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Cold shower can help fight spider mites




Brandy hybrid tea roses seem to enjoy the heat. (Photo: Debbie Arrington)


August rose care tips for Sacramento-area gardeners



Consider giving your rose bushes a shower.

More specifically, a cooling spray of water to wash away all that ash and dust on their leaves, preferably early in the morning so leaves will dry quickly. It not only refreshes the foliage, it can help fight spider mites.

Tiny as the period at the end of this sentence, spider mites are one of the few summer rose pests that can take August heat. They stipple (and eventually kill) leaves, sucking the life right out of them. Some species (but not all) leave telltale fine webbing on the underside of foliage. You need a magnifying lupe to actually see the mites.

According to University of California’s Integrated Pest Management research, spider mites love dry and dusty conditions. That’s why we often see outbreaks in the dead of summer. But these little pests can’t stand a good blast of cold water. A watering wand is ideal for this. It allows you to spray up and under the leaves, washing away mites and their webbing.

When mite populations explode, they also inhabit the top of leaves, so wash both sides. In addition, that summer cleaning can help the foliage better do its job, converting sunlight into food for the bush.

Spider mites really flare up when temperatures stay consistently above 80 degrees. Most insecticides and other chemical cures have little if any effect in controlling spider mites. Neem oil or insecticidal soap can put a dent in their numbers earlier in summer. But spraying anything besides water on bushes during this hot weather can cause more harm than good, burning foliage.

Spider mites have several natural enemies than can help keep them under control. Often, a mite infestation follows insecticide application that reduced the number of predators. So, stick to water.

Here are more tips on rose care in August:

Watch out for thrips. The other major Sacramento rose pest of summer, Western flower thrips are minute insects that love to eat rose buds. They tunnel into petals, creating brown trails of destruction. You’ll see the damage before you see the bugs. Control by chemical means is almost impossible because the thrips do their dirty work inside the rose bud.

Thrips tend to attack light-colored, white or fragrant roses. They do the most damage in gardens where roses are tightly packed together. To keep thrips’ numbers in check, dead head spent flowers and dispose of them. The good news? Western flower thrips are a natural predator of spider mites.

Dead head for more blooms. Remove spent flowers in August or bushes will start producing rose hips (their fruit) instead of fall bouquets. With sharp scissors or pruners, snip down to the first outward pointing five-leaf leaflet. The bush will produce another flush of flowers in six to eight weeks.

Water deeply. Mature rose bushes need about five gallons a week in August, more if planted in containers. Bushes in the ground can be deep-watered once a week. In pots, they may need daily watering during triple-digit temperatures.

Mulch is your rose’s friend. Organic mulch (shredded leaves, bark, etc.) maintains moisture, discourages weeds and keeps rose roots comfortable. Maintain mulch at about 3 inches deep, but don’t let it mound around the bush’s crown.

Thin competition. If you grow companion plants around your roses, make sure they’re not strangling the bushes. Those companions are also competing for water.

Feed for fall flowers. To encourage October blooms, fertilize in August. Pull back the mulch and sprinkle bone meal and worm castings around bushes, gently work those amendments into the soil, rake mulch back into place and deep water. Or feed with a half-strength liquid fertilizer after you’ve already deep watered the plants. (Roots need water in the soil to access those nutrients.)

Enjoy your roses. They’ll bloom in this heat when other shrubs shrug and give up. Pick a bouquet to bring inside.

For more on rose pests:
http://ipm.ucanr.edu/PMG/PESTNOTES/pn7466.html and http://www.sactorose.org/rosebug/index.htm

Debbie Arrington is a consulting rosarian and longtime rose grower.

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Food in My Back Yard (FIMBY) Series

WINTER:

Jan. 13: Tips for planting bare-root trees, shrubs and vegetables

Jan. 6: Hints for choosing tomato seeds

Dec. 30: Why winter is the perfect time to plant fruit trees

Dec. 23: Is edible gardening possible indoors?

FALL

Dec. 16: Add asparagus to your edible garden

Dec. 9: Soggy soil and what to do about it

Dec. 2: Plant artichokes now; enjoy for years to come

Nov. 25: It's late November, and your peach tree needs spraying

Nov. 18: What to do with all those fallen leaves?

Nov. 11: Prepare now for colder weather in the edible garden

Nov. 4: Plant a pea patch for you and your garden

Oct. 27: As citrus season begins, advice for backyard growers

Oct. 20: Change is in the autumn air 

Oct. 13: We don't talk (enough) about beets

Oct. 6: Fava beans do double duty

Sept. 30: Seeds or transplants for cool-season veggies?

Sept. 23: How to prolong the fall tomato harvest 

SUMMER

Sept. 16: Time to shut it down? 

Sept. 9: How to get the most out of your pumpkin patch

Sept. 2: Summer-to-fall transition time for evaluation, planning

Aug. 26: To pick or not to pick those tomatoes?

Aug. 19: Put worms to work for you

Aug. 12: Grow food while saving water

Aug. 5: Enhance your food with edible flowers

July 29: Why won't my tomatoes turn red?

July 22: A squash plant has mosaic virus, and it's not pretty

July 15: Does this plant need water?

July 8: Tear out that sad plant or baby it? Midsummer decisions

July 1: How to grow summer salad greens

June 24:  Weird stuff that's perfectly normal

SPRING

June 17: Help pollinators help your garden

June 10: Battling early-season tomato pests

June 3: Make your own compost

May 27: Where are the bees when you need them?

May 20: How to help tomatoes thrive on hot days

May 13: Your plants can tell you more than any calendar can

May 6: Maintain soil moisture with mulch for garden success

April 29: What's (already) wrong with my tomato plants?

April 22: Should you stock up on fertilizer? (Yes!)

April 15: Grow culinary herbs in containers

April 8: When to plant summer vegetables

April 1: Don't be fooled by these garden myths

March 25: Fertilizer tips: How to 'feed' your vegetables for healthy growth

WINTER

March 18: Time to give vegetable seedlings some more space

March 11: Ways to win the fight against weeds

March 4: Potatoes from the garden

Feb. 25: Plant a fruit tree now -- for later

Feb. 18: How to squeeze more food into less space

Feb. 11: When to plant? Consider staggering your transplants

Feb. 4: Starting in seed starting

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Garden checklist for week of Jan. 18

Make the most of these rain-free breaks. Your garden needs you!

* Transplant pansies, violas, calendulas, English daisies, snapdragons and fairy primroses.

* In the vegetable garden, plant fava beans, head lettuce, mustard, onion sets, radicchio and radishes.

* Plant bare-root asparagus and root divisions of rhubarb.

* Plant bare-root roses and fruit trees.

* In the bulb department, plant callas, anemones, ranunculus and gladiolus for bloom from late spring into summer.

* Browse through seed catalogs and start making plans for spring and summer.

* Prune, prune, prune. Now is the time to cut back most deciduous trees and shrubs. The exceptions are spring-flowering shrubs such as lilacs.

* Now is the time to prune fruit trees, except cherry and apricot trees. Clean up leaves and debris around the trees to prevent the spread of disease.

* Prune roses, even if they’re still trying to bloom. Strip off any remaining leaves, so the bush will be able to put out new growth in early spring.

* Prune Christmas camellias (Camellia sasanqua), the early-flowering varieties, after their bloom. They don’t need much, but selective pruning can promote bushiness, upright growth and more bloom next winter. Give them an acid-type fertilizer. But don’t fertilize your Japonica camellias until after they finish blooming next month. Doing that while camellias are in bloom may cause them to drop unopened buds.

* Clean up leaves and debris around your newly pruned roses and shrubs. Put down fresh mulch or bark to keep roots cozy.

* Divide daylilies, Shasta daisies and other perennials.

* Cut back and divide chrysanthemums.

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