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What's wrong with my roses? (Hint: Weird weather)


Unusual spring conditions prompt problems for Sacramento-area roses
Rose
Botrytis freckles and browns the edges of a Pink Promise rose. (Photos: Debbie Arrington)

May usually is the rosiest month in Sacramento. Warm, dry days coupled with raging growth hormones make for bountiful blooms and healthy plants.

But not this month. Sacramento area rose lovers report problems usually not seen in mid-spring: Botrytis, powdery mildew and blind shoots. All these issues can ruin rose blooms (or eliminate them all together).

Powdery mildew
Powdery mildew coats foliage on a Dorothy Perkins rambling rose.
The reason? Our yo-yo weather. Instead of consistently warmer weather, Sacramento temperatures have bounced up and down this spring. In early May, cool weather with just enough moisture to dampen foliage and blooms prompted outbreaks of two fungal diseases, botrytis (also known as gray mold) and powdery mildew.

Common in late fall, botrytis attacks buds as they open, turning them to mush. It starts out looking like freckles, then quickly turns petals brown and soft. Roses quite often refuse to fully open.

Powdery mildew is primarily a foliage fungus, covering leaves and stems with what looks like an explosion of powdered sugar. (It can coat buds, too.) Its activated by temperature; days in the 60s or 70s are its sweet spot.

The good news? When days turn 90s degrees, these fungi disappear. They can’t stand high heat. The forecast for this weekend: 92 degrees.

Infected foliage and blooms will fall off and be replaced by healthy growth. Pick up these discards and dispose of them in trash (not compost). That will help cut down on reinfection.

Blind shoot on rose
Instead of a bud, there's only a stub on this Marilyn Monroe rose.
Meanwhile, blind shoots are a reflection of weather conditions. When days go from cold to hot to cold again, roses get confused and push out stems with no terminal bud – a flower at the end. Instead, a blind shoot has an odd little stub at its bloom end and nothing but leaves. No matter how long the stem grows, it will never bloom.

The solution is easy: Cut the blind shoot off. Prune the stem back to just above the first five-leaf leaflet. The bush will soon sprout a new stem, most likely with a bud at the end.

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Garden checklist for week of Aug. 2

Get out early in the morning and monitor your garden’s moisture needs. Deep water and add temporary shade structures for plants that are feeling a little burned. In particular, protect developing peppers and eggplant.

* Put off fertilization until this heat passes; plants need to concentrate on hydration instead of growth.

* Harvest tomatoes, beans, squash, pepper and eggplants to prompt plants to keep producing. Give your plants a deep watering twice a week, more if planted in containers.

* Watch out for caterpillars and hornworms in the vegetable garden. They can strip a plant bare in one day. Pick them off plants by hand in early morning or late afternoon.

* Mulch can be your garden’s best friend – it conserves moisture while blocking out weeds. But don’t let mulch mound around stalks, stems or trunks. That can promote rot.

* Pinch off dead flowers from perennials and annuals to lengthen their summer bloom.

* Pick up after your fruit trees. Clean up debris and dropped fruit; this cuts down on insects and prevents the spread of brown rot.

* Prepare for a fall full of flowers by paying a little extra attention to your garden. Cut off spent blooms from roses, annuals and perennials. Roses will rebloom about six to eight weeks after deadheading.

* Indoors, start seedlings for fall vegetable planting, including bunching onion, cabbage, broccoli, cauliflower, kale, radicchio and lettuce.

* Sow seeds of perennials in pots for fall planting including yarrow, coneflower and salvia.

* In the garden, direct seed beets, carrots, leaf lettuce and turnips. Make sure to keep seeds and seedlings consistently moist.

* Plant potatoes.

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Food in My Back Yard (FIMBY) Series

Lessons learned during a year of edible gardening

WINTER

Is edible gardening possible indoors?

Hints for choosing tomato seeds

Starting in seed starting

Why winter is the perfect time to plant fruit trees

When to plant? Consider staggering your transplants

How to squeeze more food into less space

Potatoes from the garden

Plant a fruit tree now -- for later

Win the weed war by tackling them in winter

Tips for planting bare-root trees, shrubs and vegetables

Time to give vegetable seedlings some more space

Ways to win the fight against weeds

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