Lesson One

Welcome back to the Greenhouses! We won't be here much though, as we'll be venturing outside to undertake fieldwork in the land around the castle.

This term, we're going to be looking beyond individual plants to their natural habitats. How and where do they grow in the wild? How do they respond to what's around them? How can we apply that knowledge?

We know that nearly all plants need water, sunlight and nutrients to grow but they also rely on many other living things (organisms). That includes other plants, animals, tiny microorganisms in the soil and so much more.

For an example, let's look back at the fanged geraniums you will have studied before. They're not shy about taking a chunk out of us if we don't treat them right but you'll rarely see them snapping at a bee. That's because flowering plants need bees and other pollinators to transfer pollen from one flower to another. Otherwise, they can't produce the seeds necessary to keep their species going. The bee, on the other hand, needs the pollen and nectar from the plant to keep itself and its own species alive. There are plenty of relationships like this, connecting a huge variety of species in a complicated web (sometimes called a 'food web').

You can roughly break that web of relationships down into the following: producers (organisms that create their own energy), consumers (organisms that have to get energy from other organisms) and decomposers (organisms that live off waste matter and break it down).

On a rare occasion, a plant might be a consumer. It could be carnivorous, meaning it eats other organisms itself. For an example of that, look at our friend the venomous tentacula over there... Actually, would someone mind chucking it a handful of chizpurfles? It's looking peckish.

Plants can also be parasitic, meaning they take what they need from other plants. A parasitic plant you'll be familiar with is mistletoe: this pretty plant with its striking white berries is a common Christmas decoration and a potions ingredient too. To live, it latches onto other plants and sucks out the goodness it needs.

Decay might be a very unpleasant thing but it's incredibly useful. In fact, it's how we get compost. I have a bin behind greenhouse 3 where I collect the plant waste we generate in the greenhouses and the vegetable peelings from the Hogwarts kitchens. Over time, decomposers turn it into a material that's chock full of nutrients which we can then add back into the soil to help the plants.

All of these factors (the living and the non-living ones) ad up to create an ecosystem. That's the word we use to describe the network of living and non-living things that make a location what it is. An ecosystem could be a pond, it could be a patch of grass or it could even be a jungle. Ecosystems don't have to be large - they could be as small as a puddle. Big or small, if you change just one thing in an ecosystem, the consequences could be huge for the organisms living there.

Our greenhouses are like artificial ecosystems. We've designed things here to make sure that the plants get exactly what they need. From the glass walls to maximise the sunlight to the fertiliser we use to ad nutrients to the soil, everything is carefully managed to boost a plant's chances of doing well. As herbologists, we're a crucial part of the ecosystem. If we stopped doing what we're doing or changed something, it would make a massive difference to the plants.

Plants in the wild don't have us carefully pruning them or giving them an extra sprinkle with the watering can - they have to look out for themselves. To survive, a plant has to rely on what's around to get what it needs. Plants often have special features that enable them to make the most of the natural resources available. Those adaptations can be fascinating and they help us to understand how we can better care for the plant when we grow it, so that's why we're focusing on them for this class.

Terminology

For the rest of this lesson though, I'd like to take you through a few important terms:

Abiotic Factors: Those parts of an ecosystem that aren't alive, like the landscape, temperature, soil composition, water, climate and weather.

Biotic Factors: All the parts of an ecosystem that are alive, like plants, animals and microorganisms.

Competition: When more than one organism needs a resource and has to compete to get it. It could be members of the same species competing against each other or members of a totally different one. You can see this with plants as they grow taller and taller to make sure they get sunlight, often putting smaller plants in the shade.

Dispersal: The process where plants spread their seeds over as wide an area as they can. This can happen in many ways, like seeds being carried by the wind. Next time you blow on a dandelion clock, remember that you're helping the seeds disperse.

Indicator: A species that lets you know that a particular thing is present in the environment. They do this by just being there (moss is often an indicator of acidic soil), by not being there or by changing in a particular way (the leaves of buck's horn plantain change colour depending on the amount of salt in the soil).

Organism: A living thing. That includes animals, plants and microorganisms.

Parasitic Plants: These are plants which don't generate all their own energy. Instead, they latch onto another plant and feed on it, a little like a vampire. As previously mentioned, mistletoe is a good example of this.