eight material used for rooting. It holds water well and promotes fine root growth.
Perlite is another excellent propagation material. It is lightweight and provides good aeration for rooting. Perlite makes one of the best rooting materials when mixed with an equal volume of peat moss.
Don't use field soil as a rooting medium. It packs too tightly under wet conditions and is prone to develop diseases.
Compressed peat pellets are available for seeding and can also be used for rooting cuttings. They expand rapidly when soaked in water. Place them in plastic bags after soaking and draining; insert a single cutting in each pellet and close the bag at the top. No additional watering is necessary until the cutting is rooted and the bag opened.
Pots, medium and equipment used for rooting cuttings must be clean and sterile. Pots should be washed thoroughly using a household cleaner and disinfectant. Tools also should be washed in the same solution or dipped in alcohol. Any rooting medium which is not known to be sterile can be moistened and heated thoroughly in an oven at 150 to 200 degrees for 20 to 30 minutes. Normally, peat moss, vermiculite and perlite don't need sterilization when new.
Getting the cutting
The four main types of stem cuttings are herbaceous, softwood, semi-hardwood, and hardwood. These terms reflect the growth stage of the stock plant, which is one of the most important factors influencing whether or not cuttings will root. Calendar dates are useful only as guidelines. Refer to Table 1 for more information on the best time to root stem cuttings of particular ornamental plants.
Cuttings should generally consist of the current or past season’s growth. Avoid material with flower buds if possible. Remove any flowers and flower buds when preparing cuttings so the cutting’s energy can be used in producing new roots rather than flowers. Take cuttings from healthy, disease-free plants, preferably from the upper part of the plant.
The fertility status of the stock (parent) plant can influence rooting. Avoid taking cuttings from plants that show symptoms of mineral nutrient deficiency. Conversely, plants that have been fertilized heavily, particularly with nitrogen, may not root well. The stock plant should not be under moisture stress. In general, cuttings taken from young plants root in higher percentages than cuttings taken from older, more mature plants. Cuttings from lateral shoots often root better than cuttings from terminal shoots.
Early morning is the best time to take cuttings, because the plant is fully turgid. It is important to keep the cuttings cool and moist until they are stuck. An ice chest or dark plastic bag with wet paper towels may be used to store cuttings. If there will be a delay in sticking cuttings, store them in a plastic bag in a refrigerator.
While terminal parts of the stem are best, a long shoot can be divided into several cuttings. Cuttings are generally 4 to 6 inches long. Use a sharp, thin-bladed pocket knife or sharp pruning shears. If necessary, dip the cutting tool in rubbing alcohol or a mixture of 1 part bleach to 9 parts water to prevent transmitting diseases from infected plant parts to healthy ones.
Remove the leaves from the lower one-third to one-half of the cutting (Figure 4). On large-leafed plants, the remaining leaves may be cut in half to reduce water loss and conserve space. Species difficult to root should be wounded.
Treating cuttings with root-promoting compounds can be a valuable tool in stimulating rooting of some plants that might otherwise be difficult to root. Prevent possible contamination of the entire supply of rooting hormone by putting some in a separate container before treating cuttings. Any material that remains after treatment should be discarded and not returned to the original container. Be sure to tap the cuttings to remove excess hormone when using a powder formulation.
The rooting medium should be sterile, low in fertility, and well-drained to provide sufficient aeration. It should also retain enough moisture so that watering does not have to be done too frequently. Materials commonly used are coarse sand, a mixture of one part peat and one part perlite (by volume), or one part peat and one part sand (by volume). Vermiculite by itself is not recommended, because it compacts and tends to hold too much moisture. Media should be watered while being used.
Insert the cuttings one-third to one-half their length into the medium. Maintain the vertical orientation of the stem (do not insert the cuttings upside down). Make sure the buds are pointed up. Space cuttings just far enough apart to allow all leaves to receive sunlight. Water again after inserting the cuttings if the containers or frames are 3 or more inches in depth. Cover the cuttings with plastic and place in indirect light. Avoid direct sun. Keep the medium moist until the cuttings have rooted. Rooting will be improved if the cuttings are misted on a regular basis.
Rooting time varies with the type of cutting, the species being rooted, and environmental conditions. Conifers require more time than broadleaf plants. Late fall or early winter is a good time to root conifers. Once rooted, they may be left in the rooting structure until spring.
Newly rooted cuttings should not be transplanted directly into the landscape. Instead, transplant them into containers or into a bed. Growing them to a larger size before transplanting to a permanent location will increase the chances for survival.
Inserting the cutting
Promptly place the prepared cutting in the rooting material; stick the base of the cutting 1 or 2 inches deep, depending on the length of the cutting. Firm the material around the base and settle the medium by watering.
Care of cuttings
Never allow the propagation medium to dry out during the rooting process.
Since the cuttings have no root system, a high humidity must be maintained around them at all times. Clear plastic is inexpensive and easy to use for covering the cuttings. A plastic bag slipped over a pot is simple and airtight. Support the plastic with wire loops or stakes if need be to keep it from resting on the leaves.
Never place a plastic-covered container in direct sunlight. Too much heat will build up under the plastic and burn the foliage.
Care of rooted cuttings
The length of time needed for cuttings to form roots differs greatly among plants. Check the cuttings occasionally by carefully removing a few from the medium. When a cutting has roots at least an inch long, transplant it into a separate container.
The move from high humidity and moist rooting conditions to lower humidity and drier soil is the most critical step in successfully growing new plants from cuttings. Give these young plants close attention the first few weeks after the move.
A good potting medium designed for houseplants can be found at local garden centers or mass merchandisers and will be suitable for potting newly rooted cuttings.
After a cutting has become established in the medium, apply a soluble houseplant fertilizer according to directions. Then fertilize at monthly intervals. When the cutting is growing vigorously, normally in spring and summer, fertilizer may be applied every two weeks.
Layering is a method of rooting a new plant while the stem is still attached to the parent plant. It is simple to perform and can be done in the home without special equipment or structures. Methods of layering include simple, tip, air and compound.
Air layering is the most suitable method for use on houseplants. It is convenient to do in the home and can be used with plants that would be difficult to root by any other method.
Mature wood, about one year old, is generally best for air layering. Old branches or immature wood often root poorly or not at all.
The air layer may be made at any point on a stem of proper maturity. On many plants a convenient location is 12 inches from the tip.
- Remove all leaves several inches on either side of the point where the layer is to be made.
- From the center of the layering area, make a slanting cut upward an inch or more in length and about halfway through the branch. A preferred method of wounding is removing a strip of bark 1/2 to 1 inch wide around the branch (see Figure 7).
- Apply a rooting hormone to the wounded surface or cut.
- If a cut has been made, don't let it heal back together. Insert a small piece of wood such as a toothpick in the cut to keep the wound open.
- Take a handful of unmilled sphagnum moss that has been soaked in water and squeeze out excess water. Pack the moist sphagnum around the branch to cover the wound.
- Cover the ball of moist moss with plastic wrap. An 8- by 10-inch sheet is generally large enough. Wrap it around the moss so that it overlaps and will not allow the moss to dry out. Clear plastic permits you to see when roots have developed.
- Secure the plastic at each end with electrical tape, string, plant ties or other convenient fasteners. It will usually take a month or more before roots appear.
Compound layering is suitable for long vines that may be alternately covered and exposed. Wounds should be made on the lower portion of each curve.
After rooting, the branch can be cut into segments, each containing its own roots.
Care after rooting
Root systems of newly rooted layers are small in relation to the canopy. After they are severed from the parent plant and potted, the humidity must be kept high. Enclose them in a loose, clear plastic bag for the first week or until they are well established and do not wilt excessively.
Copyright 2000 University of Missouri. Published by
University Extension, University of Missouri-Columbia. UExtension