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Plant Answer Line Question

Keywords: Fragaria, Cutworms, Fruit--Diseases and pests

My small patch of strawberry plants has this year suffered from green fruit dropping off, forming neat piles under each plant. Each fallen fruit has a short bit of stem still attached. A few fruit are still attached. No sign of slug or squirrel damage, no signs of fungus of insect attack. The weather has been colder and wetter than average. Owing to natural layering, the plants are closer together than when first planted. This happened a couple of years ago, but we had a good crop last year. Any idea what's going wrong?


I wonder if this might be the work of cutworms. You can take a close look just under the soil surface, along the stems, and inside curled or folded leaves during the day, or take a flashlight at night, which is when they feed, and see if that may be why your strawberries are being cut away from the plant. If you find them, cut them with garden pruners.

Washington State University's pest and disease site does list the cutworm as a known pest of strawberries. Excerpt:

"Cutworms and armyworms are the larvae of noctuid moths. These common moths are medium-sized with fairly dull coloration. The greenish, grayish, or tan caterpillars are hairless, nocturnal, and generally spotted, striped, or otherwise marked. They may be 1/4" to 1" in length and tend to curl up when disturbed. They may climb into the plant and feed on foliage, buds, flowers, or fruit. Armyworm behavior is similar to that of cutworms, but armyworms feed in large groups instead of individually. They tend to be voracious feeders. The caterpillars typically spend the day just beneath the soil surface or under debris near the host. Weeds are a primary food source for both cutworms and armyworms."

I looked at Pests of the Garden and Small Farm by Mary Louise Flint (University of California, 1990), but could not find any strawberry disease resembling what you have observed in your garden, which leads me to believe it is a pest problem. Here is a link to U.C. Davis's Integrated Pest Management page on strawberries.

Date 2018-05-04
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Plant Answer Line Question

Keywords: Soils, Aegopodium, Convallaria, Oxalis oregana, Lobularia, Pachysandra, Galium, Lamium galeobdolon, Sheet mulching, Euonymus, Shade-tolerant plants, Polystichum munitum, Native plants--Washington, Fragaria, Ground cover plants, Geranium

What is a good way to deal with a gravelly area with a lot of shade? Are there good groundcovers that would be low maintenance? Can the plants grow right in the gravel, or do I need to do something to the soil?


If it's pure gravel, you can just make a border (with rocks and/or wood, preferably non-treated) and fill it with 9-12" of soil. (No need to remove the gravel.) You buy soil by the cubic yard, so to figure out how much, multiply the length (feet) x width (feet) x depth (.75 or 1), then divide by 27 to get the number of yards. One yard of soil is 3' x 3' x 3', or 27 cubic feet. My guess is that you need less than a yard, but it settles.

You can save money by buying the soil in bulk. Otherwise, you have to buy it by the bag, and they might come in cubic feet. If there is only some gravel, you may be able to get by with the soil/gravel mix that you have. See how much hardpan there is by digging around a little.

If you have lots of weeds in the gravel, cover the whole area with large sheets of cardboard or multiple layers of newspaper (about 10 sheets), overlapped to prevent light from getting through. Then put down a border and fill the area with soil. Smothering weeds depends upon complete darkness more than anything. Therefore, overlapping biodegradable stuff and deep soil is key.

Once you've done that, you can plant right away. Here are some plant suggestions. I've included links to pictures, but you can always find more on Google images or the Missouri Botanical Garden's PlantFinder.

  1. Lobularia maritima, known as sweet alyssum: You can plant seeds of this and it will come up this year. It's best to mix it with something else, since it dies down in winter (but self-seeds vigorously and will return). The white seeds the fastest (year to year), but it's nice to mix with purple. Both varieties smell good and attract beneficial insects.

  2. Fragaria x ananassa 'Pink Panda': A strawberry-potentilla hybrid that grows fast and spreads easily, is good weed suppresser, and blooms twice a year with pink flowers. This is an excellent groundcover, will probably be evergreen.

  3. Pachysandra: This plant is evergreen, and though it is not as fast growing as some groundcovers, it does spread.

  4. Hardy Geranium spp.: Geranium x oxonianum 'Claridge Druce' is a variety that spreads well. Another good variety is Geranium endressii 'Wargrave's Pink'; in particular, it seeds itself well. Geranium macrorrhizum has many cultivars, a pleasant scent, and self-seeds readily.

  5. Galium odoratum: Also called sweet woodruff, this plant is prettily scented, probably evergreen here, and spreads fairly rapidly. It produces white flowers in early spring, and it would be particularly good to mix with something taller, like Geranium species.

  6. Oxalis oregana: This native plant looks like a shamrock, and though it is slow to establish, once it has it's very tough and spreads. If you don't get the native Oxalis oregana be careful, as the other species are very aggressive.

  7. Euonymus spp.: These woody groundcover plants are evergreen, and come in lots of varieties like E. fortunei 'Emerald 'n'Gold' and 'Emerald Gaiety'. Do be sure to get a groundcover and not a shrub version of the plant. 'Emerald and Gold' is the most robust choice.

  8. Convallaria majalis: Also known as lily of the valley, this is a vigorous (aggressive!) groundcover.

  9. Maianthemum dilatatum: Called false lily of the valley, this native plant is a good choice for shade groundcover.

  10. Polystichum munitum: The native swordfern (or another fern species) might work. P. munitum is basically evergreen, though you might need to cut out some dead fronds in late winter, and makes a good mix with something else. Other deciduous ferns are higher maintenance.

There are also a couple of plants to avoid!

  1. DON'T plant Aegopodium podagraria 'Variegatum': Commonly called bishop's weed, and frequently used as a groundcover, this plant is very invasive.

  2. DON'T plant Lamium galeobdolon (formerly known as Lamiastrum), either: Yellow archangel is very invasive in Pacific Northwest forests.

Date 2017-05-25
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Plant Answer Line Question

Keywords: Vaccinium, Berries--Diseases and pests, Rubus, Fragaria, Insect pests, Prunus, Fruit--Diseases and pests, Berries

Could you tell me more about a new type of fruit fly that is supposedly infesting fruit here in the Pacific Northwest? Which fruit are affected?


The fruit fly is called the Spotted Wing Drosophila. It is known to affect strawberry, raspberry, blueberry, plum, peach, cherry, and grape. Oregon State University has created an information clearinghouse about this pest. Here is their information for home fruit growers. Washington State University has also devoted several web pages to this fly. Here is their Integrated Pest Management information, excerpted below (SWD stands for Spotted Wing Drosophila):
"Monitor for SWD using traps. [...] These vinegar traps are for monitoring purposes only and will not provide control of SWD. Remember, chemical control is not necessary if SWD is not present.
Composting fruit will likely not be effective at destroying maggots and pupae.
Remove infested and fallen fruit. Destroy or dispose of infested fruit in a sealed container.
Management recommendations are currently being developed for this pest. For the time being, good sanitation practices should be used."

Whatcom County Extension has clear, basic information for home gardeners as well. Since this insect is a relatively recent invader in the Northwest, information is constantly being adjusted and research is ongoing.

Date 2017-08-15
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Plant Answer Line Question

Keywords: Cross-pollination, Fragaria, Propagation

I have organic Rainier strawberries in a raised bed. I'd like to plant organic everbearing strawberries in the same bed. Is there a problem with cross-pollination? What would be your recommendation for the best strawberry varieties to plant in Seattle?


Strawberries can reproduce by runners or by seed. Those which are reproduced by runners will be clones of the parent plant, but those which grow from seed may cross-pollinate.

Here is more information from the Royal Horticultural Society.
"Strawberries can be propagated in late summer, but no later than early autumn, by sinking 9cm (3.5in) pots filled with potting media, such as general-purpose potting compost, into the beds and inserting individual runners into them. Sever the new young plants from the parent plant when rooted. Perpetual strawberries produce few runners and new plants are best bought in annually.
"Seed-raised cultivars are available but are not recommended*, except for alpine strawberries."
*I suspect this is because you can't know what the resulting new generation of strawberries will be like--tasty or not so tasty.

So I think as long as you harvest your fruit, and don't let fruit ripen and drop into the bed, you can allow runners to produce new plants and they should be the same varieties as their parents. That being said, it's usually good to replace strawberry plants after a few years, just to keep disease problems down (the RHS link above says to replace every 3 years or so).

I've had good luck with Shuksan (June-bearing), and I think I may have grown Tristar (ever-bearing) before, too. Oregon State University Extension has a guide entitled "Strawberry Cultivars for Western Oregon and Washington" which recommends these varieties and several others..

There are many more varieties listed in the Sunset Western Garden Book of Edibles (2010). If you are looking for sources, you might try your favorite local nurseries, but also mail order nurseries like Raintree, Cloud Mountain Farm, and Burnt Ridge. The Northwest Flower and Garden Show in February often has vendors selling strawberry plants.

Date 2018-03-14
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Garden Tip

Keywords: Strawberries, Fragaria, Fruit--Care and maintenance, Berries

If you feel cheated by the big, red, sour strawberries available in grocery stores late winter is the time to start your own little strawberry field. Starter plants are available in nurseries, but which variety to choose? If you want to harvest many berries at once for jam or pies buy "June-bearing" such as 'Shuksan' or 'Rainier'; if you want lower maintenance plants that will provides a few berries throughout the summer buy "Day-neutral" such as 'Tribute' or 'Tillicum.'

The experts all agree, you should cut off the first flush of flowers so that your plants will develop larger crowns and eventually more fruit. This means no fruit for the first year for June-bearing strawberries. Don't scrimp on water, but good drainage is also essential. Applying a mulch will help keep the soil cool and moist and protect the ripening berries from soil fungus. But mulch will also give shelter to slugs, so take care to use an organic-acceptable iron phosphate bait (such as Sluggo) regularly.
While technically perennial, strawberry plants should be replaced every 2 to 3 years with newly purchased stock. Recommended reading on growing strawberries, from Oregon State University, will get you off to a good start.

Stephen Wilhelm and James E. Sagen in their book, A History of the Strawberry: from ancient gardens to modern markets, investigate how the strawberry was named. The theory they give most credence to is that the runners are "strewed" from the mother plant. In ancient times one word used for "strew" was "straw," and thus a strewing berry became strabery (sic) which eventually became strawberry in England.
If you want to use straw as the mulch for strawberries look in the yellow pages under "feed stores."

Date: 2007-04-03
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May 31 2018 13:14:08