Iron for Moss Control and Grass Green-up

One of my readers has noticed that the iron in moss out turns grass dark green without stimulating growth. He has been applying it as a liquid solution in a sprayer. He asked if there would be any problem using this several times during the summer just for the green-up. Yes, it can be used repeatedly without any danger (liquid or granular). The effect does not last too long and it is not a complete substitute for regular lawn fertilizer, preferably 2 applications, spring and fall. Most iron compounds can stain concrete a rust color, so avoid spraying concrete. If granules land on concrete, they can be brushed off before becoming wet without any stain. If you do happen to stain concrete, several rust stain removers will remove rust stains from concrete as well as clothes or other areas.

Lime Is Your Friend

Our rainy weather turns soil acid by washing out calcium and other minerals. Garden lime products restore calcium and reduce acidification. Some of our favorite shrubs prefer acid soil and should not have lime applied. These include Rhododendron, Azalea, Andromeda (Pieris), Leucothoe, Sweet Box (Sarcoccoca), Mountain Laurel (Kalmia), Heather (Erica, Calluna), and Blueberry (Vaccinium). Most other shrubs and trees benefit from an application of lime every 3 years. Vegetables, flowers and lawns can benefit from lime application at least every other year.

Reminder: Leaf Disease on Flowering Cherry, Dogwood, Roses, Peaches

Leaves emerging in early to mid April should be protected with a fungicide application. Most effective are the systemic fungicides such as Propiconazole, Myclobutanil, and Tebuconazole. Propiconazole is available in Fertilome Systemic Fungicide. Myclobutanil is in Spectracide Immunex Fungicide. Tebuconazole is in Bayer All-in-One Rose and Flower Care and Bayer Disease Control for Roses, Flowers and Shrubs. The Bayer products are applied to the soil and taken up into the leaves from the roots. Systemic fungicides are translocated within the plant and stop disease development in already infected leaves as well as protecting new uninfected leaves. Organic gardeners can use Messenger, lime-sulfur (calcium polysulfide) or Neem oil. Photinia also develops leaf spot infections. Photinia can also be treated if spots have become severe enough to cause significant leaf drop in previous years.

Simplify Fertilization

Garden stores and departments offer numerous brands and types of fertilizers. Gardeners have been trained to think that each type of plant needs its own fertilizer. Since our soils contain a significant amount of phosphorus and potassium, I have found that lawn fertilizers, which are high in nitrogen, work very well for most trees, shrubs and flowers. The only thing I use any other fertilizer for is for containers and fruiting vegetables, especially tomatoes. General purpose fertilizers with a 1-1-1 balance of nitrogen, phosphorus and potassium, or vegetable fertilizers with a 1-2-1 balance are better for fruiting vegetables. Typical offerings are 16-16-16 or 5-10-5. For containers I use a coated fertilizer which releases gradually every time plants are watered.

Lawn fertilizers with part of the nitrogen in a slow release form are best for spring application. They will last much longer into the summer. I also like to see micro-nutrients such as iron and zinc included in mixed fertilizers. Organic fertilizers naturally contain all the micro-nutrient elements.

When Is the Best Time to Prune?

I frequently read articles indicating pruning is limited to a certain season or seasons. Some of these articles are from other parts of the country where there may be limitations. However we are fortunate in the Pacific Northwest to be virtually unlimited in when we can prune. With many years of experience, I have found only one significant reason to limit pruning to one specific time of year. If spring flowering shrubs are pruned in the fall, winter or spring after flower buds are set, pruning will reduce or eliminate spring flowering. Rhododendron is the best example. When flowering is complete in June, we have only about 8 to 10 weeks until new flower buds begin developing in August for the next spring. However, I have pruned rhododendrons when the owners were desperate enough to reduce plant size to sacrifice one year’s flower production.

Another reason often advocated for delaying pruning has been proven wrong. Certain trees such as maples and birches will lose sap from pruning cuts when pruned just before new growth occurs. The term “bleeding” applied to this condition raises unwarranted fears. I once began pruning a row of about 20 birch trees. After pruning about half of the trees they began losing sap from the pruning cuts. The owner insisted that pruning be delayed on the remainder of the trees for 6 weeks. I watched those trees for several years and there was absolutely no difference in their health based upon when they were pruned. When I asked Alex Shigo, the world renowned tree physiologist, about this practice, he cited the harvesting of sap from sugar maples as an example of sap flow with no tree damage.

Most arborists prefer to prune fruit trees in the winter or early spring before new growth starts. However, no damage occurs if pruning is delayed until after new growth occurs. In fact, waiting a year to prune will have much worse adverse affect than pruning while growth is in progress. Fruit trees need yearly pruning to avoid the development of excessive growth, especially upright water sprout growth, which limits fruit production and quality, and causes fruit production out of easy reach for picking. The very best time to remove upright water sprouts on any trees is in the summer when the sprouts are 6 to 12 inches long and soft enough to snap off. Snapping off sprouts rather than pruning eliminates the latent buds at the base which will often produce another sprout where the first one was removed.

What is “Topping” and Why Is It Bad?

According to the International Society of Arboriculture (ISA), “topping is the indiscriminate cutting back of tree branches to stubs or lateral branches that are not large enough to assume the terminal role. Other names for topping include ‘heading,’ ‘tipping,’ ‘hat-racking,’ and ’rounding over’.” Topping violates nationally accepted standards for proper pruning and seriously injures trees.

Problems caused by topping include:

Starvation. Good pruning practices rarely remove more than 1/3 of the crown, which does not seriously interfere with tree’s ability to manufacture food. Topping removes so much of the crown that it upsets an older tree’s well-developed crown to root ratio and temporarily cuts off its food-making ability. The tree goes into shock and rapidly produces new shoots.

Weak new growth. The branches that sprout following topping are much more weakly attached than a naturally developed branch. Rot at the severed end of the limb can make a bad situation even worse.

Rapid new growth. The goal of topping is usually to control the height and spread of a tree. However, it usually has exactly the opposite effect. After topping, trees vigorously re-sprout. The resulting sprouts are far more numerous than normal new growth and they elongate so rapidly that the tree returns to its original height in a very short time.

Insects and Disease. The large stubs of a topped tree have a difficult time sealing. Thus the stubs are highly vulnerable to insect invasion and decay.