Could you provide me with information on pruning Red Gravenstein?
Archives: Plant Answer Line Q & A
Plant Answer Line questions and answers.
encouraging orchids to bloom
All but one of my orchids are blooming this season! What could be the cause of the one orchid not blooming?
First of all, congratulations that you have all but one of your orchids
blooming. Orchids are plants with very particular needs, as you well know. I
have found two possibilities as to why your one orchid will not grace you with
its flowers: light and space. However, there are other possibilities as well,
which I will try to address.
Perhaps this one plant is not receiving the amount of sunlight it needs to bloom
and the others are. Are all your orchids the same species or variety? If so, are
they all in the same area of your house; i.e. same window? If they are not the
same species or variety, then they may require different amounts and levels of
intensity of light. Are they growing in a window with natural light or are you
growing them under artificial light? If you are using artificial light, orchids
do require dark as well as light. Orchids “should not receive more than 14 hours
of artificial light a day. More than that will prevent them from blooming.”
(Orchid Growing Basics by Dr. Gustav Schoser, Sterling Publishing Company, 1993)
Are you using a fertilizer? If so, and the first number is a lot higher than the
second or third (such as 15-5-5), it is likely that the plant is receiving too
much nitrogen. This will do wonders for the green leaves but nothing to promote
flowering. A fertilizer with the numbers closer together (such as 10-12-10) will
be more balanced and would be recommended. Are you monitoring the temperature?
“The effects of temperature changes are most clearly observable in the Cymbidium
orchids. Flower production begins when daytime temperatures are about 68 degrees
and nighttime temperatures are around 50-57 degrees. Phalaenopsis schilleriana
and its hybrids will only bloom when the nighttime temperature is under 68
degrees for at least 2-3 weeks.” (Orchid Growing Basics)
Here is an excerpt from a frequently asked question and answer web page from a
commercial grower: beautifulorchids.com.
Q: I am growing my phalaenopsis orchid in the house but they never bloom. What can I do?
A: The most common reason for any orchid not to bloom is insufficient light.
Move your phalaenopsis plants to a window where they will receive strong, but
indirect light (near a south-facing window is ideal). You might also try
lighting your plants with a fluorescent light fixture placed about 1-2 feet
above the foliage. Give up to 12 hours of supplemental light per day.
Phalaenopsis will also develop flower spikes in response to a cool period of
about four weeks with night temperatures of 55F. After the cool treatment, raise
the night temperature back to the normal 60-65F minimum. See if these changes to
your growing conditions help to stimulate your plants to bloom.
Another page on the same site more clearly defines good vs. bad light. They
explain that too little light may prevent the plants from blooming. They also
list specific orchids that prefer low light and those that prefer moderate to
high light.
The Brooklyn Botanic Garden All-Region Guides: The Gardener’s Guide to Growing
Orchids (2004) Handbook #178 has good information regarding light
requirements on a variety of orchids. It is noted in this book that “light is
undoubtedly the most important factor in determining whether or not an orchid
will flower.” The American Orchid Society’s page on “Light, the Key to Successful Blooming” should also be helpful.
Also, there is a possibility that the one orchid has outgrown its pot faster
than its companions and has a need for more space (and possibly more nutrients).
“Most orchids usually only bloom from new growth” (Your First Orchids and How
to Grow Them published by the Oregon Orchid Society, Inc 1988). “An orchid is in
need of repotting when the leading pseudobulb or growth has reached the rim of
the pot and there is no room for future development. (The Gardener’s Guide to
Growing Orchids by Wilma and Brian Rittershausen, David and Charles Publishers
2001) If you are getting new shoots but they are growing over the edge of the
pot and breaking off, this would also be a sign for the need to repot.
The Gardener’s Guide to Growing Orchids by Wilma and Brian Rittershausen, and The
Brooklyn Botanic Garden All-Region Guide and Orchid Growing Basics by Dr. Gustav
Schoser, offer good directions on repotting. The Schoser title even offers
recipes on how to make your own potting mixes.
rusty leaves on Asters
Our Asters are green and getting ready to bloom but the
lower 8″ are “rusty” or burnt looking. Did our bark mulch hurt them? Too much
fertilizer? This is their third year in the same spot.
There are quite a few potential causes of the rusty leaves you are
seeing. It might be entirely normal, as mature Asters (renamed Symphyotrichum) can start looking a bit ragged in late summer. It could be due to excessive heat,
overwatering (symptoms include yellowing and dropping of lower leaves),
or fertilizer burn (Asters are sensitive to soluble salts in chemical
fertilizers). It could be a fungal disease, rust, or Aster yellows, a
common disease caused by a microscopic organism (phytoplasma) and spread
from plant to plant by leafhoppers. With Aster yellows, you would notice
a loss of green in the leaf veins, and yellowing of new leaves.
Sometimes, infected outer leaves turn a rusty or reddish purple color. A
good general practice to keep your Asters looking full and less leggy is
to cut them back by one-half to two-thirds when they have reached 12 to
16 inches in late spring/early summer. (Source: The Well-Tended Perennial
Garden by Tracy DiSabato-Aust, Timber Press, 1998).) Here are
links to resources which describe other possible causes of the leaf
problem.
Connecticut Agricultural Experiment Station
To determine the exact cause, it might be worth bringing a sample to a
Master Gardener Clinic.
on replanting seed potatoes
I would like to plant a second crop of potatoes in July. Could I use
potatoes dug from my first crop this year or should I try to find seed
potatoes?
You can plant mid-season and late potatoes this month, but there are
particular varieties that are best suited to planting at this time. This
is one reason not to plant the potatoes you just dug (which are
an earlier variety).
Here are links to additional information:
From the University of Illinois Extension.
Growing Potatoes in the Home Garden from UC Santa Cruz.
Steve Solomon’s Growing Vegetables West of the Cascades (Sasquatch Books,
2000) says that because of the large number of viruses which can affect
potatoes, you should not carry over your seed (replant). It is safest to
use certified virus-free planting seed. He says that your crop might be
fine the first time you replant your own potatoes, but they will become
increasingly susceptible to viruses.
on pruning flowering bulbs
This is my first year planting spring flowering bulbs, which
grew nicely. I cut the dead flower and the stalk once it died back, and now the
foliage is yellow. What am I supposed to do with the yellow foliage? Pull it out? Cut it off? Just leave it alone? Also, will
planting some annual petunias now hurt the bulbs I have planted in the
garden? How close can I plant the petunia to the bulbs? I was going to
try and hide the yellow foliage.
The answer will depend on which bulbs you were growing. For example,
daffodil stems should not be cut back until at least 6 weeks after the
flowers have faded, and you should never tie the foliage in knots or
braid it (this is a common but ill-advised habit). You can leave
daffodils in the ground to naturalize and spread.
With tulips, you also need to wait at least 6 weeks from the fading of
the flowers before cutting back the leaves.
With hyacinths, you can pull away dead foliage and flower stems as they
fade. When the top growth has died down, you can either leave them in the
ground or dig up the bulbs, dry them off, and store them for replanting.
If you are growing iris, you can cut the dead flower stems to the base,
and cut away dead leaves in the summer. If they are bearded iris, the
fan of leaves may be cut back in the fall to about 8 inches above the
base.
(Source: The Plant Care Manual by Stefan Buczacki, Crown Publishers,
1993)
You can certainly plant your annual petunias quite close to bulbs like
daffodils and tulips and other bulbous plants which are quite vertical.
Just don’t plant right on top of the bulbs. To disguise dying bulb foliage, use perennial ground cover plants that keep their leaves over the winter, and that have stems soft enough for bulbs to emerge through them. Hardy geraniums (true geraniums, also called cranesbill) and creeping veronica, such as Veronica peduncularis ‘Georgia Blue,’ are good choices. You can remove dried leaves as needed, and they can be tidied or groomed in early spring.
on amending clay soil
I have typical Seattle clay soil and I want to amend it before planting. I’m re-grading a large (~2000 sq. foot) area and have already added copious amounts of mulch, compost, overturned sod, etc. I’m planning on planting a cover crop of clover this summer, but before doing so thought it’d be a good idea to till in some sand. I was thinking about a level inch over the whole yard before tilling. Is there a particular chemical composition to use or avoid? How about grain size?
You may find this information from Colorado State University Extension on soil amendments useful. Excerpt: Don’t add sand to clay soil–this creates a soil structure similar to concrete.
Professor Linda Chalker-Scott of Washington State University also debunks
the idea of adding sand to improve clay soil.
For good advice on amending the soil, see these links:
Building Fertile Soil and Choosing and Using Cover Crops for the Garden and Orchard from the University of California, Santa Cruz Agroecology Program.
It sounds to me as if you have already taken great steps toward improving your soil, and adding sand not only will not be necessary, but would not
be a good idea.
trees for privacy
I need a large tree for privacy and would like it to be fast growing here in Seattle. I would not like it to be much more than 15 feet wide at maturity but the height doesn’t matter, also evergreen. Would an Incense cedar grow fast?
In addition to Calocedrus decurrens (Incense Cedar), you might also consider Podocarpus or Cryptomeria.
You may want to consult the locally created web pages of Great Plant Picks, and see which evergreen trees they recommend for our area. This is their list of conifers, and here is the information on Incense Cedar.
Incidentally, Great Plant Picks says that Incense Cedar does make a good screening plant. They claim it will mature at 35-40 feet tall in garden conditions (as opposed to in the wild), and about 10 to 12 feet wide, so your original idea of planting this tree sounds like a good one.
native Northwest beach grasses
I live in a community on Camano Island. We have some communal beach front property and would like to plant some native beach grasses that are about one foot high. What species do we have to choose from and where can we purchase them?
I found a list of native Northwest beach grasses in an online symposium moderated by Alfred Wiedemann of Evergreen State College in Olympia. (The symposium was about an invasive species, Ammophila arenaria, or European beach grass, which has been crowding out native species.) Here are some of the plants he mentioned:
Elymus (Leymus) mollis (Dunegrass)
Abronia latifolia
Convolvulus (Calystegia) soldanella
Carex macrocephala
Glehnia leiocarpa
Lathyrus littoralis
Poa macrantha
Here is a Seattle Times article from May 1, 2005 about beach plants by Valerie Easton that may be of interest to you. The Miller Library has the book that is mentioned in the article, Native Plants in the Coastal Garden by April Pettinger (Timber Press, rev. and updated, 2002), and it includes a list of native grasses. These two grasses were specifically recommended for beachside gardens:
Elymus or Leymus mollis (also listed above)
Festuca rubra (Red fescue)
Washington Native Plant Society might also be a good resource for you. They provide a list of nurseries in our area which specialize in native plants. King County’s Native Plant Guide also has a list of sources.
on picking avocados
What causes an avocado to have a foul taste even when it looks superficially just fine? I’d like to know if there is a way of telling simply by looking at them, so I can avoid buying bad ones.
According to the book, Fruit & Nuts by Susanna Lyle (Timber Press, 2006), there are three main varieties of avocado: Mexican, Guatemalan, and West Indian. Mexican fruits tend to be smaller, with thin skins that turn a glossy deep green when ripe. Guatemalan fruits are round or pear-shaped and have pebbled skin. The largest avocados are West Indian, nearly round, with shiny green skin and flesh that is less rich in oil.
Avocados tend to take a long time (sometimes over a year) to reach maturity from the beginning of fruit-set, and sometimes they will not soften and become edible because the stems have a ripening inhibitor. For this reason, they must be picked while still hard, and then allowed to ripen at room temperature. Mexican fruits ripen fastest (6-8 months) but have a shorter storage life. Guatemalan fruits take 12-18 months to ripen and must be stored at about 10 degrees Fahrenheit for over a month.
This factsheet from U.C. Davis about post-harvest quality in avocados describes optimal storage temperatures, and mentions several variables that can lead to an unpleasant flavor:
- On-tree storage may result in development of off-flavors or rancidity with overmaturity
- Off-flavors may also develop when fruit are harvested during periods of hot weather
- >10% CO2 may increase skin and flesh discoloration and off-flavor development, especially when O2 is <1%
- Anthracnose: Caused by Colletotrichum gloeosporioides and appears as the fruit begins to soften as circular black spots covered with pinkish spore masses in later stages. Decay can penetrate through the flesh and induce browning and rancid flavor.
There are several scientific articles that discuss heat-induced off-flavors. In one example, “Isolation of Unpleasant Flavor Compounds in the Avocado (Persea americana)” by Brian I. Brown, certain varieties seem more prone to bad flavors than others, and some varieties lose the off-flavor once they are fully ripe.
I’m afraid there does not seem to be an easy way to know in advance which avocados will taste bad. Certainly, you should avoid fruits with dents or obvious discoloration in their skin. You might also complain to the market where you have purchased inedible avocados, and they can relay that information to their distributors and see if it has something to do with how the fruit is harvested or stored.
growing conditions for Avocados
We know avocados like dry soil, but are there specific guidelines to follow?
“Growing conditions: Give avocado direct light; insufficient light will cause spindly growth. Provide a warm temperature and medium humidity. Keep the soil evenly moist but not wet and soggy. Fertilize once a month throughout the year… Use an all-purpose soil mix for repotting… Avocado is vulnerable to aphids, mealybugs, scale insects and thrips.”
Source: The Time-Life Gardener’s Guide; Foliage Houseplants, 1988, p. 125
“Growth habit: The avocado is a dense, evergreen tree, shedding many leaves in early spring. Growth is in frequent flushes during warm weather in southern regions with only one long flush per year in cooler areas.”
“Foliage: Avocado leaves normally remain on the tree for 2 to 3 years.”