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Weed it and Reap – Container Gardening

By: Idaho Botanical Garden | 06/29/2021

Container Gardening

Want to grow plants in an area with no open soil, such as on a porch, patio, or by a door? Put them in a pot, half barrel, or other container. Container gardens also comes in handy to corral something that would take over your yard if you give it half a chance such as mint, lemon balm, or garlic chives. They also can add vertical elements to your landscape.  Here are some container gardening tips.

Container Size and Material

Larger containers hold more soil, stay moister longer, and are slower to heat and cool.  They better accommodate plants with long roots.  Once planted, a large pot is very heavy, so it is best to assemble it in the location you will want it placed.  If you have a very large container, but do not want to fill the whole thing with soil, you can place a shallower one inside the larger one and plant that. The smaller one could have a lip that hangs over that of the larger pot, or you can set it on an overturned pot that acts as a pedestal inside the larger container.

Lighter colored pots stay cooler in the sun than dark ones.  Terracotta pots may break if kept outside during the winter, while wood, concrete, metal, fiberglass, and plastic ones may be left outside.

Drainage

Your container must have drainage holes to keep roots from rotting in standing water. It is best not to cover the holes with rocks or bits of pottery before adding soil. Blocking the holes is unnecessary for keeping soil in place and can cause drainage problems.

Soil and Fertilizer

Be sure to use good potting soil formulated for use in containers. Garden soil and top soil will not work well in a container. Before placing it in your planting container, moisten the soil and mix in some slow release fertilizer.  Containerized plants need more fertilizer than those planted in the ground since potting mixes do not have the nutrients and microorganisms found in native soils.  In addition, water draining through the soil carries away some of the minerals present.

When filling the container with soil, stop when it is a couple of inches below the rim. This will allow the water to pool before it soaks into the soil when you water, instead of spilling over the rim.  

Plant Selection

Before purchasing plants, watch the location the container will go for a few days. Note how much sun the area receives, and if it becomes very sunny, whether the sun is there in the morning or afternoon.  This information will help you determine which plants will do well there.  Full-sun plants prefer 6 or more hours of sunlight each day.  Part-shade plants thrive in 3-6 hours of sun, but do not like afternoon sun. Shade plants do best with less 3 hours of sun. This includes dappled light.  

Ornamental, as well as edible plant displays, may be attractively arranged as Thrillers, Spillers, and Fillers. A thriller plant is a tall, eye-catching plant planted in the middle or back of a pot.  Spillers are long, vining plants planted at the edge that grow to hang over the side of the container.  Fillers are upright plants shorter than the Thrillers and take up the remaining space.

Make sure that all the plants that will be together have the same watering requirements.

Planting

In a container plants may be spaced much closer together than they would be when placed in the ground. After the soil is moistened, fertilized, and placed in the container to a level below the rim, dig a hole the depth of the pot the plant will be removed from.  Remove the plant and loosen the roots to encourage them to grow outward away from the stem. If the roots were circling the pot or so numerous that they are in a tangled mess, you can cut off the ones at the bottom and cut slits into the sides of the root ball with a knife or scissors. Then pull them apart gently. This will stimulate new roots to grow out into the soil. Next, place the plant in the hole so that the new soil will come up the same level as the soil it came with. Tamp it down gently so the roots have good contact with the new soil.  

Watering and Care

After planting, water them in.  Use the information on the plant tags to determine what their requirements are. In general, you want to keep the soil moist. Depending on the amount of sunlight the pot will receive, your containers may need to be watered twice a day during the hottest part of the summer.  A slow release fertilizer, such as Osmocote, lasts up to 4 months, so additional fertilizer may not be needed.  

Over the growing season, replace plants that are not thriving, prune back plants that are getting too long or leggy, and remove dead leaves and flowers to keep your container looking lovely.

June Gardening Tasks

Plant ornamental annuals, tomatoes, peppers; seeds of beans, cucumber, pumpkin.

Keep up with weeding, mulch planting beds to help conserve water and reduce weeds.

Prune spring flowering shrubs, if needed, after bloom.

Clean up bulb foliage after the leaves die back.

Watch for pests and other plant health issues.