As I look around my garden, I find myself thinking about growing flowers and herbs indoors this winter with H.I.D. (high-intensity discharge) or high-output T5 fluorescent plant grow lights. It is virtually impossible to find a source for fresh new plants late in the year unless you plan ahead by making cuttings, or clones. Now is the time to start thinking about making cuttings of your favorite plants, so that you can continue gardening indoors this winter. Propagating plants by cloning is easy if you follow a few simple, but important steps, and use the proper tools.
Step One: Assemble the Materials
- Rapid Rooters, Rockwool or Oasis® Starter Cubes
- Tray and Clear Plastic Humidity Dome
- Propagation Heating Mat
- Freshwater pH Test Kit and pH Down
- Cutting Scissors or Single-edge Razor Blade
- Rooting Hormone, Powder or Gel
- Liquid Rooting Solution
Prepare a Humidity Chamber for the Cuttings
Place a sheet of rockwool, Rapid Rooters Natural Plant Starter Cubes or Oasis starter cubes into a standard black nursery tray. Mix a gallon of water with 2 teaspoons of a mild starter fertilizer. The pH should be adjusted to 5.5 by adding between 1/4 and 1 teaspoon of pH down, depending on the pH of your tap water. Plants prefer a pH of 5.5 – 6.5. It is best to test the pH of the plant food solution with a pH test kit, but not absolutely necessary.
Soak the starter cubes with this solution. You will also want to water your cuttings for the first few weeks with the same solution. Place the tray on a propagation heat mat, and cover it with a plastic dome to warm the rooting medium. After you have prepared your tray, you are ready to begin to take cuttings.
Step Three: Take Cuttings
Choose a healthy plant that has been well-watered. Cuttings taken from the top growing shoots of the plant will root well, as long as they are sturdy enough to insert into the growing medium. Using a sharp knife or single-edged razor, select a 3-6 inch portion of the stem. Cut the stem at a 45-degree angle. Place the cuttings in water or a rooting solution. Until you are ready to insert them into the rooting medium. When all of your cuttings are made, remove the bottom two leaves of each cutting. This exposes the node area, which contains the highest concentration of rooting cells available. Also, remove any excessively large leaves, and all flowers. Prior to sticking the cutting into the rockwool or Oasis, make a fresh 45-degree cut (preferably under water), dip each cutting into a rooting gel or hormone, and insert it into the rockwool or Oasis cube. Try to be gentle when inserting the cutting into the cube. You should stick the cutting at least 1/2 the depth of the cube. Place the cubes into the tray, being certain not to overcrowd the cuttings. Cover the tray with a plastic humidity dome, and place it on a propagation heat mat. If your heating mat has a thermostat, set the temperature for about 76 degrees F.
Step Four: Provide Adequate Lighting
Cuttings require 18 hours of light each day. Using a timer will help keep your cuttings on a regular schedule. If using fluorescent grow lights, place the lights no more than 6 inches above the dome. H.I.D. grow lights may also be used but should be placed much higher, preferably two to four feet above the dome.
Step Five: Care of the Cuttings
The temperature in the humidity dome should be kept around 75 degrees, with a bottom temperature of approximately 80 degrees. Bottom heat encourages root growth. The humidity level should be kept at or near 90%. Plants do require air circulation, so remove the dome for 15 minutes at least once a day. You may also want to leave the dome slightly ajar or use spacers to elevate it about an inch above the tray. This will help to prevent disease. Check the cuttings periodically for dead leaves, and remove any diseased-looking cuttings at once. Most cuttings will root in 1-4 weeks, depending on the cultivar. At two weeks, you may pull a cutting very gently to see if there is any resistance, which indicates that callous development and/or root growth has begun.
Picture above shows cutting before callous has formed.
Picture above shows cutting after callous has formed.
Step Six: Transplant the Cutting
Once the cutting has a strong root system, as evidenced by visible roots, you should transplant it immediately. Watering with Superthrive or Vitamin B1 prior to transplanting will reduce shock. Transplant late in the day, and place the transplants in low, filtered light. Gradually, move them into full sun or place them under high-intensity plant grow lights. Fertilize with a balanced half-strength fertilizer.
If you want to grow flowers indoors in the winter, they will require supplemental lighting from either high output fluorescent grow lamps or high-intensity metal halide / high-pressure sodium lamps. Most culinary herbs will do well in a sunny window.