This is the only lesson in the course that does not touch the canvas. Before you put anything in the ground it is worth understanding what GardenCAD thinks a species is, because a species here is not a name and a picture. It is a small bundle of numbers: how far apart these plants want to be, how wide and tall one gets when it is mature, how much sun it needs, how long it takes to be ready, and what it gives you when it is. Every one of those numbers is used by something later. Spacing drives the automatic fill in the next lesson. Mature size drives the canopy shadows in the lesson after that. Sun need is what the editor compares against the light your bed actually gets when it warns you that a plant is in the wrong place. Understand the species record and the rest of the editor stops looking like magic.

Three objectives. First, you will be able to open the plant library, browse it, and make a species active, and you will know what becoming active actually does: every planting you place from that moment on inherits that species' spacing, size, colour, and sun need. Second, you will be able to add a custom species for anything the built-in catalogue does not know about, and edit the defaults on a built-in one when your variety differs from the generic entry. Third, you will be able to build a plant queue, which is the editor's version of a planting list: species and quantities you intend to grow, with a running count of how many you have actually placed against how many you planned. The queue is what the guided planter reads from two lessons on, so it is worth filling in properly.

A species record is five numbers and a name. Spacing is how far apart these plants want to be, and it is what the automatic fill uses to decide how many fit in a bed. Mature radius and mature height are how big one gets when it is grown, which is what the plan draws and what casts a canopy shadow. Sun need is the amount of direct light the plant wants, and the editor compares it against what your bed actually gets. Days to maturity is when you can start picking. And an optional yield tells the editor what one plant gives and over what period, which is what the harvest calendar on the printed plan is built from. When you click a card in the library you are not choosing a picture, you are loading those numbers into every planting you place next.

The plant queue is the second half of this lesson and it is easy to walk past, because it looks like an inventory panel and it is really a planning tool. Open it beside the library and add the species and quantities you actually intend to grow this season: twelve lettuces, six tomatoes, a dozen garlic. Each row then keeps a running count of how many of that species you have placed in the garden against how many you planned, so the queue answers a question the canvas cannot: have I finished? Two rows still at zero are two things you have forgotten. It also feeds the guided planter in Lesson 06, which reads the queue and lays it out across the beds you select. And because it is a real list with quantities, it works as a shopping list to take to the nursery.

Four steps. First, open the plant library from the tool rail and browse. Click a card to make that species active, and the rail will show it as the current species. Second, set the Plant and Seed toggle, which decides how the species goes into the ground: Plant drops individuals at the species' spacing, and Seed sows a striped patch that carries a seed count instead. That distinction matters for anything you broadcast rather than transplant. Third, if the catalogue does not have what you want, press New and add it, giving it at least a spacing, a mature size, and a sun need. Custom species save into your browser and behave exactly like built-in ones. You can also edit a built-in to match your variety, which writes an override rather than replacing it, so existing plantings keep working. Fourth, open the queue and add species with the quantities you plan to grow.

Two minutes before you go and plant anything. Think about the difference between what you want to grow and what your site can actually carry, because the editor is about to be very willing to help you overplant. Ask how much sun each thing on your list needs, and whether you have that much anywhere. Ask what the plant looks like at maturity rather than at planting, because a courgette that is charming in May is a metre across in August and the spacing number knows that even when we do not. And ask honestly how much you will actually eat, since the commonest gardening mistake is not a design error at all but twenty lettuces ready in the same week. Hold those answers, because the next lesson makes it very easy to fill a bed completely.

Three things. A species is a bundle of numbers, not a label, and clicking a card in the library loads those numbers into everything you place next, which is why the library comes before the planting. Anything the catalogue does not know can be added, and any built-in can be overridden to match your variety without breaking the plants that already reference it. And the queue is the piece that turns a canvas full of shapes into a plan you can finish, because it is the only place that knows what you intended as opposed to what you have drawn. Fill it in now. The next lesson is the one everybody wants to get to, putting plants in the ground, and it reads straight out of the list you just built.