Home & Garden Garden 4 Steps for Assembling a Great Container Garden By Katherine Martinko Senior Writer University of Toronto Katherine Martinko is a writer and expert in sustainable living. She holds a degree in English Literature and History from the University of Toronto. our editorial process Twitter Twitter Katherine Martinko Updated October 11, 2018 CC BY 2.0. Doug Beckers Share Twitter Pinterest Email Home & Garden Planting Guides Indoor Gardening Urban Farms Insects This summer, add flowery glamor to your outdoor space with potted plants. Container gardens are assortments of plants grown in pots or boxes of various sizes. They can be kept on balconies, rooftops, patios, and decks, adding visual interest, shade, and privacy, not to mention the pleasure that comes with seeing beautiful flowers and harvesting vegetables. Writing for the Washington Post, gardening expert Adrian Higgins shared his tips for putting together a show-stopping collection of containers that thrives all summer long. Some of his most useful, basic tips: 1. Learn the 'thriller-spiller-filler' rule. This is a generally accepted guideline for choosing plants to fill a container. The thriller is the focal point, a tall dominant plant that will grow upward. The spiller is a lower-height plant that will spill over the lip of the pot and downward. The filler fills in the remaining gaps. 2. Choose pot size carefully. Check the final growth size of the plant you want and pick a pot that will accommodate that. It's better to have a too-big pot than one that's too small. Higgins writes: "The larger the pot, the less stress is placed on the plants; soil temperatures are cooler, the soil dries out more slowly and roots can go deeper." Having a variety of pot sizes usually looks the best. Metal is typically not recommended because it can be too hot for plants. You can also explore fabric planter options, such as these ones outlined by Ramon Gonzalez for TreeHugger. Helen Olney/CC BY 2.0 3. Buy new potting mix. Using soil from previous years is not recommended, as it could contain residual fertilizer salts and fungus and be overly compacted. Similarly, soil from the garden should not used as it will harden when wet. From Better Homes & Gardens: "Quality potting soil should include generous helpings of some of the following amendments: peat moss, compost, perlite, vermiculite, and/or rotted manure. Inexpensive potting soils are not always a bargain, so read the label before you buy." If filling big pots, it can be expensive to buy potting soil, so consider filling the bottom half with compost. Higgins does not recommend using foam peanuts or other inert bulk material, as it results in less soil that roots may need and makes a pot top-heavy. You might have to add soil after potting and watering several times, as the soil will settle and could expose roots. 4. Water wisely. A pot should always have drainage in the bottom , as this prevents roots from rotting. Set containers on the ground, not a saucer, although being raised on legs is fine. Water daily with a watering can, where you can mix extra feed if needed, until you see water running out the drainage hole. Skip only if you've had a drenching rain. See Higgins' original article for guidance on choosing plants.