Deb Babcock: How and when to fertilize houseplants

Indoor plants need fewer nutrients during winter months

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Deb Babcock

Deb Babcock's gardening column appears Thursdays in Steamboat Today.

Find more gardening columns here.

— During winter months, with their short daylight hours, your houseplants need little to no fertilizer unless they reside under artificial lights or the plant instructions require fertilizer during more dormant periods.

Once spring arrives, however, your houseplants likely will need fertilizer — perhaps as often as once a month during summer.

Unlike their brethren out in the garden, houseplants don’t receive regular replenishment of nutrients through ongoing soil decay or airborne and animal-borne mineral deposits. Indoor gardeners need to add food supplements to the soil in our planters because the initial nutrients become used up by the plant or washed away during waterings.

The three most important nutrients that your houseplants need are nitrogen, phosphorus and potassium. The symbols you find on plant fertilizer packages will tell you how much of each of these nutrients is contained in the package. Look for NPK, which stands for Nitrogen-Phosphorus-Potassium, along with percentages such as 5-10-5, meaning the package contains 5 percent nitrogen, 10 percent phosphorus and 5 percent potassium, with the remainder of the package containing filler.

Plant fertilizer can come in a variety of forms, including liquid, granular, slow-release granular, crystalline, powder, fertilizer stakes and tablets. All forms work well.

If your houseplants are primarily foliage as opposed to flowering, a balanced 20-20-20 is an ideal fertilizer composition. Flowering plants will do better with a 15-30-15 composition. Plants in low light will need less fertilizer than those in sunny locations.

Be sure to follow the directions on the label of the fertilizer package, and don’t give in to the temptation to over-fertilize, which will cause numerous problems including burn marks on roots and foliage, an unattractive white crust on the top layer of soil, and spindly growth. Over-fertilizing also will cause your plant to outgrow its pot and space too quickly.

Apply fertilizer to somewhat moist soil, never to bone-dry soil.

Every six months or so, you should leach your pots by pouring a large volume of water through the soil and allow to flow out the bottom. Be sure to drain the saucer so the plant doesn’t sit in standing water.

If you’ve recently purchased a houseplant, chances are it won’t require any fertilizer for several months as it was probably well fed in the plant shop or department.

Deb Babcock is a Master Gard­ener through the Routt County Extension Service. Call 970-879-0825 with questions.

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