How to propagate houseplants
Source: https://www.stuff.co.nz/news/112861102/-

2019-06-11 04:25:31

If you love a lush indoor jungle, try propagating your favourite houseplants. It's easy and a great way to increase your stock, or have plants to give away.

Propagation is one of the best and cheapest ways to add to your collection of indoor plants, especially uncommon species that might be hard to find in the garden centre. It's also a hugely rewarding process, watching that new plant emerge from a piece of leaf, stem or seed.

There are many propagation methods, some easier than others and some more suitable for certain plants. The easiest and most common methods of propagating houseplants are taking stem and leaf cuttings or splitting them up into divisions.

But there are plenty of other interesting vegetative propagation methods such as layering, grafting and rooting in water, some easier than others but all worth a try. And of course you can raise new plants by germinating seed although this method is only suitable for a small number of houseplants.

GET PREPPED

​if you are taking cuttings (stem or leaf) always get the prep done in advance so that there is minimal delay, and therefore stress, on the new cutting particularly for tropical species.

Watering the parent plant well a day or two in advance also ensures a healthier cutting.

Do not use a standard potting mix for cuttings or germinating seed as the texture and high level of nutrients they contain are not suitable for root formation. For divisions, a standard potting mix is fine. There are commercial cutting mixes on the market or you can make your own using equal parts of perlite, vermiculite, coarse sand and pulverised sphagnum moss. You can play with combinations (no moss for succulents, for example) but the essential factors you want are moisture-holding capability, good drainage and sterility to reduce the risk of disease.

Sterilise pots or trays in advance, add the specified amount of the soil medium, then moisten it just prior to planting cuttings.

Other essentials are a dibber (or bamboo stem, chopstick, pencil), rooting hormone if you use it, and a water spray. You can also use a drainage tray filled with pebbles to ensure pots don't sit in water (which can cause rotting), and a propagation unit (you can buy commercial ones or rig up a DIY version using plastic salad trays).

Many plants will form roots without rooting hormone, but if you use this, always take some out of the container rather than dipping into the container to reduce bacterial contamination. There are also natural root-promoting alternatives including honey, willow water and cinnamon.

STEM CUTTINGS

This is a standard, fast propagation method used by many nurseries. It can vary slightly depending on the age of the plant stem. We are focusing on the most straightforward form: softwood (green) cuttings. The best time for propagating these is spring or early summer when the parent plant is entering its active growing period.

This is the best way to multiply a wide variety of tropical plants including Swiss cheese plant (Monstera deliciosa), string of pearls (Senecio rowleyanus), philodendron, fiddle-leaf fig (Ficus lyrata), weeping fig (Ficus benjamina), rubber plant (Ficus elastica), hoya, umbrella tree (Schefflera) and dieffenbachia. Branching succulents and cacti such as dracaena, crassula, aloe, and aeonium also suit this method.

1. Take cuttings first thing in the morning if possible. Choose a 10-15cm piece of healthy, non-flowering stem (normally the tip) with at least three leaf nodes (points where leaves or side stems grow). Cut below the bottom node with a sharp knife or pair of scissors. Make the cut as clean as possible (use a razor blade to tidy it up), as crushed plant tissue is prone to rot.

The thicker the stem, the longer it will take to root so younger stems are best.

2. Remove all lower leaves so they don't rot in the cutting mix, leaving only one or two sets at the top to reduce moisture loss through transpiration. For the same reason, any large leaves left on the cutting should be reduced in size. If possible take several cuttings at once as not all will necessarily take root.

3. If using rooting hormone cover the cut edge with it and tap off any excess. For succulents and plants with sap such as frangipani, allow the end of stem cuttings to callous. This can take anything from three days to several weeks for frangipani. For many succulents, rooting hormone is not necessary.

4. Dampen surface of mix. To reduce tissue damage, make holes in the compost to about half their depth with dibber or similar, deep enough to hold cuttings firmly.  Place several in each pot. They can remain together once rooted to form a bushy plant if desired, or be transplanted later into separate pots.  Firm up mix around cutting and use small sticks to support tall cuttings.

5. Place pots on a drainage tray if using, then cover with a plastic bag, pierced with holes for ventilation and tied loosely, or use a commercially made propagation unit. Use sticks around the edge to make sure the bag doesn't touch plant material. This will create the humid air necessary for most cuttings, particularly tropical plants, to root up. It's not required for stem (and leaf) cuttings from succulents or fleshy leaved plants such as pelargoniums, although misting such cuttings every three weeks is recommended.

AFTER CARE FOR CUTTINGS

• Stand pots (within their plastic cover or in propagator) in bright light (not direct sun) in a room where temperatures don't fall below 21°C.

• Check regularly for rot (remove any that rot) and that mix is damp (not sodden). Mist with water but avoid moisture on leaf cuttings. Lift the plastic cover occasionally to avoid moisture buildup.

• Check for rooting by gently pulling a cutting. If it resists, roots are forming. Once plenty of roots have formed, repot using a standard mix with a little perlite or coarse sand.

• Gradually acclimatise tropical species by slitting open the bag or leaving the propagation case partly open. Move succulent cuttings into direct sun once roots have formed.

DIVISIONS

Taking divisions is the method for increasing clumping and rosette forming plants such as ferns, ZZ plant (Zamioculcas zamiifolia), orchids, peace lily (Spathiphyllum), Calathea, cast iron plant (Aspidistra), bird of paradise and most rosette-forming succulents. Some experts recommend this method for clumping palms such as parlour palm (Chamaedorea elegans) but others warn that it is too tricky for home gardeners and you risk losing the plant.

Dividing clumping plants is essential for their health as pots become congested and overcrowded.  Roots coming out the bottom is an indication of this. Divisions are best done when plants are actively growing from early spring to late summer.

Ease plant out of the pot and work out the best places for the clump to be divided. Gently pull apart, shaking off potting mix if necessary to disentangle roots. Some plants such as ferns and Strelitzia form tighter clumps or have rhizomes that may need to be cut with a sharp knife. Try to ensure each division has a good set of roots.

Plant divisions into pots that are larger than their root ball. If there's very little potting mix left around the roots, fill a third of the container with standard potting mix, then hold the clump in one hand while gently adding more potting mix in and around the roots. Tap on hard surface occasionally to let mix settle into any air pockets.

Firm mix around the base of the clump and water. Place pot in same room as parent plant. If the divisions start to wilt you may need to try the plastic bag/propagation treatment for a few days.

PLANTLETS

These are ready to plant, miniature forms of parent plants that grow on the ends of leaves or stems. Popular houseplants that do this include hen and chickens fern (Asplenium bulbiferum), spider ivy (Chlorophytum comosum) and mother of thousands (Saxifraga stolonifera). Some you can detach and pot up while others should stay attached to the parent plant while pinned down into potting mix of a separate container.

OFFSETS

Many plants produce offsets or pups which are side growths that are mini versions of the parent plant, growing out of the main stem. Ctenanthe and bromeliads do this, also many succulents and cacti.

Make sure offsets are not too small before removing or they won't be able to form their own root system.  Some may have formed roots before removal, others will do so when replanted. Water parent plant well, remove offset with sharp knife and replant as you would a division, in spring/summer.

LAYERING

Used for trailing plants, this method encourages roots to form on stems while still attached to the parent plant. Pin down a piece of stem into a pot filled with cutting mix placed near the parent. If contact is good, roots will form at that point. A variation on this is air layering, used to stimulate growth on the lower stems of plants with stiff stems such as weeping fig. It involves cutting away a section of bark, dusting with rooting hormone then wrapping with sphagnum moss and plastic until roots form.

ROOTING IN WATER

Many plants can be propagated by placing a leaf or stem section in water until roots form. This works for African violets, coleus, ivy-like or trailing plants such as golden pothos (Epipremnum aureum), heart-leaf philodendron (Philodendron scandens), and Monstera deliciosa. Even stems of Dracaena marginata can grow in water-filled glass containers for years so it's worth experimenting. Pot up before roots reach 2cm length (or trim to this length), making a hole in potting mix first to avoid damaging the roots.

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