Home Propagation of Plants: Division And Layering

CROWN DIVISION
One simple and reliable method for propagating plants at home is crown division. As a general rule, plants that flower in the spring and early summer should be divided in late summer or fall. Those flowering in the summer and fall should be divided in early spring before new growth begins.

For crown division of herbaceous plants, such as irises, the clumps should be carefully lifted and some soil removed from the roots. The crown may then be cut into sections with a knife or other sharp tool. Individual shoots that contain roots may be used to form new plants, or if a larger plant is desired, several shoots may be left together. In large, old crowns, it is often best to discard the older, center portions and replant the young, more vigorous shoots that have developed on the edges of the clump.

Table 1: Some common perennials suitable for division

Plant Division Time Plant Division Time Plant Division Time
Aster (hardy) Spring Hosta (plantain lily) Spring or fall Phlox Spring
Baptisia (false indigo) Spring or fall Iris (bulbous (Dutch) Late summer, fall Primula Summer
Bleeding heart Late summer, early spring Iris, rhizomatous (German) July, August Red-hot poker (Kniphofia) Spring
Chrysanthemum Spring Iris, fibrous (Japanese) July, August Rudbeckia Spring or fall
Columbine March Lily Fall Sedum (stonecrop) Spring, July, August
Coneflower (Echinacea) Spring or fall Lily of the valley Fall Sempervivum (houseleek) Spring, summer
Coreopsis Spring Loosestrife (Lythrum) Spring Shasta daisy Spring
Daylily Late summer, spring Oriental poppy July, August Vinca (myrtle) Early spring
Delphinium Early spring Pampas grass Spring Yarrow (Achillea) Early spring
Ferns Early spring Peony Early fall Yucca Spring or fall

LAYERING
Layering is a useful and desirable method to root a new plant while the stem is still attached to the parent plant. The new plant receives nutrients and water from the parent plant until roots develop. This method of asexual propagation yields a large plant in a relatively short time and is an excellent way to produce a small number of plants in the home landscape. Layering outdoors is best performed during spring and summer months, although it can be done during any season of the year.

Healthy, maturing branches that are vigorously growing in light should be chosen for layering since they usually have more food reserves (carbohydrates) and therefore root faster. Branches from pencil size to about ¾ inch in diameter are best for layering.

Layering can be done without any special equipment or structures. Some layering techniques include simple, tip, serpentine, and air. Simple layering involves pegging down a suitable shoot into the soil. Serpentine and tip layering are similar to simple layering with flexible shoots buried in the ground. Air layering is used for plants that will not bend down to the ground. I will not go into dropping or stooling. Dropping is used for dwarf shrubs such as rhododendrons and some dwarf conifers where the whole plant is buried with only the tips of shoots exposed above ground. Stooling is a specialized technique used for some ornamental shrubs like Cornus spp. (dogwood) and Salix spp. (willow) where the soil is mounded above an existing plant to create new shoots on the buried stems.

Simple Layering
For the home gardener, simple layering may be performed whenever a plant has a branch low enough to be pulled down to the ground. It is a slow method and can take more than a year before you can separate the new plant from its parent. Simple layering is usually done in the spring when the sap is rising although it can be done from late autumn to early spring.

Many plants root when a leaf node of the shoot is buried several inches deep in the soil and the tip protrudes vertically from the soil. It is generally beneficial to wound or cut the stem at the point where it curves upward. The wounding tells the plant to send healing hormones to the cut surface. Make a slanted cut about 2 inches long either above or below the bend. Make the cut about 12 inches from the tip and dust it with a rooting hormone. Place the prepared branch or stem (A) into a hole or trench 4-6 inches deep and fasten it down to the ground with a wire peg (B). Bent U-shaped coat hangers work well. If the branch is stiff, insert a stake next to the shoot to hold the tip in an upright position (C). Fill the hole or trench and mound the soil slightly so the wounded portion of the stem will be 4-6 inches below the soil. Firm the soil.

Keep the soil around the layer moist at all times and cover with a 3”-4” layer of mulch. The layer may form roots during the first season but should not be cut form the parent plant until the following year. Some hard to root types may take two years to produce roots.

After the layer is well rooted, sever the branch where it enters the soil. Don’t disturb the roots of the layered plant for 2-6 months after it has been severed. This will allow the new plant time to grow independently. When the new plant is dormant, it can then be transplanted to a convenient protected spot or container where it can be tended carefully for one year before moving it to a permanent location.

Serpentine Layering
Serpentine layering is suitable for long vines and requires that the shoot be alternately covered and exposed. The technique is simple layering in
multiples. Wounds should be made on the lower portion of each curve between leaf nodes. Bend the shoot down so that each wounded area is in

the bottom of a hole and the shoot between is still above ground. Peg them in place as done with simple layering. Do not layer the tip of the shoot or this will root and the other layered sections behind it will rot. This method is suitable for vines such as honeysuckle, clematis, or wisteria. The branch is cut into segments after rooting has taken place.

Tip Layering
Tip layering on raspberries and blackberries is easy to do in the spring. It consists of rooting tips of the current season’s growth. The tip of the shoot is where the strongest concentration of rooting hormones is. Rooting can be stimulated in late summer as the drooping canes develop an elongated appearance and leaves become smaller. Pull the tip of these shoots down and insert them in holes 4-6 inches deep. Peg the tip down with U-shaped pieces of wire and fill the hole with free-draining soil. Rooting generally takes place rapidly and the plants may be transplanted later the same season. Survival is better if transplanting is delayed until just before growth starts in the following spring.

To stimulate more tips, pinch out the top 3-4 inches of a 2-foot tall cane in the spring. By late August or early September, the new growth will arch
down, touch the soil and turn upward. These often root without assistance at the point of the curve where they touch the soil.

Care after rooting layered plants: The root system of newly rooted layers is small in relation to the tops. As soon as the layer forms new roots, cut it from the parent plant and transplant it to a container. Prune the stems so that the leaf area is reduced to at least one-third. The new plants should be located in a lightly shaded area. Suitable shading may be made from an old window screen. After the first winter, the screen can be removed. Sufficient roots should have developed so that the plants can be moved to a permanent location.

Air Layering
Air layering is a useful method for rooting difficult to root plants, which include magnolia, witch hazel, gardenia, rose, fig, holly, camellia, azalea, and many of the fruit and nut bearing plants such as apple, pear, and pecan. The procedure is to wound the stem or branch of the plant and enclose the wounded stem with moist sphagnum moss until roots develop from the wounded area. For optimum rooting, make the air layers in the spring on shoots produced from the previous season’s growth or in midsummer on mature shoots from the current season’s growth. On woody plants, stems that are pencil size or up to ¾ inch diameter are best. The stem may be much thicker on the more herbaceous plants.

First remove leaves and twigs on the selected limb for 3-4 inches above and below the point where the air layer is to be made. The air layer is usually made 12-15 inches below the tip of the branch. The branch is wounded to induce rooting. The method of wounding woody plants such as magnolia, rose, and similar plants is to make two parallel cuts with a shape knife about 1-1/2 inches apart around the stem and through the bark and cambium layer. If the cambium layer is not removed, new bark will form instead of roots. Connect the two parallel cuts with one long cut and remove the ring of bark, leaving the inner woody tissue exposed. You may want to cover the cut nearest the tip with rooting hormone although this is seldom necessary.

Apply a handful of damp sphagnum moss so that it envelops the wounded portion of the stem. It may be necessary to wrap kitchen string around the moss to hold it in place. The sphagnum moss should be soaked several hours before using to ensure that it is thoroughly moist. Squeeze out the excess moisture, as it will result in decay of the plant tissue.

Use a sheet of polyethylene film (plastic wrap works well) about 6 inches by 12 inches to wrap around the ball of sphagnum moss. Be sure there is a good seal all around. Make sure the upper end of the film fits snugly around the stem and none of the moss is exposed. Fasten securely with twist ties but not so tight as to bite into the stem. This will allow you to open the plastic wrap to check for rooting without disturbing the new roots. You may use electrician tape instead of twist ties but take care that the tape extends beyond the film and adheres to the stem. Repeat the procedure on the lower end, making sure there is a snug fit. Moisture should not be allowed to escape from or leak into the wounded area. If necessary, support the plant with a stake or splint to prevent breakage at the wounded area. Wrap with aluminum foil large enough to completely cover the plastic wrap and extend up and down the branch a couple of inches in either direction. This will prevent heat buildup under the plastic. Crimp the foil for a good seal.

The rooting time will vary with each plant variety as well as the season in which it is performed. In 6 weeks to a year or so, you should have a new plant. If no roots are visible in the moss ball, carefully remove the plastic and moss to check the cut area. If the wound is still moist and has a swollen callus tissue at the top, then the roots should appear soon. Replace the packing with new moist moss, plastic, and aluminum foil. If the stem has healed over the wound, start again with a different shoot.

After the new roots have penetrated the moss ball and are visible on all sides, the rooted branch may be removed from the parent plant. Remove the newly rooted plant from the parent plant with a sharp knife or pruning shears, making the cut just below the ball of moss and roots. Carefully remove the aluminum foil and plastic wrap. Plant the root ball of moss in a container using a good potting mixture. Be very careful when you firm the dirt around the new plant since the new roots are easily broken off. The potted plant may be placed in a cold frame in a lightly shaded area to allow for the establishment of roots and to harden off the new plant. Keep it in a sheltered area for at least 4-6 weeks before you move them into stronger light. The plants will let you know when they are ready for more light by sending out new growth.

If you don’t have a cold frame, you can accomplish the hardening off process by placing a polyethylene tent over the newly potted plant for about 2 weeks to prevent moisture loss. Keep the plant in light shade and avoid direct sunlight until the new root system is well developed. Harden off the plant gradually by cutting a few holes in the plastic tent to reduce the humidity until it reaches the surrounding environmental conditions.

The University of Florida’s Landscape Plant Propagation Information (LPPI) website, http://hort.ifas.ufl.edu/lppi/htm, contains a lot of information on propagating many different plants.

Table 2. Some Common Plants Suitable for Layering

PLANT LAYERING TIME LAYERING METHOD ROOTING TIME
Akebia spp. Early spring to early autumn Serpentine 12-18 months
Azalea spp. Early to late winter Simple 9-12 months
Azalea spp. Early to mid-spring Air 12-18 months
Buxus spp. Early to mid-spring Dropping 6-9 months
Camellia spp. Later winter to early spring Simple 6-12 months
Campsis radicans Mid-to late autumn Simple, Serpentine 9-12 months
Clematis spp. Mid-to late autumn Simple, Serpentine 9-12 months
Daphne spp. Early to midsummer Simple 6-9 months
Euonymus spp. Early to mid-spring Simple 6-12 months
Ficus elastica (rubber plant) Mid-spring to late summer Air 6-9 months
Forsythia spp. Spring to late spring Simple 6-9 months
Fothergilla spp. Late summer to early autumn Simple 12-18 months
Hamamelis spp. (witch hazel) Early to mid-spring Air 12-18 months
Ilex spp. Late summer to autumn Air 12-18 months
Ilex spp. Early to mid-spring Simple 9-12 months
Jasminum spp. Early to mid-spring Simple 6-9 months
Magnolia spp. Early to mid-spring Simple 12-18 months
Magnolia spp. Mid-spring to late summer Air 18-24 months
Rhododendron spp. Early to mid-spring Simple 12-18 months
Rubus spp. (blackberry, etc.) Early spring to midsummer Tip 3-6 months
Viburnum spp. Early to mid-spring Simple 9-12 months
Vitis spp. Early to late winter Simple, Serpentine 9-12 months
Wisteria spp. Early to mid-spring Simple, Serpentine 12-18 months

Home Plant Propagation From Cuttings

There are many reasons to propagate plants but the basic reason is simply to make multiple plants from a single plant that is unique, attractive, or has become old and leggy. Of course, propagation can be for sentimental reasons because it grew in grandmother’s garden.

It is not possible to cover all the propagation techniques in one article but there are many reference books on the topic, some of which are given at the end of the article.

PLANT PROPAGATION METHODS
Sexual Propagation: This is the method of reproduction that yields new plants from viable seeds produced by plants. The advantage of asexual propagation is that seeds can be stored for a long period of time. Propagation from seed results in genetic variability and is useful if the intent is an improved or different plant characteristic.

Asexual Propagation: Asexual propagation results in plants that have the same characteristic as the parent plant with regard to size, form, color, and growth habit. Methods include stem cuttings, leaf cuttings, division, layering, root cuttings, and leaf bud cuttings. Commercial nursery trade methods included grafting, budding, and tissue culture.

PROPAGATING NEW PLANTS
To be successful in plant propagation, it is important to consider the rooting and growing media, rooting hormone, temperature, light, moisture, and fertilization. The most common and easiest methods of plant propagation are stem cuttings, simple division, and layering. Due to space
limitations, only propagation by stem cuttings will be covered.

Cuttings: The types of stem cuttings generally used for propagating woody plants are softwood, semihardwood, and hardwood.

Softwood cuttings are taken from new growth of the current season. They are used for propagating deciduous shrubs. The best months to take softwood cuttings of shrubs are June and July although some may be taken in August. I’ve had 100% success rate rooting acuba cuttings taken in June.

Semi-hardwood cuttings are taken in late summer but are made from the current season’s growth that has partially matured and is becoming woody. Examples are broad-leaved evergreens such as holly, euonymus, and azalea. My records indicate a survival rate for Dwarf Burford hollies of about 70% using cuttings taken in August.

Hardwood cuttings may be taken from deciduous plants and narrow-leaved evergreens. Cuttings are usually taken in late fall or early winter after the plants have gone dormant. Examples of suitable deciduous plants are althea, barberry, and spirea. Cuttings from narrow-leaved evergreen plants should be taken from the terminal growth of the previous season’s growth and contain a small portion of year-old growth. Examples are junipers and yews. My survival rate for Sargent juniper cuttings taken in August is about 60%.

PROPAGATION BY CUTTINGS
Taking the Cutting: With a sterilized sharp knife, make a slanting cut from a terminal section of an un-branched stem 8 to 10 inches long. Then trim the base to just below a node leaving a cutting of about 4 to 6 inches. Avoid taking cuttings from weak, spindly growth. Remove the lower ½ to 2/3rds of the leaves and any flower buds. Sometimes I strip away about ½ inch of the bark and cambian layer to assist in rooting. Softwood
and semi-hardwood cuttings should be taken during the cool portion of the day. As you collect the cuttings, place them in a plastic bag to avoid wilting.

Rooting Media: The rooting medium must be clean and sterile. Make sure the pots or containers, tools, and workbench are also sterilized. For sterilizing my equipment and pots, I use a solution of 10% chlorine and 90% water. The rooting medium should not contain any fertilizer. Begin fertilization only after the cuttings are rooted and have been transplanted to the growing medium.

Clean, coarse, construction sand by its self may be used as a rooting medium. Avoid fine sand since it has poor aeration that retards root formation. I have found that a generic mixture of one-part coarse sand to one-part peat moss, by volume, works well. Different media formulations, however, may be needed for specific plants (see references).

Horticultural grade (No. 2) vermiculite is suitable for rooting cuttings. Perlite gives good results when mixed with an equal volume of peat moss or vermiculite.

Garden soil should not be used for a rooting medium, even if it is sterilized, since it tends to compact and have poor aeration qualities.

Inserting the Cutting: As little time as possible should lapse from the time the cuttings are taken until they are inserted into the rooting medium. I usually dip the base of the cutting in a rooting hormone such as Rootone. Use a dibble or sharpened dowel to make a hole in the moist rooting medium and stick the cutting into the rooting medium up to the remaining leaves. Water thoroughly to settle the medium around the base of the cutting.

Care of the Cuttings: The cuttings must never be allowed to dry out but avoid excessive watering that results in poor aeration and death of new roots. Since cuttings don’t have a root system, high humidity must be maintained. Low humidity will result in wilting, scorch, leaf drop, and death. Enclosures help maintain high humidity.

If only a few cuttings are to be rooted, a miniature greenhouse can be created using a plastic pot with good drainage that is covered with a large plastic bag that is supported by wire cut from coat hangers. Monitor the plastic bag for condensate and water the medium when the condensate on the bag disappears. Never place plastic-enclosed containers in direct sunlight or excessive heat will build up. For rooting large numbers of
cuttings, use a coldframe, hotbed, or greenhouse.

My personal preference is a not-so-fancy coldframe made from scrap lumber and an old window sash. The back of the coldframe should be about 6 inches higher than the front of the frame. I stick individual cuttings in 3” pots containing a rooting medium of equal parts coarse sand and peat moss. The bottom of the coldframe contains a mixture of manure mixed with grass clippings or leaves to provide bottom heat to the pots. I mist and/or water the cuttings on a daily basis (sometimes more often) to keep high humidity in the coldframe. The coldframe is located in an area that is in indirect light for most of the day. If it gets any direct sunlight, I cover the coldframe sash with an old screen or wooden lathes.

Very Important – Care of Rooted Cuttings: This is the point where many failures occur and is seldom addressed in most books. Root formation time varies greatly depending on the plants. Most woody cuttings root in about 8 to 10 weeks (forsythia) but rhododendron can take 3 to 4 months. Check cuttings after about 6 weeks by carefully removing a couple from the rooting medium. After the cuttings have roots that are about 1-inch long, they can be transplanted into the growing medium. Remember that the move from a high humidity, moist environment to a low humidity, dryer soil is a critical transition period. Give these plants close attention for the first few weeks after the transplant. During this period keep them well watered and reduce heat stress by placing them in a shaded area.

If only a few cuttings are rooted, pot them in individual containers containing the growing medium. For most plants, a growing medium of equal parts good topsoil, coarse sand, and peat moss works well. Azaleas and rhododendrons require an acidic soil mix that can be purchased. Add about 1 cup of 10-10- 10 fertilizer and 1 cup of ground limestone to each bushel of growing mixture. Mix thoroughly before filling the containers. For the time-strapped propagator, purchased potting soil used for houseplants may be substituted.

If you have a large number of cuttings, develop a nursery bed using thoroughly pulverized soil and work in 3 to 4 inches of compost, peat moss, or other organic material. Add fertilizer and lime as directed by a soil test. Install some shade over the cuttings during the first growing season. Using laths, burlap, or old screens can provide shade.

During the first winter, provide protection to the transplanted cuttings by mulching with wheat straw or use a coldframe. If using a coldframe, remember to open the cover on hot days. After two growing seasons in the nursery bed, the new plants can be moved to their permanent location.

Please remember that these steps are generic in nature. The type of plant, the length of time needed to root, the composition of the rooting and growing medium, and the proper time of year to take cuttings is very plant specific. Please use one or more of the reference books list or talk to people who have had experience with propagating certain types of plants for more specific guidance.

PLANT SPECIFIC PROPAGATION TECHNIQUES

Plant
Cutting
Layering
Softwood
Semihardwood
Hardwood
Simple
Air
Compound
Abelia
X
X
X
Althea
X
X
Azalea
X
X
X
Barberry
X
X
X
Boxwood
X
Butterfly Bush
X
X
X
Clematis
X
X
X
Cotoneaster
X
X
X
Crape Myrtle
X
Euonymus
X
X
X
X
X
Forsythia
X
X
X
Hawthorn
X
X
Holly
X
X
X
Honeysuckle
X
X
X
Hydrangea
X
Juniper
X
X
Kerria
X
X
X
X
Magnolia
X
X
X
X
Mahonia
X
Pyracantha
X
X
Rhododendron
X
X
X
Rose
X
X
X
Spirea
X
X
Sweetshrub
X
X
X
X
Viburnum
X
X
X
Weigela
X
X
Wisteria
X
X
X
Yew
X

REFERENCES

  1. Toogood, A. 1999. American Horticultural Society Plant Propagation. DK Publishing, Inc.
  2. Cullina, W. Native Trees & Shrubs, Vines. 2002. Frances Tenenbaum Book.
  3. Cullina, W. Wildflowers. 2000. Frances Tenenbaum Book.
  4. Macdonald, B. Practical Woody Plant Propagation for Nursery Growers. 1986. Timber Press.
  5. Hartmann, H.T. and D. E. Kester. 1983. Plant Propagation Principles and Practices. Fourth Edition. Prentice-Hall, Inc.
  6. Dirr, M. and Charles Heuser. The Reference Manual of Woody Plant Propagation. 1987. Varsity Press, Inc.
  7. Dirr, M. Manual of Woody Landscape Plants. Fifth Edition. 1998. Stipes Publishing L.L.C.
  8. Free, M. Plant Propagation in Pictures. 1957. Doubleday & Company, Inc.