Container Thrillers, Fillers and Spillers

by Marilyn Odneal, Horticulture Advisor

MOUNTAIN GROVE, MO – Container gardening is fun – kind of like arranging flowers in a vase – except, of course, the plants in your container have roots and will grow. Containers allow gardeners to garden even if they have no yard at all. Containers are mobile – you can move them around to rearrange your outdoor décor. In the last column we talked about the different materials used for plant containers and the importance of holes in the bottom of the pot so the water will drain through. This week we are going to talk about planting and maintaining an ornamental container garden.    
     Sterile potting media is best for containers because regular garden soil does not drain well in a pot. You can buy pre-mixed bags of potting media and may choose some with added fertilizer and water absorbent crystals. You may also mix your own using ingredients such as sphagnum peat moss, perlite, vermiculite, shredded bark, compost and sand. You can add 5 – 15% of sterile soil for added weight and nutrient holding capacity.
     To get going, begin with a clean container and put some screen or similar material over the drainage holes so the potting media does not wash through. Fill the pot with media about 2/3 full to leave room at the top for your transplants to fit. Water the media and let it drain through. Then choose your plants, take them out of their containers, and set them on the watered media. After you arrange your plants, fill the gaps between them with more media until all the spaces are filled. Leave at least 1 inch from the top of the pot to the top of the media, so there is room to fill with water. If you are planting seeds in your container, fill it up to about 1 to 1 ½ inches from the top. The last step is to water the container again.
     A good design scheme for a mixed ornamental container is to choose an upright, tall plant; a cushion shaped plant; and a trailing plant; a thriller, a filler and a spiller. The different plant forms give interest to the container. Of course you can just choose one plant if you want to – a single geranium in a terra cotta pot is always beautiful.
     There are many fertilizer products available for your container plants, the most common being slow release pellets that are mixed into the media or soluble fertilizers that you mix in water. Make sure you follow the instructions that come with the product you choose.
     And of course, the water! We left room at the top of the container for water. Containers will dry out faster than plants in the soil, so you need to make sure you can water your containers regularly and be prepared to water them as much as twice a day in hot weather. A pot less than 10 inches in diameter will dry out too frequently outdoors, so it is best not to use a smaller size container for your patio and garden containers. Have fun!
     Please direct comments or questions concerning this column to Marilyn Odneal via email at MarilynOdneal@missouristate.edu; write to Missouri State Fruit Experiment Station, 9740 Red Spring Road, Mountain Grove, Mo. 65711; or call (417) 547-7500.