Eliminating Allergenic Mold Spores in Your Gardens
Tiny mold spores cause plenty of allergies. Often our gardens are full of molds but luckily there are many things we can do to eliminate allergy-causing mold spores. All molds produce tiny reproductive spores and the trick is to find ways to get rid of the molds themselves.
What we plant, and where, has a large influence. I continually see the flat out dumb practice of planting tall evergreen trees and shrubs on the South sides of a house. In the winter the sun is low on the horizon and we get most of our light, and warmth, from the sunlight that shines from the South. Our warm morning light comes from the East and it is never a good idea to block that with tall evergreens either.
The best place for tall evergreens is on the North side of our houses. There they can act as a windbreak and not rob us of any needed winter sunlight. A house with tall evergreen trees on the Southeast side, is one that will always be cold, and damp, in the winter months. And cold and damp is exactly what mold thrives on.
Recently I was at a store, standing outside waiting for a friend of mine to finish up inside. It was a cool wintry day and I was in the full, deep cold shade of a very large Canary Island Pine tree. I walked over about thirty feet and stood in a spot, in between the trees where the sun was shining through. There it was nice and warm. To my left was the big pine shading that store, and just to my right was another huge evergreen tree, a Ficus retusa, the Indian Laurel Fig.
The big fig cast a shade even deeper, and colder, than did the pine. I looked down at the sidewalk to my left and right, and sure enough, you could see mold growing in the cracks and along the edges. The north side of the trees, where I was, also had a good deal of mold growing on the tree leaves themselves.
Deciduous trees are perfect for these locations. In the hot summer they will be all leafed out and will cool down the buildings behind them. In the cold winter months they will be bare of leaves, and the low sunlight will come through and warm things up. In this day and age of exploding energy costs, it is just plain ignorant to plant evergreens where they don't belong. For stopping mold spores, deciduous trees on the South-Eastern exposures is the only way to go. Mulches
Many people seem unclear on just exactly what is a mulch. Very simply, a mulch is anything that covers the soil. They can be made of old leaves, straw, rocks, bark, gravel, boards, bricks, even plastic.
Mulches are almost always a very good idea but when it comes to mulches and molds, they aren't all created equally. Bark is a very good material on which to grow mold. Gravel mulches are good because they don't encourage mold growth. I like smooth gravels, river gravel, and please! No white gravel.
Flat stones and pavers work well for this too and in the right spot, they look good as well. Mulch holds down weeds and cuts down on summer water loss. Earthworms often thrive under mulch and in general mulches usually help plants grow better. The one spot where mulches are less effective is in those cold, always shaded areas. Here mulch will keep the soil from ever warming up. Every where else though, mulch is useful. Newspaper mulches by the way, not only look trashy, they also grow lots of mold.Buggy Plants and Mold
Plants that are not being grown right will usually get infested with insects. The insects secrete "honeydew" and on this very nutrient rich gooey substance molds grow quickly. The molds then start producing spores and pretty soon there is a serious allergy situation in the landscape. The insect dander itself is highly allergenic and just adds to the problem.
Buggy plants often look dirty and this is because they are covered with honeydew, mold, and yuck! They are dirty. Clean, healthy plants are what we want in our yards.Why Are the Plants Covered With Insects?
If a tree is native to the cold, damp forests of Japan or Minnesota, it just won't thrive in a place like Los Angeles. It certainly might grow in Los Angles though, and that's the problem. It will grow there but it won't thrive. Because it doesn't have the conditions it needs it will always be somewhat weakened, and pests always prey on the weak. Remember, insect pests equal mold spores.
If an area is very deficient in fertilizer the plants there won't thrive. As they grow weaker, the insects start to prey on them. If plants are getting far too much fertilizer they will also become weak.
If a tree is a type that needs regular water in the summer but never gets it, again it will become weak and soon be a target for the white flies, aphids, scale, spider mites, and mealybugs.
If shrubs or trees are native to an area with acid soil and you're growing them in alkaline dirt, sure enough they'll probably become bug infested.
If a tree is simply not tolerant of urban smog and it is planted right smack in the middle of a great metropolis, it will draw the pests.
If a row of shrubs are all the kind that loves bright sunshine, but someone has planted a fast-growing tree over them, perhaps a pine, when the whole row of shrubs is now growing in deep shade, if they live, they will certainly become an insect magnet. I know of a hedge just like this near where I live. A large old hedge of lantana, now shaded by a big pine, it is literally covered top to bottom in white flies and mold. It is growing right outside the back entrance to a health clinic!
There are many other cultural reasons for plants not to thrive and any one of them can result in weak plants and mold.A Word to the Wise on Natives
Judicious use of natives is often one of the very best ways to avoid many of these weak plants-mold problems. However, make sure the "natives" you buy are endemic to your own particular area. Also, make sure you're not getting a bunch of male ( pollen- producing ) clones. Many of the native trees, shrubs, and ground covers sold now are male clones.Air Flow
In every place there are prevailing winds. The breeze generally blows mostly from one direction. Many landscapes are so plugged up, so crowded, that the breeze simply can't penetrate the mess. A landscape with no air flow is one where molds will thrive. Molds grow best in conditions with poor air circulation.
If your own yards are over-grown and choked for lack of fresh air, then get out the pruning saw and start thinning them out. Clean, fresh air, free to move about, equals less mold and fewer mold spores.
By Thomas Leo Ogren MSc Agr.
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