Growing Together: What's ailing your houseplant?
Did you know that if you’ve had a hard day, you should spend time with your houseplants? After all, they’re rooting for you.
Sometimes, though, it looks like your houseplants have had a hard day, too. Are your plants experiencing yellow, droopy leaves or other signs they’re stressed out? It’s not easy to diagnose plant troubles, as they rarely talk about their feelings.
The basic needs of our potted houseplants can be summarized as soil, water, light and air. The easiest part is air, which is generally fine in our living spaces, although it can be a bit dry during winter’s heating season.
When our houseplants look less than vigorous, or downright sickly, problems can usually be traced to the other three necessities: soil, water or light. Watering is our most frequent interaction with houseplants, and improper watering is the leading cause of plant illness.
When deciding how much water to apply, the rule of thumb is to add enough to thoroughly wet all the soil in the pot, every time a plant is watered. Then discard any excess water in the bottom drainage dish immediately, before it soaks back up. This drainage water can contain salts that have “leached” out of the soil, so don’t dump it on another plant either.
Overwatering is a common problem, which means keeping the soil continually too soggy. It doesn’t mean applying too much at one time, as long as the excess is discarded. After watering plants thoroughly, allow them to dry before the next thorough watering.
Deciding how often to water can be tricky. Small pots need watering more often than large pots. Sun-loving plants in a bright window dry out faster than low-light plants in the corner of the room. Warm rooms and locations near heaters or air ducts increase water demand. Some plant types, such as ferns, prefer more frequent uniform moisture than cactuses and other succulents that prefer thorough drying with extended lengths between waterings.
To decide whether a houseplant needs watering, first observe the soil surface. If the soil is dark and moist-looking, it likely doesn’t need watering.
If the potting mix looks light in color, proceed with further checks. Insert a finger into the soil up to the first joint. If you can feel moisture at your fingertip, the plant is usually fine as is. Wait a day and check again. If you feel no moisture, water thoroughly.
Another good watering clue is pot weight, unless the plant is too large to lift. Develop a feel for the plant’s weight when dry, and again directly after watering, noticing the difference.
If in doubt about watering, wait. Few houseplants die from drought, while keeping plants too wet is a common killer.
Other houseplant ailments include:
• Yellowing of lower leaves can signal a root-bound plant in need of repotting or fertilizing. Some leaf drop is normal, especially as plants age.
• If the plant wilts, even though it’s wet, suspect root rot caused by waterlogged soil.
• Browning of leaf tips or margins can be caused by hot, dry air and low humidity, which often affects ferns. Or it can signal a buildup of salts or elements, such as fluoride in the soil. Flush the soil occasionally to “leach” salts out, or repot into fresh mix.
• Species like spider plants and peace lily are very susceptible to tip burn.
• Lack of light can cause leaf yellowing, accompanied by spindly, weak new growth.
• Mottled, light green leaves with pin-sized specks can indicate a spider mite infestation. Check also for light green or whitish aphids on new growth or under leaves, or white cottony mealybugs.
• If plants are sickly, fertilizing won’t cure problems caused by insects, improper watering, poor drainage or low light. Fertilizer is for healthy houseplants, and it’s best applied once a month during periods of active growth in spring and summer when days are long and light levels increase.
Q: I’m overwintering my geraniums by my south-facing window. However, they are flowering like crazy. Should I leave the flowers, or remove them? — Ann Riley, Fargo.
A: Growing geraniums in a sunny window is a great way to winter them until they’re ready for the outdoor gardening season once again. Or they can be kept growing under fluorescent lights, as we do in our basement. It’s like having springtime in winter. Geraniums can also be kept in cool basements, where they have the ability to go semi-dormant.
To encourage geranium plants to become well-branched and stocky during winter, removing the flowers helps direct energy into sprouts, stems and leaves. But if the plants are bushy and vigorous, enjoying the flowers in winter is fine. On March 1, cut the geraniums back to 4 to 6 inches above soil level, and begin fertilizing every two weeks. Keep all flower buds removed as they appear, until at least late April. That helps force out fresh new growth as days become longer and light levels increase, making fresh, robust plants.
Rotate the plants regularly so they don’t become one-sided or stretch toward the light. You might wish to raise the window shades all the way, as geraniums love the winter sun. By mid-May, the geraniums should be well-branched and blooming nicely for moving outdoors when danger of frost is less likely.
Q: Each year, my husband buys me cut flowers for Valentine’s Day. I always use the packet of preservative that comes with the flowers. When I need to add more water to the vase, I’ve heard you can add a little 7UP or sugar to the water used to refill the vase. Is that a good idea? — Judy M., Casselton, N.D.
A: The preservative that florists supply is specially formulated to help cut flowers last longer by increasing water uptake and reducing growth of harmful organisms that might block cut stem surfaces. Although 7UP might reduce the growth of organisms, and sugar might supply some saplike energy, the wrong proportions can do more harm than good.
Although homemade recipes can be found, using the florist’s preservative is the safer alternative for success. Before initially putting cut flowers in a vase, giving each stem a fresh cut can promote better water uptake and longer life.
Q: Rabbits are totally destroying my young arborvitae evergreen. There’s hardly any greenery left, and they’ve gnawed off the twigs back to stubs. Will it come back in the spring from the part that is left? — C. Hansen, Fargo.
A: Unfortunately, most evergreens, including arborvitae, don’t regenerate foliage on branches that have been chewed as severely as you describe. Last winter, rabbits chewed six of our young arborvitae, consuming branches on the way up as the snow depth increased, then finished the job on the way down, as snow melted. The shrubs required replacement.
Deciduous (leafy) shrubs have an advantage, because most have the ability to branch freely from the base if rabbits consume the upper twigs, or gnaw the bark. Damaged portions of lilac, dogwood, spirea, rose, hydrangea and other favorite rabbit edibles can be pruned back quite drastically in early spring, and most rebound fine, often better than before.