Sunday, June 23, 2019 1 comments By: Ask A Master Gardener

Oak Leaf Galls

Galls on Oak Leaves
Tom Ingram: Ask A Master Gardener
Sunday, June 23, 2019
Q: I am noticing these round things about the size of a golf ball that appear to be falling from my oak tree. What are they? CS
A: What you are referring to is an Oak Apple Gall. They are called Oak Apple Galls because they kind of look like small apples. These curious growths are caused by a small wasp called a gall wasp. When the gall wasp lays its eggs, it injects a toxin into the host plant, which stimulates the tree to produce a protective cover around the eggs.
When the eggs reach larval stage, they begin to feed and develop inside the gall. When ready, they either emerge to create another generation or overwinter inside the gall, depending on the time of year.
A variety of gall types can form on leaves, twigs or branches. Typically, these galls do not harm the tree; however, a large outbreak could disrupt nutrient flow within a twig resulting in twig die-back. But this is the exception, rather than the rule.
There is another type of gall that can be problematic that is the result of gall midges. The gall midge lays its eggs on oak leaves and injects a toxin causing the leaves to form a gall that looks like a leaf with curled up edges.
Unfortunately, the larvae of the gall midge are the preferred food for the larvae of the oak leaf itch mite. Oak leaf itch mites can be problematic in that they are microscopic, and their bite can irritate our skin. In the height of an outbreak of oak leaf itch mites, it would not be unusual for potentially 300,000 mites to fall from the tree each day. That’s right, I said each day. Their bites can be painful, and some people will develop red swollen bite marks.
Unfortunately, treating your tree with some sort of pesticide is usually not an option due to expense and the fact that the insects are living inside the gall, which makes it hard for pesticides to reach them.
If you experience an oak leaf itch mite outbreak in your yard, the best advice is to stay away from the tree or wear long-sleeved shirts, long pants and a hat when working outside. That sounds like fun in an Oklahoma summer, doesn’t it?
You can best control these leaf galls through good sanitation: disposing of leaves and galls that fall to the ground. If a branch has a lot of galls and you can reach it, you could prune that branch and dispose of it.
The good news is that large outbreaks are rare in our area, but if you come in from working in the yard and feel a bite but don’t see anything, it just might be an oak leaf itch mite.

 Garden tips

  • Vigorous, unwanted limbs should be removed or shortened on new trees. Watch for forks in the main trunk and remove the least desirable trunk as soon as it is noticed.
  • Most varieties of mums are more productive if “pinched back” now. Either pinch off with fingers or cut to remove an inch or so of limb tips above a leaf. This results in the growth of new limbs and a fuller plant. Do not pinch after mid-July or it will interfere with fall blooming.
  • Watch for tiny, sap-sucking insects called aphids on roses, perennial flowers, shrubs and vegetables (especially tomatoes). They produce a sticky substance called “honeydew.” Many can be dislodged with a hard spray from your garden hose, or two applications of insecticidal soap will usually greatly reduce any aphid damage to your plants.
  • Crapemyrtles are one of the few shrubs that should be planted in the middle of summer. Growth of new roots of these plants occurs best with summer soil temperatures.

Sunday, June 9, 2019 0 comments By: Ask A Master Gardener

Coping with Too Much Rain and Flooding

Coping with Too Much Rain

Allen Robinson: Ask A Master Gardener
Sunday, June 9, 2019
Q: The amount of rain that we have received lately has been considered by some as unprecedented. What effects will this have on my garden and what should I do about it? Rebecca T., Tulsa
A: While most of us love the rain, too much of a good thing is rarely a good thing. So you are correct — too much rain can wreak havoc in the garden, which can happen in some rather unsuspected ways, such as:
Perhaps the biggest problem is that too much rain can actually drown plants. Water sitting in the soil actually fills all of the subsurface voids that would otherwise contain essential oxygen for root and plant growth. When that happens, plants are simply not able to respire/breathe and, therefore, will eventually suffocate. Carbon dioxide and ethylene gases can also accumulate, both of which can be quite toxic to plants.
Symptoms of waterlogged soil include plant leaves turning yellow, turning brown or wilting suddenly. Short of waiting for the soil to dry out, there’s not much you can do to reverse the situation. A couple of tips to help: 1) Pull back the mulch from around plants to facilitate the drying process and 2) carefully stab a garden fork into the ground to help needed oxygen reach deeper into the soil.
Too much rain can actually leach essential nutrients out of the soil, especially nitrogen. Nitrogen easily moves through the soil with just simple watering (potassium and phosphorus do not), and heavy rains just exacerbate the situation. So once the soil dries out a bit, consider applying a fertilizer that is high in nitrogen. Common types are Ammonium Sulfate (20-0-0), Ammonium Nitrate (34-0-0) or Urea (46-0-0). Milorganite and Osmocote are also good choices. Or simply top-dress plants with compost, which contains all of the essential ingredients.
Splash down
Mud that splashes onto leaves and stems often harbors fungal spores. If this occurs, simply wash the entire plant with a gentle mist. On plants that are particularly susceptible to fungal diseases (e.g. roses, tomatoes), consider applying an all-natural fungicide as a preventive measure.
Tread lightly
Be careful where you walk. Your weight (regardless of what it is) can cause severe compaction in wet soils, which is the enemy of plants. If you have to work in the garden, first, place a board on the ground, then walk on it to minimize compaction. Walking in wet soil can also hasten the spread of fungal diseases.
Pollination can also be affected by heavy rains. This is because pollinators have a tough time flying in the rain and heavy, wet pollen simply isn’t as effective at doing its thing. There’s not much you can do to remedy this problem short of waiting for the weather to change.
Grass, anyone?
We have all been frustrated during those times when frequent rains make it impossible to get out and mow our lawns. And by the time it is dry enough to mow the grass, it’s overgrown. One way to conquer this is to double-cut the grass. Raise the mower deck to its highest notch, mow, then drop the deck height to your preferred level and mow again. The second mowing should be done in a different direction to the first mowing.
Now, we just need to find out who overdid the rain dance.
Get answers to all your gardening questions through the Tulsa Master Gardeners Help Line at 918-746-3701, at the Diagnostic Center, 4116 E. 15th St., or email
Garden tips
  • Renovate overgrown strawberry beds after the last harvest. Start by setting your lawnmower on its highest setting and mow off the foliage. Next, thin crowns 12 to 24 inches apart. Apply recommended fertilizer, pre-emergent herbicide if needed and keep watered.
  • White grubs will soon emerge as adult June beetles. Watch for high populations that can indicate potential damage from grubs of future life cycle stages later in the summer.
  • Fertilize warm-season grasses at 1 pound of nitrogen per 1,000 square feet. Don’t fertilize fescue and other cool-season grasses during the summer — wait for fall. Nitrogen, the first of the three numbers on all fertilizers, is very water soluble. So if you fertilized before the recent rains started, much of it may have been washed into deeper soil or drain water. After the rains have passed, consider re-applying a nitrogen-only fertilizer at the rate indicated above.