Frequently Asked Questions


Propagation is quite simply the creation of new plants. Many growers propagate using hydroponic techniques to benefit from premature rooting and rapid growth rates. This may be likely because hydroponic growing media provides the root zone with easy access to water, nutrients and oxygen.

Propagation: Seed vs. cuttings

To begin with, as with any type of propagation, you need to decide whether you want to grow from seed or from cuttings. In general, growers who begin propagating from seed do this because it gives them peace of mind that their plants will be disease and pest free.

However, the main disadvantage with seeds is that the characteristics of plants you produce can be inconsistent. Whereas when beginning with cuttings, you are producing plants that are identical to their healthy parent plant, this is why cuttings are also referred to as clones, as they are indistinguishable. Other benefits include:

  • Advanced flowering.
  • Enhanced plant collection.
  • Plant species which are much more adjusting to the inconsistent climatic variations.

Budding from cuttings has a range of advantages, therefore here at Rotherham Hydroponics we usually recommend our customers to use this technique of propagation. On the other hand, for your first gardening mission you will most likely have to start growing from seed.

How do I take a cutting successfully?

We have put together step-by-step instructions on how to take a cutting successfully.

First of all you will need the following items:

  • Propagation cubes/plugs.
  • Rooting hormone.
  • Heated or unheated propagator
  • Fluorescent lighting.
  • Sterile scalpel.
  • Spray bottle.
  • Nutrient.
  • Rooting stimulator.

The following article explains how to successfully propagate. The procedure is on the whole the same for all types of propagation.

The Mother Plant

First of all you will have to grow you seedlings or cuttings under 18 hours of light until they are appropriate to take cuttings from. This is generally when they are on average sized between 12 and 18 inches or have 8 to 10 internodes on them.

The best thing to do is to label your seedlings with numbers or names so that you can label your cuttings you obtain to make it easier to correspond with the parent plant.

When your seedlings are ready and prepared, activate them to flower by giving them 12 hours of light and 12 hours of darkness. Obtain the seedlings to full matirity to determine which shows favourable characteristics, for example the quickest to root, best flower progress etc.

While the plants are flowering, cuttings will need to be stored in a vegetative condition in an individual growing area with 18 hours of light and 6 hours of darkness.

The cutting with the same name/number as the plant with the most favourable characteristics will be the plant that is to be kept as the mother plant.

Mother plants can be grown in a variety of propagation systems. We highly recommend choosing a media based growing system, as the plants will typically be kept for up to a year. Whereas systems using techniques such as deep water culture and aeroponics are more appropriate to short term crops.

The most common method of keeping mother plants is by using soil, or soil-less growing media in pots, which can be maintained by being watered by hand or by an automatic delivery system.

Quality of cuttings

If you want strong, vigorous cuttings it is absolutely crucial to consider the quality of the mother plant that they are coming from. Always make sure that the mother plant is regularly trimmed and pruned to encourage side branches to grow, as this will give you lots of available sites to take cuttings from. It is highly advisable not to feed your mother plant too much, as overfed plants will produce thicker-stemmed, woodier branches and cuttings that will take much longer to root compared to your everyday average-watered mother plant. The highest focus of growth is concentrated around the bottom third of the plant section around the inside shoots where you should be taking your cuttings from, also identified as the ‘zone of juvenility’.

Without stripping away more than 25% of the foliage, you must take away as my cuttings from the mother plant as possible. However it is most preferred to use cuttings that have few leaves. Cuttings that have large leaves are often unable to soak up sufficient water through their stem, as those with thinner stems will also root much faster than cuttings with fatter stems.

Fluorescent lighting

As previously stressed, seedlings/mothers need to be grown under 18 hours of fluorescent lighting and 6 hours in darkness however once they are well rooted, you will need to change to 12 hours of HID light and 12 hours of darkness to commence the flowering or fruiting.

In the first week previous to the roots being formed, cuttings will begin to execute best with a fluorescent lighting unit which is positioned approximately 25-50cm away from the lid of the propagator. When using HID lights for the propagation, you should only choose 250w metal halide lamps. These lamps must only be positioned 1m away from your propagator. Any higher wattage of HID lamps will give off too much light and heat that will most likely result in the unfortunate event of your cuttings failing to root.

Rockwool Propagation Cubes

The main advantage of Rockwell is that it holds much more air and water than any other growing medium on the market. Not only that, but it is also inert, sterile and does not hold onto nutrient in any way. The roots are also clearly visible, therefore it is easy to identify whether the cubes are moist or dry. These can be easily transplanted into larger Rockwell blocks or any other hydroponic media with the minimalist amount of fuss to the plant.

Cuttings should take approximately 7 to 14 days to root, at this stage you will need to transfer the cuttings into much larger Rockwool cubes or your chosen hydroponic growing medium.

A simple step by step guide to taking cuttings

Finally, we are at that stage of the article that you have all been waiting for. The simple step by step guide to help you successfully take cuttings form your plants.

  • Clean down all work surfaces and wash equipment thoroughly with disinfectant.
  • Soak the Rockwell cubes in chosen nutrient solution for an hour, after which you must shake so as to get rid of any excess liquid that it may have collected.
  • Choose shoots which have at least 3 to 4 leaves, making sure that you take the cuttings from the base of the plant, around the outer shoots. Do this with a smooth motion, cutting at a 45 degree angle immediately below the joining of the branch and stem.
  • Immediately submerge the cut stems into a bowl of lukewarm water.
  • Remove the bottom leaves from the stem and if the cutting has more than one large fan leaf, remove the extra leaf.
  • Gently scrape the lower part of the stem with a scalpel to help initiate faster root growth.
  • Apply rooting hormone to the cut stem or cube exactly as directed on the packaging of the product.
  • Whilst lightly pinching the cube, gently hold in place and insert cutting into the cube.
  • Place back into plastic tray and position in propagator once all cuttings are inserted into the cubes.
  • Finely mist all cuttings with water and place propagator lid on tray.
  • Position fluorescent light over propagator.
  • Give cuttings 18 hours of light per day unless air temperature drops by more than 4ºC when the light goes out in which you must leave the lights on continuously.
  • Take off lid of propagator and finely mist propagator lid once a day.
  • Once there is evidence that roots are appearing within 7 to 14 days, the propagator vents can be opened.
  • If at this stage, you wish to transplant propagation cubes into larger Rockwool blocks, quite simply pre-soak block with suitable nutrient and rooting stimulator.
  • It’s important that Rockwell blocks are not too wet, therefore you must insert cubes into larger blocks and place them on a plastic tray or a surface where the plants can be ‘air pruned’. (see below)
  • Roots should become visible on the bottom of the blocks within 2 to 7 days and after 10 to 14 days there should be plentiful roots on the bottom of the blocks. At this point you can then plant into your chosen hydroponic system. However you must be careful not to place your plants into their system too early, only do so when there are an large quantity of roots on the bottom of the blocks should you consider planting on.

Air Pruning

Air pruning is a propagation technique that is used to help promote healthy root structure. Air pruning involves placing your plants in Rockwell blocks on a perforated tray or a wire mesh. This should be positioned carefully so that the air can naturally flow underneath the blocks. With using this technique as the root tip grows out of the blocks and detects the dry air and dies back which forces the root that is still inside the block, to branch out forming even more roots. This means that the roots will focus their growth within the block.

Eventually you will end up with a plant that has many small root tips extending beyond the block with a large mass of roots within the block. Soon after this has happened the plant is put onto its final system where the roots broaden away from the block very quickly, getting the plants existence off to a eminent start. This technique is on the whole very useful for NFT growing systems however is recommended to be employed for all types of systems.

Using Heated Propagators

If you have a propagation area that is too cold, your cuttings and seedlings will take a much longer time to begin growing. If the temperature of the propagation area is below 18ºC you will need to use a heating mat or warming pad for the bottom of the propagator or you could just buy a new heated propagator.

When using heat from a mat, pad or heated propagator we suggest that customers use a 2.5cm layer of perlite or vermiculite or also a combination of both can be used in your propagation tray. This will facilitate the spreading of the heat throughout the propagator and also avoiding the ‘hot spot’ areas at the same time.

Using ‘Aeroponic’ Propagators

Advances in propagation equipment has led to the UK’s primary systems manufacturer ‘Nutriculture’ to make a readily available and affordable compact range of media systems to be used for propagating cuttings using only aeroponics.

The use of aeroponic propagation means that there is no need for the use of any growing media at all. This is because the main stem of the cutting is clamped within a sponge collar, which is then inserted in to a net pot that is located inside the media system where the stem gets a continuous mist sprayed around it. This is done to promote the idyllic air to water ratio so that cuttings often root within an average of 5 days.

As soon as you can see that roots are beginning to develop on the cutting, you can then transplant them into a pot containing growing media. You can transplant your cuttings into Rockwell cubes and fill the space left over with perlite, vermiculite, coco coir or small clay pebbles. Or it is also viable to use small clay pebbles in the net pot, to position your unrooted cutting and place in the aeroponic propagator. This will mean that the roots will still grow out quickly and the net pot placed straight into a transplant block.


Why wont my cuttings root?

This is a regular question that is asked, and the answer is just this:

It can be caused by many different factors; the most common being that the growing media that is being used is being kept too wet. If you are using Rockwool, after pre-soaking make sure that you shake the cube well to rid all of the excess water within the cube. When you spray your cuttings, be sure that you spray the foliage very lightly and not to spray the cubes and ensure that you never leave water standing in the bottom of the propagator.

Cuttings will take a much longer time to root if they are too big, therefore try and take much smaller cuttings around 3” (7-8cm) and remove the big leaves from them to reduce the leaf surface area.

Always check that your rooting hormone is still in date before using it.

Refrain from using strong nutrients to pre-soak cubes with as this will prevent root formation.

Make sure that the temperature is between 18-24ºC at all times and is kept constant. If temperatures fall more than 4ºC between day and night make sure to change to continuously keeping lights on to maintain a steady temperature.

Make sure that you use a propagator, and that the vents of it are fully closed up until roots appear.

Be patient. The average time for cuttings to root is between 7 and 14 days.

Why are my cuttings wilting?

Wilting cuttings can soon happen after taking the original cutting, however they should come back around. If they continue wilted, then this is usually an indication that the temperatures are much too high. This can be a common problem in the summer months but can soon be cured by reducing the temperature in the propagation area.

Why is the base of the stem on my seedling/cutting turning brown/black and rotting?

Brown/black and rotting stems often happens when the growing media is kept too wet. This means that it has invited fungal diseases that attack the plant, also identified as ‘damping off’ diseases. This can often be problematic in warm and wet propagation conditions.

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