David Deardorff

We’ve been coming to the Northwest Flower and Garden show in Seattle for years and it’s always exciting to see what’s new, see the extravagant displays, and hear experts speaking on various subjects. We’re really looking forward to coming back to this lavish display of the latest and greatest in the gardening world. This year, the show starts on Wednesday, Feb. 3 and Kathryn and I are presenting a program on Sunday, Feb. 7.

I remember the first time I ever attended the show. It was many years ago. Kathryn and I went with my mother and father, and several of my siblings and their spouses. It was quite a family affair with all of us crammed into the orchid displays oohing and ahing over the amazing orchids. At the time, Kathryn and I owned an orchid nursery and tissue culture laboratory in Hawaii and my father had a greenhouse full of orchids in the backyard of his home.

BLC Larry's Gem, a hybrid in the Cattleya alliance.

This photo is of BLC Larry’s Gem, a hybrid created by Kathryn and me in our orchid nursery in Hawaii and named in honor of my father, Larry. We registered it with the Royal Horticultural Society in Great Britain, the official registrar of all orchid hybrids.  BLC Larry’s Gem is in the Cattleya alliance, with very large flowers on a large vigorous plant. Most members of this alliance are tricky to grow as houseplants because they want more light than some other kinds of orchids.

Phalaenopsis orchids come in white, pink, yellow, and can be spotted or striped as well.

Phalaenopsis hybrids are much easier to grow in the home than Cattleya alliance orchids. Called moth orchids, they prefer the low light levels and warm temperatures found in the average home.

Paphiopedilums, or slipper orchids, also have flowers in a wide range of colors.

Paphiopedilums, or slipper orchids, are also easy to grow as houseplants. Like moth orchids, they prefer the shaded warm conditions provided by the average home.

At the Northwest Flower and Garden show you will see numerous examples of these and many other kinds of orchids. Check it out. You’ll be glad you did.

Kathryn Wadsworth

David and I have been having a great time teaching Master Gardener classes the last couple of weeks.  Recently we spent six hours covering some good answers to the question they’ll get every day in Plant Clinic: “What’s Wrong With My Plant?”

Sometimes it can be difficult to determine whether you are dealing with a disorder, a disease, or a pest. But 80% of the time the problem is a “disorder”, that is, a problem with the growing conditions.

Accurate diagnosis requires detective work. Like a forensic scientist, you need to collect evidence, examine the clues, and arrive at a diagnosis. The process involves asking questions designed to detect information that eliminates, one by one, all alternative causes and results in an accurate diagnosis.

Leaf symptoms can look remarkably similar, but have very different causes. By asking the right questions about the plants’ circumstances, you can come up with an accurate diagnosis.

Yellow leaves on Pachysandra

The leaves at the tip of the branch, in other words, the young leaves, on this pachysandra (Pachysandra) turned completely yellow. Plants that require partial shade can suffer from this condition in a variety of circumstances.

Solutions include moving the plant to a shadier area, planting a larger plant nearby to give this ground cover more shade, or constructing a small trellis overhead to cast shadows below.

Yellow leaf on a pothos

This pothos (Epipremnum) grew in soggy soil because its pot stood in a water-filled saucer. The leaves at the base of stems, namely the older leaves, turned yellow and dropped off.

A simple solution. First of all, make sure the pot has good drainage and the growing media has a chance to dry out between waterings. Then, after watering your house plants, make sure the saucer does not have standing water in it. Dump the water out.

Yellow rhododendron leaf

The soil was not soggy, yet this leaf at the base of a rhododendron (Rhododendron) branch turned completely yellow and dropped off.  All leaves have a limited life span. Even conifers and broad-leaved evergreens like rhododendrons shed their oldest leaves.

The solution to this one is easy – don’t worry about it.

Yellowing lilac leaf

Leaves at the base of branches are the old, mature leaves. When they begin to turn yellow, while the main veins remain green, as they have on this lilac (Syringa), they point to nitrogen or manganese deficiency.

Maintaining healthy soil helps eliminate this problem. Add organic compost, fertilizer, and mulch twice a year to encourage all the beneficial soil organisms to thrive, thus nurturing a balanced soil micro-eco-system (boy, that’s a mouthful). If this is a nutritional emergency try a liquid fish fertilizer.

David Deardorff

Kathryn and I taught a Master Gardener training class on plant disorders, diseases, and pests yesterday. We’ve learned through experience that most plant problems result from poor growing conditions. Growing conditions are physical and cultural environmental factors that affect the well being of your plants.

Light, water, temperature and soil nutrients, for example, are all physical factors of the environment that profoundly affect plant performance. Cultural environmental factors  are the things we, as plant managers, do to the plants in our care, including pruning to improve air movement, thinning heavy crops of fruit, and avoiding overcrowding among many others. Good growing conditions are the foundation for plant health, and eighty percent of plant problems are due to poor growing conditions.

Physical environmental factors include light, water, temperature, and soil.

Sunlight is, of course, vital. All green plants manufacture food from sunlight through photosynthesis. Fertilizer and mineral nutrients are sometimes called “plant food” but that is an erroneous concept. Sugar is actually “plant food” and plants create sugar out of solar energy, water and carbon dioxide. Obviously, if a plant does not get enough sunlight it becomes malnourished and could even starve to death.

Water, like sunlight, is also absolutely vital for a plant’s well being. It moves through the plant’s veins like blood in our own bodies. Water transports food and mineral nutrients to every cell. Roots absorb water, which moves up through the stem, and is lost to the air through the leaves. Losing water through the leaves is the pump that drives water movement through the plant’s body. If the pump stops, the plant can get into serious, life-threatening trouble very quickly.

This avocado orchard in California froze during a sudden cold snap.

Many people pay attention to a plant’s temperature needs, because they are aware of the danger of winter cold. In the United States, the Department of Agriculture (USDA) created a winter hardiness zone map, and almost all plant labels in U.S. nurseries list the USDA zones to which the plant is adapted. For example, a plant label may list appropriate zones as 9 through 11. This means that the plant will freeze to death in zones 1 through 8. This zone system does not reflect other temperature factors, such as heat tolerance, or whether a plant needs winter chilling to flower and set fruit.

Healthy soil is a microcosmic ecosystem, filled with millions of bacteria and fungi, and with organic matter. This teeming micro-flora and fauna maintains mineral nutrients, out-competes pests and disease-causing pathogens, and conserves water. If your soil is healthy and rich you have met the most fundamental requirement for happy, healthy plants.

A large branch of this peach tree has broken off because the fruit crop was too heavy and should have been thinned.

Plant problems caused by inadequate growing conditions are called disorders, not diseases or pests. A disorder is caused by too much or too little of some critical factor: light, water, temperature, or nutrients. Disorders can also be caused by poor management, such as failure to thin a heavy crop of fruit, lack of dead-heading (removing the spent flower clusters before they make seeds), or pruning at the wrong time of year. By contrast, a disease is caused by a pathogen, such as a fungus, bacterium, or virus. A pest is a destructive organism, such as an insect, mite, nematode, bird, rodent or deer.

These carrots are stunted and disappointingly small due to overcrowding.

Sometimes it can be difficult to determine whether you are dealing with a disorder, a disease, or a pest. Yellowing leaves, for example, can be due to many different causes, such as lack of nitrogen (disorder), root rot fungus (disease), or aphids (pests). Accurate diagnosis requires detective work. Like a forensic scientist, you need to collect evidence, examine the clues, and arrive at a diagnosis. The process involves asking questions designed to detect information that eliminates, one by one, all alternative causes and results in an accurate diagnosis. In our book “What’s Wrong With My Plant (And How Do I Fix It)?” Kathryn and I created an innovative new diagnostic system using pairs of questions arranged in illustrated flow charts. It’s easy to use. And you don’t have to know the name of a plant in order to figure out what’s wrong with it!