Citrus Tree

The day lilies have long since faded, and the chrysanthemums have stepped up to take their place. Sure, they’ll lend an autumnal backdrop as we sip pumpkin lattes while wearing football jerseys, but then what? Once the leaves have dropped and the coneflowers have become brittle, brown shadows of their former selves, where’s a plant lover to turn?

Indoor plants offer “a multitude of benefits to residential and commercial spaces,” advises Jonathan Lehrer, chair of the horticulture department at Farmingdale State College and who teaches a course on indoor plants. And when people “become more dissociated from the natural world, indoor plants help preserve a tenuous connection,” he adds.

But take care: Houseplants, unlike garden plants, are completely reliant on their owners for sunlight and nutrition. Get grounded in these fundamentals, then consider my picks for this year’s trendsetters.

The Basics

Water, sunlight, nutrients. These ingredients sound easy enough, but the combination differs from plant to plant.

Generally speaking, too much water can kill any plant — even if you’ve tried to correct your mistake by allowing the plant and soil to dry completely. That’s because waterlogged roots rot, a state that’s difficult to reverse. Too little water can be deadly, as well, but most plants provide warning signs, like wilting, before succumbing to such neglect. Watering at the point of wilt usually avoid catastrophe.

So how much and how often should you water? Environmental conditions — the sunlight and humidity in your home, and the type of potting mix and amendments in the container — play a role. In addition, gauging the moisture level by the soil’s surface can mislead.

Instead of establishing a one-size-fits-all watering schedule, assess plants’ needs every couple of days by inserting your finger deeply into the soil. When the soil is dry at root depth, it’s time to water. Keep in mind, however, this too is a generality.

Some plants prefer a consistently moist, but not soggy, soil, while others thrive in soil that dries out before being watered. And unless otherwise recommended, lighten up on watering over winter, when plant growth slows.

The best way to water most plants is to put the pot in the sink (or bathtub or shower, if the container is large) and apply water s-l-o-w-l-y until it runs out the drainage holes in the pot’s bottom. Flushing the soil also helps prevent salt buildup from fertilizers that can stress plants and stunt their growth.

Most of our indoor houseplants are tropical plants that won’t survive winter outdoors in our climate. On their home turf, they are exposed to high humidity that can be difficult to duplicate indoors. Insufficient humidity often manifests as browning leaf tips.

Should this happen, trim affected tips with sharp scissors and expose the plant to moisture by misting daily, running a humidifier or placing the pot into a rimmed pan that contains about an inch of pebbles and water (but not so much that the pebbles float); as the water evaporates, it will create a humid microclimate.

Be sure to keep plants away from forced-air heating vents and don’t put them on radiators, which can cause soil and plant-tissue dehydration, even death.

Plants need appropriate sunlight to photosynthesize, or produce food for themselves. A southern exposure offers the brightest light. Eastern and western exposures will provide medium light, while northern exposures probably will produce lots of shadows and, therefore, a low-light environment.

While there are plants that require the brightest exposures possible and others that thrive under office lighting, most do well with lots of indirect light. Keep in mind that even your brightest window may not provide enough sunlight for those with strong light requirements over winter, when sun exposure is at its lowest.

East- and west-facing locations are ideal for most plants but keep them a foot or two from the brightest windows or place a sheer curtain over windows to filter sunlight. Flowering houseplants typically are more sensitive to drafts than foliage-only plants, but all can experience ill effects from proximity to a blowing air conditioner, window drafts or an exterior door that is opened often.

The Right Container

Can you describe what size pot one should use for what size plant initially — say that you’ve just gotten a plant from a nursery, etc.? And how can you tell if a plant needs repotting?

Plants that outgrow their pots can become “pot bound,” when roots cannot grow outward but begin to encircle themselves. To avoid this, move plants into a larger container once a year, just before they begin their active growing phase in spring.

Plants should be moved to a pot that’s 2 inches larger in diameter; don’t be tempted to progress to a larger pot than that to avoid the task for a few years. That can result in poor soil-to-plant ratio: When it’s too high, roots can’t keep up, so soil remains moist for too long, increasing the chance of root rot.

When repotting, cover the drainage hole with a small rock or fragment from a broken clay pot. This will be sufficient to keep soil in while allowing excess water to drain. Add as much potting mix as necessary to ensure the plant sits at the same level as in the old pot.

If plants are “pot bound,” gently separate roots with your fingers before replanting. This will redirect them outward into the soil for water and nutrients.

Insert the plant into the pot and fill gaps with more potting mix. Tamp down firmly to eliminate air pockets, then water well.

Proper Nutrients

Plants growing in containers, indoors or out, require more fertilizer and water than those in the ground. If the latter get thirsty (or hungry), they can grow roots toward moisture and nutrients. Not so in pots, where they are reliant on what you provide.

Choose a granular slow-release fertilizer, which gradually releases nutrients over several months, or a liquid fertilizer, which is added to the watering can, typically with every second watering. Follow label instructions and remember that less is often more: Overfeeding is worse than underfeeding. And some plants, such as African violets, require specialty fertilizers.

With few exceptions, fertilize only between the beginning of March and Thanksgiving Day, allowing the plant to rest from actively growing during winter.

Plant Safety

When babyproofing a home, we secure electrical sockets, drapery cords, cleaners and sharp objects. Many houseplants, however, pose danger as well, and should be kept out of reach of small children, who tend to put all sorts of things into their mouths.

Consider, too, the lure and accessibility of vining plants; place them on high shelves. Even if they are not poisonous, they can be pulled down and cause injury. And all plants pose choking hazards.

Check with National Capital Poison Control (poison.org/articles/plant or 800-222-1222) before bringing a houseplant into a home with children and be aware that plants labeled as safe for cats or dogs might not be safe for humans (and vice versa).

And remember that just because a substance (or plant) is not considered “poisonous,” that doesn’t mean it isn’t “toxic.” If it’s neither, it can still be harmful if eaten.

To be safe, stick with African violet, begonia, Christmas cactus, coleus, dracaena, jade, spider plant and kitchen herbs, which are among those considered safe for growing around children, according to the nonprofit National Capital Poison Center (poison.org).

Trendsetters to Try

Out with cactuses — though we still love them — and in with unusual succulents and unique (and photogenic!) houseplants. Here are my picks for the year’s hottest, which are sure to spark joy in your home.

“Krinkle Kurl” wax flower

(Hoya carnosa)

A vining plant with tightly packed, thick, cupped leaves, “Krinkle Kurl,” also known as Hindu rope plant, is a conversation piece. The slow-growing vining succulent requires at least four hours of direct sunlight daily, and it does best near a south-facing window or under fluorescent lights.

Allow soil to dry completely between waterings; water only sparingly during winter, when growth slows. Fertilize every other month during spring and summer with an all-purpose houseplant fertilizer diluted to half-strength.

It may take a few years, but eventually plants should produce clumps of small pink flowers during spring and summer.

Climbing Onion

(Bowiea volubilis)

Not an onion at all, this misnamed leafless succulent grows from an exposed bulb. The unusual climbing onion gets by on little water. Let soil dry completely between watering and stop watering altogether after it blooms in late summer, resuming in autumn when new growth emerges.

Preferring to be planted in a 50-50 mix of potting soil and sand for adequate drainage, the plant likes dry air and thrives when crowded in its pot. There is no need to fertilize, just provide climbing support or let it tangle around itself; either way, it will attract attention.

Queen of the Night Cereus (Epiphyllum oxypetalum)

Perfect for insomniacs, this blooming orchid cactus has dinner-plate-size flowers that open at sunset and bloom until morning. Keep by an east- or west-facing window during spring, summer and fall. Dilute one-quarter teaspoon of a blooming fertilizer in a gallon of water, and water with the mixture once a week, or when soil is completely dry.

To ensure blooms, a dozen or more of which may cover the plant at once, keep in a cool, dry place (32 to 60 degrees) over winter, and cease watering until new buds form. Too much water or humidity may lead to root and stem diseases or fungal infections. Flowers are prized not only for their odd blooming habit, size and beauty, but for their strong, sweet scent.

Delta Maidenhair Fern

(Adiantum raddianum)

Grow this capricious diva near a south or west window, rotating a quarter turn twice a week to ensure even exposure. A native of the tropics, it requires high humidity, so mist regularly or place in a pebble- and water-filled tray ― unless growing in a bathroom where showers are taken daily.

Keep soil consistently moist (but not soggy) and fertilize once a month with a liquid fertilizer diluted to half-strength. Repot only when pot-bound, which becomes evident when roots begin poking through the drainage holes.

Farmingdale State’s Lehrer said its “ruffled bright green leaflets held aloft on thin petioles and fine texture” combine well with the “bold-textured foliage of African violets, philodendrons and moth orchids.” He also stresses the importance of humidity for success growing maidenhair fern.

Citrus Trees

Yes, you can grow citrus indoors. You can even get fruit if you play your cards right. Try Tahitian orange, a cross between a tangerine and a lemon, the sweetly scented Satsuma tangerine, lime, or Ponderosa or Meyer lemon.

Plant trees in a rich, well-draining medium, such as one part each peat moss and vermiculite and two parts sterile potting mix. Move the plant outdoors in summer to maximize sunlight, putting the entire container into the garden soil, and apply a 20-20-20 water-soluble fertilizer monthly, according to package directions.

When flowers open, hand pollinate them by touching a cotton swab to the center of each, moving pollen from one flower to the next. This will increase fruit production.

Dig up the pot at the beginning of September, give it and the plant a good rinsing with a gentle stream from a hose to remove insects and bring it indoors, where it should be kept at 65 and 70 degrees during the day, with exposure to bright, indirect light, and at 55 to 60 degrees overnight.

Keep soil moist, but not soggy, during spring and summer; reduce watering from October to February, watering lightly and only when soil is completely dry.

Bonus Plant: Marimo Moss Ball (Cladophora aegagropila linnaei)

It’s a plant! It’s a pet! It’s an algae ball! Grow one in a tank of water, as you would a fish. You can even get it a little ceramic castle. Not technically moss, these tangled algae balls grow slowly and can outlive their human caretakers, so be sure to make arrangements for their future.

When you bring your Marimo home, place it into a clear container of water no warmer than 77 degrees (ideally between 72 and 75, but you can approximate); the water should have sat 24 hours before using to allow chlorine to dissipate. A goldfish bowl, glass vase or drinking glass all are appropriate.

Just don’t crowd Marimo — or put them in with goldfish, which are algae eaters. Change the water twice a month, washing the container when necessary (rinse well if soap or detergent is used). A typical home should provide sufficient lighting.

Now for the fun part: Every so often, swoosh your hand around in the water to give your little friend some exercise (periodic movement ensures evenly shaped growth). If you are negligent and Marimo loses its round shape, roll it between your hands to reshape. If your Marimo gets dirty, place it in clean water, agitate it and gently squeeze out excess water before returning to the container.