUN OUT; a dahlia once double is always double.

Here are my reasons for making this positive assertion. In 1899 I published my first price list, in which I described 153 varieties, about one-half of which I am still growing. To the best of my knowledge and belief not one of those dahlias ever ran out; if as some claim dahlias run out I wish they would explain how it happens that in all those 23 years none of those varieties ever ran out.

There have been years when some of them failed to make good flowers, but the next year, IF CONDITIONS WERE FAVORABLE, they were as good as ever.

When a dahlia fails to make good there is always a REASON; but it is not always easy to determine the cause.

There are some causes that are not easy to guard against among which are unfavorable climatic conditions; extremes of heat and cold, and sudden changes from one to the other are certain to cause imperfect flowers.

In Southern California after October 20th very few dahlias will come full to the center, which I believe is due to the fact that owing to the cool nights both plants and ground become chilled, and the flow of sap is thereby restricted.

Cultivation of the soil is good even this late, as soil that is loose and pulverized will better absorb both heat and moisture, and retain them longer; and that is one reason why I do not believe in mulching dahlias. It prevents the proper loosening of the soil.

It is true that mulching saves labor and moisture, and where manure is used for mulching, the flowers may show an improvement for a time after mulching as some of the fertilizer is carried to the roots, but for a long continued season of bloom I think it far better to have the manure mixed in with the soil where the plants can reach it as needed, and keep them cultivated so that the feeding rootlets will reach it.

Another very serious objection to mulching is that it is an ideal harbor for insects, and a breeding place for fungic diseases; if your chief object is to save water and labor “mulch;” but if you want fine flowers CULTIVATE, often and thoroughly, especially after each rain or irrigation. That in my opinion is the secret of producing fine flowers, and preventing them from running out or misbehaving contrary to your wishes.

And once more remember this so-called running out is only temporary, NEVER permanent, and is ALWAYS due to some CAUSE which you should endeavor to understand.