Repotting Houseplants

Houseplants on the Windowsill

By Amy McDowell

Houseplant is such an ordinary name for something really wonderful. They are one of the delights that sustain my itch to garden in winter. My favorites are the philodendrons, and I have a collection of ten different kinds. There are hundreds of species of philodendrons, from tiny vines with thumbnail-size leaves to climbing monsters that can cover a home in a tropical environment.

There are two main reasons I dearly love philodendrons. I love the way the new leaves emerge and uncurl. That tender new growth reaching out reminds me of spring. And best of all, philodendrons are rarely targeted by insects. I have never had insects on my philodendrons, although some of my other houseplants get to be a mess with pests.

This is the time of year I work on repotting. With only mountains of catalogs, books, and magazines to keep me occupied, I enjoy working my hands into the potting soil.

Most houseplants are happiest when their roots are somewhat snug in their pots, but it is a good idea to slip the root ball out of the pot annually to take a look. I generally repot a plant once every three to five years.

The standard rule of thumb is to only go one pot size larger when repotting. If you transplant into a much larger pot, the plant sits in the center of all that new soil and struggles to overcome the transplant shock. The excess soil surrounding the roots holds too much moisture, and that can lead to root rot.

Many gift plants come in decorative sleeves that don’t drain. You’ve got to toss the sleeves right into the wastebasket and give your plant a pot with good drainage and a saucer underneath so you can dump out the excess water. The pot doesn’t have to be fancy—a healthy houseplant will become the focal point and a plain plastic pot will fade into the background.

Tending to houseplants is one of winter’s joys. With a little care, your windowsill garden can carry your spirit through until spring.

Oooh, that awful dry air in winter!

Houseplants and humidity

By Amy McDowell

When I was in charge of watering inside the dome at the Des Moines Botanical Center, I watered more than just the plants. I also soaked the concrete walls and pebbled paths. The plants, screaming for moisture, needed more than just a drink of water—they needed high humidity like the tropical rainforests of their origins.

During these cold winter months, the dry outside air is sucked into our furnaces, heated, and pumped through the heat vents throughout our homes. And just as we suffer with dehydration such as thirst, dry, itchy skin, tired, burning eyes and tender sinuses, our houseplants are suffering with dehydration that shows itself as curling leaves, dry brown leaf tips, yellow leaf margins, shriveling, wilting, bud drop and limp, weak growth.

The water that houseplants take up through their roots is used for growth, but much of the moisture is released, or transpired, through tiny holes in the stems and leaves called stomata. Winter air pumped through our furnaces is so dry that it rapidly taxes houseplants beyond their capacity. There are a number of things you can do to raise the humidity level and aid plants, and it doesn’t even require watering your walls and floors.

·        Humidifiers are the simplest and most effective method to raise humidity.

·        Group plants close together so they can benefit from each other’s transpired moisture.

·        Make pebble trays. Fill sturdy plant saucers with pebbles and water and place them around your houseplants. The pebbles create more surface area than just a dish of water so it will evaporate quickly.

·        Turn down the furnace. Plants will transpire less moisture if the furnace isn’t running as often. Also, keep plants away from heat vents and drafts.

·        If the kitchen or bathroom is bright enough, move plants there, where humidity is often higher than the rest of the house.

·        Misting plants is the least effective option. It is a short-term, temporary solution that must be repeated frequently throughout the day to even make a difference. In addition, water droplets on the leaves may lead to disease.

Tropicals and Frost

Tropicals, take cover. F – f – frost is here.

By Amy McDowell

It’s time to blast the bugs off and bring your tender houseplants inside. Use a one-two punch on those insects to make sure you don’t bring them into your home. First, sprinkle systemic insecticide granules on the soil. When you water, the systemic is absorbed by the plant’s roots and circulated throughout the plant, making it toxic to insects. A systemic can last in the plant’s system for three months. Your second punch is to wash the plants thoroughly—tops and bottoms of the leaves and all along the stems—with a firm blast of water from the hose. Soft-bodied insects like aphids and spider mites can’t survive an aggressive washing. Let the plants drip dry outside before taking them in.

No doubt your tropical plants have grown over the season. You may want to prune and reshape them before taking them inside. Many plants suffer shock from being transferred indoors – you will see the telltale leaf drop. Pruning before you relocate them will not only improve their appearance, but may reduce your leaf cleanup later.

Dig ‘em up

Tender bulbs and tubers should be dug up and stored now – things like cannas, dahlias, and gladiolas. After our wonderful regular rains throughout most of the season, you will find those canna tubers underground are now huge. Pry them out of the ground with brute strength and as much gentleness as you can; they will bruise. Cut the stems back to about four-inch stubs, brush the soil off, and store them in an uncovered crate or open box in your basement. The care is the same for dahlias and glads.

Put ‘em in

Spring bulb sales in the U.S. have been declining for several years, and people in the industry believe it may be because spring bulbs don’t provide the instant gratification that other flowers in the garden do.

Here in Iowa, we tuck bulbs into the ground in October and wait for about six months before we see their bright blooms in spring. Who needs instant gratification? Just knowing those spring bulbs are nestled in the ground under the ice and snow gives us something to look forward to all through the blustery winter.

Even just a few dollars spent on a handful of bulbs can provide a cheery bouquet next spring and for many springs to come.

Amy McDowell is an Iowa Certified Nursery Professional. She has an associate’s degree in commercial horticulture and has worked in the field for ten years. She lives and gardens in Polk County.