Valley News -

By Frank Brines
Special to the Valley News 

Caring for roses in November

 

Last updated 11/16/2018 at 3:12am

Courtesy

Black spot is the most common disease of roses and is found everywhere roses are grown.

After a summer of high temperatures, fires, smoke, ash and Santa Ana winds, it feels good to have some relief. The weather has moderated slightly, and along with the change comes cooler nights with more moisture collecting on leaves. This moisture with the daily accumulation of ash and small dust particles provides a great environment for mildew, rust and black spot on roses.

Black spot is the most common and important disease of roses found everywhere roses are grown. The disease does not kill the plant outright but, over time, the loss of leaves can weaken the plant, making it more susceptible to other stresses and to winter damage. It first develops on upper leaf surfaces, later adjacent areas turn yellow and leaves drop prematurely, usually beginning at the bottom of the plant progressing upward.

A potential "look-alike" disease is spot anthracnose or shot-hole disease; it is not a major problem unless temperatures are very hot, usually too hot for black spot. Spots caused by black spot are fuzzy around the edges, then turn yellow and brown. Spots caused by anthracnose are smooth edged, and the centers turn grey and drop out. Treatment is the same, but if a fungicide is used, it must be labeled for black spot or anthracnose, whichever disease you are treating.

Roses benefit from a good rinsing to remove accumulated dust: be sure to keep moisture off the blossoms to prevent yet another fungal disease, botrytis, which will appear as rot of blossoms and will usually prevent them from opening.

Last month I included an article about chilli thrips and pictures for identifying the problem they cause. Continue treatments for these micro pests. They attack new growth, buds and blooms. Left untreated, plants are stressed greatly, often shriveling the end buds or preventing bud formation. The life cycle of chilli thrips includes falling to ground and becoming a grub and reappearing when temperatures warm up next year.

Those who completed the light mid-season pruning in September or October as suggested in an earlier article pruned out dead, crossing canes and thinned the middle of the plant. The pruning will improve air circulation through the bush and reduce possible fungal diseases. The mid-season pruning and fertilizing encourages a new blooming cycle. Feel free to cut some of early blooms now and take them inside for bouquets.

Gardeners may make a final application of fertilizer for the year before mid-November. Unless the plan is to exhibit, I do not recommend fertilizing after mid-October. If it is done, use a fertilizer lower in nitrogen and higher in phosphate and potassium; that is, if the fertilizer has an N-P-K number on it, the first digit will be lower than the other two. If it lacks an N-P-K, read the ingredients or ask your professional nursery person for guidance.

To explain, nitrogen encourages foliage growth, which is something gardeners want to discourage as the plants go into their winter dormancy; phosphate helps build root structure and resistance to stressful conditions, such as the cold at this time of year; potassium is a helper of phosphate and aids in bloom quality. If gardeners use an organic fertilizer, it will be readily available when the soil warms, adding to the nutrients needed for that spring growth spurt.

Remember to check the garden daily for any changes. Be sure to keep roses hydrated for best results. The cooler temperatures can be misleading. Roses still need to be watered, perhaps not as often.

Some people think Southern California lacks distinct seasons, but it does have seasons. They are discerned by those with a more sophisticated palette, however. So get out of the house and enjoy the subtle delights of the air, sun and the rich aroma of the magically misty fall.

When there is a moment to spare, time to get away or when the day cools down, take a favorite healthy beverage and a picnic basket and visit Rose Haven Heritage Garden, 30592 Jedediah Smith Road, in Temecula. The cross street is Cabrillo Avenue.

The early morning and late afternoon sunlight across the pass is magical this time of year – it even makes the freeway seem a little bit romantic. Find other venues of interest this time of year at http://pswdroses.org/calendat.html.

Oh, one last thing – something to do when it gets just a bit too nippy out there: Start perusing printed and online rose catalogs for that next "gotta-have" rose variety. Gardeners work hard to have lovely roses and enter that perfect bloom in the next rose show in April 2019.

Also, this time of year many nurseries and garden stores are liquidating their remaining inventory of potted roses – and November is an ideal time to purchase and plant.

Until next month, happy roses to you.

 

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