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Recently Added Questions

Question:

This is both a plant and insect question. I manage a property that has a small stand of planted English and Garry oaks. This summer, there has been a very large population of bees and yellowjackets attracted to these trees. There isn't a nest or hive on the 5 acre property that I have found, so these bees seem to be coming in from a distance. Indicators that I am observing are:
Many sap (sucker) holes on these trees, one in particular.
A heavy black dusty coating on most of the leaves.
The sound of droplets, not humming or eating.

Answer:

Based on your description, my first thought is that the coating on the leaves sounds like sooty mold. First comes the sticky honeydew left by leaf-sucking insects such as aphids, and then the sooty mold develops on the sticky substance. It would make sense that bees and wasps might be attracted by the honeydew, but might also be preying on the smaller insects that cause it.

This article, which comes from a beekeeping perspective, may also be of interest. Here is an excerpt:
"Although it may be off-putting to think of eating insect excrement, honeydew honey is prized in parts of Europe and New Zealand and often fetches higher prices than floral honey. It is rich in mineral content, amino acids, and may have stronger antibacterial properties. When a psyllid insect or aphid ingests the plants sap, it digests the small amount of protein present and expels the rest of the water, sugars, tannins and other indigestible material as honeydew. If you have ever parked your car under a tree and found it covered in a sticky substance the next morning, chances are the tree is infested with sap-sucking psyllids or aphids. For many other insects including ants, wasps, and bees, this is a valuable food source."

Your poetic description of "the sound of droplets, not humming or eating" might be the sound of transpiration from the leaves, or just the honeydew (part tree sap, part insect excrement) seeping from them.

Question:

I want to add a hydrangea to my garden but I would prefer one that is also fragrant. Are there varieties that have a noticeable pleasant scent?

Answer:

There are some species and cultivated varieties of Hydrangea that are reported to be fragrant. Bear in mind that everyone's sense of smell is different. I recommend seeking out examples when they are in flower and doing a sniff test in nurseries, gardens, or large parks and arboreta with a good selection. The ones that have a fragrant reputation are:

  • Hydrangea quercifolia: the smell is a rich honey-vanilla to my nose. This shrub is also a wonderful magnet for honeybees, bumblebees, pollen wasps, and syrphid flies. Its inner flowers are fertile, while the more dramatic outer sepals are sterile. Cultivated hydrangeas have been bred to emphasize the sterile florets, while wild hydrangeas tend to have fewer of these and are more useful for pollinators. In my garden, all the pollinator activity is humming along on the fertile inner flowers beneath those sterile four-petaled parts of the inflorescence. The showy parts of a hydrangea so prized by humans for their beauty are not what interests the pollinators .
  • Hydrangea angustipetala and its cultivar ('Golden Crane,' also called 'MonLongShou'): said to smell strongly like jasmine or sweet alyssum; of the species, Dan Hinkley says: "The deeply scalloped sepals of the infertile florets surround a disk of striking chartreuse fertile flowers while emitting a faint but beguiling fragrance." [Horticulture, Jun/Jul2009, Vol. 106, Issue 5]
  • Hydrangea scandens: Dan Hinkley says: "As its name implies, it can be a sprawling shrub but far from what would be considered disheveled. The branches possess a pleasing burgundy-brown color and the lacy cream-colored flowers pack a powerful fragrance during March and April. Hydrangea scandens 'Fragrant Splash' adds a bonus of variegated foliage." [Ibid.]
  • Some hybrids of Hydrangea macrophylla x Hydrangea angustipetala
  • Hydrangea macrophylla 'Ayesha': "one of the only Hydrangeas to have a delicate fragrance in bloom" [Great Plant Picks profile]
  • Hydrangea anomala ssp. petiolaris (a climbing hydrangea)
  • Hydrangea paniculata: "slight floral scent" or "mild fruity fragrance"

Close relations in hydrangea family:
  • Pileostegia viburnoides: "In late summer, frilly cymes of heavily-scented flowers erupt amidst its foliage, filling the air of our woodland drive with a delicious aroma of honey. Not surprisingly, honey bees are highly attracted to the flowers that rely entirely on scent." [Heronswood blog, August 29, 2018] However, not all noses smell alike. An article in Arnoldia [June 2, 1964] says "The floral odor is described as 'fragrant' or 'ill-smelling.'"
  • Decumaria barbara (woodvamp): a climber in the Hydrangea family, native to swampy areas of the southeastern U.S., with fertile flowers that are slightly fragrant or fragrant, depending on the source.

Based on the research above, Hydrangea quercifolia and Hydrangea angustipetala cultivars seem like the best choices.

Question:

Why are my rhododendrons spitting water? On hot sunny days this summer, we've been sitting in their shade and noticing occasional tiny needle-fine droplets landing on us. Is this caused by insects (I don't see obvious signs of them on the leaves), or is it normal?

Answer:

My hunch is that the leaves are transpiring. I found an article by Bill Letcher in the Journal of the American Rhododendron Society (vol. 41, no. 2) entitled "Rhododendrons with a Drinking Problem."

The article is about the importance of water in successful rhododendron cultivation, but also does a good job of explaining transpiration:
"The water absorbed by the root hairs, or rootlets, is drawn up in the stem of the plant and into the leaves, where it exits via small holes called stomata into the air as vapor. This process is called transpiration […] Transpiration requires a lot of energy, and this comes, as we might expect, from the sun. If all else is equal, transpiration amounts are directly proportional to the amount of radiant energy striking the leaf surface of a plant: the more energy, the greater the amount transpired. […] One factor of paramount importance to rhododendron growers which effects transpiration is the relative humidity of the air surrounding the leaves. Dry air causes appreciably more transpiration than humid air, and the presence of wind increases this dramatically by replacing the layer of air next to the leaf surfaces before it can become saturated. Ambient air temperatures will also markedly increase transpiration as they rise, sometimes with disastrous results. Our family of rhododendrons has less ability to extract moisture from the soil than, say, manzanita (which can pull all of the available water from the soil down as far as six feet!)."

If we have more hot weather, you may want to give your shrubs an occasional supplemental drink of water, since they are shallow-rooted, and our summer-dry climate (depending on how hot and dry it is) can cause stress to the plants. Keep an eye on how they are looking and do what you can to maintain their health (and preserve your shady refuge!). To quote Letcher again:
"The family of rhododendrons has either never been forced to adapt to very low available moisture conditions, or has not adapted well to them. Their roots tend to be quite shallow. The foliage is lush, dense, and of a dark, absorptive color instead of being light and reflective of the radiation. They display their displeasure with your attempts to wean them from the conditions they most enjoy, by doing exactly what a great many other plants will do: they shorten their internodal growth, reduce the number and size of their new leaves, drop some of their older leaves, and just plain sulk! Ultimately, they languish into a pitiful state of scrawnyness and pallor which is not a pleasant sight in your garden."

Question:

For a few years, our Liberty apple has developed tiny pouches on its leaves. Soon, the leaves turn yellow and drop prematurely. It also seems to affect the developing fruit with dimpled dark spots.

Answer:

It sounds like your tree has apple blister mites, a type of eriophyid mite. They are tiny, and you would need a magnifying lens to see them. There is information about this mite in the Pacific Northwest Insect Management Handbook, including life cycle, and methods of control with dormant sprays (some of which are accepted for use in organic orchards). The mites overwinter under the outer bud scales on the tree. In case you are wondering where to look for bud scales, when the tree loses its leaves in fall or winter, bud scales form at the ends of branches or stems. The bud scales protect new growth that will emerge here. When buds swell in spring, the mites will burrow into them to feed. Once the blossoms have fallen, they will progress to leaves and developing fruit.

Mites are attracted to drought-stressed trees, and to nearby weeds like clover, mallow, bindweed, and knotweed. They can be carried from tree to tree by wind or birds and other insects. Usually, ample rain and cold winter weather keep mite numbers down, but as the climate changes, we may be creating conditions that are more favorable to them.

You might be able to find a source for predatory mites to help control the blister mites. Washington State University’s Tree Fruit research site describes several species of phytoseiid predatory mites.

Question:

Can you identify a plant growing at my mother’s house in Georgia? We would like to know more about it.

Answer:

This is Smilax bona-nox. It goes by many evocative names, and even the scientific name had me wondering. Why is the species name "good-night?" It was named by Linnaeus and in his time bona-nox would have served as a euphemistic Latin curse (the way someone might say dadgummit, goldarnit, or flipping heck), possibly uttered after getting ensnared in this viny plant’s thorns. According to Delena Tull, author of Edible and Useful Plants of Texas and the Southwest (1999 ed.), encounters with the curved prickles give rise to common names like catbrier (or catbriar) and blaspheme-vine. Other common names include saw greenbrier (or saw briar) and tramp's trouble. It is also called zarzaparilla (Anglicized to sarsaparilla from the Spanish name which means bramble + little grape vine).

According to the Virginia Native Plant Society, the fruit of Smilax species is valued by birds, bears, foxes, possums, and squirrels. The flowers are nectar and pollen sources for bees and flies, and the leaves host the larvae of caterpillar moths. The Native American Ethnobotany Database lists medicinal uses of this species of Smilax by the Seminole, Choctaw, Houma, and Creek tribes. The Choctaw and Houma ground the dried tuberous roots into flour for use in bread and cakes. The Comanche used the leaves as cigarette rolling papers.

About the common name sarsaparilla, you may be familiar with this word as flavoring sometimes used in the beverage known as root beer. A traditional tonic made with the rhizomes was thought to ward off rheumatism. Both Smilax and Sassafras have been used in flavoring root beer, but both contain safrole which might contribute to liver cancer.