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Friday, March 22, 2019  Spokane, Washington  Est. May 19, 1883
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Gardening: Potted plants need mix of science and art

My husband’s Mother’s Day gift to me was to just turn me loose in the garden to play. I had a great time planting my deck pots. Yes, I know I’m taking a chance on a frost but that is what tarps are for.

Planting good looking summer containers is a mixture of art and science with a little gambling thrown in for excitement. The science part involves using the right size container, good-quality potting soil and an efficient watering system.

Size matters when it comes to providing enough space for plant roots and keeping the soil cool. It also depends on the space you have for the containers. Generally, the larger the container, the better the growing space for your plants. Heavily planted pots will have lots of roots that must be kept happy through the summer. Small containers sitting in the sun all day can heat up enough to cook the roots and kill the plant. In general, 18- to 24-inch diameter pots work the best. The exception is if you are placing the pots on an apartment balcony or some other unreinforced roof or deck. Wet soil is heavy and when several wet, heavy pots are in such a space, there is the potential for a collapse.

Ordinary garden soil should never be used in containers. It becomes brick-hard and can contain a lot of weed seed and diseases. Use a quality potting soil instead. Large bags of soil are available at most garden centers, and it will take about one bag to fill an 18- to 24-inch pot. Most potting soils are a mix of compost, peat or coir fiber with vermiculite or perlite added to improve drainage.

Be careful when purchasing mixes that are high in peat. In our hot, dry climate, peat dries out quickly and is very difficult to re-wet once it’s dry. It is not necessary to put fresh soil in your pots every year. Just mix in a few inches of new soil in each year and then mix in a half-cup of a low nitrogen fertilizer to perk up the nutrients in the mix.

Keeping containers watered can be a real challenge, especially when temperatures reach 90 degrees and above and the air is at 15 percent humidity in July and August. Small containers may need to be watered a couple of times a day. This can be a challenge if you work or want to take a vacation. Relying on the neighbor kid to water doesn’t always work well.

In the past few years there has been an explosion of inexpensive drip irrigation systems that can be set on battery powered timers that will water at whatever interval you need. I use a system that has heads set one to a container that spray a two-foot pattern. It comes on for 15 minutes early in the morning every other day. The kit cost me under $50 and the timer was about $30 from Lee Valley Tools;

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