effectiveness of neem oil and horticultural oils

We’ve got an established grapevine that has acquired erineum mites, and a horticulturist advised us to use dormant spray this fall. The dormant sprays are rather nasty things, and I recently ran across Neem oil, which says it acts as a miticide. It sounds like the concentrated Neem oil is pretty nasty, too, but I’m wondering: (1) will Neem oil work to get rid of the mites; and (2) is it any less harmful to the environment than the traditional dormant sprays?

According to the University of California, Davis Integrated Pest Management program, Erineum mites will not adversely affect your grape crop, they merely cause an aesthetic problem (disfigured leaves).

Washington State University Extension does mention using dormant-season horticultural oils or wettable sulfur. Excerpt:

“The grape erineum mite, Collomerus vitus, is actually a type of eriophyid mite. They are very tiny, whitish, worm-like, and spindle-shaped. Their bodies have definite annulations or rings, and only two pairs of legs directly behind the mouthparts. They overwinter under outer bud scales and feed on leaves during summer. The upper leaf surface
becomes blistered, and blisters on the lower leaf surface turn white, yellow, or brown. Colonies of mites live inside the blisters (erinea) formed by their feeding on the lower surfaces. The blisters contain masses of enlarged leaf hairs. Large infestations can cause major stress on young vines. From mid-August to leaf drop, the mites migrate back to the overwintering sites beneath bud scales.

“Apply according to label instructions. Dormant-season horticultural oils or wettable sulfur applications may be helpful.”

I have only seen references to serious damage from this pest when the grapevine affected is very young, so you may be able to do nothing at all. Neem’s effectiveness as a miticide is as yet unproven, and when selecting a Neem-based product, you have to make sure it actually contains the active ingredient said to affect insects, Azadirachtin–some “Neem” products do not. (Also, Azadirachtin affects good bugs as well as the ones you may be trying to control, so it is definitely not risk-free).

Paghat’s Garden website article on the “Myth and Reality of Neem Worship”

Although most horticultural oils are petroleum-based, there are supposedly a few out there which are being made with vegetable oil, which would be a preferable alternative if you really needed to spray for the erineum mites. Colorado State University Extension has an article on dormant oil.

conditions for growing fig trees

I purchased a fig tree and my property has very limited space. There is an ideal strip of land by the south side of the wall that gets plenty of sun. I read that fig trees should be planted near a south facing wall, but my only concern is how close can it be to the side of the house. The strip of land is only about 2 feet wide and I also read that fig roots are shallow and spread beyond the canopy. I’m worried that the root system would cause damage to the foundation/basement.

The roots of a fig tree may be shallow, but they may spread out as much as 50 feet, and if the soil conditions are right (soft, permeable), roots may go as much as 20 feet deep. I think planting so close to the house is not ideal,
unless you were to have a dwarf variety of fig in a container (such as Petite Negri or Negronne). If there are any cracks in your foundation, then tree roots may be a concern. Tree roots do not usually penetrate a solid wall, although as they grow and expand, they can exert pressure on surfaces. The other concern with planting that close is that you will find you frequently need to prune branches away from the house. There is a tradition of growing fig trees as espalier forms (trained to grow flat, on one plane), but to do this you need to restrict the tree’s roots in a container. Below are links to information on how to do espalier:

Royal Horticultural Society

The following links have excellent general information about growing fig trees:

Purdue University Extension

California Rare Fruit Growers

Here is information from Reads Nursery, a British fruit specialist.
Excerpt:

Allow 8′ – 15′ horizontally and 6′ – 10′ in height per plant. Root restriction is required. Construct a box of 2′ square paving slabs 4′ x 2′ against a wall or side of greenhouse, leaving 3 inches showing above ground. Put 9 inches of rammed brick rubble in the bottom and fill up with good soil such as John Innes No 3. [*This is a British product–you can use compost instead.] When planting loosen root ball carefully around the outside and plant 1-2″deeper than before. Water in well. Pruning. Treat as for Figs in Pots but, on a wall, the plant should be fan trained on horizontal wires 12 inches apart.

on dividing Gunneras

When and how do I divide my Gunnera?

“Divide large types before growth starts into single crowns in midspring.” (Source: American Horticultural Society Plant Propagation, ed. by A. Toogood, 1999, p. 198)

“Many gunneras are huge and so are impossible to dig up and divide in the conventional sense. For propagation, cut pieces from the edge of the clump. Pot up in a large pot and in a fibrous medium and keep moist.” (Source: The Complete Book of Plant Propagation, ed. by C. Heuser, 1997, p. 40)

The sources I looked at indicate that you should divide your Gunnera in April or May. Because of the size of the plant, it may be impractical to divide the rootball. You can use a spade or pitchfork to cut sections from the main clump, and then plant those divisions in pots, keeping them moist. Gunnera is a tough plant, and should take well to this kind of division, as long as there is adequate moisture.

Should you need to protect your Gunnera over the winter months, you can cut the leaves and use them like a tent to protect the crown of the plant during the coldest months.

edibility of Mahonia species

Are the fruits of Mahonia x media ‘Charity’ edible, similar to Mahonia x media?

First, an aside: Mahonia has been ‘moved’ to Berberis, so that now Mahonia x media is named Berberis x hortensis, and Mahonia aquifolium is now Berberis aquifolium. Since the resources I will be quoting use the former names, I will leave them as they are.

Here’s what British author Alys Fowler says in her book, The Thrifty Forager (Kyle Books, 2011):

“All Mahonia species are edible, long-used for jams and juices in their native homes […] Sometimes you’ll find Mahonia nervosa, the Oregon grape, with the roundest grape-like berries. It looks very like Mahonia aquifolium but usually fruits later, around early autumn. […] Even when fully ripe, the acidic berries [of all Mahonia species] are too bitter to eat raw–they should be cooked into pies, jellies and jams. The flowers are edible, but bitter. The fruit needs to be picked and processed into jam or jelly very quickly, and it stains everything. It’s very low in pectin, so either add crab apples or add liquid pectin, following the usual jam making rules. You can also make an Oregon grape cordial which tastes a bit like blackcurrant cordial. Because of the low sugar content, it will need to be frozen if you want to store it–it’s a very sharp cordial, I use 350-400g (just under 1 lb) if granulated sugar to 600 ml (1 pint) of fruit. If that’s still too sharp, try mixing it with concentrated apple juice to sweeten it.”

Plants for a Future Database has pages for several Mahonia and Berberis species, including Mahonia x media, and its fruit is listed as edible.

On quinoa

What is quinoa, botanically? Is it a grain, or something else?

The botanical name for Quinoa is Chenopodium quinoa. According to information from the Alternative Crops Manual produced by University of Wisconsin Extension, it is an annual plant in the goosefoot or Amaranthaceae family, which also includes the familiar weed, lambs’ quarters or Chenopodium album. This article states that “Quinoa is sometimes referred to as a ‘pseudocereal’ because it is a broadleaf non-legume that is grown for grain unlike most cereal grains which are grassy plants. It is similar in this respect to the pseudocereals buckwheat and amaranth.” Edible: An illustrated guide to the world’s food plants (National Geographic, 2008) states that true cereals are members of the Poaceae or grass family, but quinoa more closely resembles spinach. It was first used as a food plant around 5000 B.C.E. near Lake Titicaca in the Andes, where it is native. Its common name in that region is “the mother grain.”

Incidentally, the Food and Agriculture Organization of the United Nations declared 2013 the International Year of Quinoa, “recognizing the Andean indigenous peoples, who have maintained, controlled, protected and preserved quinoa as food for present and future generations thanks to their traditional knowledge and practices of living well in harmony with mother earth and nature.”

Ammonium sulfate and organic guidelines

Is ammonium sulfate considered an organic fertilizer? I’d like to use some on my blueberries, but suspect it is not organic.

According to Fertilizers and Soil Amendments by Roy Hunter Follett (and others), ammonium sulfate is one of the oldest chemical fertilizers, and is “a frequent by-product of the steel industry, particularly the coking of coal.” That doesn’t sound like it meets organic guidelines. It is also tricky to use because it can cause phosphorus and aluminum to build up in the soil. The Organic Materials Review Institute lists it as a prohibited (for certified organic growers) synthetic crop fertilizer and soil amendment. You might do better using a slow-release certified organic fertilizer labeled for acid-loving plants. Cornell University Extension’s publication, Production Guide for Organic Blueberries” mentions fish, soy, and alfalfa meal as organic-acceptable amendments.

Pine needles as mulch

Are pine needles good for mulch in the garden and for fruit trees?

Pine needles are most often used with plants that prefer acid soil, but according to Mulch It! by Stu Campbell (Storey, 2001), they can be used elsewhere, too, at a depth of one to one and a half inches. It is considered a myth (see information from Washington State University horticulture professor Linda Chalker-Scott in Organic Gardening, February 2007, p.8) that they will acidify your soil. They are good for insulation, weed control, and moisture retention, and excellent for water penetration. However, they decompose very slowly and are not liked by earthworms. You can shred the needles a bit before applying them as mulch, and that will speed their decomposition.

Toxicity of Eucalyptus trees

I have a young Eucalyptus pulverulenta tree. I’m concerned that it might be emitting toxic chemicals into the surrounding soil that will harm other plants. Is this indeed a cause for concern?

My instinct is that your Eucalpytus tree will probably not be toxic to most other plants. Eucalyptus is often seen growing in the midst of garden beds here in Seattle, to no ill effect. I have a tree growing in a perennial bed, and have noticed no problems. However, the leaves do contain essential oils (phenolics and terpenoids). This does make the tree more flammable, if that is a concern. Eucalyptus leaf litter (to a greater degree than exudates from the tree’s roots) can inhibit specific food crops, like wheat. This is what is meant in this University of Florida Extension article (now archived), which refers to “selective activity of tree allelochemicals on crops and other plants.”

To show how selective this chemical property can be, see the following documentation of a University of California, Davis experiment using composted Eucalyptus as mulch.

Excerpt:
“Mulch products made from Eucalyptus are an asset to maintenance of fine landscapes. Composted Eucalyptus makes an excellent seed cover and will aid in germination and establishment of seedlings such as California Poppy. Fresh Eucalyptus is an excellent mulch for woody landscape plant materials and palms; the main effects of its use are weed control and water conservation.”

Unless you are growing your tree in the middle of a field of wheat or among other grassy plants, your landscape is probably in no danger of inhibited growth from the Eucalyptus.

You may find the following veterinary perspective (from Cornell University) on the toxicity of Eucalyptus of peripheral interest.

Liquidambar and its Latin roots

How on earth did Liquidambar enter the otherwise Latin list of genera? I have asked a lot of gardening experts, and no one else seems bothered by this. Can you assuage my anguish?

There are quite a few botanical (scientific) names that are not Latin in origin–many are Greek, or modeled after the name of the plant explorer who ‘discovered’ them, or the plant’s geographical origins, to name a few possibilities.

Liquidambar actually does have Latin roots. According to Geoffrey Grigson’s A Dictionary of English Plant Names (Allen Lane, 1974), Liquidambar styraciflua, a native of North America and Mexico, was introduced in 1683. The name refers to the tree’s fragrant gum or resin:

liquidambar (liquidus, ‘liquid,’ + medieval Latin ambra, ‘amber’)

A Spanish physician, Francisco Hernandez, coined the name in the 16th century. “The gum was sold in apothecaries’ shops as Balsamum liquidambrae.” The species name, styraciflua, is derived from a Latin phrase meaning ‘storax fluid.’ From the following article in the Bulletin of Hispanic Studies, Volume 86, I discovered more information about storax:

“According to Dioscorides:

storax is the sap of a tree which resembles the quince tree. The best is yellow, fatty and resinous; it has whitish lumps, its scent lasts for a very long time and when softened, it releases some honey-like moisture.“

Propagating asparagus plants

I planted young asparagus plants a couple of springs ago. This past fall, one of the plants produced fruits (small red balls like I’ve seen on Asparagus sprengeri.) I looked in my Hartman and Kester, but it did not mention means of using asparagus seeds to make more plants. Can this be done? If I left them on the plant outside all winter, are they still viable?

According to Franklin Herm Fitz in A Gardener’s Guide to Propagating Food Plants, it is possible to grow asparagus from seed, but possibly not if the seeds have been out in freezing weather:

“Collect the red berries from two-year-old or older female plants, harvesting before the first frost. Crush the berries and separate the seeds by hand (the seeds are large, shiny, and black) or by immersing them in water. The pulp will float as the seeds sink. Dry the seeds for 2 to 3 weeks. In the spring grow the new plants in deep, loose soil. After one season transplant them to a permanent bed (…) in early spring before growth resumes or in the fall after growth has ceased.”

Alternatively, as you probably know, asparagus roots may be divided and replanted, with the knowledge that each smaller root will take a year to become established so that it can produce a good crop.