Thanks again, Kathryn Wadsworth and David Deardorff, authors of What’s Wrong With My Plant, for undertaking to diagnose 10 plant problems sent in by Rant readers. Here’s the second set.
The Plant Doctors Report, II
Christopher has 10,000 daffodils all blooming profusely in his annual
“bulbapaloozathon” except for this one double flowered variety. Great photos
show a daffodil with aborted flowers.
The daffodil in question didn’t really fail to flower. It
actually produced flower stalks with flower buds (as shown in the photos). The
flowers, however, aborted and turned brown inside the sheath before opening. No
insects (thrips, for example) occur inside the buds. And to round out the
mystery, 9,999 other daffodils bloom profusely under exactly the same cultural
and environmental conditions in the same location.
Specific cultivars of double daffodils react to unseasonal
cold snaps of freezing temperatures during bud formation by aborting the
flowers. Daffodils in general are extremely hardy to cold temperatures, but a
few are not. Many factors cause daffodil flowers to fail to form (overcrowding,
undersized bulbs, removing foliage too soon, temperatures exceeding 80 degrees
F) but this doesn’t apply here because there are a heck of a lot of daffodils
all blooming their heads off, and only one that does not. Most likely, it is an
issue with the particular cultivar in question, a double, and probably it was
just too cold for that variety at a critical moment in its development.
Note to Christopher from Elizabeth: I have the same problem (doubles and planted in a clump just like yours), but I have found that the daffs can and will blossom after being duds the previous season. It is totally arbitrary. You say in comments that you are going to dig them up, but I think you should keep that in mind.
Insect larvae of gall wasps cause these galls to form. Mom
lays her eggs under the bark of the tree. When the egg hatches, the baby wasp
(a maggot-like grub) starts to feed on the tree and the grub’s saliva contains
chemicals that cause the tree to build a house (the gall) around him. When he
matures he chews a hole in the gall and flies away.
These galls do not threaten the life or health of your tree.
You can simply prune them off if they’re unsightly. If you do your pruning
while the babies are still inside their galls and destroy them before they
mature you disrupt the life cycle and gain a measure of control over the
problem. Examine the galls closely and, if there are no exit holes, the wasp
larva is still inside. But, of course, many more gall wasps exist in the
neighborhood and surrounding forest lands. So, complete control is not an
6. Kathy Purdy sent us photos of her Juneberry (Amelanchier
x grandiflora ‘Autumn Brilliance’) because every summer it drops seventy five
percent of its leaves. The original set of photos weren’t up close enough to
see the leaves in detail, so we asked for more photos. Kathy posted six more
photos with good close ups of the leaves and we’ve looked at all of them.
We looked carefully for tell-tale signs of leaf-spot fungi.
But none of the spots demonstrated those signs. In addition, this hybrid
juneberry (Amelanchier laevis and A. intermedia) is resistant to the leaf spot
fungus disease (Coccomyces tumidus) that causes juneberry leaves to fall off in
The spots appear to be the angular patches left by the pear
slug, a sawfly larva which rasps away the soft green tissue from the surface of
the leaves. Although this is a common problem on juneberries, it does not cause
the leaves to fall off.
We observed that several leaves in the photos turned yellow
from the tip, a characteristic symptom of insufficient water.
Kathy’s email said that the leaf drop problem occurs in wet and
dry years, regardless of how well hydrated the soil is. Thus, we conclude that
insufficient water is not due to simple drought. In this case, some other
factor impacts the plant’s ability to bring water from the roots to the leaves.
Possibilities include: 1. Too much fertilizer or other salts in the soil. 2. Damage to the root system by insects,
rodents, root rot or other pathogenic fungi. 3. Construction/digging in the
root zone. 4. A combination of wind, bright sun, and high temperature at the
The bottom line — we don’t have enough information to build
a case history and come to an accurate diagnosis. But Kathy certainly does, and
she should be able to examine those factors and solve the problem. By the way,
this little tree is gorgeous in full bloom. A real knock-out. (See all the pictures and more on this problem on Kathy’s blog, here.)
7. Kathleen Sherin sent photos of a young ‘Reliance’ peach
tree with ugly lesions on the trunk and branches that look like they’re oozing
gum. She says it’s a young tree, less than one year in the ground.
The lesions on this peach tree, blackish cankers oozing gum,
typify bacterial infections in stonefruit trees. ‘Reliance’ is supposed to be
resistant to bacterial spot (caused by Xanthomonas pruni) so we have to suspect
it is the other common bacterial disease of stonefruits, bacterial canker
(caused by Pseudomonas syringae).
These bacterial infections are common on cherries, peaches,
plums and other stonefruits. Very difficult to cure, they can eventually kill
your tree. To treat it, prune away all the infected tissue (and then sterilize
your tools!). Then, spray the tree with a copper-based remedy. Copper is
effective against both fungi and bacteria and is a good organic choice for your
tree. But in spite of your best efforts you will probably lose this tree sooner
or later. And, as stated in your notes, the lesions are everywhere and if you
prune them all away there will be nothing left.
Our best recommendation: remove this sick tree and get a healthy
one. Look for a tree that’s fully leafed out and growing in a pot. Examine it
carefully for signs of cankers or oozing gum. Choose a healthy one to take
home. Do not plant it in the same hole where the sick one was. Treat the new tree
with a copper-based remedy to prevent future bacterial infections.
Tomorrow: the final set of problems and the announcement of book winners!Posted by Elizabeth Licata on April 27, 2010 at 4:18 am, in the category Unusually Clever People.