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.
Warm growing medium temperatures accelerate cell division which leads to faster callusing, root initial development and subsequent root growth. It also speeds up the dry-down rate of the growing medium, which also helps encourage better rooting. The best way to warm the growing medium is through bottom heat.
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. This plant has heavy rooting and is ready to be moved to a pot with potting soil.
Providing light is essential for successful rooting of these cuttings. Check for roots once a month. It may take three or four months for roots to develop. Acclimate rooted cuttings as described above.
Roots need air in order to grow. You should try and change the water with fresh tap water every 2-3 days or so for best results because oxygen in the water will be depleted.
Just Add Water
Put your cutting in a clear glass jar or vase so the roots can get some sun. Use a beaker or bottle-shaped vase so the cutting stays nicely in place. That's it! You may need to change the water every few weeks or trim back the roots in a year, but until then, it's completely self-sustainable.
However, we like to keep them in water on their germination plate forever, so we can enjoy the root growth as well as the foliage :-). As long as you give them proper nutrients in the water, they can thrive indefinitely without soil.
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.
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.
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.
If you root your cutting in water, it develops roots that are best adapted to get what they need from water rather than from soil, Clark pointed out. If you move the plant immediately from water to soil, the plant may be stressed. Instead, add a small amount of soil to the water that you're using to root your cutting.
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.
The two main nutrients that support excellent root growth in plants are phosphorous and potassium. These two ingredients are extremely helpful in any fertilizer mix that needs to encourage a thick, healthy collection of brand-new roots, or to strengthen and stimulate existing systems.
Asexual plant propagation allows for the reproduction of plants that don't produce seeds. This method is faster than sexual plant propagation, and allows you to save damaged or diseased plants.
Auxins stimulate root formation on the stem cuttings, e.g., IBA, IBA-alanine, NAA. NAA is synthetic auxin while IBA is considered as both natural and synthetic.
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.
Controversially, I'm gonna suggest you don't water them very often. I would start with very evenly moist airy soil – water in sans cutting, and mix it round so it's not saturated at the bottom. Add your cutting, and then mist the surface thoroughly daily (trying not to get the cutting). Twice a day if it's hot or dry.
Try to wait until at least 50% of the cuttings have good rooting before potting them up; however, for some hard-to-root species, you may be lucky with only 10% to 20% success.
Cuttings planted in soil will grow roots more slowly. Make sure to keep soil / moss moist. This is easiest if you tent with a plastic bag or use a covered container such as a clean, lidded take-out food container. Check the plants weekly for moisture and growth.
Most indoor and some outdoor plant species can be propagated in water. The rule is simple - trees, shrubs, and herbaceous plants that grow in humid areas or reproduce vegetatively (for example, Aroids) can be propagated in a humid environment, i.e., water. Such plants as succulents can be rooted in water too.
You can do this the easy way, or you can do this the hard way. The easy way is just potting up the cutting like you would any other plant you're repotting. Fill your pot with a bit of soil, hold your cutting so that the roots are below the rim of the pot, and gently fill the rest of the way with soil.
Managing photosynthetic light during callusing is a balancing act. Enough light should be provided so cuttings can photosynthesize, producing the carbohydrates required to sustain the cutting as well as promote new growth, including root development.