David Deardorff

We’ve prepared a list of the ten most common problems of houseplants. If you’re having a problem with a houseplant, it’s most likely going to be due to one of the following.

1. Overwatering.

More houseplants die from overwatering than from any other cause. Never let the pot sit in water in a saucer. Put marbles or pebbles in the saucer and set your pot on top of them to raise the pot up and away from the water in the saucer. Make sure the pot has adequate drainage holes. Allow soil to dry out in between watering. When you water, water the root zone of the plant, not the foliage.

This crown-of-thorns houseplant struggles to survive in a pot without drainage holes.

2. Air is too dry.

Keep all your houseplants away from heat sources like heat registers, electric heaters, or radiators. Hot air blowing on a plant will quickly desiccate it. Mist plants to increase humidity, especially if you live in a dry climate. It also helps to place pots on shallow gravel filled trays of water.

Dry, brown, dead tissue shaped like an upside down V at the tips of the leaves tells you conditions are too dry for your plant.

3. Not enough light.

Put the right plant in the right place. Consult plant labels and packaging, and reliable books, magazines, and internet sites to determine a plant’s light requirements. Plants that need full sun rarely make good houseplants. Plants adapted to the low light levels of tropical forests do quite well in our homes.

4. Ambient (room) temperature too hot (especially at night).

The best houseplants are all tropical species that are able to tolerate the warm nighttime temperatures we keep in our homes. Temperate zone plants are often killed by warm nights because they burn up more fuel than they are able to make. That’s why miniature roses do not survive indoors, they starve to death. Turn the thermostat down, especially at night, to 60 degrees.

5. Pot bound.

If your plant sucks up all the water you give it and then wilts a short time later it’s probably pot bound. Up-pot the plant to a larger pot and add fresh soil. This way you give the plant a larger volume of soil to plumb for moisture. Alternatively, take the plant out of its pot, shave off an inch of roots and soil around the sides and bottom of the root ball, then put the plant back in its pot with fresh soil.

5. Temperature, humidity and/or light regime changes, as when the plant is moved.

Some plants, like Bougainvillea and weeping figs, drop most of their leaves when you move them to a new location. Make the change gradually, if possible, and give the plant extra nutrients and water to cope with the shock.

6. Not enough water.

Determine the right amount of water for the particular plant (read the tag or look it up). Some plants, like cactus and succulents, require very little water. Other plants will tolerate being constantly waterlogged. Most plants, however, fall somewhere in the middle. In general, allow the soil to dry out in between watering and mist plants to increase humidity. Make sure the plant is not pot bound.

Mealybugs on the underside of this Hoya look like fluffy wads of cotton.

7. Insect pests, such as fungus gnats, whiteflies, mealybugs, and scale insects.

Plants under stress are more susceptible to pests. Make sure you put the right plant in the right place to reduce stress. Give it the proper amount of light and water, the best temperature regime, and soil conditions to allow it to thrive and you’ll have fewer problems. Wherever possible, choose resistant cultivars and always inspect and quarantine plants when you first bring them home.

Mulch or top dress containers. This helps to control fungus gnats.

Sanitize. Remove and destroy insect infested leaves or stems.

Remove any pests you can capture, either with your hands or use a vacuum cleaner.

Physical barriers like sticky cards work well for adult whiteflies and fungus gnats.

Provide air movement with a fan set on low.

Make sure your windows and doors have screens to reduce the number of insects in the house.

Insecticidal soap sprayed directly onto the pests will kill them and is safe to use in your home.

Use rubbing alcohol on Q-tips to grub out mealybugs.

Drench the pot with Bt-i (Bacillus thuringiensis israelensis) for fungus gnats

Spray Neem oil to control most houseplant insect pests.

Horticultural oil (look for ones made from vegetable oil).

Pyrethrins made from botanical sources also work well.

8. Spider Mites.

This is a common problem under dry, dusty conditions. Mites are not insects, they’re related to spiders. They are very tiny and hard to see. They come in to your house on infested plants.

Quarantine new plants until you’re sure they’re mite free.

Sanitize. Remove badly infested leaves and discard them.

Blast leaves with water to wash mites away. Keep the leaves free of dust.

Misting the foliage discourages mites (they don’t like water).

Insecticidal soap sprayed directly on the pests will kill them.

Neem oil controls mites.

Horticultural oil (vegetable oil base) smothers mites and their eggs.

Sulfur is a natural element that mites don’t like.

Pyrethrins made from botanical sources also work.

This philodendron shows the watersoaking typical of bacterial infections on the leaves.

9. Diseases, such as fungus and bacteria.

Sanitize. Pluck off infected leaves and put them in the garbage. Do not compost.

Mulch. Top dress containers to reduce splash up from the soil to the leaves.

Provide air movement with a fan set on low. Don’t crowd plants. Put the right plant in the right place. Choose resistant cultivars and keep the foliage dry when watering.

A simple spray made from baking soda prevents fungal spores from germinating.

Sulfur sprayed onto the foliage also prevents fungal spores from germinating.

Copper sprayed on the leaves will kill bacterial pathogens.

Bacterial fungicide (Bacillus subtilis) is a living bacterial culture which kills fungi.

Neem (has a strong odor for some people) Keep it away from aquaria.

10. Nutrient deficiencies.

Start with a good quality potting soil, an artificial mix that contains perlite, vermiculite, and other materials that create space and air pockets, yet retain water. Some plants, such as orchids or cactus, need special mixes. Never use garden soil in a container because it will become very compacted over time. Use a good organic fertilizer whenever possible.

Kathryn Wadsworth

Today is Christmas day and I thought I’d share with you a few photos of some of my favorite native plants of the Northwest. All of the plants featured here are evergreen shrubs or trees. All of them produce berries that attract birds to your garden. All the fruits are edible by us humans too and are quite tasty.

David and I went out for a walk on Christmas eve and took these photos to share with you. We walked along the shores of Hood Canal on the Kitsap Peninsula up in Washington State. Winters are mild here and there is no snow on the ground. Plants that keep their leaves all winter are especially valued in the landscape in the Northwest.

The Olympic Mountains form a spectacular backdrop to this scene of Hood Canal

Evergreen huckleberry (Vaccinium ovatum) has very pretty evergreen foliage. Its berries are small, black, and extremely tasty.

Oregon grape (Mahonia aquifolium) carries its shiny compound leaves all year long. Yellow flowers in spring become blue berries by the end of summer. The tart berries make excellent jams and jellies.

Leaves of salal (Gaultheria shallon), called "lemon leaf" by florists, find wide commercial use in bouquets. This plant also makes very tasty berries, sweet and juicy.

David Deardorff

‘Tis the time of year when I find myself standing under a sprig of mistletoe expecting to be kissed! We’re putting branches of bright green holly with brilliant red berries in bouquets and wreaths to decorate the house for the holidays. And I see out the window, in the snow, that the ivy is in full bloom. What a crazy plant, to burst into bloom in winter.

The ivy featured in the carols and cultural traditions of Great Britain and Northern Europe is the English ivy, Hedera helix. It is in full bloom at the moment, covering itself with silver dollar sized umbels of small, inconspicuous flowers. No wonder the ancients regarded this plant with awe – it flowers in winter. Today, in the Pacific Northwest, we also regard it with awe, as a noxious weed! Each small flower will mature into a pea-sized, black-purple berry in spring. Birds love these berries and spread the seeds of this plant far and wide. The seeds survive passage through the gut of a bird to be pooped out in a new location.

Curiously, English ivy flowers in winter when few other plants bloom.

English ivy’s long juvenile period lasts ten to thirty years. The juvenile plants are the familiar ornamental vines with the palmately-lobed leaves available in numerous named cultivars. Eventually the plant becomes sexually mature. It flowers, makes seeds, and changes its growth habit. Its a vine with long flexible stems as a juvenile, but a shrub with short, stiff stems at maturity.

The bright green leaves and brilliant red berries of English holly are widely used for decoration during the winter holiday season.

The holly featured in Christmas carols is the English holly, Ilex aquifolium. The stiff leaves of this plant are heavily armed with spines around the edges. The bright green leaves contrast nicely with the bright red berries on the female plants. Male plants, of course, have no berries. This plant, like the English ivy, is another invasive species in the Pacific Northwest. Birds eat the berries and spread the seeds.

The holiday mistletoe of legend, Viscum album, unlike the previous two plants, is a parasite. It comes from Northern Europe and Great Britain where it grows on tree branches and sends its specialized roots (haustoria) down into the tissues of its host to steal water, food, and mineral nutrients (much like a tapeworm in animals). Female mistletoes bear berries, which are white, and the seeds are spread by birds. Mistletoe has green leaves and is able to manufacture some of its food by photosynthesis, but it has to get all of its water and mineral nutrients from its host. Tradition dictates that you will get kissed if you stand under mistletoe so hang it above doorways or other places people use frequently.

In the USA, the holiday mistletoe from Europe has escaped into the wild in California. California also has native species of mistletoe in a completely different genus (Phoradendron). These parasites are easily spotted in winter when they show up as leafy green balls on the leafless branches of their host trees. Healthy trees can stand a few of these parasites, but a large number of them can kill your tree. The best way to deal with them is to prune them away by cutting off the infected branches.

Native mistletoe on white oak in Southern Oregon.

Today is December 21, the Winter Solstice. Tonight is the longest night of the year in the northern hemisphere. This is the turning point, the time when the solar cycle begins to turn toward the light and the days begin to get longer. Solstice is, of course, cause for celebration, and many cultural traditions call for mistletoe over doorways, and holly and ivy around the fireplace.

In ancient times it was extremely important to know when the winter solstice, the moment of the sun’s rebirth, would occur. Communities needed to ration their food supplies in order to survive the famine months of winter. Stonehenge, for example, is a giant calendar that specifically marks the winter and summer solstices. Built nearly five thousand years ago as an astronomical observatory, it stands today as testament to its usefulness to the people who built it.

To the ancients, plants that kept their green leaves through the harshest winter storms, the holly, ivy, and mistletoe, must have seemed mysterious and magical. These plants were often considered sacred. People cut sprigs, bring them into their homes, and have done so for thousands of years. We do so to celebrate midwinter festivals, traditions to continue various pagan and Christian festivities. At our house, Kathryn and I bring the holly and the ivy into our home . . . and mistletoe too. We love to celebrate the turning of the wheel, the eternal cycles of nature. And we like kissing too!