on hard-pruning English laurel hedges

We have inherited a 25-foot tall English laurel hedge. The former owner never took care of of so most of the ‘inside’ is just dead branches, but the rest is VERY healthy. Our neighbors would like us to prune it so it’s not obstructing their view, and I’d like to reduce its size so I don’t need to climb a ladder to prune it in the future. Can I cut it back severely, and regrow it into a more manageable hedge? I don’t have the energy to remove it entirely.

I doubt that anyone would ever consider English laurel (Prunus laurocerasus) a manageable hedge plant since what it really wants is to be a tree, but since you want to keep it as a screen, you should be able to cut it back quite hard. It will most likely put on new growth. However, it will look fairly awful while you are waiting for this to happen. According to local Plant Amnesty pruning expert Cass Turnbull (in her Guide to Pruning, Sasquatch Books, 2006), “radical renovations of laurel hedges are common. In the spring, saw the overgrown hedge into the desired shape, except perhaps a foot or two smaller than the final desired size. That’s because it will need that room to resprout and be sheared into a thick green coat again. Be sure to cut your hedge narrow as well as short. It should be narrow enough for one gardener to reach across with a hedge shear. I have only seen one laurel hedge that didn’t recover from this radical treatment. (…) Please avoid heavy pruning on a hot July or August day, as you might burn up some internal leaves or scald the bark.”

on fertilizing and pruning grape vines

My grape vine is about 8 years old. Every year the grapes fall before they are ripe, around late July. The plant looks very healthy and has a lot of foliage. It is growing horizontally on several cable lines against a concrete wall. I don’t water and fertilize the plant much except for half a bag or a bag of manure in mid- to late winter.
At first I thought the fruit wasn’t getting enough sun, so early on, I cut all the leaves around the grapes, but they all fell off the vine from mid-July onward.
I prune the grape vine very aggressively in fall, leaving only several year-old branches with several buds on them. The vine is very healthy and grows about 30 feet a season. Could the problem be due to too much foliage?

According to The Grape Grower by Lon Rombough (Chelsea Green, 2002), the premature dropping of fruit is called ‘shatter,’ and excessive shatter can be caused by nutrient deficiencies. It’s normal for a certain amount of unfertilized berries (i.e., grapes) to drop a week or so after the bloom stage, but dropping of fruit in July is a problem.

I wonder if you are giving them overly rich soil (by adding manure). If the manure is high in nitrogen, this encourages a lot of leafy growth, often at the expense of flowers and fruit. I grow grapes and have never fertilized them. The book mentioned above says not to apply fertilizer unless you know there is some kind of deficiency. Note in particular this quotation from the book:
“Excess nitrogen causes flower clusters to ‘shatter’ (flowers fall off), reducing fruit set. In fact, mature vines should not need any supplemental nitrogen when grown in a healthy soil with plenty of organic matter. A good general rule for fertilizing grapes is to use a mulch of well-rotted compost, which will supply small, but regular essential amounts of nutrients.”

Also, the usual time to prune grapes is in mid- to late winter–I do mine in February. Pruning in the fall may be contributing to the problem your vine is having with poor fruit set.

on tomato blossom drop

It’s midsummer, and I have a bunch of healthy-looking green tomato plants without any fruit. Shortly after I planted the starts, the flowers developed, and promptly fell off, taking a bit of the stem-end with them. The spot where I’ve planted them is in full sun, they have good soil, and they get watered as they should. Any idea what might be going wrong?

The problem which most closely resembles your description of what is happening with your tomato plants (flowers falling off shortly after planting, and taking a bit of the stem as they drop) is called ‘blossom drop.’ According to D. G. Hessayon’s Vegetable Expert (PBI, 1990), blossom drop occurs when pollination fails to take place, and there is dryness at the roots or in the air. There is no treatment for this malady, but watering regularly, spraying flowers in the morning, and tapping the plants to aid pollination are preventive measures. Attracting beneficial insects to your garden will also help with pollination.

Here are links to more information that may be useful to you:

University of California Integrated Pest Management pages on tomato problems and pollination
Washington State University – Spokane County Extension: Why Blossoms Fail. Note also that WSU Extension in Spokane County says cool night temperatures may cause blossom drop.
University of Illinois Extension:”Tomato blossom drop is very common with high summer temperatures. Tomatoes will drop blossoms when daytime temperatures in the summer are above 90 degrees F. Blossoms will also drop earlier in the growing season when night temperatures drop below 55 degrees F.”
This article from the spruce provides a lot of detail about the problem and how to prevent it:
Blossom drop can be attributed to several causes, most often related to either temperature and/or stress.
1. Temperature too high or too low
2. Lack of pollination
3. Nitrogen: too much or too little
4. Humidity too high or low humidity
5. Lack of water
6. Stress from insect damage or disease
7. Too heavy fruit set
This article recommends planting varieties known to do well in your climate, ensuring pollination, avoiding over-fertilizing, taking note of humidity levels, and watering deeply once a week in dry weather.

Magnolia grandiflora and failure to flower

I have a Magnolia grandiflora ‘Little Gem’ – I’ve noticed it is not
flowering very much any more and when it does produce flower buds, they turn
brown and start to die before they have fully bloomed. Can you tell me what
causes this and what I can do to keep this from happening. The tree itself
seems quite healthy and is growing very well.

There are a number of reasons that plants may fail to flower, and it may be difficult to pinpoint precisely why for your Magnolia grandiflora.

If this is a newly planted Magnolia, it may be too young to flower. Magnolias are somewhat notorious for being slow to flower.

Sometimes, cold temperatures kill off flower buds. This could cause bud browning and failure to flower. Magnolias can be quite sensitive to cold temperatures and to wind, in particular (see the picture of another Magnolia species with frost damaged flowers here). In some cases, frost damage can be severe enough that the flower buds die entirely.

There is a chance that the M. grandiflora’s failure to flower could be related to fertilizers, as well. Making more phosphorus and micronutrients available to the tree, or avoiding adding nitrogen, can help balance this out. Rankin’s book says that a Magnolia which is mulched once or twice a year does not need supplemental fertilizer, and adding it can encourage excessive vegetative growth at the expense of flowers. When there is a high quantity of nitrogen, plants tend to grow leaves rather than flowers. For example, flowering trees planted in lawns that are
heavily fertilized with nitrogen may flower much less or not at all.

Finally, M. grandiflora tends to need a fair amount of sun in order to blossom. On one gardening web page, I found an anecdote where the author talks about a M. grandiflora tree they own, half of which is shaded and flowerless, and the other half of which gets sun and flowers profusely. According to Magnolias: A Care Manual by Graham Rankin (Laurel Glen, 1999), any Magnolia planted in heavy shade will flower very weakly at best.

pruning and propagating angel’s trumpet

When should I cut back angel’s trumpet and can I replant the part that was cut?

I’ve checked a book called Brugmansia and
Datura: Angel’s Trumpets and Thorn Apples by Ulrike and Hans-Georg Preissel.
It has a whole chapter on growing angel’s trumpets from cuttings as well as a
section on pruning them, which should be done after they bloom. As you probably
know, they can’t take freezing temperatures, so people often prune them in the
fall to make them easier to bring into a greenhouse (for overwintering warm) or
41-50 degree room (for overwintering cool). The important thing to remember is
to confine your pruning to the flowering part of the plant, so you don’t have to
wait as long for more flowers. The book says you can tell the flowering part of
the plant by looking closely at the leaves–the flowering part has an
asymmetrical leaf base on each leaf, but the base of the “vegetative” leaves is
symmetrical.

The cuttings you take can be used to start new plants, and the success rate will
vary depending on the time of year (spring and summer cuttings work best) and
the variety of angel’s trumpet you have. Viruses can be a problem, so keep your
shears very clean. You can often get them to form roots by placing them in a
jar of water so that only the lowest 1.5 inches of the stalk are under water.
Alternatively, place woody fall cuttings “about 10 inches long…in a mixture of
peat and sand, in vermiculite, or in pumice… temperature between 53 and 64
degrees… Many of these cuttings will form roots by the following spring. For
root development the cuttings need the same light levels as for good growing
conditions… It is a good idea to pot all cuttings into a nutrient-rich soil as
soon as possible after they have formed roots.”

on naming dog rose

How did the dog rose get its name?

The name dog rose, or Rosa canina, can be traced as far back as ancient Greece. The Greek physician Hippocrates, and later the Roman naturalist Pliny, believed that a cure for the bite of a rabid dog could be made from the roots. There are alternate theories but their histories cannot reach back as far. Some say the name is from ‘dag’ rather than dog, and that it refers to the dagger-sharp thorns. But this seems implausible, given how many fiercely thorny rose species there are. Some also claim that is it a pejorative name, as in ‘a dog of a rose,’ an inferior flower. Again, there is no history backing this theory.
According to Elsevier’s Dictionary of Plant Lore (edited by D. C. Watt, Academic Press, 2007), the medicinal property of the the rose’s roots came from a mother’s dream about her soldier son who had been bitten by a mad dog. In the dream, a voice told her to make a decoction of a wild rose’s roots, “which they call Cynorrhodon,” and she followed this advice, healing her son of his ailment.

a gelatinous substance called nostoc

I wonder if you can tell me what this gelatinous greenish substance is that is spreading all over the gravel driveway at our house. It looks kind of like seaweed. We tried spraying pesticide on it, but it came back with a vengeance. I’m worried about slipping on it, and would like to know how to get rid of it.

What you are describing sounds a lot like Nostoc, also known as witches’ butter, which is a type of cyanobacterium (blue-green algae). It is often found on surfaces which are made of some form of calcium carbonate rock (such as gravel, steps, and sidewalks). According to The Seaweed Site, nostoc is “common on limestone gravel near path edgings […], particularly in autumn. It can suddenly appear after rain, seemingly from nowhere, on paths, on roofs and sometimes in poorly-growing lawns. This gave rise to an early belief that it was material from shooting stars that had fallen to earth, hence some of the English common names Fallen Star, Star Jelly and Witches’ Butter.”

It apparently causes trouble in plant nurseries, too, as this document entitled “Nasty Nostoc” describes. (Source: Heather Stoven and Jennifer Parke in Digger magazine, June 2014, Oregon State University.) Many of the treatments mentioned in the article are not appropriate for use on gravel, and with any treatment, care must be taken not to contribute to toxic runoff into stormdrains. Avoid using phosphorus fertilizer, as that can encourage development of nostoc. Try to keep water from pooling on the gravel (hard to do in a rainy Seattle fall season). If the algae is only on a small area, you may be able to shovel it up and dispose of it. If you can solarize the area during the hottest weeks of the summer, that may also be helpful (covering with clear plastic for two to four weeks).

the color blue in conifers

What makes the blue color on some conifers?

I am by no means an expert on plant physiology, but I believe it is the waxy coating (cuticle) on the needles that makes them look blue, as confirmed in this article about a variety of Colorado blue spruce by Edward Gilman and Dennis Watson on the website of University of Florida Extension:

“[….] the wax coating on the needles of Blue Spruce which give
the blue color can be washed off by some pesticides.”

Here is similar information from Montana State University Extension (page 14):

Excerpt re: Colorado blue spruce:
“The bluish color of the leaves of some of the trees results from a wax (cutin) accumulation, which is genetically controlled.
This doesn’t satisfactorily explain why blue conifer needles would be any different from those of green conifers (whose needles are also waxy), though.”

The following article by John Clark and Geoffrey Lister in Plant Physiology, vol. 55, 1975 has a complex technical explanation:

Excerpt:
“The observed differences in relative pigment complements can, therefore, partially account for the differences between the action spectrum for red alder and those of the conifers as a whole. In particular, the increasing carotenoid-Chl ratios determined for red alder (0.38) and the two green conifers, Douglas fir (0.54) and Sitka spruce (0.67) would seem to be the factor responsible for the differences between their action spectra. The same explanation, however, cannot alone account for the range of differences seen in the action spectra for the four conifers. No evidence was found to support differential degrees of screening by an extrachloroplast blue-absorbing pigment reportedly present in some conifer needles (2). One is therefore led to believe that an additional factor must be
responsible for the differences between the green and ‘blue’ spruces. Differences in apparent leaf coloration, arising from changes in relative spectral reflectance attributable to varying leaf cuticle structure, seems to be the most plausible explanation.”

Monarch butterflies and plant damage

Will Monarch butterflies do damage to plants if they are released in a garden at their adult stage?

The adult Monarch butterfly eats flower nectar, not leaves (the caterpillar form eats the leaves of one plant, milkweed–Asclepias), so that should not be damaging in any way.

I would question the practice of purchasing and releasing butterflies, though. It is not a good environmental practice, and can be harmful to the released butterflies and native butterfly populations. The North American Butterfly Association has information on this issue, excerpted below.

“Most fifth graders can tell you how the magnificent Monarch butterflies migrate thousands of miles every autumn from the United States and Canada to a few small mountain tops in Mexico. There they find the right environmental conditions that allow them to survive the winter. With the advent of spring, they begin their return journey. This migratory phenomenon is truly a wonder of nature that sparks the imagination.

Now imagine tens of thousands of mixed-up Monarchs unable to find the way to their overwintering grounds. This depressing image may become a reality if the rapidly-growing fad of releasing butterflies, including Monarch butterflies, at weddings, state fairs, and other public events continues to spread. Because the released Monarchs may have come from California, for instance, where they do not migrate to Mexico, their offspring may not be able to orient properly,. Because the Monarchs were raised inside under unnatural conditions, it is possible that their delicate migratory physiology may not have been turned on.

Public interest in butterflies is increasing dramatically. We hope and expect this greater involvement with butterflies will eventually lead to much-needed support for butterfly conservation and studies, but the release of live butterflies is the dark side of this increase in popularity. Although this practice is understandable to naive newlyweds-to-be (what could be more beautiful than adding butterflies to the environment?) it is really a particularly long-lasting form of environmental pollution.

Butterflies raised by unregulated commercial interests may spread diseases and parasites to wild populations, with devastating results. Often, butterflies are released great distances from their points of origin, resulting in inappropriate genetic mixing of different populations when the same species is locally present. When it is not, a non-native species is being introduced in the area of release. At best, this confuses studies of butterfly distribution and migration; at worst, it may result in deleterious changes to the local ecology. The Hollywood Jurassic park message, “Don’t fool with Mother Nature,” has scientific foundations. Recently a high profile report in Science magazine found that even the careful introduction of species for biological control often causes unexpected negative results.

In addition, these releases create a commercial market for live butterflies (currently about $10/apiece), with the result that, for example, the Monarch overwintering sites in Mexico and on the California coast are now targets for poachers.

Currently, the interstate shipment of live butterflies requires a permit from the U.S. Department of Agriculture but this law is not usually enforced. In general, the Dept. of Agriculture may issue a permit for shipping any of the following species: Monarch, Painted Lady, American Lady, Red Admiral, Giant Swallowtail, Gulf Fritillary, Zebra (Heliconian), and Mourning Cloak. Shipping Red Admirals, Giant Swallowtails, Gulf Fritillaries and Zebra (Heliconians) is particularly inappropriate because they are not naturally found over much of the United States.

A solution that better serves the public interest with less regulatory burden is to ban the environmental release of commercially-obtained butterflies (we would exempt education institutions, although even here we would encourage schools to keep commercially-obtained butterflies within the confines of the school). The intentional release of native birds was outlawed in 1947. The time has come to do the same with butterflies.”

Cryptomeria japonica’s root systems

I have a question about Cryptomeria japonica ‘Black Dragon.’ I would like to know the approximate diameter and depth of the root system at full growth. I am trying to convince the local cemetery to permit me to plant one there.

According to Richard Bitner’s Conifers for Gardens (Timber Press, 2007) Cryptomeria japonica ‘Black Dragon’ typically grows to about 6 feet tall. As a dwarf form of C. japonica, I would expect its roots not to be much of a problem. The (non-dwarf) species can grow to 160 feet, in which case, roots would extend a considerable distance. The local website, Great Plant Picks, features the variety ‘Black Dragon’ and says it grows to about 7’H x 8’W.

Here is general information on trees and their root systems, from Tree Roots in the Built Environment (Roberts et al., Centre for Ecology & Hydrology, 2006):

About root depth:
“A further misconception about tree roots is that they occur typically in significant quantities at substantial depths (i.e. greater than 3 m.) in the soil profile. […] from numerous studies involving comprehensive root excavations the indication is that typically as much as 90% of the tree root length occurs in the upper metre of soil.” According to this same source, conifers usually have about 70% of their roots in the upper 50 cm. of soil.”

About root extent:
“[…] large species differences exist but it is also the case that the horizontal extent of tree roots substantially exceeds the perimeter ‘dripline’ of the crown. […] there is a good relationship between crown spread and root radius but the relationship tends to be very species specific. Roots extending furthest from the tree trunk are usually found in the soil surface. […] the maximum extent ot the tree roots is reached before the canopy has completed expanding, suggesting that the ratio of root spread to crown spread may decrease as trees become older.”

This same source also says the root extent is highly dependent on soil environment (richness of soil, access to water and nutrients).

To summarize, what all this means is that the width of your tree’s crown will give you only some idea of the extent of the roots, and most of those roots will be shallow.