Ideally, the bag can be kept shut from the time the cuttings are inserted until they are rooted in 10 days to a month. Another related hazard is seepage of moisture from the bottom of the bag to the surface on which it is resting.
With the exception of succulents, most cuttings need high humidity in order to grow properly. Until cuttings develop roots, they are very susceptible to drying out. If you don't have a bright area with high humidity, you can create a humid environment around the cutting by placing a clear plastic bag over it.
Storage of cuttings
It is best to harvest cuttings in early spring and plant immediately but if this is not possible, cuttings can be stored safely for about 4 months. Store cuttings in a cool, dark, and moist place. Do NOT store in a wet area as this will promote root growth and weaken the cutting.
Covering Plants with Plastic Bags
Plants under plastic bags retain moisture and even capture what the plants produce by transpiration. Don't use plastic bags as a greenhouse for succulents, though, as they can definitely tolerate neglect, but won't tolerate this kind of moisture.
Yes, that's right: plants provide all the “air” they need for their own survival. They're perfectly happy sealed in a plastic bag. How long can you keep your plants sealed up like this? Easily 6 months, quite possibly up to a year.
Plastic can be used to protect plants from frost, but it's not the best or most effective material. In fact, the horticultural experts here at Green Impressions actually recommend against it. Plastic materials such as vinyl and traditional camping tarps aren't breathable, causing moisture to get trapped inside.
The sooner you can get your cuttings into a more normal environment with air flow and no dome, the better off they'll be. After about a week, remove the dome and monitor your cuttings to see if they begin to wilt. If they do, they're not ready to go dome-less, so try again in 1-2 days.
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.
Place your stem cutting in your vessel with enough water to cover the node. The water level will drop due to evaporation, so you should add water every 3-5 days as needed. You can watch the roots develop if you have chosen a clear vessel for your cutting.
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.
Maintain high humidity by covering the pot with a bottomless milk jug or by placing the pot into a clear plastic bag. Cuttings can also be placed in plastic trays covered with clear plastic stretched over a wire frame (Figure 2).
Usually, covering plants with any plastic material isn't safe. However, you can cover your plants with garbage bags to protect them from pests and pest-carried diseases and sometimes excess moisture from too much rainfall.
Carefully remove excess leaves to reduce transpiration, so cuttings do not wilt. However, some foliage should be retained to allow photosynthesis to occur. Keep cuttings moist, cool and shaded (collecting in a damp plastic bag is a good idea) until you are ready to put them in a propagation medium.
Transport of Plastic in Root Tissue. The uptake of MPs and NPs in plants has been detected and plastic particles are especially absorbed on root hairs.
Auxin, a naturally occurring plant hormone, stimulates root formation. Several synthetic forms of auxin are sold as “rooting hormone.” Though some plants will root readily without treatment, application of rooting hormone to the base of the cutting will often improve your chance for success.
The technique is the same for almost all cuttings – cut a length of stem without flowers about the length of a pencil. Trim it neatly just below a node (the point where the leaves branch from the stem), and cut off the lower leaves to give you a bare stem. Put it down the side of a pot into gritty, free-draining 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.
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.
Give cuttings bright light but not sun. Keep soil moist but not wet. The cuttings should root within three weeks. Admit air gradually to wean the cuttings from their humid environment, then pot singly before outdoor planting.
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.
Over time, soil underneath the plastic loses breathability, and plant roots suffer from lack of air and, in some cases, water. Plastic sheets are a total waste of money when it comes to plants, but the strongest negative is that plastic sheets or fabrics hurt the most important part of the soil — the surface.
In soil, plastics have the potential to cause problems at the chemical level. Like a magnetic attraction, contaminants can bind to plastics, resulting in toxic accumulation. Contaminants can also hitch a free ride on plastics and potentially make their way into plants.
The plastics that are already used for food storage tend to also be safe to garden with. Like its older cousin, HDPE, LDPE plastic is very safe in a wide range of temperatures and can even be used in the microwave. You're likely to find LDPE in your garden in the hoses you use to water.