Planters 101: Quick Tips on Designing and Planting Annuals for Maximum Impact

As spring bulbs fade and flowering trees begin their parade of blooms, gardeners in Northern Michigan prepare for Memorial Day weekend–not only for the family barbeques, but also for all of the planting that’s sure to happen! This far north, Memorial Day weekend is typically when people begin to plant new flowers in their gardens, as we’re finally safe from any surprise frosts.

With that in mind, we wanted to share some tips with you about a spring gardening project that, when done well, gets better and better as the season progresses: planters! In this blog, we’ll cover the concept of thrillers, spillers, and fillers, as well as share some tips on plant choices and how to use planters in your landscape.

Designing a planter: Fillers, Spillers, and Thrillers

A popular planter principle is the idea of fillers, spillers, and thrillers. These terms refer to the different functions different kinds of plants play in a planter design. Fillers are plants that take up space within a planter; spillers are those that grow to drape over the side, spilling out of the planter; thrillers are typically tall and add drama to the overall design. Put together, these plants create a statement piece that brings unique visual interest to new areas of the garden.

While fillers, spillers, and thrillers is a common planter design principle, it’s certainly not the only way to fill a planter! Many people appreciate the look of only spillers, like petunias, and these work especially well in hanging baskets or elevated planters where they have plenty of room to cascade down the sides. The most important planter design principle is to find what brings a smile to your face, which will likely mean experimenting with different designs and flowers–but that’s a big part of what makes planters so much fun!

Here, an artistic flower pot is filled with a combination of blue Torenia (a spiller), white Euphorbia (a filler), and a multi-colored Coleus (a thriller). In the background, the taller flower pot carries a silvery Supertunia (a spiller), light blue Lobelia (a spiller), hot pink Sunpatiens (a filler), and a spikey Dracaena (a thriller).

What plants should you use in a planter?

Picking what flowers you’ll use in your planter is one of the most fun parts of filling a planter–and also one of the most intimidating! With a seemingly endless variety of plants to choose from, it can feel overwhelming to stand in the garden center with an empty flower pot. As you look at plants, keep in mind where you’ll be placing your planter–sun or shade will help narrow down your selection–and consider what plants are already growing in your garden. Do you want to echo the colors and textures that are already there, or are you looking to create something that will stand out from the rest? This decision will also help you narrow down which plants to choose from.

We’ve collected a short list of some of our favorite plants to use in planters and separated them by sun and shade, as well as noting whether they’re fillers, spillers, or thrillers. These plants consistently perform well in planters on our client sites and can be combined for some truly unique looks.

For planters in sunny locations, try:

• Supertunias (spiller)
• Pennisetums (thriller)
• Geraniums (thriller/filler)
• Sunpatiens (filler)
• Lemon Coral Sedum (spiller)
• Señorita Rosalita Cleome (thriller)
• Begonias (thriller/filler)
• Lemon Licorice licorice plant (spiller)

For planters in shaded locations, try:

• Impatiens (filler)
• Dracaena (thriller)
• Coleus (thriller)
• Asparagus fern (spiller)
• Sweet potato vines (spiller)
• Euphorbia (filler)

How to plant an annual planter

All right, you’ve picked your plants and have your planter–now what? Here’s a step-by-step guide to help you put your planter together:

1. Fill your planter to a couple inches below the top with the potting soil of your choice. This will give you space to add your plants without having to remove too much soil along the way.
2. Add a slow-release fertilizer to the potting soil. This will provide nutrients for your plants as they settle into the planter and put out new roots. Whatever fertilizer you choose to use, make sure to follow the directions carefully.
3. Arrange your plants in the planter–before you plant! Even if you’ve got a firm idea of how you think the plants should be arranged, laying them out in the planter before digging in will help you decide if you like that idea or if you want to try something else.
4. Once you’ve decided on your ideal arrangement, remove the plants from their containers and start digging in. As you plant, you might find that you put too much soil in your planter in the beginning. That’s okay! Take some out and put it in the empty plant containers, and once all your plants are in, you can use it to fill in any empty spaces between the plants.
5. After everything is planted in, water the planter well. During this stage, you might notice the soil settling around your plants. If it settles too much, revealing the plant roots, just add more potting soil to fill it in. Water until you see water trickling out of the bottom of the pot.
6. Take a step back and admire your work! For best growth, be sure to water your planter regularly and add fertilizer as the season progresses. Fertilizing throughout the season will give your plants the nutrients they need to thrive all season long.

How you can use planters in your garden design

When it comes to how you use planters, the options are nearly as limitless as what plants you can put in them. Often, planters are placed on porches or patios. This brings the garden a little closer to where people tend to gather and puts color and texture in places it might otherwise not reach.

Some planters can also double as statement pieces within flowerbeds. Planters that are particularly tall or placed on elevated stands are often used strategically in garden beds as a visual focal point, bringing another layer of interest to the planting design. These planters are often bold and artistic, utilizing the concept of fillers, spillers, and thrillers to become a statement piece that adds continuing interest all season long.

Planters can also be used as seasonal decorations–meaning they get emptied and refilled throughout the year to accommodate the current season. Spring planters often feature spring bulbs, like hyacinths and tulips, which are later replaced with summertime annuals. In fall, pumpkins or other gourds can be incorporated into planters with ornamental kale and mums, and winter planters frequently feature evergreens and the bright branches of red twig dogwood.

Planters are an incredibly fun way to experiment with new plants in new places and let your creativity run wild. We covered a lot in this article, but the most important thing we want you to remember is that, when it comes to your annual planters, you’re the boss! You get to decide what you like–and that’s allowed to change every year. After all, the most important part of putting together a planter is the fun you have while doing it. Happy planting!