This applies to most lavenders including L x intermedia 'Grosso' (pictured
above)...
Timing
Propagate during spring and summer when there is nice green growth on plants. Woody
material doesn't root as well as new growth. If you have supplementary light and a warm greenhouse it can be done in winter/autumn
but with reduced success.
Medium
I use a basic well draining seed raising
mix or good quality fine potting mix. Oasis also works very well and I have had good results with this. We can get it in blocks
with individual cells for propagating here. Saturate the potting medium (whatever you use) with water prior to putting in
your cuttings.
Cuttings
Cuttings should be around 4-8 cm long
and don't necessarily have to have growing tip on them. Sections of stem work fine too. Generally they should have at a minimum
of three nodes (sets of leaves). Cut the cutting just below the last node and strip off one or two sets of leaves including
those at the base node (this is generally where the roots will come out). You can cut with scissors but it is quicker to strip
them off between your finger and thumb. You should then have a cutting with two or three sets of leaves left and about 1-2
cm of stripped stem. Sometimes a side shoot can be taken as a cutting and this should be pulled off the stem downwards. It
leaves a 'heel' at the end. Cuttings should be free from disease and pests like fungi and insects.
Hormones
Immediately dip the stripped end in rooting
hormone (I use one called Clonex which contains indole butyric acid (IBA) 3g/L). I have tried various other hormones which
have not been as good. I recommend IBA for lavender. When using rooting hormones always wear gloves and wash your hands after.
The effects of these are not fully understood or known and there is evidence that some can be mutagenic or carcinogenic so
be sensible.
Maintenance of Cuttings
Place cuttings in your
potting medium so that one or two stripped nodes are below the surface. If the cuttings are particularly leafy you can cut
off the tips of the leaves. Plants will lose water through these so too much leaf on a cutting will cause it to wilt from
water loss. Conversely, the cuttings need to photosynthesise and so require some
leaf material to do this. There is a balance
here. Ideally a temperature controlled bed is used on which your cuttings are placed, which is kept at around 25 C with misting
or fogging to maintain humidity. The cuttings are watered on a daily basis after the first day (leave a day so that the hormone
has chance to work). A greenhouse will do to maintain humidity but watch it doesn't get too hot in summer. Cuttings need to
be kept really quite moist until they have roots. If you let them dry out they will die quickly. They can also be done in
the garden but keep them in shade all the time, e.g. on a veranda. Roots should appear in one to three weeks. Allow them to
grow a little before transplanting into pots so root growth is good and maintain some shade and water well until they are
established. Late summer cuttings will take much longer to root than early spring cuttings.
As I work for a University I have to put in a disclaimer and this
method is personally given by me and not given by the University. I accept no responsibility for loss of plant material or
injury caused by using the above methods and you use the methods at your own risk.
Dr. Nigel Urwin
Lecturer in Plant Sciences
School of Agricultural
and Veterinary Sciences
Charles Sturt University
Wagga Wagga
NSW 2678
Australia
ph: +61-269-332450
fax:+61-269-332812
