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Propagation

Propagating Plants from Seeds

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A plant started from seed receives its genetics in a manner similar to the way humans receive genetics. Just as we are made up of a combination of our father and mother, a plant started from seed is made from the genetics of its father and mother. As with humans, some traits can skip generations and there is no guarantee that a plant started from seed will inherit specific traits from its mother or father. This is the main reason the majority of commercial plant propagation is done by clone or tissue culture. Starting from seed is unpredictable but it is also a chance to start a completely unique plant that will add more biodiversity to our wonderful planet.

Temperature and Humidity for Starting Seeds

Germination is the process in which the plant emerges from the seed to start its life. For most plants germination is best done in a very moist (high humidity) environment at a reasonably warm temperature, usually around 75-85 degrees F (the exception to this would be seeds that are generally planted in early spring when the ground temperature is much cooler). Propagation trays with humidity domes are great for starting seeds because they create a microclimate that is more easily controlled. Seeds can be placed directly into a moist medium in the tray and covered with the humidity dome. If the environment is not at least 75 degrees F consistently, it is advised to place a seedling heat mat under the tray to keep a constant temperature. Plants, in general, respond better to consistency and this is especially true with seeds or clones. Keep the top portion of the medium moist until all of the seeds have sprouted. Once the seedlings have broken the surface, lift the dome off periodically to bring in fresh air and also acclimate the seedlings to the lower humidity of the environment. Slowly increase the amount of time each day the dome is removed until it is removed entirely. Most varieties of plants can be acclimated in a matter of a few days. Follow the seed packet’s instructions for thinning, spacing, and transplanting.

Another popular germination method is the wet paper towel technique. Place your seeds in a damp paper towel and fold the paper towel over the seeds. Put the paper towel in a ziplock bag and place it on top of your refrigerator (toward the back; this keeps the seeds at a consistent temperature). Check daily by gently unfolding the paper towel to examine the seeds. Keep the paper towel moist; adding water if necessary. In a few days you should see the first root coming out of the seed (radicle root). Gently, using a tweezers if necessary, place the seed into the soil with the radicle root facing downward. Cover the seed and keep the top layer of soil moist until the plant breaks the soil’s surface. The paper towel technique is a fun way to teach children how plants start from seeds. This technique works best with larger seeds (melons, cucumbers, squash, corn, sunflower, etc.). Most smaller seeds, such as lettuce, are best planted directly into the soil.

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Propagation

Tips for Cloning Success

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Most of these tips will work for traditional cuttings as well as hydroponic cloning.

Select the plant you plan to clone. Select only plants that are in good health and are at least two months old.  New growth is best if it’s available, however, any healthy stem with at least two or three healthy sets of leaves will work. Only take cuttings from well hydrated plants.  Plants that are dry will not perform as well as cuttings.

Hygiene cannot be stressed enough.  Disease, fungus and viruses spread quickly and are a primary cause of failure.  Luckily, a few easy steps will ensure healthy cuttings.  It may be tempting to skip the cleaning steps, but you will be rewarded with quick healthy cuttings by spending a few extra seconds.

  • Gather your tools: A sharp craft knife or razor blade, cutting shears, container with water, rooting hormone, clean cutting mat, cloning system.
  • Prepare the water bath in the cloner.  Measure nutrients carefully.
  • Select a 2”-3” stem of plant, ideally with new growth.  (Note: fall is the ideal time to find new growth, but cuttings will work in spring) cut below the intersection of leaves on the stem.  Immediately place cutting into water until you are ready to process all cuttings.
  • Remove lower leaves by carefully slicing them at the stem.  Leave several leaves at the top of the stem. If leaves are too large for the cloning space, cut then lengthwise.
  • Place cutting on a clean cutting mat. Sterilize blade with alcohol and carefully cut the stem diagonally at a 45° angle to expose as much of the plant’s cambium as possible. Be careful not to crush any tissues. Dip knife in alcohol between each cutting.
  • Place a small amount of rooting hormone in a small Dixie cup or small glass and dip cutting into hormone.  Do not dip the cutting directly into main container to avoid contamination.  Throw the excess compound away; do not add back to the original container. Note: Commercial growers typically use liquid rooting hormone because the plant absorbs the liquid faster than the powder.
  • Secure the cutting in the basket and place in cloner.

Check your cuttings frequently.  In a few days you will start to see nodes forming just prior to root development.  Change the water once a week or per the manufacturer’s instructions.  Once roots are formed, transplant into 4” pots.  Placing them in a cool greenhouse with bottom heat will encourage healthy root growth while keeping top growth compact and healthy.

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Propagation

A Consistent Environment is a Key Factor in Successful Plant Propagation

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Although germination and rooting techniques vary depending on the specific plant species, there are some general guidelines that can be followed for propagating the majority of greenhouse ornamentals and vegetable plants.

From Seed (Sexual Propagation)

A plant started from seed receives its genetics in a manner similar to the way humans receive genetics. Just as we are made up of a combination of our father and mother, a plant started from seed is made from the genetics of its father and mother. As with humans, some traits can skip generations and there is no guarantee that a plant started from seed will inherit specific traits from its mother or father. This is the main reason the majority of commercial plant propagation is done by clone or tissue culture. Starting from seed is unpredictable but it is also a chance to start a completely unique plant that will add more biodiversity to our wonderful planet.

Temperature and Humidity for Starting Seeds

Germination is the process in which the plant emerges from the seed to start its life. For most plants germination is best done in a very moist (high humidity) environment at a reasonably warm temperature, usually around 75-85 degrees F (the exception to this would be seeds that are generally planted in early spring when the ground temperature is much cooler). Propagation trays with humidity domes are great for starting seeds because they create a microclimate that is more easily controlled. Seeds can be placed directly into a moist medium in the tray and covered with the humidity dome. If the environment is not at least 75 degrees F consistently, it is advised to place a seedling heat mat under the tray to keep a constant temperature. Plants, in general, respond better to consistency and this is especially true with seeds or clones. Keep the top portion of the medium moist until all of the seeds have sprouted. Once the seedlings have broken the surface, lift the dome off periodically to bring in fresh air and also acclimate the seedlings to the lower humidity of the environment. Slowly increase the amount of time each day the dome is removed until it is removed entirely. Most varieties of plants can be acclimated in a matter of a few days. Follow the seed packet’s instructions for thinning, spacing, and transplanting.

Another popular germination method is the wet paper towel technique. Place your seeds in a damp paper towel and fold the paper towel over the seeds. Put the paper towel in a ziplock bag and place it on top of your refrigerator (toward the back; this keeps the seeds at a consistent temperature). Check daily by gently unfolding the paper towel to examine the seeds. Keep the paper towel moist; adding water if necessary. In a few days you should see the first root coming out of the seed (radicle root). Gently, using a tweezers if necessary, place the seed into the soil with the radicle root facing downward. Cover the seed and keep the top layer of soil moist until the plant breaks the soil’s surface. The paper towel technique is a fun way to teach children how plants start from seeds. This technique works best with larger seeds (melons, cucumbers, squash, corn, sunflower, etc.). Most smaller seeds, such as lettuce, are best planted directly into the soil.

From Clone (Asexual Propagation)

Starting a plant from a donor or mother plant is a form of cloning or asexual propagation. Some plants naturally propagate themselves this way; a good example is the inch plant (wandering jew). Cloning has become the most popular method among commercial growers because the offspring are identical to the donor plant so the growers know exactly what they are going to get. It also allows the gardener to replicate plants with desirable qualities such as a certain fragrance, color, resistance to pathogens, or any other trait that could be deemed as beneficial.

There are two popular types of cloning techniques: cuttings and tissue culture. Hobbyist gardeners generally take cuttings to replicate their favorite plants because tissue culture is a more involved process that requires special equipment. African violets, pothos, gardenia, crepe myrtle, cyperus, geranium, wandering jew, coleus, impatiens, spider plants and hibiscus are all easily propagated by cutting. Many vegetables, including peppers, tomatoes, cucumber and squash, can also be propagated by cutting. Some vegetables, like cabbage, can be cloned via their root.  Although there is a slight variance in cloning techniques (depending on plant species) the majority of the focus should be on environmental conditions as they are usually the determining factor in cloning success.

Temperature for Cloning

Like plants started from seed, plants propagated from cuttings respond best to consistent temperatures. Ideally the root zone (or potential root zone) is kept at a temperature of 75-85 degrees F. If the environment where the clones are kept has fluctuating temperatures it is best to utilize a heat mat or heat cables to rectify this problem and maintain consistent temperatures. For most species of plants, if temperatures are too low or continually fluctuate below the desired range, the plants enter what I refer to as a state of suspended animation. In other words, they remain green and healthy looking but fail to create roots or carry out any vital functions needed to stimulate new growth. Eventually these clones will die without ever creating a root.

In cases where humidity levels are high and temperatures are low a cutting or seedling will dampen off. Damping off is a horticultural disease caused by pathogenic microorganisms which destroy a seedling or cutting before it has a chance to grow. On the other end of the spectrum, clones that are kept in temperature ranges above the desired range will commonly wilt or rot and turn into mush long before they develop a new root zone. An inexpensive digital thermometer is a great way to monitor the temperature of the root zone. Make sure to monitor the temperature during the coldest and hottest points of the day to ensure you stay within the desired range even when the atmospheric conditions are the most volatile.

Humidity for Cloning

Humidity levels for cuttings should be kept high for at least the first few days. Although they are not yet established plants, cuttings still transpire moisture through their stomata and without the ability to absorb replacement moisture through a root zone a cutting can quickly wilt in lower humidity environments. Ideally, the humidity level for cuttings should be kept at 80-100% for the first few days. Humidity domes, plastic bags, or any way you can temporarily enclose the cuttings to retain a high humidity environment will suffice. I prefer the humidity domes sold at local gardening centers because they make it very easy to acclimate the plants to their future environment.

After you take your cuttings, lightly spray the inside of the humidity dome with water and place it on the tray. In the subsequent days remove the humidity dome for a few minutes each day to give the cuttings some fresh air; very similarly to the way you would acclimate seedlings. After four days, you can incrementally increase the amount of time you remove the dome each day until the cuttings are completely acclimated to their environment. Although some plant species are more finicky than others, generally speaking, the cuttings will have created their own roots in 7-14 days and at that time should be completely acclimated to the environment.

Sterilize Equipment

Seedlings and cuttings are more sensitive, not only to environmental conditions but also to pests and pathogenic microorganisms, than adult plants. Before planting seeds or taking cuttings completely sterilize all the equipment you plan on using. Diluted bleach or hydrogen peroxide are great ways to effectively sterilize your propagation equipment before each use. Make sure the medium you choose is sterile as well. Prepackaged propagation mediums offer the peace of mind of a sterilized medium and ensure the seedlings or cuttings aren’t being placed in a compromised medium.

There are many products on the market designed to aid the propagation process. Rooting hormones, seedling heat mats, aeroponic clone machines, humidity domes, sterile disposable scalpels and numerous prepackaged mediums are all products that can help achieve successful propagation. Just remember, there is no magic product that will automatically guarantee propagation success. These products teamed with sound environmental conditions are the keys to thriving seedlings and clones. Stable environmental conditions are the foundation for making any aspect of greenhouse gardening flourish and propagation is no different.

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Propagation

A Stable Atmosphere Equals More Success with Plant Clones

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Unstable atmospheric conditions may be the biggest cause of failure in cloning by novice gardeners. Some plant varieties are resilient and will not be adversely affected by large temperature or humidity swings. However, many plant varieties require uniform atmospheric conditions during the initial rooting stage.

A temperature range of 70-80 degrees F for clones is generally accepted. If this is not possible in your greenhouse or indoor garden it may be necessary to create a small sub-climate elsewhere. Uniform temperature is probably the single largest factor for cloning success. If the temperature gets too hot, the clones will wilt and die before creating roots and if the temperature gets too cold, the clones will enter a state of suspended animation and never create the root systems they need to become individual plants.

Seedling heat mats are a great way for horticulturists to maintain the proper temperature during the cloning process. Humidity is also a large contributing factor to successful cloning. Many plant varieties do best with a high humidity (80-99%) during the beginning stages of cloning.

The cutting, once removed from the donor plant, has no root system to bring in moisture. It is, however, able to lose moisture through the surface of its leaves. This makes the cutting rely heavily on the moisture in the surrounding air to maintain health, especially for the first few days. Humidity domes or humidity chambers are great ways for a gardener to maintain a higher level of humidity for the initial stages of cloning. Generally speaking, it is a good idea to acclimate the clone to the ambient humidity after three to seven days. This can be done by taking off the humidity dome each day for a few minutes and then increasing the duration of removal each day.

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Propagation

What to do With a Fresh Cutting

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After selecting, inspecting, and preparing the donor plant, a gardener may begin taking cuttings. Generally speaking, it is best to make a 45 degree angle cut just above a node site (the place where a leaf or branch attaches to the main stem). There are some varieties of plants that create roots very easily. Those plants can be placed directly into a cup of water after being cut from the donor plant. For example, spider plants, wandering jew, and coleus can all be easily rooted in a cup of water. However, some plant varieties need a little extra care to ensure rooting success. For these plants it may be necessary to use a rooting hormone or cloning gel. These products aid in speeding up the cloning process by immediately providing the cutting with the hormones necessary for root production. When using a rooting hormone or cloning gel, the freshly cut end should be dipped into the hormone right after it has been taken from the donor plant. After dipping the cutting, it can be placed into the chosen medium.

Some plants can be rooted directly in water and do not require a special medium for rooting. Many plant varieties clone best when placed in some sort of inert grow medium designed for root development. Stonewool, coco fiber, peat moss, perlite and clay pebbles are all examples of inert media that gardeners commonly use to root clones. Some gardeners even choose to place the freshly cut clones into a light soil mix for rooting. In many ways the medium chosen is personal preference. As long as the medium has the ability to hold some moisture and provide oxygen to the developing roots, it will work just fine. Nutrition is not as important in the medium during the early stages of root development. In fact, soils rich in nutrients (especially high nitrogen soils) can slow or inhibit early root development. Most gardeners use no fertilizers during the cloning process; although I have had more than a few people swear by using a very diluted blooming fertilizer (less nitrogen) until the clone has developed a healthy root system.

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Propagation

Selecting a Donor Plant for Plant Cuttings

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One of the most important aspects of cloning by taking cuttings is selecting an appropriate donor plant. The idea is to select a plant variety that has the traits a grower wishes to replicate. However, it is also very important to select a donor plant that is in good health. If the donor plant has diseases, pest insects, or other pathogens chances are good that any clones taken from that plant will have those same problems. Always inspect a potential donor plant carefully before taking cuttings.

Once a donor plant is selected, it can be prepared for the cloning procedure. One technique that helps to increase cloning success rates is to limit the donor plant’s exposure to intense light for 24 hour prior to taking clones. The plant does not need to be moved into complete darkness. Moving the donor plant to a shaded section of the greenhouse or removing the plant from direct horticultural lighting will help to prepare the plant for cloning purposes. It is also important that the donor plant is not showing any signs of environmental stresses. In other words, it is not wise to take clones from a donor plant that is wilted due to heat or lack of water. If possible, try to make sure the donor plant is at the highest level of health before taking clones.

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Propagation

Ten General Houseplant Propagation Rules

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There are several easy propagation methods you can use for houseplants. There are some basic concepts that apply to all propagation methods, rather you are try plant plant cuttings, plant division, offsets, air layering, or plantlets.

General Propagation Rules

  1. Always use clean sharp utensils that have been sterilized in alcohol.
  2. Whichever propagation method you select, the parent plant must be healthy. Cuttings taken from a sick or dying plant are doomed to fail.
  3. Rooting hormone helps roots develop; but too much is worse than none at all.
  4. Since moist conditions are needed for rooting to be successful, it is important to use a rooting hormone that contains a fungicide to prevent plant diseases.
  5. The rooting medium should be light and fast draining. If you purchase new construction sand, vermiculite, peat moss, or perlite, it can be used directly from the bag. Medium taken from any other source should be sterilized by heating it in the oven at 200 degrees for 30 minutes.
  6. Pots or containers for the new plants must be clean and free of old soil and plant material; if using old pots be sure to wash them well with a household disinfectant. It’s important to use very small containers when you propagate to prevent over watering and help roots development. 2” or 4” pots work well for a single cutting or use a 6” pot for several cuttings.
  7. Roots that form in water are different than roots that form in soil. If possible, use soil rather than water to propagate plants.
  8. Indirect light and temperatures between 70-80 degrees are best for propagation.
  9. Never allow the soil of newly propagated plants to dry out, but on the other hand, the soil should never be soggy. If the planting medium is too dry or too wet, roots don’t develop.
  10. To increase the humidity and keep the soil from drying out place newly propagated plants into a plastic bag and seal the top or cover the plants with a sheet of plastic. You can use small picks or sticks to keep the plastic from resting on the plants.
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Propagation

Tips for Tissue Culture Cloning

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Tissue culture, in horticulture, refers to the replication of a plant from its cells or tissue which are grown in a nutrient culture medium under sterile conditions. Basically, tissue culture is like growing a plant in a petri dish from just the tiniest slice of tissue. Most plant varieties can be successfully duplicated with tissue collected from the root, stem, leaves, seed, flower, or virtually any other part of the plant. Sterile conditions are crucial for the tissue culture technique because living plant materials are naturally contaminated with microorganisms. Tissue culturists must sterilize the starting plant material in a chemical solution, usually consisting of alcohol and sodium hypochlorite. After sterilization, the starting plant material is placed in a sterilized container which contains the nutrient culture medium. The nutrient culture medium consists of a correct balance of plant hormones (auxin and cytokinin) and a nitrogen source. Too much auxin will result in excess root growth, whereas too much cytokinin will result in excess shoot growth. Once the specimens grow large enough, they can be transplanted into potting soil or other desired medium to grow like normal plants.

Tissue culture offers the horticulturist many different advantages. Like conventional cloning, tissue culture offers the ability to create large numbers of genetic copies of a desirable plant. Unlike conventional cloning, tissue culture can be used as a way to preserve rare or endangered plant species and can also be used to rescue embryos in distantly related cross pollinated species. The biopharmaceutical industry uses massive bioreactors filled with tissue cultures which can produce valuable compounds used as biopharmaceuticals. Another huge advantage of tissue culture is the ability to “clean” plant material of contaminates. In other words, a plant that has developed a disease or virus can still be propagated without bringing the pathogen along with it. This advantage alone provides an invaluable asset of preservation to modern horticulture.

Tissue culture kits are available for hobbyists to use. There are even some recipes online for creating tissue culture kits out of mostly around-the-house items. Because sterilization is so important, hobbyists who want to experiment with tissue culture need to have a dedicated area. Although tissue culture may be a fun experiment, other asexual propagation techniques are more practical for the average greenhouse hobbyist.

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Propagation

Asexual Propagation Using Cuttings is Easy and Effective

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For years commercial horticulturists have been taking advantage of the multiple advantages offered by asexual propagation. These advantages are now being reaped not only by the commercial growers but by hobbyists as well. One of the largest advantages of asexual propagation is the reduced time it takes for a plant to reach maturity or get to a sellable size. This has obvious advantages for the commercial grower but the advantages extend to the hobbyist as well. The faster the plants can reach maturity, the longer the hobbyist can literally enjoy the fruits of his or her labor. Asexual propagation also gives the gardener the ability to create identical replicas of the most prized plants. This can be especially advantageous for the vegetable grower who wishes to replicate the plants with desirable traits. The best tasting tomatoes or crispest cucumbers can be perpetually grown and cloned in a hobby greenhouse and enjoyed year after year. Aside from flavor and aroma, plants can be cloned to preserve other desirable traits like a heightened resistance to stress or disease. Cloning by taking cuttings is the most common asexual propagation technique used by the hobbyist.

This technique is very effective on a wide variety of plants and is also relatively easy to master. The process of cloning some varieties of plants may only consist of cutting a small branch off the plant and placing the stem in water. After a few days roots will begin to form and the plant can be transplanted into soil or another desired medium. The once part-of-a-plant becomes a plant itself; a genetic duplicate of its donor plant. Spider plants, wandering jew, and coleus are a few plants that clone very easily in straight water and with very little effort.

However, not all plants will root as easily as a coleus. Other plant varieties require a little more attention to obtain a high propagation success rate. These varieties usually root better with the aid of a rooting hormone and more precise control over temperature and humidity. Tomatoes, peppers, cucumbers and many other vegetable varieties clone best in a consistent environment. Geraniums, hibiscus, and some African Violet varieties will root much faster and at a higher percentage within a consistent environment. When cloning these more finicky plants, try to keep the temperature consistently between 72-85 degrees F, especially in the root zone. A seedling heat mat may be necessary to ensure a consistent temperature during the night hours. The optimal humidity for clones during the first stages of propagation is 80-100%. After the plants create their own roots they can be acclimated into the ambient humidity. Humidity domes placed over the propagation trays are a great way to control the higher humidity needs of clones and seedlings without affecting the ambient humidity of the greenhouse. Clones that are kept in a consistent environment will root faster and also have a higher overall success rate.

Tip for the Hobbyist

When taking a cutting off a plant, it is best to do so just above a node site (a site where a branch occurs). A 45 degree angle cut just above a node site is my preferred method for most soft stemmed plant varieties. After cutting, place the clone directly into a rooting compound or water. Not only does this method create healthy clones, it also promotes the donor plant to multiply its shoots.

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