Scarification Activity
How Tough is Your Seed?

Mike 'the Spike' Medic is one tough character. He's got a hard seed coat that water just can't get through. But once you scratch his surface and get to his inner core, he responds the way any other plant would - he swells with pride and grows to his full potential.

In "Busting Out", Billie Bean explained that Spike Medic only comes up after his hard seed coat is scarified - that's a fancy word which means the seed coats are scratched or worn down in the soil. There's an advantage for pasture plants like Spike to be hard seeded. It means all the seeds don't come up at the same time and there's pasture seed ready to come up every year when the season breaks.

Use this activity to check out how tough different seeds are.

What do you need?

Category A

Category B

Wattle seed can be purchased from suppliers of Australian native seeds companies, look in the yellow pages under Seedsmen.

What to do

1. Place cotton wool on the saucers and moisten it with water.
2. Take 10 seeds of easch type and place on the cotton wool. Label these saucers: 'control'.
3. Take 10 seeds of each type and either scratch with sandpaper or dip into boiling water for 5 seconds.
4. Place on the other saucers with cotton wool.
5. Keep cotton wool moist for 2 - 3 weeks.
6. Keep a daily record of how many seeds from each group have germinated.

Results

Which plants are hard seeded and which are soft seeded?

Has scratching or heating the seeds helped the hard seeds germinate?

Has scratching or heating the seeds helped the soft seeds germinate?

Write a paragraph to explain what you've found.

Challenge questions:

• How can hard seeds help plants survive?
• Are different strategies better for different plants?
• Are there disadvantages for farmers if plants are hard seeded?

Many Australian native plants and pasture plants are hard seeded but crop plants are soft seeded. Use the internet and/or a library to research this question. Here are some hints:-

• What is the climate like in Australian mediterranean regions?
• Can rainfall be unpredictable? What would happen if some rain falls but there is no 'follow-up' rain?
• Is it better for all seeds to come up at once or for some to be kept in reserve in the seed bank in the soil?