The Science of Watering
Ask yourself the following questions to develop a feel for watering frequency:
1. How long since transplanting? Newly planted plants require more frequent watering than established plants. Begin to cut back the frequency after 2 to 3 weeks as the plant roots start growing out into the surrounding soil and the above ground portion of the plant shows strong signs of new growth.
2. How hot and windy is it? Heat and wind cause increased water loss by plants. When daytime temperatures move into the 80s, water newly transplanted plants every other day. Once the air temperature hits the 90 degree mark, check the plants morning and evening, looking for wilted leaves as an indicator of dryness. Initially, a daily watering will be needed for small plants.
3. How deep did that last rain soak the soil? Rain amounts can be deceiving. Always stick a shovel into the ground after a rain and do a visual check as to how deeply the water soaked into the soil. The soil needs to be damp at least 4 inches deep to do new transplants any good.
4. What pot size was the plant grown in? Small perennials and bedding plants transplanted from 4 or 6 packs and 4″ pots will need more frequent irrigation than 1 or 5 gallon sized trees. Do not water 4″ and 5 gallon plants on the same schedule as they have entirely different requirements.
5. Have the plants been mulched? Mulching plants can cut watering frequency in half! For example, if you were to mulch, daily watering would be reduced to every other day, twice weekly instead of every other day, etc.
6. What type of soil do you have? Compost enriched soils hold more water in the root zone than unprepared soils. Clay and loam type soils hold more water than sandy soils. Sandy soils dry out very quickly and plants will need very frequent irrigation when first planted. Also keep in mind that when climate conditions are very dry, extra water is needed to replace moisture lost to the dry soil surrounding the planting hole.
How Much Water?
Knowing how to properly water your plants is key to good plant health. Always construct an ample water ring — a well — around each plant and be sure to mulch. When it is time to water, fill the water well twice allowing the water to be absorbed completely before filling it a second time. During the dry, hot months of the summer, conventional turf lawns and groundcover beds will need one inch of water every week. Native grass lawns and xeric groundcovers will need once inch every other week. Set out a rain gauge or coffee can to measure the amount applied.
When you water, soak the soil thoroughly. It is preferable and more efficient to water heavily and less frequently than to water lightly with much greater frequency. Deep watering promotes deep root growth.
Signs of Over-Watering
When the soil stays wet and the leaves of recent transplants become yellow and chlorinated looking, cut back your watering by half — not half the amount, but half the frequency. If you are watering every other day, cut back to once every fourth day.
If you are watering regularly but the leaves look wilted all the time, the plant roots are dying of suffocation. Too much water keeps the soil waterlogged and oxygen deficient. If this occurs, pull back the mulch from the plant and let the top inch of the soil dry between watering.
Remember, the difference between too much and too little water can be confusing. But, a general rule is that under-watered plants wilt while over-watered plants yellow.
Establishing Xeric Plants
“I planted xeric Penstemon and watered it that day. I came back two weeks later and it was dead! I thought this plant did not need any extra water.” To this we say, “yes and no.” No, xeric plants do not need much water once established, but yes, even xeric plants need careful attention to their watering needs during the first growing season. Xeric plants have extensive root systems that pull water from the surrounding soil, but until a new transplant can re-establish its root system, it needs regular irrigation during rainless periods to grow and prosper.
Avoiding Wasteful Run-Off
When hand watering on a slope, water until the water is not being absorbed by the soil and begins to run-off. Stop, let it soak in a few minutes and start again. Repeat this process 4 or 5 times until the soil is wet to a depth of 4 or more inches. This technique will reduce the amount of run-off and slope erosion, and will promote deep root growth in your plants which is key to drought-tolerance.
Plants Depend Upon Us
Please remember, plants are living, breathing organisms and they depend upon us for their health, their protection and their survival. Their livelihood is a responsibility not to be taken lightly! With good care, many plants can be life-long companions that bring years of comfort and joy to our lives.
For more information contact Dry Creek Garden Co., 7250 S. Virginia St., Reno; 775-851-0353 or visit their website at http://www.drycreekgarden.com/about/map.cfm.