Propagation – a talk by Adam from the Gardens group3rd March 2017
Adam’s illustrated talk attracted a record crowd and he did not disappoint. Adam has worked with the Gardens Group for the last 12 years however prior to that he worked on his family wholesale nursery where he learnt everything there was to know about raising hardy shrubs from cuttings for the garden centre industry. He illustrated his talk with a flip chart of A1 colour photographs of the nursery and different stages in the propagation process plus real life plants and demonstrations of how to take cuttings and formative pruning.
Advantages – cheap, most annuals are easy, F1 hybrids produce identical plants
Disadvantages – slow to produce a plant of a good size, many trees and shrubs have complicated germination requirements, can get variation in plants (this may be desirable or not) from risk of cross pollination.
Examples: Holly seed requires 20oC to germinate whilst Ash seed requires 2oC
Vegetative propagation (i.e. cuttings)
This is a vast subject and ranges from simple methods to more elaborate ones! Generally propagation from cuttings produces larger plants faster than from seed, all plants are identical however a little more skill may be involved.
All stock plant (mother plant) material must be:
a) pest & disease free
b) non flowering
c) cuttings are best taken in early morning (more water in the plant – plants are more turgid)
d) all tools and propagation equipment must be clean (e.g. use Jeyes Fluid)
1 Soft wood cuttings
These are taken during the growing season (April – June/ July), soft shoots approximately 5cm long. These root fast but require a plastic bag over them to help reduce excessive water loss.
2 Semi ripe wood cuttings
Adam takes these all year round in preference to soft wood cuttings (however you will find that the text books say that these are taken from about late July – September once the base of the new shoots starts to get a bit woody). Adam’s test for selecting the right shoots for is:
Soft tip that has grown during the summer with a slightly hardened base of the shoot (test by bending the cutting 180 degrees back on itself, if it springs back nicely then this is perfect)
a) Cuttings are approximately 8cm long (1.5 inches)
c) Trim base of cutting diagonally just below a node (all tools must be clean)
d) Remove the very tip of the cutting (the top 2 soft leaves would probably wilt otherwise)
e) Fill a multi-cell tray with seed & cutting compost (has a higher peat content and sand content than multi-purpose compost which is much coarser). Cuttings (and seeds) do not require any fertiliser for rooting (germinating) as they use their own energy supplies for this.
f) Insert small leaved cuttings (e.g. Hebe, Buxus) into the side of the cells in the tray as you will be able to get another cutting on the other side. For large leaved cuttings (e.g. Laurel, also known as Prunus laurocerassus or spotted laurel, Aucuba japonica) place cutting in the centre of the cell. Push cuttings in so that the two remaining leaves are just above the compost level.
g) Large leaved species have their leaves cut in half to reduce water loss from the cutting which has no roots to support big leaves anymore
h) Rooting hormone is only used on difficult species such as Daphne and Viburnum
i) Place tray in propagator although Adam’s nursery have large custom made propagation benches (thick polystyrene sheets or sand beds with heating cables laid (easy to make at home!)). Water trays. Cover trays with thin clear plastic sheeting (winter) or milky plastic (summer as it provides a bit of shading) ensuring that the plastic sheet is not touching the cuttings. Label the trays
j) Rooting should take place within 10-12 weeks depending on the season and whether it is a heated propagation bench. The plastic sheeting can be removed during the daytime after about 2 weeks
k) Harden off cuttings for 4-6 weeks, this means removing the plastic sheeting completely and removing all sources of heat
l) The young plants will now be ready to be potted up (e.g. into a 10cm pot) and they should be trimmed to encourage branching to create a nice bushy plant. Use a fertilizer in the compost as now we want the cuttings to grow fast, Rootgrow (mycorrhiza) is also recommended. Place under cover in an unheated polytunnel or cold frame allowing plenty of air flow during the day to reduce diseases (e.g. Botrytis / grey mould).
m) Once the 10cm pot is full of root (about 8 weeks) these can be potted up into 2 or 3 litre pots, which when rooted through, will be ready for sale to garden centres.
3 Hardwood cuttings
These are taken during the winter months (November – February) from 1 or 2 year old wood.
Straight cut at base below a node, slanting cut at top just above a node (this helps you to remember which is the top and bottom of your cutting!)
Most deciduous shrubs (e.g. dogwoods (Cornus), willow (Salix), Hydrangea, Ribes, Forsythia and hedging plants (e.g. privet (Ligustrum) are propagated in this way
Plant the cuttings either individually or in bundles outside in pots, in a sand bed or directly into the soil. Plant ½ to 2/3 deep so that the cuttings do not dry out. Label the cuttings
If rooting in bundles, pot up as soon as roots appear.
Suitable for most herbaceous perennials (e.g. Aster, Iris, Geranium, Agapanthus…), all new clumps of roots must have some shoots.
Usually done in the spring or the autumn after flowering
Cut up like a cake with an old bread knife every 3-4 years (or use two forks to split clump apart) this keeps the plants young and vigorous, keeps your borders in balance with out some plants taking over, also gives you the opportunity to do some serious weeding!
This will produce only one of two plants depending upon the technique you use (e.g. tip layering (this is what brambles do) or serpentine layering). In this technique the plant’s root system provides energy for the cutting to grow roots, once rooting has taken place then the ‘rooted sections’ are cut away and planted in their new position (or potted up).
Suitable for plants with long bendy stems (e.g. dogwood, gooseberry, blackcurrant, Forsythia, Cotoneaster), many shrubs do this in the garden on their own (e.g. Cotoneaster)
Bend down a shoot to ground level and make a nick in the bark just below a bud, pin down into the soil (there must be good contact with the soil) or place a rock on the stem to weigh it down. You can also pin into a pot but this is a bit trickier and the soil in the pot will need to be kept moist.
Serpentine layering is where every alternate bud is ‘nicked’ and pinned to the ground.
a) Aerial roots – Hydrangea seemanii, Hydrangea petiolaris & Ivy produce aerial roots as they climb, these can be bend over into a pot or the soil where they will root and create new plants that can be detached
b) Air layering – This is used on plants that are difficult to propagate by other means (e.g. Rhododendron, Azalea, Camelia (I have used it on house plants e.g. Scheflera and rubber plants). It is also a good technique if you are moving house and want to take a bit of an established plant from the garden with you – or for very tall growing house plants.
In Spring or Autumn (when plant is not in flower), select a 1 or 2 year old stem, make a small cut to create a ‘flap’ immediately below / just touching a bud. Choose a position close to the top of the branch / stem so that the new plant will have enough roots to support the top of the plant.
Prise open this flap, apply some rooting hormone and insert some moss into the gap, then wrap small amounts of moss around this wounded area until you have created a ball the size of a golf or tennis ball. Wrap it all up with some clear (or black) polythene using all weather tape. The aim is to keep the air in there but to keep the weather out.
This is a big subject and requiring skill. Reasons for grafting include:
a) Plants that do not grow vigorously on their own roots (e.g. Magnolia ‘Yellow Bird’)
b) To control the vigour of plants (e.g. MM106, M9, M26, M25 apple rootstocks)
c) to control the shape of plants (e.g. top grafting of a prostrate plant onto a straight stem creates a weeping tree (e.g. Kilmarnock willow or weeping rose).
d) combine a nice bark with a pretty flowering top (e.g. a red cherry bark with pretty flowering top)
notes by Angela Morley www.wildgardens.co.uk