Growing rhubarb with other edible plants

I just moved into a house with a beautiful vegetable garden with lettuce, kale, arugula and rhubarb (planted next to the lettuce). We have a 7-month old who will likely be all over the back yard in the next few months, and we have a few concerns about the rhubarb leaves, as we’ve heard they are poisonous.

Could rainwater roll off the rhubarb leaves and contaminate the lettuce? Could leaves left on the ground contaminate the soil? And if we touch the leaves, will the rhubarb’s poisonous properties contaminate our hands?

We aren’t huge rhubarb fans, so we will likely be taking them out at the end of this summer. Any tips on removing them to make sure they would not grow back?

Lastly, unrelated to rhubarb, we have some arugula that’s bolted (flowered). Is there anything we can do, like cutting it back, so it won’t be bitter and we can eat it? I assume we have to just replant it.

The toxic parts of rhubarb (Rheum x hybridum) are the leaves and the roots, as described by University of Illinois Extension:

“One characteristic consistent with all rhubarb is the toxicity of the leaves and roots. The rhubarb leaves contain high amounts of oxalic acid, a toxic and potentially deadly poison.”

Rhubarb is a frequently grown vegetable garden plant, and is often grown in close quarters (in the same soil, with the same irrigation) with other edible plants. As long as you are careful when harvesting your lettuce not to get pieces of rhubarb leaf at the same time, you should be safe. Here is what Plant Alert: A Garden Guide for Parents by Catherine Collins (Master Craftsman, 2001) says: “The leaf blade contains high concentrations of oxalic acid […] The stem is safe to eat, providing the leaf is removed with at least 2 inches of stalk below.” (By the way, rhubarb stalks or stems, spinach, beet greens, and chard all contain lesser amounts of oxalic acid–that’s what gives the chalky sensation you get on your teeth sometimes when you eat them.)

You will not be affected by the plant’s leaves or roots unless you ingest them.

There aren’t any special precautions you need to take in order to dig up your rhubarb, although gloves are always a good idea–you never know if your skin may be sensitive to particular plants.

About your arugula (Eruca vesicaria ssp. sativa): I usually cut the bolting stalks back, and new (and less bitter) leaves grow lower down on the plant. You could let one or two plants flower and go to seed–then you wouldn’t need to buy more seed. If you still have extra seed, you can sow more (called “succession planting,” described in this Fine Gardening article), in addition to cutting back the leggy stalks.

Controlling milk thistle

Silybum marianum: Should I give away baby plants? I bought the original “rare” plant from a local Perennial Society (can’t remember exact name)15 years ago. 4 feet tall, and prickly. I decided to get rid of it, but baby plants still pop up every year. Variegated, dramatic, but too prickly for a small garden!

I’m glad you asked about your Silybum marianum (milk thistle) starts. This plant is considered an invasive species in many places, including Washington State. King County lists it as a Class A noxious weed, meaning that eradication of the plant is required by law. Below is information excerpted from King County’s site:

This Class A noxious weed has a very limited distribution in Washington State, and eradication is required. The largest infestations in the state are in pastures in the southeastern section of King County but infestations are occasionally found elsewhere. Early detection and rapid, effective response is of the highest priority for this noxious weed.

Although occasionally found in gardens, it is illegal to sell or buy milk thistle in Washington State and all existing plantings should be removed in order to prevent accidental spread.

Milk thistle is toxic to livestock when consumed in large quantities, and it forms dense stands in pastures and rangelands. California reports up to 4 tons per acre in heavily infested areas. The leaves are very distinctive, with white marbling on the shiny green leaves.
Control Methods:
Manual: For small sites with few plants, pull or dig up rosettes or the bolted plants before seed heads form. Use a shovel to cut the plant off about one inch below the ground so the plant will not re-sprout. Chopping the leaves from one side of a rosette can provide access to the central growing point. Wear protective clothing. To be fully effective, all mature seed heads need to be bagged and removed so no new seeds are left on the site. Immature seeds can continue to develop in cut plants, and the less stem that remains attached to the flower head, the faster the seed head will dry out.

I highly recommend you do what you can to eradicate this plant and prevent its spread. Do not put it into the compost but instead bag and dispose of it as trash.

Ornamental grasses and their risk of reseeding

I have neighbors who are asking questions about ornamental grasses and their risk of reseeding. They are specifically interested in Pennisetum ‘Hameln’ and Cortaderia ‘Richardii.’ I have known Stipa (Nassella) to reseed but I have never noticed any reseeding from either of these two groups in the Seattle area. I know they can reseed freely in other parts of the country, but I suspect the seeds rot in our winters. How can I find out?

I consulted online lists of invasive species and found a few references to Pennisetum species (but not the cultivar you mention) which are problematic in Oregon and California.

According to the University of Florida Extension, the variety Pennisetum alopecuroides ‘Hameln,’ is not known to be invasive.

Although not classified as invasive, the species P. alopecuroides is still a spreader by self-sowing. Rick Darke, author of The Encyclopedia of Grasses for Livable Landscapes (Timber Press, 2007) and a Pennsylvanian, says it “self-sows, usually at a manageable level; however, some of the fall-blooming varieties such as ‘Moudry’ and ‘National Arboretum’ are particularly fertile and can be very weedy if conditions are suitably moist. They often become established in irrigated cool-season turf.”

The Royal Horticultural Society plant profile for ‘Hameln’ says it is early-flowering (which might mean that seeds have time to establish themselves, though a droughty summer such as we sometimes have in the Seattle area might prevent this).

One sterile cultivar is Pennisetum advena ‘Rubrum’.

As with Pennisetum, there are species of Cortaderia (C. selloana, C. jubata) which are listed as invasive in various parts of the world. Here is an excerpt from Los Angeles & San Gabriel Watershed Invasive Plant-Monitoring and Outreach Program’s WeedWatch information on Cortaderia:

“It is unknown whether the cultivated and ‘sterile’ varieties of Cortaderia are able to cross with the wild species of Cortaderia and produce viable offspring. Until this scientific research is conducted, and considering the rampant ecological damage already caused by both C. selloana and C. jubata, it is not recommended to plant any members of the species, including cultivars, varieties and supposed ‘sterile’ varieties.”

Author Rick Darke says that all species of Cortaderia may be grown from seed (therefore, species are not sterile).

A Pacific Northwest palms and subtropical plant online discussion group, Cloud Forest, (no longer available online) includes some dialog on Cortaderia richardii:

“Another terrific grass is Cortaderia richardii, which is a NZ form of the humongous pampas. It is short (to 5 ft.) with elegant flowering pattern (circular and reaching instead of vertical). It’s evergreen and a great specimen. Needs a 6 x 6 space minimum. ”

“Cortaderias scare me a little, ever since my neighbor’s specimen seeded itself all over my poor rock garden (heck it is all over the neighborhood). Obviously sellowiana; I don’t think C. richardii is as aggressive. The other one is a devil to try to remove once it gets wedged in! The leaves cut like razor blades and the crown is extremely persistent. I actually think they look kinda grand, and if I lived on the coast I’d be willing to use them as windbreaks (which is how they got all over the place). I don’t think a hurricane would injure them.”
“Cortaderia richardii is the magnificent cousin of the monstrous pampas grass. Petite and elegant in comparison. Mine have never self-seeded. My friend’s seeded a bit. It may be hotter by his house.”

Stopping raspberries from spreading

We are expanding our vegetable garden, and I wanted to put in a row of raspberries (hardly vegetables but you get the idea). My wife is against it because raspberries spread so many underground roots and sap the energy of the rest of the soil and interfere with other plants. I’m sure she’s right. What do gardeners do to stop the spread of raspberries?

To keep the raspberries from infiltrating the vegetable bed, you could install a root barrier such as gardeners use to contain bamboo. Even more simply, you could set the planting area apart from the veggies with fairly deep edging material–such as one might use to keep grass from invading garden beds. I’m sensitive to proposing something that is a lot of work, but you could make a dedicated raised bed for raspberries along the edge of the vegetable bed. I’m a fairly lazy gardener, and I planted raspberries amongst all my other plants. When the berries run to areas where they are unwanted, I just pull them out. But you will get a better, easier to harvest crop if you provide them with their own area. This Fine Gardening article addresses the issue of running, as well as ideal planting conditions:

Excerpts:
“Raspberries are joyfully exuberant about procreating by underground runners, poking up impressive numbers of healthy new plants all around your original patch. I don’t consider this to be a problem, though, because one whack of the hoe takes care of them. You can also present them to a friend or use them to extend your patch. […] If you have rich, deep soil that drains well year-round, you can simply plant your raspberries in a permanent garden site. Not us. The Pacific Northwest gets rain all winter, and many gardeners lose raspberries to root rot because they make the mistake of planting their raspberries’ fussy little toes directly in the ground, which is often soggy clay covered with a skim of topsoil. We also experience a two-month drought most summers. Raised beds allow us to have deep soil that holds moisture evenly yet drains well.”

Best apple varieties to grow in the Olympic Peninsula

My class is planting a tree in honor of our school advisor. Which apples varieties will do best in our area (Olympic Peninsula, WA)?

Washington State University Extension’s publication, Apple Cultivars for Puget Sound by Robert Norton (1997, revised edition) has suggestions of some varieties which will succeed in our area. The lists are grouped by type of apple and type of flavor. For your situation, it would make sense to choose a variety which is known for disease resistance. I will include an excerpt from the list below.

Disease-resistant varieties:

Pristine: Ripe early to mid August. Clear yellow skin is very attractive. One of the
earliest disease resistant varieties, with a refreshing flavor and firm crisp flesh.
Moderately tart, holds well on the tree.
Williams’ Pride: Ripe early to mid August. Attractive red stripe over yellow, good flavor but susceptible to mildew.
Chehalis: Ripe early to mid September. Yellow apple with good natural resistance
to scab but susceptible to mildew. Thin skin bruises easily. Good dual purpose for fresh eating and sauce but too soft for pies.
Prima: Ripe early to mid September. Attractive bright red over yellow, at its best
when fresh from the tree but texture softens rapidly in storage. Good mildew resistance.
Dayton: Ripe early to mid September. Trees are vigorous and crop well, but may need
a year or two in production to reach good quality. Fruit is unattractive dark orange red
over yellow. Flesh is crisp, juicy, with sweettart flavor. Stores better than Prima.
Liberty: Ripe early to mid October. Attractive, uniform red fruit with good flavor,
very similar to Spartan in appearance and quality. Trees are very productive and need
effective thinning for good fruit size. Well adapted to western Washington conditions.
Enterprise: Ripe mid to late October. Mac type, flavor fair to good, firm, crisp.
Moderately productive. Stores well until December, then flavor starts to decline.
Belmac: Ripe late October. Late season Mac type, good flavor, firm and crisp. Productive, vigorous trees. Fruits store well until February.

City Fruit, a fruit-growing advice group in Seattle, recommends these varieties:
Akane, Chehalis, Corail, Elstar, Empire, Fiesta, Jonagold, Gravenstein, Honeycrisp, Karmijn De Sonneville (unusually scab prone, but delicious), Liberty, Rubinette, Sansa, Spitzenburg, Sweet Sixteen, and Williams Pride all have had good comments. They have different flavors and characteristics. Apples and Asian Pear-apples are subject to the Apple maggot and codling moth pests.

You may want to make sure there is a designated “tree steward” or volunteer who will maintain the tree over time. Fruit trees need regular care: watering, mulching, pest prevention, pruning. Here is more information:

Home Orchard Society
City Fruit pruning article
City Fruit resources
U.C. Santa Cruz Center for Agroecology guide, Apple Trees for Every Garden

Atlas cedar and its qualities

Given that the Atlas cedar is a true cedar (as opposed to the Western red cedar), does the wood have any particular aromatic or bug-resistant qualities?

I checked The International Book of Wood (edited by Martyn Bramwell; Emblem, 1979), and here is what it says about Cedrus:
“True cedar is a softwood produced by three species. The cedar of antiquity is the cedar of Lebanon, used in the construction of the royal tombs of the early kings of Egypt and by Solomon in the building of the Temple; the deodar of northern India is almost as famous, and the third species is the Atlas cedar [Cedrus atlantica] of the mountains of Algeria and Morocco. […] The wood of the three species is similar, pale-brown, with a fairly well-defined growth ring, and characterized by a fragrant smell. It is of medium weight for a softwood, a little heavier than European redwood. Cedar dries readily though with a tendency to distort. It is inclined to be brittle and, generally, is not a strong wood; it works easily and takes a fine finish. It is noted for its resistance to both fungi and termites.”

This link from Plants for a Future database mentions its fragrance, as well as its fungus- and insect-repelling qualities:

“An essential oil obtained from the distilled branches is a good antiseptic and fungicide that stimulates the circulatory and respiratory systems and also calms the nerves. […] An essential oil obtained from the distilled branches is used in perfumery, notably in jasmine-scented soaps. The essential oil also repels insects.[…] Wood – fragrant and durable. It is prized for joinery and veneer and is also used in construction. It is also used for making insect-repellent articles for storing textiles.”

Pear rust and lack of fruitfulness

I have a ‘Rescue’ pear which has gotten pear rust. It is about 3 years old. I also have an ‘Orca’ pear tree that so far this season does not have rust. Last year we had terrible rust. We thought maybe it came from a secondary host, because there were Juniper bushes. Now those bushes are all gone and I did clean up the leaves from last year to try and avoid contamination from the rust.

Also, I have never gotten any pears on either tree. The Orca tree is a bit older, about 5 years old. They both were bought from Raintree Nursery.

Sorry to hear about your pear with rust, and about the lack of fruit. Washington State University’s HortSense website says there are two types of rust that affect pears in our area:

“Two pear rusts which occur in Washington are Pacific Coast pear rust and pear trellis rust. Both require an alternate host. The rust fungus causing Pacific Coast pear rust is also found on hawthorn, apple, crabapple, serviceberry, quince, and mountain ash. The alternate host is the incense cedar (Calocedrus decurrens), which develops witches’ brooms. Infected fruits of pear are deformed and drop prematurely. On the surface of the fruit, yellowish spots with cup-shaped pustules develop. Leaves and green shoots may also be infected. Symptoms are most obvious after flowering and before July. Pear trellis rust may also infect pears, causing reddish to orange blotches on leaves. The alternate host is juniper, which develops elongate, swollen galls along branches.”

The only controls they recommend are cultural:

Avoid susceptible varieties such as ‘Winter Nelis’.
Collect and destroy fallen fruit beneath trees.
Plant resistant varieties such as ‘Bartlett’.
Prune out and destroy rust-infected tissues in pears and alternate hosts.
Remove alternate hosts in the vicinity of pear trees, when practical.

Here is an article from British Columbia Ministry of Agriculture and Food on managing this disease in the home orchard.

It sounds as if you are doing everything you can to prevent a recurrence. The web resource above also states that fungicide is probably not a worthwhile approach to managing rust on pears or junipers.

As for the lack of fruit on your trees, Raintree’s pollination chart shows that ‘Rescue’ and ‘Orcas’ should cross-pollinate. It is possible that the ‘Rescue’ pear is not mature enough, or that its bout with disease slowed it down.
Here is an article about failure to produce fruit, from University of Maine. It mentions possibilities such as immature tree(s), lack of sun, and frost damage to flower buds.

I have an ‘Orcas’ growing without other pears in the garden, and yet it produces fruit, so I wonder if something else may be happening. Do you have a good number of bees and other pollinators in your garden? Do you or nearby households use pesticides that might interfere with pollinators? Here is information on protecting and encouraging pollinators, from U.S. Fish and Wildlife.

I also recommend contacting Raintree to see if they have any advice.

Growing wild garlic or ramps

Could you tell me about wild garlic, or ramps? What is the best planting location for it, and how is it used in cooking?

Ramps, or Allium tricoccum, is sometimes referred to as wild leek or ramsons (which may also refer to Allium ursinum). An article about this plant from North Carolina State University (no longer available online) mentions ramp or ramps festivals, most of which are held in the southeastern U.S., where this plant is native. According to Alliums: The Ornamental Onions by Dilys Davies (Timber Press,1992), ramps thrive (or grow rampantly) in damp woodlands or hillsides. The author says that neither Ramps nor Ramsons “should be introduced into the civilised areas of the garden unless a takeover is acceptable.”

Another consideration is that the leaves resemble lily of the valley (Convallaria majalis), which is poisonous, so you would not want to grow the two plants close together. According to the Lady Bird Johnson Wildflower Center, this Allium itself has toxic properties (but relatively low toxicity), and should only be consumed in small quantities. The leaves, bulbs, and bulblets all have edible uses:
“Gather leaves during spring and fall. Gather bulbs in the second year when they are large enough to use like cultivated onions. Flower stem bulblets are collected during the summer. Use as domestic onions, for seasoning or raw in salads. Bulbs can be used raw, boiled, pickled or for seasoning. Their strong taste can be reduced by parboiling and discarding the water. […] use flower bulbs to flavor soup or for pickling.” (Poisonous Plants of N.C.)

Oak trees and leaves retention

I have a large lawn with a southern exposure, and fairly good drainage. I would like to plant 1-3 large shade trees. I have been considering northern red oaks for the location, as they seem to grow well in this climate, should provide good shade, and they have nice fall color. However, I don’t like oaks which keep their dead leaves through the winter (as Scarlet oaks do). I find the dead leaves unsightly and messy, and I will not want the shade in the winter. Do red oaks also keep their dead leaves on their branches in this manner? If so, have you another recommendation, other than maples?

According to the Sunset Western Garden Book, pin oak (Quercus palustris) keeps its brown leaves through the winter, but Northern red oak (Quercus rubra) loses them in fall. The retention of leaves in fall (meaning that they delay dropping them until spring) is a phenomenon called marcescence. At times young trees of other oak species, even Quercus rubra, can keep their leaves all winter, particularly if it is an unusual winter. You might consider Katsura tree (Cercidiphyllum japonicum) or sweet gum (Liquidambar styraciflua) for fall color with more reliable leaf drop.

Dividing Calla lilies

Can I divide my Calla lily? When should I do this?

According to Sunset Western Garden Book (2007), Calla lily (Zantedeschia) should only be divided if it shows signs of decline. The Royal Horticultural Society suggests dividing in spring, if needed:

“Propagate by division, in spring. Small rhizomes that have been overwintered in pots under cover can literally be cut up into sections, each with a visible bud.

Large overwintered clumps in the garden can be divided in the same way as other perennials, by lifting the plant before there is much top growth, and chopping through the roots with a spade and dividing into smaller sections.”