Master Gardeners: Tips for successful container gardening

Apr 29, 2023

Spiller, thriller and filler: Container gardening can provide year-round beauty, but there are some do's and don'ts.

Editor's note: This is part one of a three-part series on container gardening.

Containers are great for people with limited mobility as well as people living in apartments or who have minimal space in a yard. But another option is bringing plants in during the winter, especially herbs and vegetables that can be harvested and eaten.

If you have a sunny window, a protected balcony or patio, you can have fruits, vegetables, herbs and flowers. Annuals and vegetables look great in containers, and you don't need to be concerned about hardiness zones when growing them indoors. Containers with flowers look best with spillers (a vine or trailing plant), fillers (the middle layer), and thrillers (usually the tallest and most dramatic plant).

Growing in containers requires some special instructions. Here are some tips on how to best grow in containers:

Use an all-purpose potting mix that includes a blend of ingredients, such as peat, vermiculite, perlite, sand and bark. There are special mixes such as extra-sandy for succulents or an organic, compost-enriched mix for edibles. Or enhance a lightweight, peat-based mix with compost and polymer crystals, making it more moisture retentive for window boxes, hanging baskets and other containers that dry out quickly.

Refresh the soil annually with fresh potting mix plus a dose of slow-release fertilizer.

Place a heavy container where you want it before planting.

If using a terra-cotta pot, soak it in water first. If the pot's drainage hole is large, cover it with screening, newspaper or a coffee filter to prevent soil from leaking out. If a container has no drainage hole, it is best if you poke a hole or two in the bottom if possible. It is then necessary to put a tray beneath the pot to ensure that water is seen in order to make sure the roots have adequate moisture. If your containers have no holes, you can also accidentally drown the plant.

It is best to lay a coffee filter or hardware cloth to cover the hole so soil does not come out the bottom. Fill the container three-fourths full; blend in slow-release fertilizer and water-retentive crystals and then top with plain potting mix. Arrange plants in their original containers in the pot, starting with the largest or tallest, and finish with the smallest ones. Place the largest plant in the center for a symmetrical design or off to one side for an asymmetrical balance. Rearrange the plants until you’re satisfied with the arrangement.

Just before planting, dip each plant's root ball in a solution of water and root stimulator formulated for transplants. Remove the largest plant from its nursery pot and set it in the container, adding potting mix around the root ball. Set the smaller plants in place. Fill in between plants with soil mix without packing it.

If you want to plant seeds, sow them directly, following packet directions. Leave 2 inches between the top of the soil mix and the container for water and mulch. After planting, moisten the potting mix throughout (until water runs out the pot's drainage hole). Place the plants in shade for a few days to help them recover from transplanting before placing them in their permanent positions.

Containers usually require watering daily during summer or every two or three days during cooler periods unless it rains. Hot, dry weather and small pots can necessitate twice-daily watering. Plants suffer from too much water as much as from too little. Determine if a container garden needs water by poking your finger into the soil up to the second knuckle or use a soil moisture meter. If the soil feels dry, it's time to water. Check pots daily. Saturate the potting mix thoroughly. Excess water should drain away from the containers. Soil sours, roots rot, and root-killing mineral salts build up in a container that drains poorly. If a soil-less mix dries out completely, re-wet it by standing the pot in a large vessel of water overnight.

Watering early in the day is best. It allows plants to soak up what they need before afternoon heat causes excessive evaporation. Watering in the evening can leave moisture on foliage and promote disease. Use a watering can to water if you have just a few containers; use drip irrigation set up on a timer if you have more than a few containers. This takes the work out of watering. A drip system also saves water by delivering it near plants’ root zones with as little evaporation and runoff as possible.

Check the system seasonally, especially in hard-water areas to make sure the timer works, and lines are not clogged or punctured. Self-watering pots have a built-in reservoir that delivers moisture to the soil. They require watering less frequently. Water-holding mats fit into the bottom of hanging baskets and other containers, wicking moisture into the soil.

• If you have gardening questions, feel free to call 509-574-1604 or email [email protected] and ask a Master Gardener.

Comments can only be made on article within the first 3 days of publication.

Please select all the ways you would like to hear from us:

You can unsubscribe at any time by clicking the link in the footer of our emails. For information about our privacy practices, please visit our website.

We use Mailchimp as our marketing platform. By clicking below to subscribe, you acknowledge that your information will be transferred to Mailchimp for processing. Learn more about Mailchimp's privacy practices here.

The Yakima Herald-Republic is hiring.