It’s time for summer rose care preparations

Gardeners must become water-wise and learn as much as possible ways to use water efficiently. Some districts may have restriction on how and when water can be used for outside use. We must vigilantly manage our water use.

There are a few things we can do now to provide some relief for the rose in the coming warmer months if we hope to maintain our cherished roses.

Cut back on fertilizing established roses to encourage plants to slow down for the hot summer.

Water roses deeply as temperatures rise.

Hose off roses in the early morning to increase humidity and control spider mites, which are found mostly on the underside of the leaf. A strong forceful spray from below will be needed to dislodge these mites. I’ve already noticed spider mites even though the temperature hasn’t been hot which usually is conducive for mites.

Keeping vegetation approximately 8 inches from the soil level will help as well. Typical mature, full-size hybrid teas in Southern California soil require about 6-9 gallons of water a week when temperatures are high. As temperatures rise into the 80s, the rose will require about 9 gallons of water per week. In the 90s, the rose will require about 12 gallons per week and even more. These figures are rough and based on the amount of water needed to maintain the highest level of show quality; the rose will stay alive on considerably less. In 2015, water agencies advised customers to “Water... roses no more than once each week... with three to four gallons of water, allowing it to soak in slowly.” I think you’ll agree that “three to four gallons” is considerably less than the recommendations for maintaining the highest level of show quality.

The past few years of drought experience has made gardeners aware that we must be watchful and learn how to efficiently manage the amount of water we apply in our yards. The strategies I will discuss are delivering water efficiently, keeping water in the soil using mulch and allowing your roses a summer dormancy period.

Drip systems provide the most efficient way to deliver water to your roses because they don’t produce a water spray that can be carried away by winds and because they deliver water slowly, allowing it to soak deep into the root zone rather than running off.

If you have a drip system, be sure it’s in good shape before you cover it with mulch. Open each irrigation valve one at a time and inspect how it is performing. Repair any leaks, including emitters that are spraying from their attachment point on the tubing – you may have to remove the emitter, insert a “goof plug” and install a new emitter an inch or two away from the original one. My gardening friends are recommending the more efficient drip system called Netafim. Find more information at www.netafimusa.com.

One more thing, you’ll want to estimate the volume of water the system is delivering so you can better manage your use. For example, if every rose has two emitters that deliver 8 liters or about 2 gallons per hour, then to deliver 4 gallons to the plant you’ll need to run the system for an hour. This method 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 of irrigation may waste some of that water, and you might be better off running the system twice a week for half as long. I recommend experimenting. After all, gardening is a scientific pursuit.

If you have read my past columns you know that I have been advocating the application of a deep layer of mulch for years. Mulch provides many benefits. It moderates the soil temperatures, retains moisture, allows water to spread more uniformly throughout the root zone, discourages weeds and maintains a soft soil surface. A four-inch layer of mulch is recommended. I highly suggest composted mulch. There are many materials you can use. You might want to experiment with a variety of them, but you will probably get the best results if you don’t mix them in any one garden bed.

One material that some gardeners have in abundance is pine needles. They provide an airy cooling 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. Some possible drawbacks include the potential for matting due to fungal growth if the wood chips are not specifically manufactured for garden use because the wood chip layer becomes impermeable to water and the need to apply added nitrogen to break down the wood fibers.

I prefer composted mulch that is light and fluffy, so it doesn’t pack down, and contains a higher proportion of humus that slowly integrates with and enriches the soil. One drawback of composted mulch is that after several years you may find that your garden soil level has risen. If this ends up burying the bud unions, it can be helpful to “lift” the rose—essentially, digging to release a large root ball, levering it up, filling in several inches of good garden soil beneath it and resetting the root ball in the hole to maintain a clear well around the base of the bush.

Whatever mulching 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 in diameter. If you can maintain that distance, then as your composted mulch disintegrates it will not raise the soil level around the bud unions.

Allowing your roses to go dormant during the hot summer months will reduce water use as well as the stress on your plants. You won’t be missing out much because if you allowed your roses to power through the summer, most blooms would be of poor quality and have burned petals and leaves. So as your roses complete the current bloom cycle, remove only the petals as the flowers fade – do not deadhead them – that is, allow hips to form. This will discourage new growth and flower formation, thus reducing demand for water. Remove any 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 burned leaves because they provide shade for the cane which can be damaged or killed by sunburn. Discontinue your feeding program – we do not want to encourage growth at this time because it will only stress the bush more.

In summary, until at least September make sure your water delivery system is operating efficiently, apply 4 inches of mulch over the entire bed, remove petals as flowers mature, allow hips to form, do not prune or cut back, leave brown leaves on the plant and do not feed your roses.

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