on dodders

While hiking on San Juan Island, I saw these strangely beautiful, fluorescent orange clumps of hair-like substance (plant? fungus? something from outer space??) interwoven through the succulent-looking marsh plants. Can you tell me what this is?

That weaving (or strangling!) habit you describe calls dodder to mind, and there is a native coastal salt marsh dodder in that area called Cuscuta pacifica. Dodder is related to morning glories (the plant family Convolvulaceae). It is a rootless parasitic plant with nearly no chlorophyll and barely any leaves, and cannot photosynthesize on its own. It sustains itself by twining around other flowering plants and infiltrating their tissues with specialized branches on its stems, and coiling around them repeatedly as it grows. It may even be able to “smell” potential host plants.

Dodder can weaken its host plants, rendering them vulnerable to disease. However, there is some evidence that by thinning out the dominant host plants in a given area, it makes room for other species to take hold, increasing diversity.

The Washington State Noxious Weed Control Board lists a non-native species (Cuscuta approximata, smoothseed alfalfa dodder) as a Class C noxious weed, but it is not found in the area where you were. It is mainly a problem in agricultural land east of the Cascades. Dodder has various unfriendly nicknames in farming land: Devil’s Guts, Witches’ Shoelaces, Strangleweed, to list a few.

a flower called ‘town hall clock’

While reading a book on British woodlands, I came across a reference to a flower whose common name is ‘town hall clock.’ Can you tell me what plant it is, and why it has this name?

Townhall Clock’s scientific name is Adoxa moschatellina, in the Adoxaceae family. Other common names for this native British wildflower are Moschatel, Five-Faced Bishop, Muskroot, Tuberous Crowfoot, and Hollowroot. All of those names are descriptive of various aspects of the plant’s appearance, but the name Townhall Clock is evocative of the way this pale yellow-green early spring flower rises up on a slender stem. According to Sarah Raven (in her book Wild Flowers, Bloomsbury, 2012), four faces of the flower are “arranged as if on the surface of a cube, the fifth facing upwards.” The aroma of the flowers is musky, or like “elder blossom with a bit of almond.”

There are some detailed photos of it on this Finnish plant identification website. Despite the name Townhall Clock, it’s a subtle flower that might easily be overlooked. In fact, its genus name means “without glory,” due to its unshowy blooms.

on fertilizing peach trees

We have a white peach tree that was just OK this year. I am wondering what I can do to get the most out of it next year – what is the best fertilizer for peaches?

According to Sunset’s Western Garden Book of Edibles (2010), peach trees may be fertilized with a 10-10-10 complete fertilizer (the numbers correspond to N-P-K, nitrogen, phosphorus, potassium) at bud break in late March. “Give young trees 1/2 pound per year of age and give mature trees up to 5 pounds (for full-size, full-grown trees). Spread fertilizer evenly over the entire root zone.”

Washington State University Extension has general information on fertilizing for home orchardists. Here is a relevant excerpt:

“Nitrogen is not needed in most of western Washington since we have such high levels of organic matter in our soil, and it is continually released during the summers. Nitrogen controls growth. With excess we get rank growth. Fruit maturity is delayed; and storage life of apples and pears is reduced. Peaches need more nitrogen so applications may be necessary.”

on the parasitic plant dodder

I’m doing a science fair project on dodder plant and I’m seeking information about the plant, and a source of seeds or plants for the project.

Dodder is a parasitic plant that lives on crops, ornamentals, native plants, and weeds. Because it has limited chlorophyll, it can’t make enough food to support
itself, and so relies on the plants it colonizes for nourishment. It belongs to the genus Cuscuta, in the family Convolvulaceae (same family as morning glory). It was formerly referred to as Grammica.

Perhaps the reason that seeds and plants are not readily available is that dodder causes great damage to the plants it parasitizes. The U.S. Department of Agriculture’s plant protection and quarantine office states that “products, including foods, containing whole dodder seeds (Cuscuta spp.) are prohibited entry into the United States. APHIS regulates whole dodder seeds, both as a parasitic plant pest under Title 7 Code of Federal Regulations (CFR), Part 330 and as a Federal noxious weed under Title 7 CFR, Part 360.”

Here is additional information from University of California, Davis’s Integrated Pest Management website. Dodder is sometimes referred to as the “Vampire Plant,” as this University of Florida Extension page explains. Although your project, safe within the confines of a lab or classroom, might pose no threat, it is not legal to sell Cuscuta seeds or plants in the U.S.

harvesting rooftop runoff water for vegetable gardens

I need to replace my roof, and I am thinking of installing asphalt or composite shingles because they’re what I can afford. I planned to capture rain water to irrigate my vegetable garden, but I’m concerned about toxicity. Is runoff from the shingled roof likely to be toxic?

I would not recommend using reclaimed rainwater from an asphalt shingle roof for any edible crop. Asphalt is petroleum-based. The runoff might be acceptable for ornamental plants, but the fact that asphalt or composite shingles tend to shed tiny particles means that those particles would be introduced to the soil around your crops.

An article from North Carolina State University Extension discusses “Water Quality of Rooftop Runoff.” It doesn’t specifically mention asphalt, but I don’t think it would be wise to use the reclaimed water on food crops.

Green Living Journal (now archived) has an article about roofing materials, and discusses asphalt shingles as well as alternatives.

The National Gardening Association site has a report, no longer available online, that describes rainwater harvesting.
Excerpt:
“Water from the rain barrel is, of course, not potable, but some experts also raise concern about possible contaminants from rooftops that can make the water unsuitable for edible gardens. According to an article in Landscape Architecture magazine, asphalt shingles and other porous or rough roofing materials can hold particulates such as bird droppings and other debris, as well as heavy metals from the air, which then wash into the rain barrel. Wood shingles that are chemically treated to resist rot and algae can leach the chemicals into the rainwater running off the roof. Zinc strips that prevent moss build-up can also be problematic. Some large-scale rainwater collection systems are even designed to allow for the first flush of water off the roof — which carries the majority of the questionable substances — to be diverted.

“Other people dispute these risks and say washing your garden produce is all that’s needed. It’s a judgment call. I tend to research things to death so I think it would be interesting to have some of my rooftop runoff tested at the health department.”

There is a very detailed and technical document entitled “Roofing Materials Assessment” from Washington State Department of Ecology (2013-2014 study results) if you wish to pursue the topic further.

If installing slate, clay tiles, untreated wood shingles, or a green roof is prohibitively expensive, the best solution might be to landscape the garden in such a way that you can reclaim runoff from the roof for non-edible plants.

dividing and propagating Dierama

Could you provide some information on the propagation and division of Dierama (not sure if the species I have is D. pendulum or D. pulcherrimum. It has pink flowers and is also known as Angel’s Fishing Rod)? The clump has gotten large and I’d like to see if I can divide it now in fall.

The Royal Horticultural Society has an advice page on how to divide and propagate Dierama.

Excerpt:
Named cultivars can be propagated by division in spring or immediately after flowering; but this should only be undertaken occasionally as plants are slow to re-establish. Plants grow from corms that build up year by year into chains, similar to Crocosmia.

Lift plants and separate corms, reducing the foliage by half with secateurs.

Take care not to damage the brittle, fleshy roots.

Divisions take one to two years to flower freely again.

For an answer from local experts, I consulted Perennials: The Gardener’s Reference by Carter, Becker, and Lilly (Timber Press, 2007). The authors say that “it’s best not to transplant, divide, or groom in the fall.” Instead, if you must divide, do so in April or May and include several corms in each clump. You can also sow ripe seed at that time. Seed may be harvested by shaking the stems.

fragrance in Hamamelis

I visited the Washington Park Arboretum in January and admired the blooming Hamamelis. There was strong fragrance in the air, but we were unable to tell which tree was the most fragrant. Can you tell me which variety is most fragrant of the ones in the Arboretum?

Also, I have read that Hamamelis virginiana is very fragrant but I don’t know if it does well here in the Northwest.

Scent can be a subjective matter, but the local group Great Plant Picks does have an evaluation of various Hamamelis species and cultivars, and according to their list, Hamamelis mollis is exceptionally fragrant compared to the rest.

Missouri Botanical Garden agrees with this assessment, stating that Chinese witch hazel (H. mollis and its cultivars) is the most fragrant species.

About the scent of Hamamelis virginiana, Chris Lane’s book Witch Hazels (Timber Press, 2005) only says “sweet scent.” In his book, Winter-flowering Shrubs, Michael Buffin rates the scent of various witch hazels as follows:

H. mollis: highly scented
H. x intermedia: varies; ‘Pallida’ has most scent; ‘Aphrodite’ slightly scented; ‘Allgold’ is strong but slightly musky; ‘Arnold Promise’ has strong scent; ‘Barmstedt Gold’ is very slightly scented; ‘Dishi’ is highly scented; ‘Diane’ nearly scentless; ‘Hiltingbury’ weakly scented; ‘Jelena’ moderate; ‘Moonlight’ strong, sweet; ‘Orange Peel’ reasonably good scent; ‘Sunburst’ lacks scent; ‘Vesna’ very sweet; ‘Westerdale’ moderate; ‘Winter Beauty’ scentless.
H. japonica: sweet but faint
H. vernalis: musky
H. virginiana: slightly scented

Hamamelis virginiana is more commonly grown for providing astringent, or as commercial rootstock than as a garden plant. It is native to eastern North America, though it will also grow here in the Northwest. It has a habit of holding onto its dead leaves.

Here is another article which discusses fragrance in Hamamelis, from Swarthmore College’s Scott Arboretum blog (posted 2/25/2011). the author says: “Getting my top ranking was H. mollis ‘Wisley Supreme’ and ‘Early Bright’ which do hold some leaves but have fantastic fragrance.”

As an example of the subjectivity of smell, see the following from Val Easton’s Seattle Times column:
“Q: I have purchased a Hamamelis virginiana and I don’t think it is anything like (the fragrant plant) you have written about. Will you let me know exactly which witch hazel has great fragrance and blooms in January/February?
A: The liniment witch hazel is made from the bark of Hamamelis virginiana, but that’s your plant’s main claim to fame. The Chinese witch hazels (Hamamelis mollis), and plants crossed with them, are supremely fragrant and bloom in winter (H. virginiana blooms in autumn and its flowers are so small they’re often lost beneath the leaves). Some of the earliest-blooming witch hazels are Hamamelis x intermedia, which have the Chinese witch hazels as one of their parents; ‘Pallida’ blooms earliest in late January or February; ‘Diane’ has dark red flowers, and ‘Arnold’s Promise’ has large, bright yellow flowers a little later in the winter. All are deliciously fragrant.”

pruning Crocosmia

Can Crocosmia be pruned or cut way down? When? The tall leaves are looking ungainly.

According to The Plant Care Manual by Stefan Buczacki (Crown, 1993), you should cut back the foliage as it discolors.

According to the Royal Horticultural Society, perennials that produce leaves and flower stems from below the soil level, such as crocosmia and peony, are cut back to soil level.

on tree topping

What is the definition of topping a tree?

The Morton Arboretum Tree-Care Handbook calls topping “indiscriminately sawing off large branches.” (1994)

According to the Washington State Department of Ecology’s Vegetation Management: A Guide for Puget Sound Bluff Property Owners (May 1993, p.23), the practice of topping usually refers to cutting the upper portion of the main leader (trunk) in conifers and to the removal of all branches at a particular height in deciduous trees. Topping is not advised.

Plant Amnesty has loads of information about topping – including why it should not be done – at the following link: 5 Reasons Not to Top.

parsley: a perennial or a biennial?

Is Italian parsley a perennial or a biennial?

The Sunset Western Garden Book says that parsley (Petroselinum species) is a biennial grown as an annual.

University of Arkansas Extension provides additional information on growing parsley, including the Italian variety, which is Petroselinum neapolitanum, and curly leaf parsley, Petroselinum crispum.