Leaf cuttings: how and why

 Everything a RHS Level 2 Practical student needs to know about leaf cuttings

Whether you're studying the RHS Level 2 Certificate in Practical Horticulture, or just want to propagate your own houseplants, you'll need to know about leaf cuttings. 

Plants are weird. Cut a bit off, stick it in compost, and you may get a new plant that's an exact copy of the original. It's a great shame that humans can't do this. Just by popping a few bits of hair into the front garden, I could have armies of myself wandering around, going to work while I relaxed in the garden with a glass of wine... 

Different plants grow from different bits. A small number of plants can be propagated from a leaf, or even just part of a leaf. This is where different styles of leaf cuttings come in.

Apologies for the mixture of cms and inches below - it's how my brain works when judging things by eye! It's also a bit text-y. I'll add photos and videos soon. 

Leaf cutting styles

There are two main types. Firstly, whole-leaf cuttings - exactly what they sound like, a whole leaf. Secondly, part-leaf cuttings, which involve a divided leaf. There are several different subcategories of part-leaf cuttings, and different plants do better when divided in different ways.

Which plants can be propagated from leaf cuttings?

Leaf cuttings are mostly for tender, indoor plants and succulents. 

Whole-leaf cuttings are suitable for:

• Sinningia (aka Gloxinia)
• Streptocarpus syn. Saintpaulia (African violet)
• Peperomia
• Kalanchoe (e.g. mother-of-thousands)
• Echeveria (e.g. Mexican hens)
• Crassula (e.g. jade plant/money tree)
• Some sedums

Part-leaf cuttings are suitable for:

• Streptocarpus syn. Saintpaulia (African violet)
• Sanseveria (e.g. snake plant/mother-in-law's tongue)
• Eucomis (aka pineapple plant)
• Sinningia (aka Gloxinia)
• Begonia masononia (Iron Cross begonia)
• Begonia rex (fancy-leaf begonia)

The science: why do leaf cuttings work?

The plants that can do this are the ones that develop plantlets on their leaves. These are highly specialised plants which produce foliar embryos. The plant isolates simple cells in small areas of its leaves, and these can produce new plants.

When you take a leaf cutting, you're artificially inducing these foliar embryos to develop. 

It's important to plant your cuttings the 'right' way up or they won't grow, so pay attention to which end started as the 'bottom' of your leaf nearest the earth. Hygiene is also really important, as leaf cuttings are prone to rot. 

How to do leaf cuttings in the RHS Level 2 exam

Leaf cuttings may be one of the three horticultural tasks that come up in your RHS practical exam. Don't worry, though - they're fairly straightforward, and you can practice them at home with no need for a garden!

These instructions are for a tray containing several different cuttings of common plants. You may have to take cuttings of just one plant. You're smart, so adjust the info below accordingly.

You will need:

• A cutting tile or mat
• A potting bench (if you're practising at home, use a dry kitchen counter or garden table)
• A sharp, clean scalpel
• Shears/scissors (must be clean!)
• Gloves if preferred (I don't use them for this task)
• Dibber or plant label
• A tub/bucket for compost
• A seed tray
• A tamper
• A strike stick (at home, a ruler will do)
• A brush for tidying up your workbench
• Compost suitable for cuttings - that's either seed and cutting compost, or multipurpose compost mixed 50:50 with perlite or sharp sand/grit
• Plants! In the image at the top, I have used (top to bottom) Peperomia, Sanseveria, Streptocarpus syn. Saintpaulia, and Begonia rex. 
• A watering can and water

1. Collect your cuttings

Choose leaves that look healthy, with no damage or disease. It's important to take leaves that are fresh and strong - not so young they haven't developed yet, but not so old that they're starting to slow down, as it can take months for the cuttings to develop into new plants. 

Take more than you need and then 'grade' them - lay them out on your potting bench in order of weakest to strongest, then keep the strongest. In these examples, you should end up with:

• Five Peperomia leaves, cut off at the base of the stalk. Select leaves of similar size
• One Sanseveria leaf
• One Streptocarpus leaf
• One Begonia leaf

2. Prepare your cuttings

Use the scalpel and tile to safely carry out any trimming. Take care to cut, not crush, the plant tissue. 

• Peperomia - trim if necessary, leaving about 2 in of stalk attached to the entire leaf. This is a leaf petiole cutting.
• Sanseveria - cut into chevrons, each about 1in tall. There are lots of different ways to do this, but I find it easiest to have all the chevron's points towards the top of the leaf. This helps you to ensure you plant the cuttings the right way up later. This is a monocot cutting (which means the plant is monocotyledonous... you don't need to know this for the Practical certificate!)
• Streptocarpus - lie upside down on tile. Remove the midrib (vein down middle of leaf) so the two halves of the leaf are separated and all the veins 'flow' from the cut edge to the leaf edges. Discard the midrib. This is a midrib lateral vein cutting.
• Begonia - place face down on tile and cut off the leaf stalk. Make a 2cm cut across a major vein (not down it - horizontally across it). Do this every square inch of the leaf. This is leaf slashing.

3. Put your compost in your tray

Use the tub/bucket to get a good amount of compost, more than you'll need. Pile it up in the seed tray, allowing it to overflow and pushing it into the corners.

4. Strike for a flat surface

Turn your strike stick or ruler so the thin side is 90 degrees to the top of your seed tray, positioned at the centre of the tray. Press down and move it left to right in a sawing motion, removing all the excess compost from that side of the tray and leaving a nice flat, neat top. Place it back in the centre and do the same right to left. 

Use the tamper to press down the compost. Press it down in the middle, then into all four corners.

This is tricky to describe, so I'll add a video!

5. Tidy up

Move your tray to the side and use your strike stick to move all that excess compost to part of your workbench that you aren't using. It doesn't need to be perfectly clean, but you do need to show you can keep your work area tidy.

6. Put your cuttings in the compost

Place your tray in front of you with the short side at the top. Plant in rows as follows:

• Peperomia leaf petiole cuttings: Work left to right in a row of five at the top of your tray. Make a shallow hole with dibber. Insert cutting at 90-degree angle to compost, so the leaf sticks straight up. Firm the compost gently around the cutting.
• Sanseveria - Poke each of the chevrons into the compost so they stand about 1 inch apart, with the top point upwards. To save space in the tray, I plant mine 'vertically' in the row with the long sides facing each other. Firm them in.
• Streptocarpus midrib lateral vein cuttings: In the next row, make two shallow trenches and plant the cuttings with their long cut edges in the trench. Firm the compost around them. Don't cover too much of the leaf, but support it to stand upright. It's OK for these to curve a bit. 
• Begonia slashed leaf: Place the whole leaf top-side-up onto the compost. Try to make sure the cut veins are touching the compost. You can pin it down with a wire staple. 

7. Water them

Label your cuttings first! Their names, the date, and your name.

Place the seed tray on the ground, away from your potting bench. Fit a rose to the watering-can, fill it and water from a height, swinging the can gently round in a circle so your cuttings are evenly watered. Be careful not to disturb the cuttings - starting your watering arc over a patch of ground and moving over the tray once your can is fully tipped can help. 

8. Tidy up

Don't forget to clear up! Brush all the compost on the bench back into your tub and put it in the spent compost bin, put everything away and leave the workstation ready for the next person.

Next steps

That's the RHS exam way of doing things. If I were doing cuttings to grow at home, there are some extra things I would do:

• Keep them somewhere fairly shady but not dark, warm but not scorching, with good airflow
• Be aware it could be months before anything happens! It's now almost December, and the Peperomia cuttings I took in mid-September have just started to grow. 
• You could spray the cuttings with a fungicide occasionally to reduce chances of rot. 
• Some of my classmates have had success just spraying their cuttings daily with water. Mine have been OK with a small watering can with a rose every few days. Experiment!
• A heat mat can really boost your cuttings' chances and speed things up. The Begonia and Streptocarpus cuttings failed for most of my class, except the one lady who used a heat mat!
• You could also use a propagator lid or clear plastic bag as a cloche, but be careful - this can encourage mildew which will kill off your cuttings
• Apply a liquid feed once your plantlets start developing. Pot them on once they're established enough to handle.
• In 'real life', I wouldn't often put different cuttings in the same tray, as they all have slightly different needs for watering, feeding and position. Check your individual plants and treat accordingly.

I'm currently studying the RHS Level 2 Certificate in Practical Horticulture at Capel Manor College. If you're interested, read along!