Houseplant Care Headed Into the Cooler Months

As the garden plants begin to brown and the leaves on the trees fade from green to gold, tan and even red, the signals are clear. Yes, we’re moving from summer into fall. For me, the days of visiting the displays in the nurseries and garden centers in the outdoor lots are about over. Not the gardening season though.

Last week I made my first foray into my local garden center’s greenhouse because in there is a wonderful world of tropical foliage and flowering plants that will get you and me through the dark days of winter. So this week and next, we’ll begin my annual ritual of reviewing what we call “houseplants.” There are some pretty cool new varieties, and it’s time to pick up a few. But first, we need to deal with the houseplants that you already have.

While it’s still warm outside we’ve got an opportunity to give your existing houseplants a spa day — some TLC that may have been missed or avoided in the past few months. This attention will help them get these plants through the cooler and darker months. This ensures that the care and joy that you share with them now will surely pay dividends as our time outdoors in the garden wanes.

There are two major situations to consider here, and time is of the essence. If you kept some or all of your houseplants outdoors for the warmer months they need to come indoors. Now though, not in November. And if you simply pick them up and move them back indoors you may be asking for trouble.

Likewise, if you keep your plants indoors year round then this is the time to get them outdoors, just for a day, to examine the plants, the pots and to discover problems that you can solve outdoors that can’t be addressed while your plants are indoors. Housekeeping so to speak.

First though, let’s look at what we can do and what we shouldn’t do. This is not the best time for repotting. Even our houseplants are going into a semi-dormant stage and repotting at this time of the year may encourage root and shoot growth that’s contrary to most of your plants’ natural growth habits. The exceptions will be those plants that are literally busting out of their pots.

A healthy asparagus plant (aka asparagus fern, though it’s not a fern) will push itself up and out of its pots, and I’ve even seen some split a clay pot with the pressure from the swelling roots. If these aren’t repotted the foliage or needles will begin to brown and drop as the plant tries to balance its root system with its shoot system. And since it can’t easily grow new roots it compensates by dropping the ferny foliage.

Larger plants like Ficus and Dracaenas will just drop lower leaves and continue to do so until there is space (as in a larger pot) for new roots to form. Remember that a houseplant will always seek a balance between the root system and shoot system, and when this balance gets out of whack from being pot bound, overwatering or underwatering, it will express its distress by dropping foliage — leaves and/or fronds.

But what do you do if this isn’t the right time of the year for repotting? Ah, so glad you asked. You can root prune. It takes some courage and practice, but with many plants our goal is to get the plant through the winter months. You can root prune most houseplants by getting the plant out of the pot (after watering it well) and begin to untangle the root mass. Tease the roots out gently, and with a sharp hand pruner begin to reduce the roots by trimming them back. Make sharp cuts without leaving strings and strands, and never remove more than a quarter of the root mass. Do not repot in a larger pot. Use the same pot. Add some new soil to the bottom and place the root mass on top of the soil. Next, slowly add new soil between the remaining roots using your fingers to work the soil into the spaces where the old soil has fallen off or been removed. Be gentle and use your fingers to push the soil into the spaces, but no forcing or hard pushing.

When the potting is done, tap the pot gently a few times on a table or the floor to remove air spaces then set the pot in a saucer of water and let water soak up into the pot. The plant should sit in the pot with the soil level slightly below the pot rim. If the water is gone in a few minutes then add more but don’t let the pot sit in standing water for more than a half hour.

When doing this repotting be sure not to use potting mixes that contain fertilizers, and don’t add any fertilizer. From now until spring most houseplants will need only a tiny amount of fertilizer, and this should be in the form of a low analysis organic product like deodorized fish emulsion added to your watering at half the label rate every two to three weeks. Remember, during the darker and cooler months you simply want to maintain your foliage plants, not encourage them to grow.

You might be tempted to trim back the aboveground shoots and stems at the same time. DON’T! This will stimulate the growth of new shoots as well as new roots, which isn’t what we want. We’re only looking to let the trimmed and pruned roots grow a bit and not to make the plant “think” it’s time to get taller and wider. And this should not be a practice for all your houseplants, only those that are truly pot bound and in desperate need.

The other attention that your outdoor tropicals will need before bringing them back indoors is an insect inspection. You’re looking for scale on the foliage and stems, aphids on flower buds and spider mites on the foliage. Scale has to be controlled with an oil that smothers them, and this can be any number of oils from neem oil (70 percent or lower) to light horticultural oil. If you do find scale, one spray may not be enough. Plan on getting the infected plants outside about a week to 10 days later for another application. These oils can also manage spider mites, and if you don’t eradicate them now they’ll “bloom” indoors in the dead of winter and be nearly impossible to control. Keep in mind that spider mites are tiny, and if you’re not familiar with them you will need a magnifier to spot them. A good indication that you’ve got insect problems is if the plant foliage feels sticky. This is the residue from the insects feeding that we call honeydew.

You can also use insecticidal soaps — not on ferns though — for whitefly, aphids and mites. You can also make your own spray using a soap like Joy (not detergents) at the rate of 2.5 tablespoons per one gallon of warm water. Spray upper and lower foliage surfaces completely and repeat in a week to 10 days.

When bringing houseplants that have been outdoors for the summer back indoors, try to find a spot that gets the same amount of light. More light may be tolerated in the winter months, but less light will result in stems and branches elongating and thinning out. Don’t wait. Get this work done now. Next week, new houseplants and maple for your window sill. And of course, keep growing.

Garden Notes

Garden looking a bit drab? Most of your perennials have long since flowered, leaving lackluster spots in the perennial border. Try some Eriocapitella hupehensis and Eriocapitella japonica (formerly known as Anemone hupehensis and Anemone japonica, respectively). These are perennial anemones — not the small windflowers that bloom in the spring and are planted from small bulbs.

Also called Japanese anemones, E. hupehensis and E. japonica are carefree perennials that bloom from late August into October, and at 2 to 3 feet tall they draw the viewer’s eye away from the garden below with their profusion of white, pink, rose and purple flowers that can be single or double. They’re virtually trouble free and offer late pollinators a late feeding spot. They’re slow to establish so you need to be patient, but a small potted plant from a vendor like Bluestone Perennials will be well established by its third year.

They prefer a rich but well drained soil, and don’t be surprised if they’re the last plant in the garden to break dormancy in the spring. Some varieties naturalize better than others, but all will spread slowly. There are close to 50 named varieties; however, some hybrids can get 5 feet tall, making them poor choices unless staked. I have “September Charm,” “Little Princess” and “Margarette.” Deer, rabbits and even groundhogs seem to ignore them. The plants prefer about six hours of sun but will take more if lightly shaded during the heat of the day.