Growing Together: 10 steps to better houseplants

Don Kinzler
Forum News Service

Have you ever wondered who first brought a plant indoors and declared it a houseplant? Cave people were probably busy with other pursuits, so it likely came later.

We know that by medieval times, indoor plants were grown in grand conservatories on royal estates. When did houseplants become a popular pastime for the rest of us?

We can thank the Victorians and the development of central heating in the late 1800s for creating a home environment with a temperature stable enough for houseplants, which are mostly tropical natives accustomed to consistent warmth.

Gardening remains America’s leading pastime, and tending houseplants tops the list with many homes and apartments having at least a houseplant or two.

The following are steps to greater houseplant success:

  • Deciding when to water is the most challenging part of houseplant care. As a guideline, whenever we water, enough should be applied to wet the soil thoroughly so a small amount seeps out the bottom drainage hole. Then let the soil dry considerably before the next watering, which pulls necessary oxygen inward. When a finger inserted up to the first joint feels dry or barely moist at the tip, the plant is ready to be watered again. If the soil feels quite moist at the fingertip, delay watering a day or two. Develop a cycle of thorough watering followed by considerable drying. Experience is the best teacher as we develop a feel for watering.
  • I’m often asked how often to water houseplants, such as once or twice a week. Watering on a set scheduled can be difficult. Instead, we can schedule certain days to check our plants, but water only if needed. Frequency varies by size of pot, type of plant, amount of light, indoor humidity and season of the year. Overwatering is a common killer of houseplants, which means the soil is kept continually too soggy. It doesn’t mean applying too much at one time, because the excess will escape through the pot’s drain hole, and should be discarded immediately. Watering too frequently with small amounts contributes to overwatering.
  • The best water for houseplants is rainwater, melted snow and reverse osmosis water. Water purified by city water systems using ozone is better than chlorinated water. Water run through a mechanical softener is high in salts and is best avoided.
  • Top-quality potting mix is essential. Inexpensive bargain mixes are heavy and poorly aerated and contribute to overwatering problems. Instead use high-quality products like Miracle-Gro Potting Mix, or mixes recommended by your locally owned garden centers. Because these mixes are usually sold dry, add water to the bag and mix well the day before using to create a mellow, workable moisture content.
  • When potting a houseplant, fill the pot to the rim with soil mix, which will settle when watered. If the “headspace” between the pot’s rim and the soil surface is greater than about a half inch, chances of overwatering and other problems increase. When I’ve observed failing houseplants, a too-deep headspace is often visible.
  • There’s great leeway in how often to repot houseplants, and once every two to three years is average. Some plants grow beautifully in the same pot for decades. Most plants enjoy being slightly pot-bound, rather than wallowing in a too-large pot and soil volume.
  • Drainage pebbles or stones aren’t needed inside the bottom of a pot. Although they were standard practice years ago, research has shown these materials cause a layer of change, which actually impedes the drainage they were intended to provide. Best drainage occurs when a pot is filled top to bottom with potting mix. High-quality mix rarely seeps out the bottom drain hole, so there’s no need for a coffee filter or diaper to be added.
  • Reserve fertilizer for healthy plants. If plants are in a downward spiral, insufficient nutrition is rarely the cause, and fertilizer isn’t medicine to revive a sick specimen. Fertilize once a month March through September when daylight is long. Plants require less during the short days from October through February.
  • Houseplant types vary by light requirement, so investigation is needed to determine whether a specific plant must be near a window or can be located in a room’s dimmer interior.
  • Most of all, enjoy your plants, and they’ll respond like a well-cared-for pet.
Fielding questions

Question: I have two basswood trees in my backyard that appear to be struggling this year. Normally they are very full with leaves, but this year they were sparse. Also, the leaves have bumps on them and there are small holes in the bark. — Pauline D.

Answer: Bumps on tree leaves are usually galls caused by mites and don’t often affect a tree’s overall health. The thin leaf canopy of your basswoods is most likely the result of the holes in the tree trunk.

Sapsucker woodpeckers create neat rows of holes in which tree sap accumulates for them to drink. A hole or two is less cause for concern, but when they drill a continuous row, it interrupts the flow of water and nutrients up and down within the tree’s system. Decline in tree growth results, and death can occur if the sapsucker’s activity continues.

To halt the problem, it’s necessary to break the sapsucker’s habit. Wrapping the area of activity with burlap, if reachable, has proven successful. Or apply sticky Tanglefoot, available at garden centers. Balloons, aluminum pie tins and other scare devices have mixed results. It’s possible for trees to recover, depending on the extent of damage, and if additional injury is prevented.

UPDATE: In last week’s column, we shared the fascinating question of a Bigfoot lookalike that ended up being wild cucumber vines totally obscuring whatever object they were climbing upon. I asked the Roeslers, who are from Leonard, N.D., to check under the humongous vine, if they got a chance, and let us know what they found.

Kent and Deb responded back, and found a poor, weak tree underneath, which the massive vines were using for support. Bigfoot remains at large. — Don Kinzler.

Q: With the recent cold weather, should I cover the perennials I planted this fall with mulch? — Dean S.

A: With the unusually cold weather, it’s a good idea to mulch around the perennials that were planted this fall. Many parts of the region have already received snow, which insulates the ground also. The snow isn’t likely to remain, though, which will leave the soil bare.

Adding a layer of mulch over perennials and bulbs that were planted this fall, especially those planted late, prevents cold from entering the soil quite so soon, giving a few extra weeks for the perennials to settle in before the soil freezes solid. Twelve to 18 inches of leaves or straw is usually enough to allow at least two extended weeks of unfrozen soil. The mulch can be left in place until early next spring, and then removed in late March or early April.

Q: I have a huge hydrangea bush and I’ve read conflicting articles on when to trim them back. Is it better to trim them in the fall to prevent the snow from snapping them off? If so, how short should they be trimmed back? — Sandy T.

A: Hydrangea pruning differs between the two types that are adapted to our region. The round-flowered Hydrangea arborescens, often called Annabelle types, die back each winter to near ground level. Their pruning consists of cutting back the stems in spring to about 6 inches above ground level. Pruning is best delayed until spring, except to possibly remove the large flower clusters, as they can tend to weigh down the branches under heavy snow. Winter branch breakage is less problematic, though, because spring growth arises mostly from near ground level anyway.

The other category of adapted hydrangeas are the panicle types, Hydrangea paniculata, with cone-shaped, pyramidal flower clusters. Instead of dying back each winter like the Annabelle types, panicle types act like “normal” shrubs, leafing out from the upper branches each spring. Pruning in spring can be done to shape the shrub. Limit fall pruning to removing the old flower heads, which can break branches if they become snow-laden.

Most houseplants can be grown successfully by following basic guidelines.
Don Kinzler says the thin leaf on the canopy of this basswood is most likely the result of the holes in the tree trunk.