Category Archives: Disease

Advice, Annuals, Disease, Forcing Plants, Planting, Seeds

Horticultural Hiccups

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By Marilyn Homewood, Master Gardener

At times, these blogs seem a little like an Instagram Post. We show our successes in the hope of inspiring you and in turn, provide something of value to you.  However, that can be a little intimidating to less experienced gardeners. Today, I thought I would showcase some of my 2025 failures (so far).

Lisianthus germination (or not)

Lisianthus

This one is a heartbreaker! In January, I had almost 100% germination of my lisianthus. A couple weeks after germination, they looked like this.

What happened? After reading somewhere that cinnamon prevents growth of algae, this grower overzealously applied cinnamon (I had purchased a large bottle at Costco). The covering of spice initially smothered some of the young seedlings.  I then tried to rectify the situation by wetting the plants (cinnamon is extremely hard to wet). 

The overwatering led to a slow decline, killing more seedlings by rotting the roots.  All was not lost however, I potted up the remaining seedlings into other containers and they have been growing on.  Hopefully they will catch up in size over the long growing season.

As Julia Child was fond of saying “everything in moderation….including moderation”

Bells of Ireland

Bells of Ireland

These seeds are notoriously hard to germinate.  They need to be stratified by exposing the seed to cool, moist conditions to help to break dormancy.  The seed is placed on moistened paper towel that is then folded and placed into a Ziploc bag.  Then placed into the fridge for a couple of weeks. After that, remove to a warm place (I use a heat mat). 

After a period of time, the seeds are checked for germination and placed on the surface of prepared soil.  The daily checking goes on for a few days and hopefully you get enough germinated seeds.  This years’ results speak for themselves.  Hard to know what went wrong but it may be the seed source.  My usual source (that does germination testing on every lot) was out of seed so I purchased from another.

Dahlia Splitting

Last fall I used a new method of splitting dahlias that saved time.  I use flagging tape to identify the plants dug up and the tubers being stored.  As the dahlia afternoon wore on, some of the tubers seem to get mixed up and the quality of the labeling seemed to decrease. This tuber might be a Ferncliff Copper and then again, it might not be. Note to self – Take a little more care with the labelling.

Forcing Tulips in Bulb Crates

Seemed like a great idea last October. I do not have a cool place that does not freeze so I opted to chill my bulbs in the refrigerator. Bulbs in paper bags went into the crispers of the fridge for over 14 weeks.  During that time ethylene producing produce could not be kept in the fridge as ethylene can negatively affect bulbs and their bloom. 

After the chill period, bulbs were planted in soiless mix in bulb crates and kept dark for a couple of weeks to develop roots.  The crates were then placed in a sunroom to grow.

I got a total of 20 lovely tulips from about 150 bulbs.  Other bulbs did grow leaves but produced no flowers, some did not grow at all.  When I removed the bulbs from the soil, I did notice reduced root growth on many of the bulbs. This may be from inadequate chilling. 

The crate method is clearly more successful when you can plant the bulbs up in the fall and place in a very cool spot that does not freeze (or a cooler like the flower farmer).  Bulb crates full of soil is messy in the house even if they are on tarps!

Despite these hiccups, I have a roomful of healthy seedlings and large landscape beds awaiting more garden gaffes. 

In the words of Janet Kilburn Phillips “There are no gardening mistakes, only experiments.”

Disease, Garden Cleanup, Garden rejuvenation, Planting, Pruning, Shrubs & Trees

November Reflections

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by Lois Scott, Peterborough Master Gardener

Even though we are more than half way through November many gardeners are still finding things to do, enjoy or plan for in the garden.

This fall I planted a number of woody plants including three small trees and 2 shrubs which have required ongoing watering. With new woody plantings it is important to water them well, right up to the time that the ground freezes, paying attention to not drowning them but preventing the roots from drying out.

Tree roots are actively growing in the cool fall weather so they need the moisture. Here’s how to do it right.

As the season advances and the trees are bare it is an excellent time to see if there are any pruning needs. Wood that is diseased, damaged or dead/dying should be pruned sooner rather than later.

According to Lee Reich, author of ‘The Pruning Book’, pruning for structure is best left until late winter after the coldest part of the winter is past. Wounds in wood heal most quickly just as plant growth is getting underway rather than the fall when wounds heal poorly and many fungi are spreading their ‘disease producing spores’.

Of particular note is the caution to not prune any Oak species during the growing season due to Oak Wilt disease. If you do need to prune during the growing season apply wound paint to the cut area.

I am planning for some structural pruning on a Star Magnolia in late winter 2025 and I can now see the tree’s structure to plan for that which is a process I enjoy.

This November I am still enjoying the frost tolerant kale and arugula that were started in grow bags in late summer. They have stopped actively growing with the cold temperatures but are still very edible. At this time of year there is no concern about them bolting (going to seed)!

Walking our neighbourhood has also afforded me the opportunity to see and enjoy what nature and gardens have to offer in November. Oaks still bearing their beautiful fall foliage and my neighbour’s fabulous roses are just a few of the visual treats.

I hope your November garden reflections are enjoyable and satisfying!

Advice, Disease, Garden Design, Shrubs & Trees

Love Your Trees

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By Christine Freeburn, Master Gardener

As gardeners, we are aware of the importance of trees. In our yards they give us shade from the hot sun, dropping the temperature beneath them and cooling the air. They give habitat to birds and insects. They purify the air and help reduce greenhouse gases. They anchor the soil and
help with soil erosion. They give us privacy. Studies have shown that trees also help our mental health. In the past few years, ice storms, spongy moths, wind storms, and the recent derecho have damaged many trees in our area. Around every neighbourhood, you hear the buzz of chainsaws throughout the year. Last week, we had one of our lovely big sugar maples cut down because it became diseased. Heartbreaking but necessary to have it taken down.

Fungal diseases are often the culprit of the decline and death of many species of trees. Trees that are planted where their roots have no good earth to grow in become stressed. A stressed plant is easier for pests and diseases to invade. Our sugar maple was close to our driveway and although it is not paved, the ground is compacted.

Years of drought also affect a tree’s health. Wind storms can damage branches and leave open wounds where disease can find its way in. We are all familiar with Dutch Elm disease which has been in Ontario since 1946. It is a highly contagious fungal disease that has almost wiped out elm trees. Many of the dead trees you see along roadsides are elms.

Anthracnose is a common disease in maple and oak trees. It often appears after a damp cool spring. Brown blotches appear on leaves, they dry up and fall off. When combating this disease, you need to rake up and dispose of infected leaves. Tar Spot is common on norway maples. Although it may not kill your tree, it is a fungal disease and will continue to spread. It is recommended to rake up leaves and dispose of them rather than mulching them.

Spruce trees were stressed by the spongy moths and drought and we are seeing them suffering with Cytospora Canker. Signs of this disease are needles turning purple, then brown, then dropping off leaving branches bare but covered with a white resin. Cankers appear on the branches near the trunk.

Last week’s post was on Oak Wilt, a recent fungal disease which has no chemical control yet. Pests are also a huge problem with our trees. Emerald Ash Borer has been in Ontario since 2002. The metallic green beetle emerges in late June, laying eggs in crevices of bark. Larvae overwinter under bark and tunnel under the bark leaving “S” shaped marks which cuts off the trees ability to draw food and water. There is an insecticide that a professional can inject into the tree.

Spruce budworm is native to North America. It attacks balsam fir (Abies balsamea), white and black spruce (Picea), hemlock (Tsuga), jack and eastern white pine (Pinus) and Larch (Larix). BTK has been used to control, however if you have a mature tree this option is overwhelming. We all need to be aware of the health of the mature trees on our property. Ensure they are getting enough water, watch for small leaves or broken branches and pest infestations. Call an expert arborist to give advice on an ailing trees. They can also help with any pruning issues that might need to be addressed.

If you are investing in a tree for your property, be sure to do some research and find the right tree for the right spot. Take into consideration how big the tree will get, where the sun will shine on it, how much ground it will have to absorb moisture and what competition it might have. Young trees need lots of water to get established and grow. What’s that old saying? Hug a tree? Well, after you hug your tree, check out the references below for more information on diseases and pests and ways to help your trees.

References


https://www.toronto.ca/services-payments/water-environment/trees/forest-management/threats-to-trees-diseases/
https://www.ontario.ca/page/dutch-elm-disease
https://extension.umn.edu/plant-diseases/cytospora-canker
https://www.canr.msu.edu/news/black_polka_dots_on_maple_tar_spot

Advice, Disease, Shrubs & Trees

Oak Wilt: A Primer for Prevention

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By Mary-Jane Pilgrim, Master Gardener

Oak trees are an essential part of Ontario’s natural beauty, providing shade, wildlife habitat, and a sense of nostalgia. However, these majestic trees face a silent threat known as oak wilt, a deadly fungal disease that can devastate entire oak populations if left unchecked. In this article, we’ll discuss what oak wilt is and how you can help prevent its spread.

What is Oak Wilt? Oak wilt is a disease caused by the fungus Bretziella fagacearum. It primarily affects oak trees, especially red oaks and pin oaks. The fungus clogs the tree’s water-conducting vessels, causing wilting, leaf loss, and eventually death. Oak wilt is highly contagious, spreading through root grafts between neighboring trees or by sap-feeding beetles that transport the fungus spores.

Oak Wilt: Photo credit Canadian Food Inspection Agency.

Preventing Oak Wilt:

  1. Avoid Pruning Oaks in Spring and Early Summer: Oak wilt spores are most active during these seasons. Pruning creates wounds that can attract sap-feeding beetles carrying the fungus. Instead, prune oak trees during the dormant season in late fall or winter.
  2. Use Pruning Paint: After pruning, seal the wounds with pruning paint or a latex-based paint to prevent beetles from entering and spreading the disease.
  3. Dispose of Infected Wood Properly: If you suspect oak wilt, remove and destroy infected wood by burning or burying it. Do not use it for firewood or mulch.
  4. Report Suspected Cases: If you notice oak trees showing signs of oak wilt, contact your local forestry department or arborist immediately. Early detection and intervention can help contain the disease. This link may help: Signs and Symptoms of Oak Wilt.
  5. Promote Tree Health: Healthy trees are less susceptible to oak wilt. Ensure your oaks receive proper care, including regular watering, fertilization, and protection from other stressors like construction damage.

Oak Wilt has been found in the following locations in Ontario: City of Niagara Falls, township of Springwater (north of Barrie), and Niagara-on-the-Lake, ON.

There is currently no available treatment for oak wilt.

We must take collective action to protect our oak trees from oak wilt. By following these prevention measures and staying vigilant, we can help preserve the beauty and ecological importance of these remarkable trees for generations to come.

Resources

https://www.michiganoakwilt.org/oak-wilt-101, especially this image showing the disease on both red and white oak leaves.

https://www.invasivespeciescentre.ca/invasive-species/meet-the-species/invasive-pathogens/oak-wilt/

https://inspection.canada.ca/plant-health/invasive-species/plant-diseases/oak-wilt/eng/1325624048625/1325624535106