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`MG Foundation of Washington State`⁠
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`Seeds For Thought Newsletter`⁠
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(Examples of Recent Content)

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`Dealing with Slugs`⁠
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Essential Oils or Caffeine to Deal with Slugs!?

~~ Alice Slusher, Cowlitz County Master Gardener

I’ve been researching two recent announcements by OSU professors about slug and snail management options–caffeine and essential oils. I’m reporting my findings. Thought you all might be interested.

Disclaimer: Both of these solutions are still being researched and have not been approved by WSU for pest management. This means that we cannot, as Master Gardeners, share this information with people who ask us about managing slugs and snails. These are PNW Handbook’s recommendations for managing slugs.

https://pnwhandbooks.org/insect/ipm/slug⁠

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Here are a couple of ideas that are being researched, and both are easy to test at home.

Rory McDonnell, OSU’s premier slug-guru, is currently doing research about using essential oils to repel and kill slugs. In a

recent interview,⁠

he says that cloves, thyme, and spearmint essential oils are even more effective at killing slugs than the currently available products containing metaldehyde (which is toxic to humans, pets, wildlife, and aquatic life). In the interview, he said that thyme seemed to be most effective. It doesn’t take much—only 1%-2% essential oil in water works well and does not cause phytotoxicity (plant tissue damage) on leaves. (Note: products like Sluggo that contain iron phosphate as the active ingredient are considered to be non-toxic)

To make a spray: To create a 2% solution in 1 quart of water, use a little less than four teaspoons of clove, thyme, or spearmint essential oil. Shake well. If spraying on leaves, be sure to first test it on a leaf after it’s been exposed to the sun over several days.

Another trick he uses for container plants is to mix a little essential oil with petroleum jelly and smear it around the edge of the pot.

There are at least two commercially available products approved for use in WA that contain essential oils as active ingredients. Of course, read and follow the label directions:

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All Natural Snail & Slug Spray Rtu⁠

(ready to use)

Dr. Earth Final Stop Snail & Slug Killer Spray⁠

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photo by lunahaarmann via Pixabay, used under the Pixabay Content License

Another

article from the University of Hawaii⁠

suggests that using strong brewed coffee in a 1:9 ratio with water is an effective molluscicide spray, too.

“Large slugs were killed by spray applications containing 1–2% caffeine… We conclude that slugs can discriminate between treated and untreated leaves and that caffeine significantly reduces feeding at a concentration of only 0.01%. We found that large slugs placed on loose soil and sprayed with a 1 or 2% solution of caffeine responded with uncoordinated writhing; the only survivors were the few that were able to burrow into the soil soon after treatment.”

Linda Brewer, a

soil scientist from OSU⁠

suggests:

To make a 1% to 2% soil drench, add 1 part water to 2 parts strong brewed coffee. For example, use 1 cup of water for 2 cups of coffee. To reduce slug feeding on foliage, add 9 parts water to 1 part brewed coffee and apply as a spray. “A sensible approach would be to apply diluted coffee to a sample of leaves and wait for a few hot and sunny days to watch for leaf burn or other damage,” Brewer said. “If there’s no damage, go ahead with spraying.”

More resources:

Gardening with (and without) slugs and snails | OSU Extension Service (oregonstate.edu)⁠

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Grow Smart Grow Safe—controlling slugs and snails—options:

https://www.growsmartgrowsafe.org/Products?pesticideTypeId=16⁠

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Know thy slugs:

https://www.oregon.gov/oda/shared/Documents/Publications/IPPM/ODAGuideMolluscs2016ForPress.pdf⁠

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Slug Portal⁠

—OSU—everything you EVER wanted to know about slugs

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`Winter Rose Pruning`⁠

~~ Barbara Faurot, Jefferson County Master Gardener

“I love to prune my roses … you can forget everything else while you’re doing it.” – Julie Andrews, actress, author, and rosarian

It’s time to prune our roses. The Seattle Rose Society recommends pruning between Feb. 22 and mid-March, when forsythia is blooming in your neighborhood. The plants are still dormant, but the likelihood of a hard freeze has passed. Winter pruning accomplishes several tasks: improving structure, encouraging new flowering wood, increasing sunlight and air circulation, and reducing fungal pathogens.

Within the Rose family (Rosaceae), the genus Rosa includes more than 100 species and thousands of cultivars. Species roses, with 22 native to North America, are those that occur naturally in the Northern Hemisphere.

Modern roses are considered to be those bred and cultivated after 1867, the year the first hybrid tea rose was developed. Hybrids and cultivars developed prior to 1867 are known as old garden, heritage, or heirloom roses.

It’s important to note that old garden roses typically bloom on the prior year’s growth, so they should not be pruned in winter. After flowering, they can be pruned very lightly to remove any old, unproductive canes.

The basic pruning steps for modern roses are similar to other cane growers like mahonia, kerria, nandina, or forsythia. As with most plants, prune lightly during the first year or two while the root system is still developing.

Start with clean, sharp pruning tools. Remove dead wood, diseased or spindly canes, rubbing or crossing canes, and rootstock suckers if you have a grafted rose. Prune die-back to bright green cambium just beneath the bark, with clean white pith inside.

Old leaves remaining after the winter can harbor disease, so they should be removed. If rose hips remain, they can also be removed when they begin to look spent. In all cases, pruned materials – canes, leaves, or hips – may contain disease-carrying spores, so they should be discarded and not added to compost.

Since most modern roses produce flowers on new growth, our main objective is to select the strong, healthy canes that will support this year’s growth. These canes can be shortened to an outward-facing bud above a leaf scar (the intersection of the cane and a leaflet). Cut at a 45-degree angle about 1/4” above an emerging bud so that water will flow away from the bud and growth will be forced outward, opening up the plant to sunlight and air circulation. For spreading roses, you can also prune to some inward-facing buds to encourage a more upright habit.

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Most modern roses bloom on new growth. Late winter is the best time to prune to stimulate new canes and flowers. This hybrid tea rose shows healthy new growth above a good pruning cut made at a 45 degree angle about 1/4″ above the bud. Photo courtesy of Amanda Jarrett,

thegardenwebsite.com⁠

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Hybrid tea roses are a cross between hybrid perpetual roses and old garden tea roses. They have a large bloom on a single upright stem and a deep root system. Floribunda roses, smaller than hybrid tea roses but larger than shrub roses, have small flowers grouped in clusters. Grandiflora roses, usually larger than the floribunda, are a cross between a hybrid tea and floribunda. They have large, showy blooms like hybrid teas, but grow in clusters like the floribunda.

Well-established hybrid tea, floribunda, and grandiflora roses can be pruned moderately to fairly hard in spring. Too little pruning can result in a weak, spindly plant. As a rough guideline, prune strong plants moderately – removing at least ⅓ and up to ⅔ of the plant, and prune weaker plants severely to renovate them – leaving only 3-4 canes about 8-12” long.

Shrub roses, including groundcover roses, have a more shallow root system, a spreading habit, smaller flowers, and dense foliage. They tend to be more disease-resistant and need less maintenance. Start by reaching inside to remove any old or crowded canes and open up light and air circulation. Reduce some of the remaining canes to 6-18” tall, depending on the plant’s size. Cut to a healthy bud, facing in the desired direction for new growth. For established groundcover roses, prune off about 6” before new buds begin to form.

Climbing roses are either old garden varieties that bloom once a season, or modern varieties that re-bloom like their parent hybrid tea, floribunda, or grandiflora roses. They bloom on horizontal canes and can be fastened to a fence, trellis, or wall. For the first few years, limit pruning to the removal of dead or weak canes. Once the plant is established on its support, shorten side canes to the edge of the structure to stimulate lateral bud growth. In subsequent years, remove the oldest canes and prune lateral growth to a healthy bud.

David Austin roses, sometimes called English shrub roses, combine the qualities and fragrance of old garden roses with the re-blooming and color range of modern roses. Follow the same basic pruning guidelines depending on their form (shrub or climbing).

Native wild roses like Nootka rose, bald-hip rose, or pea-fruit rose can be pruned if needed like any cane grower. After removing dead or damaged branches, cut a few of the older canes to the ground and remove some of the new shoots.

Looking ahead to spring and summer, stimulate re-blooming by deadheading faded blooms. For healthy plants, prune canes to a leaf node with 5-7 leaflets. In fall, discontinue pruning as the plant prepares to go dormant, and leave the rose hips for winter color and wildlife. Next winter, the pruning cycle can begin again, when the forsythia blooms.

The nonprofit Seattle Rose Society

https://www.seattlerosesociety.com/⁠

offers useful articles, resources, and access to consulting rosarians.