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Plant propagation

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Generative vs vegetative propagation[edit]

Generative Vegetative
Very variable Invariable
Seed Plant parts (clones)
Self-pollinators: usually less seed-variable, cross-pollinators: more seed-variable
F1: first filial series, F2:second filial series

F1: first line after crossing A7 and B7 (parental lines or P1, P2, ...) F2: cross between 2 F1 plants

Generative propagation (from seed)[edit]

Pre-sowing steps[edit]

Stratifiying or layer stacking: some seeds require more than one year of stratification (hot-cold-hot period or cold-hot-cold); others only require a short germ resting time or none at all.

Pre-germing or imbibition; soak for 24 hours in water and then plant in the soil (do not leave to germ). Placement on wet kitchen paper is also a possibility. It is done with seeds that have a long germination period (3-4 weeks), the seeds can be inhibited. The seeds are allowed to swell up to 24 hours in water and are then laid out in a box with damp toilet paper, covered with a glass or foil. From the moment the seeds begin to germinate, we carefully sow them.

Sowing[edit]

Scattered sowing using line sowing; useful if seed is too small to handle

Favorable sowing and planting times takes into account not only the state of the soil, temperature requirements, and correct growing season, but also the magnitude of the risk of damage by parasitic and non-parasitic causes (eg frost), ...

The sowing in full soil is done from late March. With this on site-sowing, the sowed plants are not transplanted. They are later thinned-out at the desired spacing. The sowing can be done scatted or in lines. We prefer to sow in lines because the weeding can then be done with a hoe or hoe machine.

Sowing depth= 2 to 3 times the thickness of the seed; however sowing needs to be done deeper with dry weather (the deeper= the more moisture), and shallower with wet weather.

Sowing by hand done in sowing trenches that are drawn near the sowing line. For this, we use the handle of a rake or the blade of a hoe. The depth of the sowing trench is related to:

  • The size of the seeds. The smaller, the shallower.
  • The expected weather, with rainy weather shallower, deeper with dry weather.
  • The germination period, seeds with a long germination period are sowed deeper.

Take care to not to sow with a too small spacing, the plants will then quickly compete with each other making them weaker and too lengthy. Divide the seeds on equally spaced distances.

After sowing, the sowing trench is gently filled by raking the soil over it, and slightly pressing it (i.e., with the back of the rake), so that the seeds make good contact with the soil. With light-based germers, the seed is pressed but little or not covered.

Note that the larger the seed; the larger the lumps of soil can be for the sowing, as the soil consolidation increases.

After the sowing, depending on the moisture content of the soil, it is watered. This is done with a fine spraying to avoid the consolidating of the soil. Often we will, to avoid the hardening of the soil, need to keep the soil moist, until the germs emergence.

When sowing in pots (rather than in the soil) we can use sowing soil: mixture of compost/green fertiliser: often too wet, since it keeps too much moisture, add sand, dough watch the PH (other substances can be added to attain the correct balance again). The sowing soil needs to be sieved first. We also need sowing trays

The germination[edit]

Requirements[edit]

Internal requirements

  • The seed is in good condition, if:

Morphologically: all parts are present and intact Physiologically: sufficient food reserves are present that are enough dehydrated and do not have vacuoles

  • The seed must be ripe: Some seeds do not germinate in spite of favorable conditions. They must undergo a maturation process. For certain seeds, a fairly severe frost period is required (apple, pear). The reserve nutrition is be converted into assimilatable form and inhibitor compounds must have been dissolved (stratification process).
  • The seed must be germamble: it needs to be capable of germing under the normal conditions. The germination is greatly reduced with the age of the seed.
    • Seeds that lose germination strength quickly: food reserves stored in the form of oil or fat (coffee and oil seeds)
    • Seeds that keep their germination strength a long time: food reserves stored in the form of carbohydrates (cereals, broom)

External requirements

  • Sufficient moisture for seed skin and germination: Water can more difficultly penetrate into a hard seed coat and germination lasts longer eg: clover.
  • Suitable temperature: germination is only barely possible at the minimum temperature. At the optimum temperature, the germination is the fastest. Above the maximum temperature, the germination strength is destroyed. Ex: grain 4-43°C.
  • Presence of oxygen (air): seeds that are too deep do not germinate.

Germination process[edit]

  • Due to the water penetrating the seed coat and entering the germ further via osmosis, the seed starts to swell. Under the pressure of the swelling of the germ, the seed coat starts to crack. The bursting of the seed coat allows the germ to release itself: this is the germination.
  • method of germing: The root always first appears, it always grows downwards or it attempts to do so. After this, the stem appears, it is often first still bent in a sharp angle, then it will erect itself and the plume can grow. With the common bean, maple, and the spruce, the cotyledons appear above the soil surface and then usually fall off. This is called an epigeïc germination. With the pea, rye and horse chestnut, the cotyledons remain in the seed coat below the soil surface. This is called a hypogeïc germination.
  • seedling: the first leaves that emergence from the plume are different from the next ones and are called youth leaves or primary leaves. They are e.g. singular, while the others are composed (Umbelliferae-ic). With dicots and gymnosperms secondary roots appear shortly after on the main root. With the monocots, this is not the case, but a number of roots appear at the base of the stem, so that the main root is no longer visible among the others, these roots are side roots (they shoot off the stem). If the cotyledons are pushed above the soil surface, we call the part between the attachment point of the cotyledons and the actual root the hypocotyl axis. This is part of the stem and will thicken with some crops e.g., radish, turnip.
Agriculture manual 1 2 1 image 12.JPG
Agriculture manual 1 2 1 image 13.JPG

Vegetative reproduction[edit]

Roots, tubers and bulbs[edit]

Stolons[edit]

Easy and fast Not with all plants, only with plants that have adventive buds on their roots

  • Rhus, Robinia, Ailanthus, Rubus, Chaenomeles

Large rootwig

stolons of roots that are left undisturbed in the soil even though their stems are removed blackberry species

Root cuttings[edit]

  • Anchusa, Anemone, Erodium, Geranium, Primula denticulata, Pulsatille, Verbascum
  • Acanthus, Eryngium, Limonium, Papaver, Phlox

Tubers[edit]

Plants of which the above-soil surface dies off. RV in a tuber. Tubers are not able to make adventive buds on a root.

A. One-year WK that needs to be remade each year Dahlias develop themselves on side roots, swell during the season are packed together in clusters. Each year, another plant.

Perennial tubers that grow in size Begonia

Derived stems[edit]

Definition: organs that contain RV on which they can survive a resting period. They are built the same way as normal stems but usually live underground and have spare food. 6 types of derived stems:

  1. corm: wears buds, end bud too. Few plants have such a propagation form, the most famous one being the potato. Some plants also have small nodules in the axillary buds: lilies. cut in X's, fungicide
  2. Rhizome: grows horizontally in the soil. Knots (not buds) and clearly identifiable internodes. from the nodes the above-ground shoots and roots grow. Several years old. iris, bamboo species, mint, Elytrigia repens, calla lilies, Asparagus (short rhizomes), Canna, bearded irises (Germanica), Convellaria majalis, peony, rhubarb, Polygonatum, Sanseveria, ...

Tubers[edit]

The difference between a tuber and a bulb is that a tuber is a swollen stem part and it is shorter and wider than a bulb. The leaves of the stem are thin, membranous and protect the tuber from drying out. The end bud grows from the flowering stem, the roots from the tuber base. The swollen area below the stem is surrounded by fleshy leaves: lilies. The end bud bud will result in a flowering stem.

Bulbs[edit]

Have a stem with very short internodes. The growing point is surrounded by thick fleshy leaves: scales or skirts (eg onion and tulip). Flowering bud and above-soil leaves develop themselves in the center of the bulb. Bulbs with skirts: daffodils and tulips, fleshy and very broad leaves Bulbs with scales: Fritillaria; no dry membranous covering scales, are very membranous and cover each other only partially. Bulbs multiply by division. With Lilium lancifolium and Lilium tigrinum: brood balls in the armpits. Propagation by planting off the scales.

Rosettes grown out of the stem[edit]

With some species shoots grow from a leaf axil: Sempervivum tectorum

Stolons[edit]

Stolons are vegetative shoots without food reserve that grow in the horizontal plane beneath the soil surface. Stolons will produce in their knots roots and erecting stems. Appear at the base of a stem from a leaf axil. Grows horizontally and again produces the same stolons: strawberry, Potentilla, Ajuga, reptans Geum, Potentilla, Saxifraga sarmentosa A new plant is made if the connection is broken with the mother plant. The young plants that already have some roots are cut from the parent plant and are planted in open-field or in a pot. It then grows to a full plant. Is, amongst others, applied with mint.

Divisioning[edit]

With this, the plant is divisioned into several pieces. It is important that:

  • Each piece contains at least 1 eye
  • Each part has enough roots
  • Each part contains sufficient food reserves

When divisioning, we follow these steps: The mother plants are uprooted and the excess soil is shaken off. The excess in leaves is removed. Make sure that growing points, shoots and roots are not damaged. Hold the plant with both hands, the thumbs as close as possible to the breaking point. Breaking causes less damage than cutting through. If breaking is not possible, the woody or fleshy part is prepared with a knife or scissors, never cut through the roots. Torn plant parts are never allowed dry out. As soon as possible plant it out in a pot of in the open-field so as to ensure a smooth regrowth in sufficiently nutrient-rich soil. Water the plants. In sunny weather we cover the plants to fight dehydration. Among others, used with chives, lemon balm, tarragon, lovage, oregano, sage, thyme, fennel.

Widely used technique with perennials and herbs. Also used to rejuvenate the plant. Also shrubs such as Hypericum, Spiraea. Time: best immediately after flowering (new shoots). With late bloomers: divisioning in spring. VP with fleshy root collar: Astilbe and Hosta VP with spontaneous divisioning: Aubrieta, Campanula, primroses

Propogating with stems[edit]

most used method.

  • Ground layering: from the parent plant a branch bend
  • Air layering: good method, cumbersome and time consuming

Aloysia, Ficus, Hamamelis, Magnolia, Rhododendron, lilac

Ground/air layering can be applied with thyme. With ground layering, an adult branch is deflected to the soil and is fixed with a clamp or a bracket. At the spot where the plant touches the soil, it is covered with a layer of soil. The branch's head will be placed slightly above the soil surface. After the branch has made underground roots, it can be cut from the mother plant. This young plant can then be transplanted. With the air layering, we cover the heart of the plant with a layer of soil. Once the branches have made roots, they can be cut from the mother plant. Ground and air layering happens in spring, where the rooted plant can be cut in summer.

Digging in[edit]

Used with ericaceae: Plants do not develop pretty however. A mature plant is extracted from the soil with a big root ball and then buried deep into an airy mixture in which only the young tops are left above ground. These will start to root.

Cuttings[edit]

When taking cuttings, we take a part of the plant without the roots and allow it to root in the soil or in a substrate. When taking cuttings from herbs, we usually take a shoot cutting with a heel (heel cutting). We rip off a young side shoot from an older branch so that a thin slice of wood with bark (the heel) also comes along. This piece contains cambium or divisioning tissue that provides a smooth rooting. The point of the heel is cut and the leaves near to it are removed. The bottom of the cutting is then dipped 1 cm deep in growth hormone and the excess liquid is removed (optional !). The plant contains several natural growth hormones. The plant hormone auxin is formed in the young green plant parts and is transported downwards. On his way down, auxin inhibits the growing of eyes (side shoots). In plants without roots an accumulation is created at the wound surface. This accumulation promotes the formation of callus and roots (auxin promotes cell divisioning). With some plants that root difficultly, a shortage of this plant hormone occurs. They succeeded in making this plant hormone chemically. Brand names of these chemical growth hormones are Rhizopon, Aglukon, Stimroot.

Then the cutting is placed into cutting soil as soon as possible in order to allow rooting. This can be in a cuttings box, a pot or multi-plates in which 1 cutting is placed per cell. The cutting should not be placed to deep, only the portion of the cutting that is free of leaves. The air humidity needs to be sufficiently high enough when cutting. The plant can evaporate, but does not yet have roots to absorb moisture. To counteract evaporation, the cuttings boxes or cutting plates are placed under plastic film. The cuttings are lightly moistened after the placement and are placed under a plastic foil. When the air humidity is too low, the cuttings will start to hang over. When there is much water in the air, then the cutting does not have the tendency to evaporate water. At professional companies, the cuttings are placed under water mist. With a rain pipe, a water mist is made that applies a thin layer of water over the leaves. The cutting can not evaporate. Between the cuttings, there is an electric sensor that, when the humidity is below 95%, causes the water line to start spraying.

Light and heat promote the rooting of the cuttings. The temperature in the seed box is best 2-5°C above normal cultivation temperature (17-20°C). We will have to cover the plants from the sun during periods of high solar intensity. The temperature would otherwise rise too high. After the cutting has rooted enough, we will plant it outside or in a pot after hardening off.

Stem cuttings[edit]

Most used method, most economically interesting method for many plants.

General rule:

  • cuttings of herbaceous plants in spring
  • cuttings of woody plants: in the resting period.
  • Choice of cuttings:
  • mother plant needs to be cut back significantly to attain a a variety of young twigs
  • season plays a major role: woody cuttings in spring just after the buds begin to sprout, in autumn there is less chance of success but stronger material is attained that will dry out less quickly
  • heat: too hot; development of growing point but no root formation

cool above ground, hot below ground

Leaf bud cuttings[edit]

of evergreen plants possible with any type of stem, woody, semi-woody, herbaceous Aucuba, Ceanothus, Daphne, Elaeagnus, Cherry laurel taken from matured stems that are almost completely woody, have leaves and therefore no complete resting period. Time: end of summer, early autumn

Heely stem cuttings[edit]

a young side shoots pulled from the parent plant in which a heel (= a piece of bark) is torn along. Reason: increased density of cells with growth opportunities in cambium. Very good for plants that require a longer time to root. Eg: Buxus

Herbaceous top cuttings[edit]

Not yet matured and ripened off branches. Are very fragile but root fast. The younger the shoot, the faster they will catch on. Herbaceous shoots develop during growth and lignify as they get grow older. Herbaceous shoots are taken from rapidly growing top shoots in the spring . It is done the minute the buds start to grow and when the root formation is very active. Later is also possible, but then we need to climatise the cuttings as they are very sensitive to dehydration. When a cutting has wilted, there is even no more root formation. Swell in water. Perovska, Hypericum.

Halfwoody cuttings[edit]

more woody cuttings berries. Ceanothus, Chrysanthemum, Delphinium, Forsythia, Geranoum, Philadelphus. Time: end of spring when growth begins to weaken.

Almost matured cuttings[edit]

Deutzia, Cornus species with colored bark At the end of the growing season, stronger, thicker cuttings much growing strength but increased risk of dehydration

Woody cuttings[edit]

With plants with strong growing strength: Salix, Cotoneaster, poplar, wild roses, ornamental plums, Spiraea, Viburnum, ... Made from strong shoots. Time: in autumn after the leaves have fallen off, at the formation of the cork layer between leaf and stem. Length: 25-35 cm. Top: Oblique. Bottom: straight

Cuttings of semi-shrubs[edit]

Some low growing plants, often herbaceous, are called semi-shrubs: Artemisia, Hypericum calycinum, lavender, rosemary, rue, sage, santolina Cutting back in winter to obtain strong shoots. End of summer, preferably cut-off non-flowering shoots, otherwise cut-off the flower

Notes[edit]

Vegetative propagation Roots: by adventitious buds on the roots Root propagation: somewhat larger pieces of the root are cut into pieces, they are planted and left for some time (wound can then dry) and planted (this technique is mostly done with tuberous roots)

Air layering: soil is put unto one-year old twigs (not with woody stems)

Bulbs: left to lie for a while until the bulbs become well visible

Stem cuttings: only with very young twigs

Period:

  • herbal cuttings (woody plants) : (for temperate climate countries) spring and early summer (May-June), remark: not strong, fragile, do root rapidly
  • woody cuttings: late summer, fall (for non-deciduous plants) or winter (for deciduous plants)

types of cuttings: leaf bud cutting (eg with vitis vinfera, ...) or stem cutting (oblique cut above the bud for the top, straight at the bottom)

head stem cutting is not equal to a stem cutting

cutting with a heel: the heel contains more auxines, causing it to root quicker

fungicide: will slow down the rooting at temperatures above 15-20°C

a too wet space to do the cutting in is also disadvantageous, plant pots also need to be placed off the ground to allow moisture to ooze out

note: stem cuttings can be cut through slightly (up to the cambium) at the bottom on both ends to root more quickly

head stem cutting: top of the head needs to be cut off (decays quickly)

woody cuttings: old wood needs to be cut in winter and can be planted with the head slightly above the soil (e.g., raspberry).

Source[edit]

This article is made using information from the coursebook: Cultivation techniques </br> Part 3: PLANT PROPAGATION</br> Course from: 1st year of Herbalism</br> Course year: 2005 - 2006</br> Education center: Syntra, Asse-establisment</br> Teacher: Leo Van Crombrugge