How To Divide Dahlia Rhizomes Correctly?

Lush, regal, massive and colorful dahlia inflorescences are hard to miss in any garden. This true queen of autumn knows no equal in the size of their inflorescences, nor in their picturesqueness during the second half of the garden season. Unfortunately, to be able to admire the luxurious blooming of dahlias, you have to work hard. Dahlias bloom spectacularly only when the plants are rejuvenated in time and the number of shoots is controlled. Too large, overgrown dahlias will not produce equally large and beautiful inflorescences. Dahlia division is a simple process, but it still has its subtleties.

How to divide dahlia rhizomes correctly?
Dahlia rhizome division. © sina


  • Separation of tubers is essential to flowering and health of dahlias
  • Separation timing for garden dahlias
  • Conditional standard for dividing dahlias
  • Technology for dividing Dahlia tubers

Separation of tubers - the key to flowering and health of dahlias

Dahlias are far from the easiest plants in the bulb and tuber category to grow. This winter-hardy, grown only with digging out for the winter, is a rather capricious plant, requiring considerable effort from gardeners. Of course, dahlias will fully repay their care by fast growth, unprecedented size and beauty of flowering. But to enjoy them, you will have to take care not only about proper care, annual digging for winter, proper storage and planting.

Timely reproduction and rejuvenation of dahlias is one of the most important points in the care of this plant. Of course, in some cases getting as many plants as possible, increasing the number of planting material is a very important task. But to rejuvenate dahlias, first of all, it is necessary for the most colorful blooming and preservation of their health. Dahlia rhizomes need to be divided frequently, timely and correctly.

The main goal of division is to obtain root tubers of optimal size, when the number of growth points, and therefore the number of shoots on them, will allow the most lush flowering and proper plant development. Dahlias build up their nests very actively, they proliferate over the summer, and if the plants are not divided in time, they will start to degenerate.

And the more the process is started, the more signs of shrinkage and loss of ornamentality will be manifested. It is believed that in the absence of regular division, dahlias will completely degenerate, age and die in 5-6 years.

One important aspect of dividing dahlias is prevention. Not only do dahlias become degenerate when nests are spread, but their immunity is significantly impaired. The ability of the plant to resist viruses and infections, the ability not to react to bad weather, resistance to pests and other negative factors decreases almost in direct proportion when the nest grows.

But timely separation has just the opposite effect: dahlias show stronger protective responses during cutting and separation. Plants fight infections more easily, are more resistant to weather, viruses and any negative factors.

Separation is not necessary every year and not for all dahlias. It is only carried out on those specimens that have strong, healthy, large, sprawling tubers with numerous growth points.

Never divide:

  • very small rhizomes;
  • plants with 1-3 points of growth;
  • varieties and species with very thin stems and root necks.
How to divide dahlia rhizomes correctly?
Georgina - queen of autumn garden. © nihon-kankou

Separation timing for garden dahlias

Separate dahlias, rejuvenating them and leaving root tubers of optimal size, at a time when they are out of the soil - before or after they are put into storage. The choice between autumn and spring division should be made according to convenience, habits or opportunities, the peculiarities of the weather in autumn at the time of digging and even the conditions in which the rhizomes are stored.

Each of the two division options has its advantages and disadvantages:

Autumn division of dahlias

It is considered the easiest and most productive method. In the fall, when rhizomes are dug up, they still have to be cleaned, treated with fungicides, inspected, and damaged parts removed. Therefore, already clean and ready to go to storage, the dividers can only be divided, so that in spring they can immediately start preparing for planting.

The main advantages of this method are less risk of viruses and diseases, the simplicity of the process itself. But the risks are also big:

  • smaller divisions are less tolerant of wintering outside the soil;
  • higher risk of shrinkage or disease.

Spring division of dahlias

It is carried out before the beginning of the awakening of rhizomes, before the start of the gardening season. Overwintered dahlias are re-inspected and culled. In spring you can assess their real condition, buds by the end of March (and with proper storage, this is when the dormancy period ends) are well highlighted, they are easy to detect and evaluate.

Read our detailed material: Preparation, germination and planting of dahlia tubers.

The percentage of planting material loss is less, and the size and quality of the divisions are easier to determine. Larger dahlias store better, so many people prefer to divide before preparing for planting rather than after digging. True, the difficulty of separation, the hardness and flaccidity of the rind, the greater risk that a large nest will spread infection, is not always compensated by the advantages.

Whatever option of separation is chosen, you should remember that careful work and careful inspections, no hurry - the key to success in both cases.

How to divide dahlia rhizomes correctly?
Fall division of dahlia rhizome. © uneruta

Conditional standard for dahlia divisions

"A "planting unit," or standard dahlia division, is one tuber with 1-3 strong, quality buds and well-developed, quality roots. Sometimes it is one "rhizomeshishka", and sometimes - several, if the bud is single and common.

To ensure that dahlias develop normally, the inflorescences are not shallow, the plant is not depleted and normally mature, it is worth leaving two, at most - three stems on each bush. Excess shoots are recommended to be removed in the early stages of development, but it is better if the maximum number of shoots is limited even before germination or planting by controlling the number of buds.

From this standard or norm can be deviated. In each case, the method of division, the lines along which the rhizomes should be cut and how many buds and tubers should be left should be determined individually. It is always best to begin by carefully inspecting the rhizomes and identifying the buds that are present on each rootstock. If it is difficult to orient, you can mark off the lines and buds with a marker.

If you have bought a rare variety, have only one division, have overwintered badly and have only one tuber with a couple of buds left, it is about saving the variety or trying to grow a couple of bushes from one root, you can split the rootpod in half, leaving 1-2 buds in each part. If the tuber forms strong roots and only one bud, you can safely separate it to grow a strong single-stem bush.

The principle of individual selection of division size also works in the "opposite" direction. If the plant has been sick, weakened, the rhizomes are in bad condition, the roots are almost undeveloped and the buds are very weak, then, regardless of the number of buds, it is better to leave large pieces of rhizome so that the plant will recover and build up a quality mass over the summer. In such a case, 2-3 tubers with standard 1-3 buds are left in the division.

How to divide dahlia rhizomes correctly?
Small, but viable dahlia root-tub. © sina

Technology for splitting dahlia tubers

Any splitting of dahlias, both fall and spring, should be preceded by a thorough inspection of the plant; removal of all dry, damaged, dead parts. Sanitary cleaning of tubers, as well as their soaking in fungicides and washing, should be carried out before dividing. Tubers that exceed 15 cm in length are better to shorten.

The stems are shortened to a height of 1-2 cm before dividing, and the mother, the largest and darkest tuber, is cut out (as are small, upper, weak side tubers less than 1.5 cm thick and without buds).

The easiest option for dividing dahlia is to do everything by hand. If the plant had several stems, the tubers are easily separated, there is no need to cut. It is enough, gently holding the rhizomes from below, to loosen the tuber a little and carefully break the nests into several pieces or separate cones.

If the plant has a single stem or if the tubers are densely arranged, fused, and it is impossible to break them apart gently by hand, it is better to use the cutting method immediately instead of causing injury.

Cut dahlia tubers with a sharp, disinfected, thin knife. Sometimes pruning shears or scissors are used for cutting. But the knife is preferred because it does not squeeze the root tissue. The blade should be treated and disinfected after each cut.

When dividing a single stump rhizome, carefully cut in half the stem, leaving buds on either side, and then stretch the divisions apart. The tightly spaced tubers are carefully separated from each other.

If the resulting divisions are too large, you can continue dividing the stem in half with the parts stretched out. If you want a larger number of divisions, strong, well-developed tubers with large buds are carefully cut in half with an even cut.

Whenever cutting "rootlets", it is important to move along the tuber, to watch where the growth buds and roots are. The cuts are made away from the sprouts, leaving enough space for the wound to heal and never getting close to the growth points.

Whether the dahlias had to be broken up or cut, any wound on the plant should be treated with a protective compound after splitting. Common ground charcoal, manganese, in extreme cases - green, sulfur, fungicide or a special product for bulbs is applied to the entire surface of the cut. After separation, the cuttings are allowed to dry for 2-3 days.

If the goal is to build up as large a rhizome as possible in a season in order to reproduce or save the variety, dahlia divisions should be planted in quality soil and carefully select the conditions.

In the season, you must not allow the soil to dry out for long periods, provide regular watering and fertilizing. Cutting off some of the flowers or preventing flowering altogether will produce larger nests that can be divided the following fall.

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