Sometimes I see an interesting plant on the
roadside or poking through a neighbour's fence.

Is it possible to propagate any plant from a leaf
or small stem? What is the best growth hormone
to use? If I cut a sample from some desired
plant how do I transport this home, in wet cloth
or tissue?

Peter

No, but most will grow from 'tip cuttings', humidity is the key (make yourself a mini greenhouse with plastic bag and pot) try various sizes and lengths of new growth material and you should get a 50% success rate.
Very few will grow from the leaves themselves, and most that do, you do not want.(invasive).
Any rooting hormone will do, just do not smother your cutting in it.. a light dusting is fine.(honey has been used for centuries and is a cheaper option), ( beware of ants).
As for transport, anything that will keep your material cool and moist is great, even in a bucket of water.
If you at first fail, you could always ask the owners for some advice/plant material, they can only say no. cheers.

In article ,
Peter Jason wrote:
Sometimes I see an interesting plant on the
roadside or poking through a neighbour's fence.

Is it possible to propagate any plant from a leaf
or small stem? What is the best growth hormone
to use? If I cut a sample from some desired
plant how do I transport this home, in wet cloth
or tissue?

Your best bet is to identify the plant and look up methods of propagating
it vegetatively. While some plants will root in water or a loose damp
medium effortlessly, others require more complex methods and have low
success rates. On the other hand, you don't have much to lose with
"poached" material, do you? :-)

Hormones may or may not be necessary -- too strong a concentration can
actually inhibit rooting. Many plants, especially those you might see
on the roadside, are almost invariably propagated by seed. Some plants
are best propagated with material collected at a particular time of year
or stage of growth.

A plastic bag is a convenient container for propagating material.

Btw, if you see someone working in their garden, strike up a conversation
by admiring a plant. IME, you'll be offered more material (including
whole plants) than you want and will be informed about plants until your
bladder is about to burst. If someone is trying to give away plants,
you're pretty nearly assured that it will do well until local conditions.
I've been on both sides of such conversations many times!

Have fun!