How do seeds travel?

The overall challenge

How seeds spread is very important for the survival of native plants and in the control of weeds in native areas, on farms, in horticulture and in gardens. This challenge is split into five lessons and is about how seeds spread away from the parent plant. This leads us to how we can help seeds from native plants to spread, and, how we can slow the spread of weed seeds.

So, how do you think certain seeds might spread away (disperse) from the parent plant? To answer this you need to:

• research ideas
• make observations
• make predictions
• gather and interpret data from measurements, undergo trial and error and simulations
• perform experiments
• use evidence to support claims about how seeds disperse.

What you will need

Lesson 1: How do seeds disperse?

Seeds are spread (dispersed) by:

• gravity
• wind
• water
• animals (birds, insects, bats and mammals, including humans who sometimes spread them on purpose and on other occasions, by mistake)
• explosive (release by bursting open)
• fire.

And, some disperse in more than one way.

The challenge

Use the pictures below to decide how each seed is dispersed:

• For each seed explain why and list the special features (adaptations) that allow it to disperse this way.
• You may also need to think about the position of the seeds on the plant and the natural habitat of the plant.
• Discuss with your classmates to see if you agree.
• Research to find out more.

Download 'How do these seeds disperse?' (5MB pdf)

Find out more

Click on this link to read about ways seeds are dispersed.

Lesson 2: Gather evidence

It's easy to predict or guess how a seed is spread. But, how do we gather evidence to support our ideas so that we know that they are correct? Use these starter questions to help you with the challenge below.

The challenge

Your teacher will supply several different types of seeds for you to investigate. The picture below shows examples.

How are the seeds you are supplied likely to be dispersed?

• Give your reasons based on evidence from observations, measurements, simulations, trial and error and experiments.
• If you think animals are involved in dispersing the seeds, give evidence for what animals they might be.
• Use a magnifying glass or microscope to help with your observations.
• Draw and label each seed and add notes.

Lesson 3: Study seeds in the wild

The challenge

In Autumn, search high and low for seeding plants.

Possible collection sites include:

• roadsides
• parks
• wasteland areas
• native bush (but not reserves)
• school grounds
• home gardens.

Take photos of each plant and closeups of where the seeds are on the plant. Collect samples of the seeds and the structures they are found within, like pods, stalks, fruits and cones. Collect at least 10 different samples. Scissors and secateurs will be helpful.

Back in class

Using what you have learnt:

• use evidence to decide how each type of seed is dispersed
• discuss and debate your claims with your classmates
• see if you can agree on the most likely way or ways the seeds are dispersed
• decide on a way to communicate your findings to others (examples: poster, digital display, demonstration, a talk).

Lesson 4: Can we help native plants to spread?

The challenge

Now that you know how seeds can be spread, come up with a plan to help the spread of native seeds in an area you choose. The seeds could be from native trees, shrubs, flaxes, toetoe, tussocks and other small native plants. Organise the resources you need and put your plan into action.

Starter hints

• A lot of large fruits produced by native plants are spread by kererū (otherwise known as NZ pigeons or wood pigeons). But unfortunately rats, stoats, feral cats and possums are eating kererū eggs and chicks in large numbers. These introduced predators also kill korimako/bellbirds, tūī and tauhou/silvereyes that spread smaller fruit. What could you do about the predators so you can help the birds that in turn help plants disperse their seeds?
• Seed bombs can be used to spread seeds over 'throwing distances'. Can you use them to spread seeds? Make sure you only use native seeds from plants that are naturally found in your area.
• Some seeds can be easily spread freely and widely. This is because they can be collected in huge numbers and scattered in the wind. Which seeds could you use this way?
• Some seeds like kōwhai are easy to germinate, then plant by hand. This link shows you how.

Lesson 5: Can we slow the spread of weeds?

The challenge

Weeds compete with native plants, suffocating them and slowing regrowth. Now that you know how seeds can be spread, come up with a plan to slow the spread of weeds in an area you choose. For example, this could be in a regenerating native bush area or in a garden.

Starter hints

• How could you stop some weeds from releasing their seeds?
• How could you remove the weeds altogether?
• Different types of weeds release their seeds at different times of the year. How does that knowledge help us?
• Some weeds are persistent, meaning they keep growing back after you cut them down. How could you destroy them forever?

Going further

• Find out about local native area restoration projects.
• Find out how some plants have become nuisance or noxious weeds because of how they grow and how they disperse their seeds.