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Elisabeth C. Miller Library

Archives: Plant Answer Line Q & A

Plant Answer Line questions and answers.

plants at the Washington Park Arboretum

I’m thinking of planting the following plants in my garden but would like to see them first. Can you tell me if they are at the Washington
Park Arboretum? The plants are: Chinese Witchhazel, Witch Alder, Mountain Laurel, Soft Shield Fern, and Variegated Kiwi Vine.

 

The Washington Park Arboretum has many examples of Hamamelis mollis, or
Chinese witch hazel (unless you meant Corylopsis sinensis or Loropetalum
chinense, which also go by the common name ‘Chinese witch hazel’). Kalmia
latifolia (Mountain laurel) and Fothergilla (but not Fothergilla
gardenii, which is Witch alder) are also in the Arboretum. The variegated
kiwi, Actinidia kolomikta, used to be grown here at the Center for Urban
Horticulture. Soft shield fern, or Polystichum setiferum, may be in the
Arboretum, but is not listed, as it is not a woody plant. You can search the Washington Park Arboretum’s Living Collections database by the plants’ scientific or common names (sometimes it’s best to search the scientific name, for clarity). You can search the Arboretum’s interactive map and there is also a trail map linked here which provides information on large collections of plants, so you can get a sense of where to find things. You can go to the Graham Visitors Center in the Arboretum and ask for assistance in locating the witch hazels (some are in the Witt Winter Garden, and
others are in a grove on the south end of the park) and other plants.

All of these plants grow well in our area. I have a dwarf form of
Fothergilla in my garden, and it has been thriving. I have also seen many
of the other plants in your list growing happily in private gardens in
Seattle. Since you wish to know what they look like, here are several links to
additional information with pictures.

Hamamelis mollis picture >

Fothergilla gardenii Picture 1
Picture 2

Kalmia latifolia Picture 1
Picture 2

Actinidia kolomikta Picture 1

Picture 2

Polystichum setiferum
Picture 1 (from a local gardener)

Picture 2

protecting figs from birds

Starlings eat our figs before we can partake. Is netting the only sure solution or are there other methods?

 

Washington State Department of Fish and Wildlife’s Living with Wildlife page on starlings mentions netting as well as bird-scare tape and other devices. Other sources suggest picking just-ripe figs early in the morning, and not leaving ripe figs on the tree–the birds know perhaps better than we do when the fruit it ripe.

The netting is probably your best bet for the fig tree, although it is a bit cumbersome and unsightly. I imagine the figs are worth it, despite the aesthetic sacrifice.

transplanting Ivies

Do you have any information on how to transplant Hedera colchica?

 

Before you transplant your ivy, be sure to verify that it is not on your county’s noxious weed list. Hedera colchica, or Persian ivy, is not listed on King County’s site, but it may still share some of the self-perpetuating and plant- and structure-damaging properties of English ivy (Hedera helix).

I searched our books on ivies as well as our periodicals databases, and did not come across anything specifically about moving Hedera colchica. I would assume that what applies to the genus, as far as the procedure for transplanting, should apply to this species also. Below is general information I located.

The American Ivy Society has general information on moving outdoor ivies. Search under “Resources: Q & A.”(You may wish to contact them directly for information specific to Hedera colchica). Here is an excerpt:

“You can dig up ivy fall or early spring and move it. If you are in a really cold climate you will best results transplanting in the spring.

“Dig around the base of the ivy stem leaving as much root & soil as possible. Dig the new hole wider and deeper than the root ball. It is good to plant ivy deeper– as much as 3-4” deeper if possible. That will secure the ivy in the ground and help to prevent drying while it acclimates to the new location. Water regularly making sure the ivy does not dry out but do not keep the soil too wet.

“I would suggest mulching with almost any organic mulch like pine needles, leaves or chipped bark. This also helps to keep the soil moist and the temperature even.

“You will need to give the ivy some TLC for the first few months but once it gets started it should be fine. It is always a good idea to keep newly planted ivy carefully water for the first year or so. After that you can practically ignore it (depending on your climate) and it will survive with the natural rains or normal garden irrigation.”

From The Helpful Gardener, an online garden forum:

  • First thoroughly water the plants and cut off a lot of the top growth to prevent dehydration (down to where there is growth evident – don’t cut into old wood where there isn’t anything growing from it).
  • Then dig the new holes for them – making them large and deep – and dig in some compost. Carefully dig up the ivies, taking all the roots and some soil around them, and put each in a bucket or piece of sacking.
  • Next, making sure the new hole is big enough, replant the ivies in their new homes, shaking the plant gently so that the soil settles around the roots.
  • Heel in gently, water generously, put some shredded bark or shingle on top to keep in the moisture, and keep well watered during dry spells.

on Cistus x purpureus and Nandina domestica

My landscaper has planted several Cistus marked Cistus x purpurea. He said it was a solid colored [pink/lavender] flower without spots at the base of petals. I have spent hours searching for a photo, all photos that refer to purpurea are spotted. They also are
referred to as orchid rock rose. Once there was a picture of a unspotted shrub, referred to as Cistus and next to it was a spotted one that had the purpurea label. Can you shed some light?

Also planted is Nandina domestica “Royal Princess.” There is hardly any information available on my search for this. It appears to be pretty, but I did read that outside of Seattle, some nurseries on the west coast stopped selling it. Should I anticipate a problem with this plant ? I also read that in some eastern states Nandina domestica is invasive.

 

Here is what I found on the web page of the Royal Horticultural Society.
The correct name is Cistus x purpureus. It has deep pink flowers with burgundy blotches at the base of the petals.

The Cistus website (a British site), in addition to its gallery of pictures of different species of Cistus, has some information about misnamed plants, which may be what you and your landscaper encountered.

Here is information from The National Gardening Association about Nandina domestica ‘Royal Princess.’

Here is an excerpt from San Marcos Growers site:

Nandina domestica ‘Royal Princess’ (Heavenly Bamboo) – This is an upright growing shrub to 6 to 8 feet tall has very lacy foliage. Pinkish white flowers bloom in clusters at the ends of branches in the late spring and summer followed by a heavy set of red berries ( notably heavier than most Nandina cultivars). The foliage turns to burgundy in spring and later a orange-red in fall. Branching stands stiffly upright unlike typical Nandina domestica and the foliage has a much finer texture. Plant in sun or shade. Tolerates fairly dry conditions but looks better when given water occasionally. It is hardy to about 10 degrees F.

Nandina is widely grown in our area, and so far has not exhibited the
invasive properties it has in the Southern U.S. Several cultivars are
listed on the Great Plant Picks website, which is created by local
gardening experts, so I am assuming there should not be a problem with
growing it here. If you are still concerned about it, the main way it
becomes invasive is from the berries setting seed and spreading. You
could plant native ornamentals in its place, if you wish. Here are links
to information about native plant landscaping:

Washington Native Plant Society
PlantNative.org
King County’s Native Plant Guide

on the use of water-absorbing polymers in gardening

I am doing container plantings for clients (some of them big — the containers, not the clients), and have water concerns. Have you received any feedback on use of those “soil moist” granules that are supposed to cut down on waterings? My fear is that over time, especially with shrubs in a container, there may be some root rot.

 

Although there is not any conclusive information on whether use of water-absorbing polymers will contribute to root rot in planters, there are quite a few other causes for concern. Local gardener and writer Jessica Salmonson discusses the matter on her web site, Paghat’s Garden.
Here is a brief excerpt:

Many of the ‘superabsorbent’ properties claimed by polymer manufacturers are exaggerated, and during biodegradation these polymers even reverse their effect, depriving plants of moisture. Woodchips, quality compost, or peat do the same job adequately, plus the woodchips or compost provide safe plant nutrients and a medium for beneficial microorganisms such as polymers retard.

And, inevitably, it turns out that some polymers do in fact reach the foodchain, especially the allegedly safer-to-the-environment biodegradable synthetic polymers. These are fed directly to livestock as feed supplements, are dispersed over crops in herbicides & pesticides, & are mixed into garden soils because of preposterous claims of doing away with a need ever again to water the garden.

Extension horticulturist and Washington State University Professor Linda Chalker-Scott has also written on this issue, and states that even beyond the health and environmental concerns, hydrogels do not work well in clay soils, and can decrease a plant’s ability to absorb essential nutrients.

Local garden writer Ann Lovejoy writes about a non-polymer alternative in this article in the Seattle Post Intelligencer: “The newest such water holder I’ve tried is called Quench. This is a granular, sand-colored material that turns cloudy-translucent in water. Unlike polymers, Quench is based on a natural material (cornstarch) in a form that can absorb up to 400 times its weight in water, right up there with good compost or forest duff.
Unlike the usual polymers, this stuff lets go with grace. About 95 percent of the stored water is released to plant roots in midsummer, making plants a lot less dependent on people in hot weather.”

vegetables that can tolerate partial shade

What herbs and vegetables grow well in very little sun?

 

The following is a list of vegetables that can tolerate partial shade. While productions may be greater in the sun, these plants will produce an edible crop when grown in a shady location.

From an article on The Old House Web (no longer available online):

VEGETABLES

Arugula

Beans

Beets

Broccoli

Brussels sprouts

Cabbage

Cauliflower

Celery

Cress

Endive

Kale

Kohlrabi

Leeks

Parsnips

Peas

Potatoes

Radish

Rhubarb

Rutabagas

Salad Burnet

Sorrel

Spinach

Summer Squash

Turnips

HERBS

Garlic

Angelica

Borage

Caraway

Chervil

Coriander

Parsley

Lemon Balm

Lovage

Mint

Tarragon

Thyme

This article (“Best Shade-Tolerant Vegetables”) in Mother Earth News offers more detail about the amount of sun or shade needed.

Remember that most of these plants do not grow in complete shade. Plants will need some morning, evening or filtered sun; a total of two to six hours of direct sun is the minimum.

managing mildew on Euonymus

I am considering using Euonymus ‘Green Spire’ for a hedge. My experience with Euonymus japonicus is that every year it seems to get mildew and drop leaves. Is this likely to happen with the ‘Green Spire’ as well? Do you have any suggestions about how to treat the mildew or avoid it?

 

‘Green Spire’ is a variety of Euonymus japonicus. This plant can suffer from a fungus, Oidium euonymus japonici, which occurs only on Euonymus japonicus, and is found wherever the host grows. Clemson University Extension says that fallen leaves and heavily affected branches should be disposed of. Plant in a sunny site which is not overcrowded, and do not water from above.

According to University of California, Davis’s Integrated Pest Management site, variegated forms of Euonymus are less susceptible to mildew. Preventive measures are the first step, but if your plants already have mildew, this resource lists less toxic fungicides, such as Neem oil, jojoba oil, baking soda spray, potassium bicarbonate, and biological fungicides: “With the exception of the oils, these materials are primarily preventive, although potassium bicarbonate has some eradicant activity. Oils work best as eradicants but also have some protectant activity.”

Eucalyptus care

I recently purchased two Eucalyptus gunnii trees and one E. dalrympleana, which are still in their pots. I have them in full sun, facing south. I have been watering them every day – is this appropriate? I know that the gunnii tolerates waterlogged soil.

 

All Eucalyptus prefer full sun and well-drained soil. They are very drought tolerant when established.

Source: Manual of Woody Landscape Plants, by M. Dirr, 1998, p. 352.

If your plants are in terracotta containers they will need daily water. If they are in non-porous containers you have a bit more leeway, but do not let them dry out while they are young.

Another consideration is whether you plan to grow these trees in containers permanently, or if you are going to be moving them into the garden. If you plan to keep them in pots, bear in mind that these trees will get quite large (70 feet tall by 20 or more feet wide), so you may end up needing to do a lot of pruning from the top as well as root pruning. Sometimes, even when planted out into the garden, urban gardeners with small lots will coppice a tree like Eucalyptus gunnii or E. dalrympleana annually so that it does not overgrow its site, and so that the rounded, juvenile leaves are maintained. See the Royal Horticultural Society’s page on eucalyptus pruning for additional details.

If your plan is to move the trees into the garden, it is best to do it when they are relatively young and small, as Eucalyptus generally dislikes root disturbance.

on the use of wine corks as garden mulch

I attended a garden lecture where the speaker recommended using wine corks in the garden, either ground up as a mulch, or whole in containers. She said cork would help with moisture retention in the soil. Do you agree?

 

The primary source of wine corks is the cork oak tree, Quercus suber. The species name is a clue to the fact that cork is largely made of suberin, a waxy hydrophobic (water-repelling) substance found in other woody plants.

It does not make sense to use a hydrophobic substance as a mulch, since mulch is meant to allow moisture to reach the roots of your plants, not to repel water. For the same reason, it does not make sense to add cork to your containers, either. Professor Linda Chalker-Scott of Washington State University says that cork will not in any way help the soil retain water.

Chalker-Scott has long advocated using arborists’ wood chips as a mulch rather than bark mulch, for similar reasons:
“Bark does not function like wood chips in its water holding capacity. Bark is the outer covering of the tree and is heavily suberized to prevent water loss. Suberin is a waxy substance that will repel water, and in fact helps explain why fresh bark mulch always seems dry. Wood chips, on the other hand, consist primarily of the inner wood, which is not suberized and has the capacity to absorb and hold moisture.”