Elisabeth C. Miller Library logo Miller Library Home UW Botanic Gardens Home UW Botanic Gardens Home book graphic

3501 NE 41st Street, Seattle, WA 98195 | (206) 543 0415 | Open: | Library Schedule

Gardening Answers Knowledgebase

Browse the Knowledgebase

Search for gardening questions with researched answers, plus gardening tips, book reviews and recommended websites.




Recently Added Questions


Is it safe to eat pickles made from unripe walnuts (including hulls)? Are some types of unripe walnuts safe to eat and others not safe? I am not sure what kind of walnut is in my garden.

I am also a bit worried by articles I found online which say that juglone from walnuts can cause cell damage. Maybe I should skip this culinary adventure?


Pickled walnuts (from English walnut, Juglans regia) are a traditional British delicacy. The Royal Horticultural Society even mentions them. Alys Fowler's book, The Thrifty Forager (2011), says the walnuts for pickling must be picked in early summer before they harden. Traditionally, walnuts for pickling were harvested June 15, St. John's feast day. The famous 16th century herbalist John Gerard said, "the green and tender Nuts boyled in Sugar eaten as a Suckad, are a most pleasant and delectable meat, comfort the stomacke, and expell poison."

All walnut species have edible properties, though black walnut may be more bitter than English walnut. Edible East Bay published an article by Kristen Rasmussen in summer 2015 on pickling green walnuts from a native Californian species of walnut, Juglans californica.

Anyone who is sensitive to walnuts probably should avoid the pickled ones, too. Like many plants, walnuts have both edible uses and toxic properties. If you do not consume large quantities of walnuts (pickled or otherwise), I do not think there should be dire medical consequences. Toxic Plants of North America, 2nd ed., 2013 (Burrows and Tyrl) has a section on walnut (Juglans). The main toxicity concern discussed is that to horses, and in their case, it is mainly due to the use of walnut wood shavings in horse stalls.

A word about finding random articles on the internet: Context matters, and the citation you found about cell damage is in the context of using juglone (administered in a medical research facility) to kill cancer cells. It is not the context of everyday consumption of walnuts. Reliable sources are hard to find via the internet, and I would view with skepticism any site that is primarily commercial and does not cite trustworthy sources.

I could not find any references to the effects of pickling on the chemical composition of walnuts. Certainly, pickling (like any form of food preparation) will have some effects on nutrients. But since pickled walnuts are likely an occasional snack and not a staple upon which one's diet is founded, there is no cause for concern.


I saw some moss balls for sale in the gift shop of the new Nordic Museum. What type of moss is used? Is it native to Nordic countries? How do I care for one indoors?


The "moss" is actually a type of freshwater alga, Aegagropila linnaei, found in only a small number of northern hemisphere lakes. Other common names are lake ball or Cladophora ball. In Japan, they are called marimo (meaning a bouncy ball that is in water). The Ainu people of Hokkaido hold an annual Marimo Festival at Lake Akan to celebrate these charming lake goblins.

Iceland's Lake Mývatn once had the world's largest colony of lake balls but pollution has been altering the ecosystem there, and the mats of algae balls (colloquially called round sh*t or muck balls by the fishing community) began dying out. Their disappearance was first noted in 2013. There are some recent signs that the nutrient imbalance of the lake (caused by fertilizer runoff, and accumulation of bacteria) is correcting itself and that the ecosystem of the lake is bouncing back to better health.

To grow marimo inside, you will need a container that holds water, and a spot where the algae receive indirect sunlight. They prefer cool locations in nature, so they will do best if they do not get too hot (don't put them near a heat source, and if it gets hot in your home, you can cool them off in water in the refrigerator). To keep the balls floating, squeeze out some of the water from time to time. To propagate the algae, use scissors to divide the marimo in half after squeezing out some of the water (you can repeat this process and cut into fourths or eighths). Use thread to wrap the cut algae back into a rounded shape, tie the thread close to the ball, and put back into the water. Some people combine them with other plants and tiny shrimp in indoor aquascapes.


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.


I'm ready to call it quits...ia! How can I tell the difference between Weigela, Dipelta, and Kolkwitzia?


All three of these opposite-leaved shrubs are in the honeysuckle family, Caprifoliceae. However, some taxonomists split Kolkwitzia and Dipelta (along with Abelia and Linnaea) into Linnaeaceae, while Weigela joins Diervilla in Diervillaceae.

Although spring is the time when most plant lovers notice these flowering shrubs, it is easier to tell them apart when they develop dry fruit. Dipelta floribunda and Kolkwitzia amabilis produce achenes (dry, single-seeded fruits that do not split open), whereas Weigela florida fruits are capsules (clustered together like a tiny bunch of bananas, and developing from green or red to brown as they mature). Dipelta bracts are ornamental, papery, and colorful before they dry to brown. Kolkwitzia bracts are weird-looking, like bristly chicken feet.

If you are eager to know what you are looking at while the shrub is still in flower, it is easy to rule out Dipelta and Kolkwitzia if the flowers are red or yellow, in which case, it's Weigela. Bear in mind that Kolkwitzia and Weigela are common in home gardens, while Dipelta is much less so. Dipelta and Kolkwitzia have pale pink to whitish flowers with markings on the petals; Weigela lacks such markings. Weigela petals also differ from the other two genera in that they are all about the same size (radially symmetrical, or actinomorphic), while in Dipelta and Kolkwitzia, the lower petals are larger than the upper two (that is, bilaterally symmetrical, or zygomorphic). The bristly characteristics of Kolkwitzia that are so notable in the dried fruit are also visible in the white bristles at the flower’s base. The Dipelta flower's base is concealed between a pair of circular bracts. To summarize: Bracts? Dipelta. Bristles? Kolkwitzia.



I just saw a ball of tiny yellow spiders with black dots clustered on the end of a Santolina stem. Are they beneficial in the garden, or should I remove them?


Your description sounds like the cross orbweaver (also called cross spider, because of the white markings on the back of its abdomen), Araneus diadematus. Its baby spiders (spiderlings) are yellow with black markings, and they crowd together and seem to move as one if disturbed. They hatch (in groups of hundreds to almost a thousand) from a fluffy-looking pale yellow egg sac. The Washington NatureMapping website has a factsheet about this species.

These industrious spiders build a new web each day (after eating the previous day's web). They are often found close to houses and illumination (at my house, the nests appear behind the porch light) and in gardens. Their diet consists of invertebrates, so in that sense, they do provide some benefit in the garden.

Cross orbweavers in your garden are not a problem, though humans occasionally encroach on their space, and the spiders may bite in reaction to the disturbance. Some people are more sensitive to the bites than others. My strong recommendation is to let them be, and enjoy observing them.