I do presentations and classes frequently and generally let the organization pick the topic. If you haven't done this much and that sounds like it's opening a large can of worms, then pick a gardening topic near and dear to your heart. Something that you are very familiar with and are passionate about. That way you will be comfortable speaking about it in front of a group and if the topic is familiar, you won't need to rely much on notes and/or rehersing and it will sound much more natural and extemporary.

And something appropriate to the season is always a good choice. Or, you could talk about the MG program itself......how it operates in your area, what the classes consist of, how you fill your volunteer hours and the benefit it has to the gardening community. Who knows - maybe you'll stimulate some new members!

Care to share some of the topics you spoke about?

I recently did one on raising healthy butterflies.I touched on the predators and diseases as well as how to raise them indoors. I put together a slideshow of all the butterfly,caterpillar and the larval and host plant pictures I took.Also brought in live caterpillars and a Black swallowtail butterfly in jars. But that is because it is something I do and know about.
Also did one on Hypoxylon Oak canker which no one knew about but its main cause is constuction damage to the tree roots. We are in a high growth area so it is pertinant.I think raising earthworms or composting is good but then again I have experience at it and like to garden organically.I have a speaker coming that use to work at Lowes but opened his own landscaping biz so I want him to talk on how to BUY plants and how to know HOW Many. Also focal points in the garden. What ever you do you must really research it and have some props. Either REAL plants or subject matter or slides. We always get new warnings from the ext office so those topics are good . You know Africanized Honey Bees, Chili Thrips, or whatever the latest threat to us is.
How about healthy soil? Photography in the Garden?
Basically many of the titles of these forums could be your next presentation

GREAT! THANKS!!!

I want to bring in a list of suggestions and see if any of them excite the group. It is helpful to have a nice LONG list of possibilities.

I have footage of monarchs from eggs to butterflies I forgot all about it until I read your suggestions. also I did a report on composting as part of my MG training and a guest speaker did a nice presentation on raising worms. Gosh, I taught photography for 13 years that would be a good one too.

Thanks for the suggestions, any others folks? Maybe some presentations you really enjoyed?

Landscape design
Small space gardening
Organic gardening
Organic lawn care
Soils, mulches and compost
Low maintenance gardening
Hellebores
Groundcovers
Container planting and design
Winterizing the garden
Drought tolerant plantings/waterwise gardening
Shade plants
Small trees for small gardens
Lavender
Attracting hummingbirds
Long blooming perennials, late season perennials, early season perennials, etc.
Growing great roses
Potager gardens
Herb and knot gardens
Hydrangeas
Clematis and other vines
Green thumb plants - the plants anyone can grow
Hardy geraniums
Creating a tropical look
Winter interest plants
Dwarf conifers
Ornamental grasses
Garden thugs and exotic invasives
Variegated plants and how to use them
Japanese maples
Plants for privacy screening
How to create "curb appeal"
Lawn alternatives
Great plant combinations
Native plants
Attracting wildlife