Adding supplemental lighting to cutting (clone) production can greatly increase the chances of a successful crop, along with faster root emergence and crop times. If the Daily Light Integral (DLI) is too low during propagation, leaves will be unable to get enough light for photosynthesis and rooting can be delayed.
Light provides the energy for callus formation and the subsequent generation of adventitious roots. At the same time, light increases plant temperature and accelerates the drying of leaves, which can quickly dehydrate cuttings.
We recommend a photoperiod of 12-13 hours for the propagation of most annuals, especially for long-day plants such as petunia. Light Intensity. Desirable levels of light vary, depending primarily on the stage of root development. The following is a guideline for managing light intensity for high-light crops.
It's important that your water propagated plants receive some light, but bright indirect light with no direct sun is important. They are growing new root systems and are fragile.
Roots grow in the dark soil to anchor the plant and to absorb mineral nutrients and water. It has been reported that light can penetrate less than several millimeters due to the rather high absorbance of soil (Woolley and Stoller, 1978).
Tend the Cuttings
Most plants will not root well in full sun, so place the cuttings in a location where they will receive a 50/50 ratio of shade to dappled sunlight. For most plants, cuttings thrive on warmth and humidity, and the growing medium should be kept evenly moist but not drenched while roots develop.
Cuttings will root more quickly and reliably in warm rooting mix. Keep your cuttings between 65°F and 75°F, avoiding excessive heat. If your area is too cold, consider a heating mat or cable especially designed for this purpose.
The reason cuttings rot is that over time, the oxygen level of the water drops unless it's moving or oxygen is added. Not only do plants need oxygen in order to grow roots (and, indeed everything else), but the bacteria that cause rotting thrive in low-oxygen environments.
Clip off the leaves on the lower half of the shoot so you have a bare stem to insert into your potting mix. Then, if you want, dip the end of your stem in rooting hormone. This generally helps cuttings root more quickly.
The problem is if the cutting is too long the plant is more likely to wilt and stress. If the cutting is wilting it's far more likely to fail and not generate roots. Smaller cuttings will lead to better success rates and overall better outcomes for you and your cuttings.
That's why many growers choose Philips as the best LED propagation light. Faster and stronger rooting, more uniform, compact plants and higher propagation success rates. With Philips LED plant grow lights, flowers, perennials and potted plants get the right start so you can deliver the very best across the board.
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.
You can replace the water every few days, or simply top off the vessel with fresh water when it's looking low—as long as there is no murkiness or fungi growing. If the water is murky, we recommend replacing it for the health of the growing root system.
Some plants will root in water, but cuttings will develop a better root system when rooted in a soil-less potting mix. Sand or perlite can also be used, especially for cuttings that need good drainage and may rot if kept too wet.
Cuttings need water for hydration, but also enough oxygen for roots to respire and grow. Using a substrate with adequate air porosity, and using the 1 to 5 moisture scale can help to prevent overwatering that leads to slow rooting and increased risk of disease.
Herbaceous cuttings can be taken throughout the growing season (spring to late fall), while softwood cuttings should be taken in spring or early summer. Cuttings can be taken as long as the parent plant is healthy and in active growth.
Technically, you can transfer your cuttings to soil at any time. In fact, you can actually propagate directly into soil, however, it's much harder to do within your home. When you propagate in soil, you have to keep a good balance of soil moisture, air flow, and humidity.
Too much or too frequent application of mist / fog keeps the growing medium saturated, excess water will flow from the bottom of the trays and rooting will be delayed. Applying mist / fog too infrequently will increase transpiration from the leaves and cuttings will lose turgidity and could die from drying out.
Several cuttings may be placed together in one container. Be sure to add fresh water as needed until the cuttings are fully rooted. Rooting will generally occur in 3-4 weeks but some plants will take longer. When the roots are 1-2 inches long or longer the cutting is ready to be potted up.
From stick to root development (Stages 1-3), propagators sometimes use too little water or moisture, but most often provide too much water, which leads to leaching and waterlogged propagation substrates (Fig. 1), uneven rooting and loss of cuttings due to rot (Fig. 2) or botrytis.
Hydrogen peroxide can help to control fungal growth and fungal infection, such as root rot, by preventing the growth of fungi. It can also help kill fungus and bacteria on plant roots.
Ideally, the temperature of the medium should be maintained slightly higher (5°F-8°F) than the air so that callus and root growth occur faster than shoot growth. To accomplish this, bottom heat- ing is required. Desirable propaga- tion temperatures are 73°F-77°F for the medium and 68°F-73°F for the air.
Plant cuttings mistakes can range from using dirty tools to potting up your cuttings in the incorrect potting soil. Too much harsh sun, too much or not enough water, and using offcuts from plants that are sickly or flowering can also put your cuttings at risk.