-
- Articles
Index : Plant Care
-
-
- 28. Most Common Plant Problems - Top
- Hundreds of plant samples are brought into the Pima County Extension Plant Clinic each year. Most are samples from dead or dying plants of various species. In all these samples there are some causes of plant failure that seem most prevalent.
Probably the single most common cause of plant failure is planting too deep. Trees, shrubs, flowers or vegetables all can succumb from being planted too deep. In the case of small herbaceous plants, death occurs rapidly. Stems covered with soil are attacked by soil inhabiting disease organisms. Stem and root rots develop, and the plant quickly wilts. Digging around the base of the plant will reveal a shriveled, sometimes black or brown stem.
When trees, shrubs, and other woody stemmed plants are planted too deep, death is gradual. It may take several years for trees to die from the effects of planting too deep. Smaller shrubs and perennial flowers and ground covers will usually succumb within a year of planting.
Plants should be placed in the ground so that the top set of roots, out of the container or box, are set level or slightly above the surrounding soil surface. Small flower and vegetable transplants should be set in with the top of the soil ball level with the surrounding soil surface.
If you suspect a plant was planted too deep, dig down around the main trunk until you come to the first set of roots. If you must dig down more than an inch or two to find roots, the plant is too deep. Soil should be raked back away from the trunk. This will help prevent the trunk wood from dying, but will not help the roots farther out that may be covered with soil. If you rake the soil back, construct a barrier to keep this soil from washing back in around the plant. You can use landscape edging, or berm the soil up as you would when creating a watering basin.
Poor soils are another common cause of plant failure. This is especially true of herbaceous plants such as flowers and vegetables. Their fragile roots have real problems growing out into our hard, gravelly soils. The best way to improve desert soils for garden planting is to add lots of organic matter. Compost, aged manure, and peat moss are all good choices to mix into the soil. These organic matters will loosen the soil, making it easier for tender roots to grow in.
Organic matter should be mixed evenly into the soil prior to planting beds of flowers, vegetables or herbs. Incorporate as much as possible, but at minimum put down a layer of 4 inches of organic matter to mix into the top foot of soil. Do not use wood products such as forest mulch, chunk bark or ground wood mulch as organic amendments. These materials are not decomposed and will rob nitrogen from the soil, thus depriving plants of needed nutrients.
When desert soils are just too difficult to work in, consider container or raised bed gardens. Pots and frame structures for raised beds can be filled with quality potting soil, compost, or bagged top soil.
As could be expected one of the most common reasons for plant failure here in the desert is incorrect watering. During the cool weather of late autumn and winter over-watering is the culprit. As temperatures cool, many gardeners forget to reduce their watering. Plants that are irrigated at the same frequency they were in the summer are subject to root and stem rots. If you were watering say, twice weekly during the summer, then a single watering every week or two should be adequate during the winter months.
When spring arrives and temperature climb, the frequency of watering must once again be increased. But regardless of the season or frequency of application, it is critical to apply enough water when you do. Irrigate to wet the soil to the proper depth. Trees, should be watered long enough to wet the top two to three feet of soil. For shrubs, wet the soil down 18 inches or so. And for shallow-rooted flowers and vegetables one foot deep wetting is sufficient.
To determine the depth of wetting, after irrigation, push a soil probe (metal rod) down into the soil. The probe will push down through wet soil but will stop when it hits dry soil. If water isn't getting down deep enough, increase the length of time your watering.
Finally, when selecting plants, remember to choose desert adapted plants. They can tolerate wide swings in temperature, intense heat and sun, drought, low humidity, drying winds, alkaline soils, high salts, and desert critters. Plants not adapted to the desert struggle and often fail.
--------------------------------------------------------------------------------
Written by John Begeman, College of Agriculture and Life Sciences, the University of Arizona, 520-626-5161.
Material originally appeared in Arizona Daily Star gardening column, on November 14, 1999
- Updated: November 14, 1999
-
-
[e-Mail me
the Articles] - [Search
the Articles]
-
|
