Dahlia Propagation by Seed (1847)

This article is adapted from the series The Gardener’s Monthly Volume of September, 1847. It was published under the title "The Dahlia; Its Culture, Uses and History."

This book—at 111 pages, it is indeed such—was written by George William Johnson (1802-1886) and J. Turner. It was published in London by Simpkin, Marshall, & Company.

Although the original work is in the public domain, this article has been edited for the modern reader and contains new material. This version is Copyright © 2024 by Steve K. Lloyd and may not be reproduced without permission.

Dahlia Propagation—Part 1

Dahlia Propagation by Seed

by G. W. Johnson and J. Turner (1847)

Edited with revisions by Steve K. Lloyd © 2024

Like other tuberous-rooted plants, the dahlia can be propagated in more modes than can other plants of a different form.

By Seed.—Varieties only can be obtained in this mode, for no seedling exactly resembles its parent, although cross-breeding—an intermixture of parents—has great influence in determining the properties or characteristics of the offspring.

Although the parentage has great influence, yet the influence is not paramount, for as Mr. Wildman has justly observed, so much depends upon accident, or circumstances over which we have no control, that it is difficult to recommend one in particular as a desirable parent to breed from. 

The amateur should be warned, however, that seeds from thin flowers generally, although their style be good, produce seedlings that end in disappointment. Windsor Rival is an example. 

Constancy in the parent Mr. Wildman thinks a matter of little moment, provided defective blooms are immediately removed, and none but the best left for seed. Brightness and clearness of color are desirable, but no dependence can be placed upon the exact colors that will be produced. 

If hybridization is resorted to, the best blooms, whether occasional or otherwise, from which seed might be obtainable should be selected, the colors chosen being distinct and contrasted, and not compound. 

To those who would not take the trouble to resort to artificial fertilization (which is not needed if a few of the very best varieties, including one or two that seed most freely), dahlias which you select for cross-pollination should be planted together, apart from all others. The chances then would be far more in favor of valuable seedlings being engendered.

In making a selection to seed from, the habit of the plant should not be overlooked, there being but little beauty in those flowering beneath the foliage, or of drooping habit, unless the latter are tall growers, such as the Countess of Liverpool. 

Substance of petal is perhaps the most important point. Without this, the color, or the bloom itself, but stands a very short time. Those varieties possessing this quality in the greatest degree have the most glossy or velvety appearance on the face of the petal. 

The following dahlias would be a good dozen to plant out for this purpose:

1. Marchioness of Cornwallis
2. Berryer
3. Beauty of Sussex
4. Lady St. Maur
5. Nonpareil
6. Standard of Perfection
7. Scarlet Gem
8. Queen of Sheba
9. Master George Clayton
10. Yellow Standard
11. Princess Radziwill
12. Beeswing

Even the finest, and what are termed the most constant flowers, produce blooms that should at once be removed. For this purpose the plants should often be examined, as it is impossible to distinguish the good from the bad when gathering the seed. And more, the thin blooms possess so much fertilizing matter, from which the bees would injure the whole.

For the production of seed the plants should be devoted to the purpose. All but a few of the uppermost shoots should be pruned away as they appear, and from these, the first flowers, which are rarely good, should be removed.

Mr. Paxton adds that about twenty or thirty flowers should be left, and of these only the finest and best formed be bred from. As soon as each reserved disk begins to expand, it should be covered with thin muslin or gauze to prevent any fertilization by the wind or by bees, from other and undesired varieties. 

As soon as the florets open, the pollen from the wished-for male parent may be introduced to them during two or three successive days, by the aid of a camel’s-hair pencil. This operation is repeated to each floret as it expands, and the flowers kept covered as before directed, until the danger of casual fertilization is passed.

In collecting the seeds, Mr. Paxton recommends that the outer circle of them, and those in the very center of the disc, should be discarded, the first usually producing single flowers, and the others being imperfectly formed. (Paxton on the Dahlia, 68.)

• Editor’s note: This probably refers to A Practical Treatise on the Cultivation of the Dahlia by Sir Joseph Paxton; London: W.S. Orr & Co., 1838.

Glory of Plymouth has, to the great astonishment of all who possessed the slightest knowledge of the parts of the flower, been repeatedly recommended as a good flower from which to save seed. Now, Glory of Plymouth is one of the most double flowers that has ever yet been raised, and, like Globe Crimson, full to the center. It might be asserted, without fear of contradiction, that it never has been seeded from, and that it is incapable of bearing seed. This is not a matter of opinion, but one of fact,and any misstatement can be easily disproved.

If all the imperfect blooms had been removed from Windsor Rival, not more than one pod of seed could have been obtained in a season.

We have already noticed which seed should be rejected. We may now observe that which seed is to be preserved should be collected on a fine day, and, after drying thoroughly, be rubbed out from the heads, and kept dry until required for sowing. If kept in the heads they are liable to become moldy.

The seed ought to be sown about the middle of March on a slight hotbed, to get the plants up early. If properly attended to, they will flower the same year. The young plants ought to be pricked out as soon as they are fit—three or four in a No. 48 pot. As they advance in growth, they may be shifted a month after into small 60 pots, one in each pot. After it has grown in strength and size, the plant may be shifted again into a 48, there to remain, till turned into the ground about the third week of May.

In their young and tender state, take care to protect them from cold and frost, so that they receive no check either to retard or spoil their growth. (Hogg’s App. 196.) Our own practice is to prick the seedlings, singly, into 48s, to remain until fit to be planted out in the open border.

Where seedlings are grown by the florist, it is, generally, in such numbers that protection at night is impossible. The fault of protection being required lies in almost everyone sowing too early. It was usual at one time to sow about Christmas; we now sow the first of April, and bloom them a month sooner than formerly, with half the trouble. 

If planted early, the check is mostly from cutting, cold winds, throwing them back several weeks. Hence the principal object being to keep the plants dwarf.

Mr. Sabine, late secretary to the Horticulture Society of London, has left on record suggestions for raising seedlings that are still worthy of attention. 

The seed, he says, should be gathered from those plants whose colors and character are most likely to please, always taking from the dwarfer ones, where no preference exists on other accounts. Many of the seedlings will follow their parent. Therefore, all that are raised will now be new varieties. 

Double flowering plants are more likely to spring from the seeds of semi-double flowers, than from those of quite single ones. Chances are that seeds obtained from those particular florets of the disc, which have altered their form, may have a greater tendency than others to produce plants with double flowers.

The young plants, pricked out into pots or boxes, and left under cover in warmth until the end of April, may be planted out then where they are to remain. Cover each plant for some time with an empty pot at night, to avoid injury from spring frosts. 

Where single dahlias have been planted the preceding year, many young plants will arise from self-sown seed. These may remain in their original place, or be removed. 

The seedlings should be planted in rows three feet apart, and two feet distant from each other in the row. This will allow sufficient space for a person to walk between them to examine the different varieties. Every alternate row may be two feet, if space is an object, thus forming them into beds, leaving plenty of room to look over them twice a week to weed out the single flowers, thus giving sufficient space for the promising plants to bloom in character. 

They thrive best in rich loam, and require a clear open space to grow, the shelter of trees or of walls being injurious to them. They seem to suffer in some gardens, if planted often in the same place. Therefore, where there is not space to enable the grower to move their quarters in successive years, it will be advisable to add some fresh maiden earth to the soil, when they are to be continued in the same spot.

As dahlias are liable to much damage from the wind, they should be carefully tied to stakes as they grow. The seedling plants thus treated will bloom in July, and will continue in perfection till the autumn, but the first frost injures their foliage. The beauty of the flowers may, however, be preserved somewhat longer. To do so, move the smaller plants with balls of earth into large pots, and keep them under cover in the greenhouse or conservatory.

Until a seedling plant shows its flowers, there are no means of ascertaining its value. The stems of those which produce dark flowers are generally brown, or a dark purple. Pale flowers grow on plants with lighter stems, and the white flowering ones with perfectly green stems.

But even these distinctions are not constant. It is worthy of remark, that those seedlings that take the lead and bloom first, seldom—if ever—produce a flower worth preserving. These are from the finest seeds and thinnest blooms. They germinate first, and keep ahead all through the season. They can easily be distinguished by their tall habit, without side-branches. 

In contrast, the late, small plants that require nursing to make them bloom before the frost arrives generally produce the best flowers. It is well known that very few of our best seedlings are ever shown in the first season of their blooming. These are from the smallest seeds, and very double flowers. 

The proper time to judge of the full merit of the flowers, and consequently to select the plants, is the morning, for the sun injures the brilliancy of the flowers. Plus, the summer’s flowers are much superior in beauty to those produced later in the season. In September and October, before any frost comes, the quantity of flowers which are then in bloom at once, makes the show at that period the most splendid.

Mr. Glenny says that as the seedlings come up, air should be given to them, to prevent them drawing. As soon as they are large enough, which will be when they have six leaves, they may be planted singly in thumb-pots, and replaced in the frame. 

Alternatively, three, four, or more small dahlias can be placed in pots of a larger size. By the time the heat of the frame has declined, they will be strong enough to withstand the weather, if they are covered at night and during frosts.

Those who sow in large quantities will do well to defer sowing until the beginning of April, inserting the seed in pans or boxes, or broadcast in a frame. They may then remain until planting time, when they may be planted out according to the convenience of the grower.

For large quantities, it would not do to let them remain in the seed-pan. To do so, it must be small quantities, and sown very thin. A moderate heat should never be used, but always a very strong one, otherwise the most likely and promising seeds would never make an appearance. The small seeds being from the finest blooms, they perish from the moisture if not sufficient heat to make them germinate at once.

Those who do not possess facilities for potting their seedlings singly should make a slight hotbed, as heat is required for the first few days only. 

• Editor’s note: A hotbed is a container or box containing freshly-composted manure, collected from the nearest stable or barnyard and moistened thoroughly to hasten decomposition. As modern gardeners know, compost generates a fair amount of heat as it rots. Before the days of electric seed-starting heat mats, the use of a manure hotbed was a technique to most serious gardeners.

Place a common cucumber-frame, with rich light soil, over the manure to the depth of four or five inches. Into this, the young plants should be placed three to four inches from each other. In a few days the plants will allow lights [glass or fleece covering] to be pulled back, should the weather be fine. In fact, on all occasions, night or day, when this is the case, the great object being to keep them dwarf.

A week before planting out for blooming, let the frame be taken away as well. The young plants should be carefully drawn from the seed pans, beginning with the most forward, leaving the late ones for another day, between which a little fine soil should be shaken, and watered with a fine rose before placing the pans again in the hotbed.

Plants will continue to make their appearance, which would be lost if Mr. Glenny’s plan was adopted, by giving air as soon as the first plants are large enough. If properly done, with moderate attention, stove plants can be produced from four to six inches in height. Such, of course, would bloom in excellent time.

• Editor’s note: I had never encountered the phrase “stove plant” before reading this paragraph. I found a definition on a website of gardening terms that defines a “stove plant" as “a plant which requires warm greenhouse conditions in winter.” Even so, I can’t quite make out the author’s meaning. My best guess is that late-germinating dahlia seeds may eventually grow, but since they got such a delayed start, the resulting plants can only be grown to maturity in a greenhouse. If you can figure out what Mr. Johnson meant, please let me know!