While most of us would like to have an attractive landscape, if we aren't careful with management practices, we have the potential to pollute local water supplies and harm wildlife in the area. We've all heard about the potentially harmful effects on water quality, wildlife, and the ecosystem of runoff from agricultural lands, but what most people don't realize is that runoff from home gardens and urban landscapes (urban runoff) can be just as harmful. Depending on management practices, your yard can have a positive impact on water quality by slowing down runoff and acting as a filter for potential pollutants, or it can contribute to water pollution, harming the environment and wildlife living in the area. The main contributors to urban runoff are: improper use of fertilizers, herbicides, and pesticides; poor soil drainage; over-watering; and steep slope.

When excessive amounts of nutrients, especially nitrogen and phosphorous, runoff into lakes and ponds, over-abundant growth of algae and aquatic weeds can occur, disrupting the aquatic ecosystem. In addition, oxygen depletion may become severe enough that many of the plants and animals in the ecosystem may die.

Similarly, the over-use of herbicides and pesticides in the home landscape can lead to the introduction of toxic chemicals into local bodies of water through urban runoff as well as into the ground water supply. It is imperative to exactly follow the directions on any fertilizer, herbicide, or pesticide applied to the home landscape to prevent any excess from contaminating local water supplies.

Over-watering of lawns and landscape plants results in excess water running off lawn areas and garden beds because the soil becomes too saturated to absorb any additional water. The runoff water will carry any excess fertilizer or pesticides / herbicides that have not been taken up by the plants or broken down in the soil. Excess water also may percolate below the root zone leading to potential contamination of the ground water if fertilizers or pesticides / herbicides are leached down with the water.

The following is a list of tips you can use to help avoid urban runoff and contamination of local water supplies:

1. When mowing, leave grass clipping on the lawn to provide a source of nitrogen and reduce the amount of fertilizer needed for maintaining healthy plant growth.

2. Aerate your lawn at least once a year to encourage good root growth and better water penetration into the soil.

3. Make sure gutter downspouts drain onto a lawn or landscape area rather than a paved (non-vegetated) area.

4. Planting a landscape with low water requirements (xeriscape) will greatly reduce the need for water and, in turn, reduce the potential for runoff or percolation of excess water.

5. Water lawns and landscape plants only as needed. Check the soil for adequate moisture before watering, rather than watering on a set schedule.

6. Automatic sprinkler systems should be adjusted throughout the year to account for seasonal differences in plant growth and water requirements. It is also a good idea to manually override the timing mechanism on automatic sprinkler systems when sufficient rainfall has occurred and during cool spells when the plants require less water.

7. When using a sprinkler system, it is also important to make sure that all sprinkler heads are adjusted properly such that non-vegetated (paved) areas are not being "watered". By watering paved areas, not only will you be wasting water, but the water hitting the paved areas is most likely going to runoff into the storm drains, carrying with it any oil, gas, antifreeze, deicing products, and any other potentially toxic substances that were spilled on the paved areas. Because the neighborhood storm drains typically drain into local lakes and streams, the wildlife in the area may be exposed to harmful levels of toxins.

8. If your landscape area is sloped, terraced gardens or berms can be constructed to prevent, or at least greatly reduce, both water runoff and soil erosion. Utilizing low-growing, densely planted ground covers on sloping areas will help to trap the water and any dissolved chemicals carried in it and prevent loose soil from washing away.

9. Never pour leftover fertilizer, pesticides / herbicides, oil, cleaners, or other chemicals down the storm drains, and don't rinse out used chemical containers or sprayers into storm drains or over paved areas where the water can runoff into storm drains.

10. Apply fertilizer only as needed and only at the rates suggested by the manufacturer. In the case of fertilizer, "more" is not "better"! Not only can excess fertilizer wash into the water supply, but it can also harm your plants. If possible, have a soil test done before applying fertilizer to determine whether you need to supply supplemental nutrients.

11. To reduce the need for fertilizer applications on garden beds and landscape plants, try adding compost, which breaks down slowly, releasing nutrients over time. Compost can be incorporated when the beds are being prepared for planting, added to the soil around individual plants, or made into a "tea" and used to water plants. Because the nutrients are released slowly from compost, there is much less chance of excess nutrients reaching water supplies.

12. Apply pesticides only as needed and not as a preventative measure. Also, keep in mind that many pesticides are harmful to beneficial insects as well as to the insects you are trying to control. Try living with a certain level of insect pests. Some pests are only around for a short period of time and do very little damage to the plants before moving on or completing their life cycle. You can also try various non-chemical controls (hand-picking, encouraging predators of pest insects, garlic or hot pepper spray, etc.) before resorting to chemical control measures.

Q: Is now a good time to fertilize my bluegrass lawn?

A: Bluegrass lawns in Colorado only require fertilizing in the spring and fall for best results. Apply about one pound of nitrogen per 1000 square feet of lawn area. Mowing regularly at 2½ to 3 inches in height and leaving the clippings on the lawn can reduce the nitrogen requirements by one third and does not affect the build up of thatch. However, annual core aerating is recommended.

Q: I would like to plant some raspberries in my garden. What varieties do you recommend?

A: Summer-bearing (Latham, Boyne, Newburgh, Canby and Titan) and fall-bearing varieties (Redwing, August Red, Heritage, Fall Red, Fall Gold September, Pathfinder and Trailblazer) are available. Fall- bearing varieties are easier to manage with Heritage and Redwing recommended for the Front Range. Raspberries require adequate drainage and ample organic matter in the soil. Apply 4 pounds of ammonium sulfate and 2 pounds of treble super phosphate per 1,000 square feet before planting and each spring as fertilizer. Summer-bearing raspberries require the canes to be protected in winter by placing them in a shallow furrow and covering them with dirt whereas fall-bearing plants can be mowed off after harvest and require no winter covering. Water so that adequate moisture is maintained in the root zone. During dry winters, water occasionally to prevent winter drying.

Q: With the West Nile Virus scare in Colorado, how can I still enjoy my birdbath and backyard pond without breeding mosquitoes?

A: Dump the water and clean bird baths every few days and refill with clean water to eliminate mosquito larvae. Ponds are a little more difficult. Gambusia is a mosquito eating fish which can be put in ponds but will have to be released annually. You can also use the microbial insecticide Bti (Bacillus thuringiensis israeliensis ) which is toxic only to mosquito and midge larvae or the chemical insecticide methoprene (Altosid) which is toxic only to insects and other arthropods. Both of these can affect the amount of food available for fish or other wildlife but will not harm them directly.

Start harvesting potatoes as the tops die down. Let the potatoes cure for 2 to 3 weeks in a warm spot out of direct sunlight. For long term storage, keep the tubers at 38 - 45 degrees and 90% humidity. Do not store potatoes with fruit as that will hasten sprouting.

Parasitic wasps in the genera Encarsia and Eretomocerus can effectively control whiteflies out of doors and in greenhouses. These "good" bugs are available from commercial sources. Pyrethroid insecticides are effective against adult whiteflies and horticultural oil, Neem oil and insecticidal soaps are effective against the nymphs on the leaves. Make sure to spray the underside of the leaves where the insects "hang out".

Stop fertilizing your roses and gradually cut back on watering. This will harden them off and prepare them for winter dormancy. Treat black spot, mildew or rust with fungicidal soap spray or sulphur.

This is the best time of year to plant new peonies or divide established plants. The "eyes" on the tubers should be no more than 2" deep. Peonies like soil with lots of organic matter so amend your clay soil before planting.

Start checking catalogs and nurseries for fall bulbs. Order early for the best selection of the varieties you want in your garden. Look for bulbs that are large, firm and free of mold or disease.

The authors have received training through Colorado State University Cooperative Extension's Master Gardener program and is a Master Gardener volunteer for Larimer County.

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This page updated:  August 23, 2004