Verticillium Wilt, a Soil Pathogen

Verticillium wilt is a soil-borne pathogen that affects 300+ plant species. The name is derived from two types of fungus: Verticillium albo-atrum and Verticillium dahliae. Trees, crops and woody ornamentals can all succumb to this devastating fungal disease. Plants affected with verticillium wilt may decline or die. Annual plants often die quickly, while large trees may experience a slow decline over several years. In Idaho we commonly see verticillium wilt affect maple and ash trees, elderberry, lilac, viburnum, roses, tomatoes, potatoes, mint and peppers, just to name a few. It is also an important disease in Idaho potato production and landscape trees.

This fungus starts in the soil and infects plant roots. It then spreads through the plant’s vascular system, affecting the xylem and its ability to take up water and transport nutrients. The fungus survives in the soil as tiny resting structures (microsclerotia), which can persist for many years, even without a host plant.

Symptoms The infection is marked by sudden wilting of branches, often on one side of the plant. Other common symptoms include faded green or yellowing foliage, browning leaf edges, and stunted growth. You will eventually see dieback in branches.

During periods of heat or drought stress, symptoms often become more noticeable. Plants may wilt even when soil moisture is adequate.

If you cut open a branch of an infected plant, you may notice dark staining following the wood grain—an indicator of vascular involvement.

Quick identification tips:

• Wilting on only one side of the plant or branch
• Yellowing or browning leaves
• Branch dieback
• Dark streaking in the sapwood

Note: Verticillium wilt can be confused with drought stress, herbicide damage, or other diseases such as Fusarium wilt. A laboratory diagnosis is sometimes needed for confirmation.

How Does it Spread? Verticillium wilt is primarily spread through contaminated soil and plant material. The fungus moves when infested soil is transported on tools, shoes, plant roots, or transplants. It can also spread through root contact between plants and by moving soil with water runoff or equipment. The disease is rarely spread aboveground. Insects such as aphids may stress plants or create wounds, but they are not considered a primary means of spreading this disease.

How to Manage Verticillium Wilt In most cases, it is best to remove infected plants, as there is no cure once a plant is infected. If there is limited dieback in tree branches, a certified arborist may be able to prune out affected wood. If you remove affected branches, be sure to clean your pruners between cuts to avoid spreading contaminated soil or plant material.

You can sanitize tools with a 10% bleach solution (1 part household bleach to 9 parts water). Keep in mind bleach solutions lose effectiveness over time and can be corrosive to tools, so rinse and dry tools after use.

Verticillium can remain in the soil for many years, so replanting requires careful plant selection. Choose plant species that are resistant or less susceptible to verticillium wilt.

Crop rotation for 3–5 years may help reduce disease pressure, especially in vegetable gardens, but it may not eliminate the fungus due to its long survival in soil.

Additional management tips:

• Avoid planting highly susceptible species in infested areas
• Rotate with non-host plants such as grasses when possible
• Maintain healthy soil and proper irrigation—stressed plants are more susceptible
• Avoid damaging roots during planting or cultivation
• Remove and dispose of infected plant material (do not compost unless at high temperatures)

For vegetables like tomatoes, look for resistant varieties labeled “V” or “VFN.”

Sweet Scent, Strong Vines: A Guide to Growing Honeysuckle

Trumpet Honeysuckle

Looking to charm the bees, butterflies and hummingbirds?  Honeysuckle is perfect for you.  With its sweet scent, vibrant blooms and easy-going nature Honeysuckle is a garden favorite.  There are about 180 identified species that are characterized by long, trumpet-shaped flowers in bright red, orange and yellow colors, most with yellow centers. 

Heaven Scent Honeysuckle

 

Native Honeysuckles are an essential food source for many Lepidoptera species.  In addition to providing nectar and pollen, the plants are critical larval hosts for species like the Snowberry Clear Wing Moth, which mimics the look of a giant bumble bee. 

Two popular varieties are the Trumpet Honeysuckle and the Heaven Scent Honeysuckle.  Beware of the invasive Japanese Honeysuckle.

The 'Trumpet Honeysuckle' (Sempervirens) or 'Coral' Honeysuckle is known for its brilliant red to orange trumpet flowers that bloom profusely from Spring into Summer.  The foliage is bluish-green and slightly leathery.  This plant is not only decorative but also non-invasive, making it a favorite among native plant growers. However, it is non-fragrant, sadly!!                                       

The 'Heaven Scent' Honeysuckle Lonicera periclymenum is a deciduous vine loved for its highly fragrant, creamy pink and yellow flowers that open in midsummer and continue through early Fall.  Its blooms are very fragrant in the evening making it an interesting addition near patios or walkways.  The green foliage provides a dense backdrop, and red berries may follow the flowers.  It also serves as a host plant for the larvae of the Admiral butterfly and the Twenty-Plume moth.   

Goldflame Honeysuckle

While not a native, ‘Goldflame Honeysuckle’ (Lonicera × heckrottii) is a cultivated hybrid that provides many benefits similar to natives. It is non-invasive, produces highly fragrant, nectar-rich flowers that are excellent for attracting hummingbirds and butterflies.

Honeysuckles are susceptible to powdery mildew, aphids, scale insects and caterpillars. Honeysuckle aphids are small grey-green colored.  They feed on new growth, causing leaves to curl and twigs to form stunted “witch’s brooms” (clustered deformed twigs). They are particularly damaging to Tatarian Honeysuckle.  

Aphids are often managed by natural predators, but if they return yearly, apply insecticidal soap.  Pruning and on occasion, chemical intervention may be required to save the plant. 

Honeysuckles will grow in light shade and full sun.  You are likely to get more blooms if  you plant in a location with 6 hours of sunshine per day and most varieties are hardy to USDA Zones 4-9. 

Resources:

https://extension.usu.edu/yardandgarden/research/vines-in-the-landscape-goldflame-honeysuckle

https://plants.ces.ncsu.edu/plants/lonicera-sempervirens

Why Are My New Plants Struggling? It Might Be the Soil.

Every spring, gardeners add fresh compost, topsoil, or raised bed mix and expect their new plants to thrive. Instead, plants may wilt, grow slowly, or struggle to establish despite regular watering.

Before reaching for fertilizer, consider a common issue with newly installed soil: it may not be fully hydrated. When very dry, some soil mixes can become hydrophobic, meaning they repel water rather than absorb it.

New Soil Can Be Hard to Wet

Many soil blends contain peat moss, compost, bark fines, or coconut coir. When these materials become very dry during storage or transport, they can resist water instead of absorbing it.

Gardeners may notice water pooling on the surface, running off the bed, or disappearing quickly while parts of the soil remain dry.

The soil isn't necessarily poor quality—it may simply need time to rehydrate.

Infiltration vs. Retention

A common misunderstanding is confusing water infiltration with water retention.

Infiltration is how water enters the soil.

Retention is how well the soil holds that water for plant roots.

A bed may appear to take water because it disappears from the surface, but water can move through cracks or channels in dry soil without fully wetting the root zone. For plants to thrive, soil must both absorb water and hold it where roots can use it.

Rewetting Takes Time

One of the biggest surprises for gardeners is how long it can take to fully hydrate a new bed.

A couple of waterings may not be enough. Depending on the soil mix and how dry it was, it can take several days—or even a week or more—of repeated irrigation to evenly moisten the entire bed. 

The goal is not simply to wet the surface. The goal is to hydrate the entire root zone.

Why New Plants May Struggle

Plants growing in partially hydrated soil often show signs of stress even when watered regularly.

Common symptoms include:

• Wilting during warm afternoons

• Slow or stalled growth

• Yellowing leaves

• Blossom drop on vegetables

• Uneven growth across the bed

The soil surface may appear damp while just a few inches below remains dry. Young transplants are especially vulnerable because their roots are still small and concentrated near the planting hole.

Check Below the Surface

A soil moisture meter can help identify dry pockets that aren't visible from above. However, newly filled beds with coarse compost, bark, or large air spaces can sometimes produce inconsistent readings.

The best method is still to dig down a few inches with a trowel and feel the soil with your hand. Ideally, it should feel cool and slightly moist throughout the root zone, not dry and dusty below the surface.

Give the Soil Time to Catch Up

Water slowly, water repeatedly, and check moisture below the surface. Once the soil is evenly moist, apply mulch to help retain that moisture.

Many struggling transplants don't need more fertilizer—they need soil that can absorb and hold water consistently.

Sometimes the healthiest thing you can do for a new garden isn't feed the plants—it's help the soil learn to hold a drink.

Who Sneezed on the Tomatoes? What Treasure Valley Gardeners Should Know About Plant Viruses

If you've gardened in the Treasure Valley for very long, chances are you've seen a tomato plant suddenly stop growing, develop curled leaves, and never recover. While insects, weather, and nutrient issues often get the blame, sometimes the culprit is a plant virus.

Plant viruses are not as common as fungal diseases, but they do occur in Idaho gardens. Unlike fungal diseases, plant viruses cannot be cured once a plant becomes infected. Understanding how they spread can help gardeners recognize problems early and make informed decisions.

One common misconception is that plant viruses come from the soil. In reality, most plant viruses do not survive freely in garden soil. Instead, they persist in infected plants, weeds, volunteer seedlings, perennial hosts, or occasionally seed. Insects then move the virus from one plant to another.

One of the most common viral diseases in the Treasure Valley is Beet Curly Top Virus (BCTV). It is spread by the beet leafhopper, an insect that migrates from weedy and rangeland areas into gardens and agricultural fields. Tomatoes, peppers, beans, potatoes, squash, and beets can all be affected. Symptoms often include upward leaf curling, thickened leaves, stunted growth, yellowing, and poor fruit production. Unfortunately, once a plant develops curly top, there is no cure.

Other viral diseases found in Idaho gardens include Cucumber Mosaic Virus (CMV), Tomato Mosaic Virus (ToMV), and Tobacco Mosaic Virus (TMV). These viruses can affect vegetables, flowers, and weeds. Symptoms may include mottled or "mosaic" patterns on leaves, leaf distortion, yellowing, reduced vigor, and stunted growth.

One challenge with diagnosing viral diseases is that many other problems can look similar. Herbicide drift, nutrient deficiencies, environmental stress, insect feeding, and even natural genetic variation can sometimes mimic virus damage. A plant with curled or mottled leaves does not automatically have a viral disease.

Viruses are commonly spread by insects such as aphids and leafhoppers. An aphid may feed briefly on an infected weed, pick up virus particles, and then transfer them while feeding on a healthy garden plant. In some cases, transmission can occur in just a few seconds.

Because viruses are spread by insect vectors, gardeners may occasionally see viral diseases even in gardens filled with beneficial insects. Lacewings, lady beetles, spiders, assassin bugs, and other predators help reduce pest populations, but they cannot always prevent a virus from being transmitted before the insect is eaten.

So what should a gardener do if a viral disease is suspected?

First, take a closer look before removing a plant. Not every unusual symptom is caused by a virus. If the diagnosis is uncertain and the plant is otherwise healthy, monitor it closely while watching for additional symptoms. However, if growth becomes severely stunted, symptoms worsen, or a viral disease is strongly suspected, removing the plant is often the best course of action.

Finally, practice good Integrated Pest Management (IPM). Manage weeds that may serve as virus reservoirs, encourage beneficial insects, keep tools clean, and maintain healthy growing conditions.

Most importantly, remember that not every odd-looking plant has a virus. Careful observation, patience, and a healthy dose of curiosity remain some of the gardener's most valuable tools.

Fire Blight: Recognizing and Managing a Common Fruit Tree Disease

If you grow apples, pears, crabapples, quince, or hawthorn in the Treasure Valley, fire blight is a disease worth watching for. Caused by the bacterium Erwinia amylovora, fire blight is one of the most destructive diseases affecting pome fruits and many ornamental plants in the rose family.

Fire blight affects apple, pear, crabapple, quince, hawthorn, cotoneaster, pyracantha, and mountain ash. While apples and pears often receive the most attention, many homeowners first notice the disease on ornamental landscape plants.

The bacterium survives the winter in cankers—sunken, infected areas on branches and trunks. As temperatures warm in spring, bacteria become active and may ooze from these cankers as sticky, amber-colored droplets. Insects attracted to the ooze can carry the bacteria to open blossoms. Rain, heavy dew, and splashing water can also spread the disease.

Infection is most common during bloom when temperatures are warm and moisture is present. One of the earliest signs is the characteristic "shepherd's crook," where young shoot tips wilt and bend over. Blossoms may turn brown or black and appear scorched. Leaves often remain attached to infected shoots, giving the tree a burned appearance. As the disease progresses, it can move into larger branches and form cankers. If a canker develops on the trunk or rootstock, it may girdle and kill the entire tree.

Prevention is the best defense against fire blight. When planting new fruit trees, select varieties and rootstocks with documented fire blight resistance whenever possible. Avoid excessive nitrogen fertilizer applications, which encourage lush, succulent growth that is more susceptible to infection. Proper spacing, pruning, and weed management can improve air circulation and help reduce humidity around trees.

Pruning is an important management tool. During the dormant season, remove old cankers and infected branches. Once fire blight is detected during the growing season, prune out infected shoots 12 to 18 inches below visible symptoms. Avoid pruning during wet weather, as bacteria can be spread by tools and splashing water. Severely infected young trees may need to be removed entirely.

Chemical controls are available but must be properly timed. Commercial growers may use antibiotic sprays during bloom when infection risk is high. Homeowners may have access to copper-based products labeled for fire blight suppression. Always read and follow label directions and apply products only according to label instructions.

Monitoring weather conditions and local fire blight forecasts can help determine when infection risk is greatest and when management practices will be most effective.

Spotlight on Hardy Geraniums

Geraniums often bring visions of Grandma’s garden with their robust, scented foliage and dazzling flower heads. These geraniums are annuals for most regions and belong to a separate genus in the Geranium family known as Pelargoniums. Today, however, we are going to take a look at another type of perennial geranium in the same plant family known as hardy geraniums or cranesbills.

Max Frei Bloody Cranesbil first bloom of the season

Hardy geraniums come in a variety of growth habits, flower color and bloom time.  They can be hardy for zones 5-81.  Geranium flowers have 5 sepals, 5 petals and stamens in groups of 52.  Some are long season repeat bloomers while others give a flush of blooms once a season.  The leaves are lobed and can have varying degrees of dissection between cultivars.   Some cultivars have foliage that turns a beautiful red color in the fall, extending their season of interest.   

Rozanne Geranium using Gaura as a support

One of the best known varieties of cranesbill geranium is Rozanne with its purple-blue flowers.   Rozanne is a vigorous perennial that plays well with other plants, using them as support as it winds and weaves its way around. It has a growth spread of up to 3 feet3 but can be sheared back to rejuvenate if it begins to appear leggy. It blooms from late spring through autumn.   

In contrast to its more vigorous
growing cousin, Max Frei Bloody cranesbill grows in a tidy, mounding clump of 12-18 inches with small bright magenta flowers against its rich green foliage. A perfect front-of-the-border perennial.   The foliage turns brilliant red in the fall extending its season of interest.  

There are also varieties of hardy geraniums that have deep dark foliage such as midnight ghost with its chocolatey brown leaves, wine colored stems and white flowers.  In all, there are around 300 different cultivars4 of hardy geraniums and many of the lesser known varieties can be purchased online as bareroot plants.  They are wonderful plants that can add a pop of color to a garden or be used in a mass planting for ground cover.  

1. Cranesbill, Hardy Geranium

https://extension.illinois.edu/flowers/cranesbill-hardy-geranium

2. The Genus Geranium:  https://canr.udel.edu/udbg/wp-content/uploads/sites/16/2024/02/Geranium-Featured-Plant-Article.pdf

3. Geranium ‘Rozanne’ the 2008 Perennial of the Year

https://www.purdue.edu/hla/sites/yardandgarden/geranium-rozanne-the-2008-perennial-of-the-year/

4. Hardy Geraniums for Northern Gardens

https://www.chicagobotanic.org/downloads/planteval_notes/no22_geraniums.pdf

Container Gardening - Tomatoes...and more!

Container vegetable gardening is an accessible and rewarding way to grow your own food, whether you have a sprawling backyard or just a sunny balcony. Choosing the right vessel is the foundation of a successful container garden. Most vegetables need at least 12 inches of depth, and larger is generally better. A 5-gallon container works for compact plants, while tomatoes thrive in 10 to 15-gallon pots.

Make sure every container has drainage holes to prevent waterlogged roots. Skip regular garden soil, which compacts easily in pots. Instead, use a high-quality potting mix blended with compost for nutrients and perlite or vermiculite to keep it light and well-draining.

When it comes to what to grow, a classic and productive combination is tomatoes, basil and pollinator-friendly flowers. Tomatoes are a container garden staple.

“Compact” or "patio" varieties do especially well in pots. Look for “determinate” tomatoes if you seed start or purchasing starts for your container. These are the type of tomatoes that mature to a certain height and won’t overwhelm a container/small space. Basil is a natural companion plant that repels certain pests and thrives in the same sunny, warm conditions as tomatoes. Tuck in a few flowers like marigolds, nasturtiums, or zinnias to attract bees and butterflies, which are essential for pollinating your tomatoes and keeping your garden productive.

With the right size pot, a good quality potting mix, and a thoughtful combination of plants like tomatoes, basil, and pollinator flowers, you can create a thriving mini-garden almost anywhere. Keep up with watering — containers dry out faster than garden beds — and you'll be rewarded with a beautiful, productive space all season long.

For even more information on other vegetables and plants to grow in pots, go here: 
https://extension.oregonstate.edu/news/container-gardening-grow-vegetables-even-without-yard-space