Iron Chlorosis in Maple Trees

  Strolling the grounds of my one acre “estate” on a warm summer day, I was distressed to see something wrong with two of my Sycamore trees.  While two of the trees looked great, nice dark green leaves everywhere, the other two had sections of leaves that had yellowed.  Upon further inspection, I noted that the veins of the leaves were still green, but the areas between the veins had turned yellow.  In some cases the edges of the leaves were brown. “What is wrong?” I wondered.

What was wrong with my trees was something called, Iron Chlorosis. This problem is apparently common in places that have high alkalinity soil (pH above 7.0). My soil was significantly above this level. It is believed that there is a link between alkalinity and iron in the soil. The problem isn’t a lack of iron, but the inability of the plant to benefit from the iron that is there. For some reason, chemical reactions render the iron unusable to the tree.                                 

So, now that I know what is causing the trees’ problem, is there anything I can do about it? Yes, there are a number of things that can be done to deal with this problem. The best solution is prevention.  Do a soil test to determine the soil pH and then select species that will do well in a particular soil. However, if the trees are already there, like mine, you have several options.  One option is to add elemental Sulphur to the ground around the tree.  The Sulphur will help free up iron for the tree to take up.  This is a slow process and may take a year or more before seeing results.  Another option is to inject iron directly into the trunk.  This involves drilling a series of holes in the tree. This procedure should not be done more than once a year.  Finally, the foliage can be sprayed with an iron solution.  This usually provides the quickest results, however as new leaves come on they most likely will exhibit the problem. Solving the problem of iron chlorosis is a difficult and time consuming challenge.  Research and careful planning and follow up are keys to your success. Saving all of your beautiful plantings are worth the effort.  

Good luck!

Happy Lawn, Happy Gardener

The first step to having a healthy and attractive lawn and controlling weeds is choosing a grass variety best adapted to your lifestyle and available resources. Factors to consider would be high traffic, shaded and sunny areas, type of soil, available water and amount of time available to care for the lawn.

Irrigate properly to help reduce annual weed infestation. Light frequent irrigation encourages weed seed germination, even if a pre-emergence herbicide has been applied. Water 1- 1.5 inches per watering. Do not water again until you see signs of wilt. Turf will also turn a shade of blue green when it is water stressed. The best time to irrigate your lawn is between 10p.m and 6a.m. 

Mowing  The preferred mowing height for all species of grass is 2 ½ - 3 inches. The minimum height that any lawn should be mowed is 2 inches. Mowing to heights less than 2 inches results in decreased drought and heat tolerance plus higher incidences of insect, disease, and weed problems.  The seeds of some weeds require high light intensity to germinate. The shaded environment near the soil surface in a high mown lawn helps deter weed germination. Mowing frequently enough that no more than one third of the grass height is removed at any single mowing. If the mowing height is two inches the grass should be mowed when it is 3 inches tall. If the mowing height is 3 inches, it should be mowed when it's about 4 inches. Keep your mower blade sharp to avoid shredding and fraying leaf blades.  Grass clippings should be allowed to fall back into the yard to provide natural nitrogen in the soil. 

Pre-emergence herbicides   A Pre-emergent is activated in the top layer of soil where the weed seeds sprout, and by design it stops the plant from growing. A pre-emergent is NOT effective once the weeds are showing. Spreading out the herbicide so that it is evenly distributed is critical. It must also be watered into the soil within the appointed time period. The soil must remain undisturbed in order to maintain the barrier. A pre-emergent has to be replaced, or replenished. Pre-emergence should be applied two to four weeks before the seeds start to germinate in mid  March to early April depending on weather. Warm moist springs cause earlier germination. The temperature of the soil ( 55-60 degrees)  as it starts to warm up in the spring is going to be the primary indicator of the pending arrival of various weed species. With normal weather patterns pre-emergence herbicides give good to excellent control of crabgrass, foxtail, and barnyard grass.  Do not over seed into areas that have recently been treated with pre- emergence.

Post- emergence herbicides Perennial broadleaf weeds can be controlled by post emergent herbicides. It is important to properly identify the weed before choosing an herbicide. Some common perennial  broadleaf weeds in lawns are dandelion, field bindweed  ( morning glory), White clover, curly dock, ground ivy, Canada thistle, broad leaf plantain, buckhorn plantain and yarrow. The best time to control perennial weeds is in late summer or early fall when weeds are preparing for winter. 

Core cultivate ( aerate) the lawn at least once a year to reduce compaction and to  control thatch. 

Fertilization Fertilizer may be needed if the lawn has poor color and vigor, doesn’t recover from traffic or more weeds are present. Nitrogen is the most important nutrient for lawns. Do not use Phosphorus or Potassium unless soil test indicates it is needed. Cool season grasses should be fertilized in fall, late spring and little in the summer. Warm season grasses should be fertilized late May, June, avoid fertilizing in late summer and fall.