Roses need water and mulch for summer temperatures

The past few years of drought experience has made gardeners aware that they must be watchful and learn how to efficiently manage the amount of water they apply in their gardens. Here are a few strategies for delivering water efficiently, keeping water in the soil using mulch and allowing your roses a summer dormancy period.

Delivering water efficiently

Gardeners must learn to use water efficiently. Installing the most efficient delivery system is one method to save and conserve water. Learning your garden's soil type will help you make a decision on which systems work best and how much water to deliver at any one time. Growing in pots is another story.

Typical mature, full-size hybrid teas in Southern California require about 6-9 gallons of water a week in moderate temperatures, such as 70s. As temperatures rise into the 80s, they require about 9 gallons per week. In the 90s, about 12 gallons or more. A rose can stay alive on considerably less, but they may come through the experience debilitated.

Drip systems are the most efficient way to deliver water because they don't produce a spray that can be carried away by the slightest breeze and deliver water slowly so it soaks deep rather than running off. If you have a drip system, be sure it's in good shape before you go on to the next step and cover it with mulch. Open each irrigation valve one at a time and repair leaks.

I like Netafim products for their integrated pressure-regulating emitters. Find the information at http://netafimusa.com.

Lastly, estimate how long to run each system: Multiply the number of emitters by their delivery rate, such as 1 gallon per hour, then divide by the number of roses. For example: if you have 40 emitters, each delivering 1 gallon an hour, you deliver 40 gallons per hour. If you have 10 roses, that's 4 gallons per rose. To deliver 12 gallons per week, run for one hour three times a week.

This watering schedule should work well in a typical loam soil. You want the water to soak down at least 12 inches for optimal rose health. A loam soil doesn't allow water to just run through it, so irrigating for an hour at a time can be fairly efficient. On the other hand, if your soil is particularly sandy, which allows water to permeate more quickly, an hour may waste water, so run the system twice as often for half as long.

Mulch

If you have read my past columns, you know that I advocate a 4-inch layer of mulch. Mulch moderates the soil temperatures, retains moisture and allows it to spread throughout the root zone, discourages weeds and enriches with nutrients and bio mass. There are many materials you can use, but I recommend composted mulch.

You might experiment with a variety of material, but you'll probably get the best results if you don't mix them in any one garden bed. For example, some gardeners have access to pine needles. They provide a cool airy barrier and break down very slowly to impart a more acidic soil environment which makes mineral nutrients more available to plants.

Another material is any size of wood chip specifically intended as mulch; I recommend the finer cut forms. Possible drawbacks: if not specifically manufactured for garden use, there is the potential for matting due to fungal growth, which can make the mulch impermeable to water – and the need to apply added nitrogen to break down the wood fibers. I'm not an advocate for dyed wood products.

Whatever material you choose, be careful to not apply it up to or over the bud union. Leave an area around the base of the plant of about 12 inches diameter. If you can maintain that distance, then as your composted mulch disintegrates it will not raise the soil level around the bud unions. Also, keep foliage pruned to at least 8 inches above the mulch layer to reduce infestations from pests like spider mites.

Summer dormancy

Allowing your roses to go dormant during the hot summer months will reduce the stress on your plants. You won't be missing out much because when you allow roses to power through the summer, most blooms are poor quality with burned petals and leaves. To encourage this dormancy, stop feeding established roses near the end of June and be sure to water them deeply.

As blossoms fade, remove only the petals – do not deadhead them – that is, allow hips to form. This discourages new growth and flower formation, thus reducing demand for water. Remove fallen leaves and discard them along with the petals into your green yard waste bin – do not compost them.

It is always a good practice to keep the garden clean in order to reduce fungal diseases and insect pests, particularly in hot dry weather.

Do not remove sunburned leaves because they provide shade for the cane which can be damaged or killed by sunburn. See the images of sun and heat damaged blooms and leaves.

In summary, until at least September: do not feed your roses.

Make sure your water delivery system is operating efficiently. Apply 4 inches of mulch over the entire bed.

Remove petals as flowers mature. Do not prune or cut back: Allow hips to form.

Leave burned leaves on the plant.

Potted plants will require more diligent watching, resources and attention to what they are experiencing during this period. Learn to listen to your plants and observe their reaction to the elements.

Doesn't look like much work, right? Well, since you'll be taking it easy or the summer, go visit Rose Haven, located at 30592 Jedediah Smith Road in Temecula. The cross street is Cabrillo Avenue. Also, visit http://www.TemeculaValleyRoseSociety.org.