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What makes rose buds turn brown?

This First Prize bud never got to bloom -- it's been infected by botrytis ci nerea. (Photos: Debbie Arrington)

Rotten roses follow botrytis fungal outbreak

My bushes are full of rotten roses. I know I'm not alone.

Blame botrytis. That fungus put a real damper on my December garden. Warm weather in early November pushed out new growth and a late round of blooms, just in time for Christmas.

That got me excited. I could fill the house with holiday bouquets or bring arrangements to December gatherings. After an often-difficult year, my roses were going to be gorgeous.

Instead, Marilyn Monroe turned to mush. First Prize was a total loss. These beautiful big buds became brown and died before they ever opened. Other roses developed odd discolorations. Irresistible, a cute white mini, looks like it has measles. Bruises cover the petals of Pink Promise.


Marilyn Monroe is no beauty in this case.
Fog creates ideal
conditions for botrytis.
Rain and fog brought on the outbreak, and this fungal infection quickly spread. The opportunistic spores are everywhere. Botrytis cinerea loves high humidity, according to the UC Cooperative Extension master gardeners. Nicknamed gray mold and blossom blight, this fungus can be a real problem for fruit growers in coastal areas. In cherry orchards, it rots blossoms and ruins the crop. Grape growers often have to deal with botrytis.

In Sacramento, it shows up in late fall to attack roses and other flowering shrubs. It forms masses of gray brown spores that can move around by wind or water. The spores linger on dead buds or fallen leaves, waiting for moisture before attacking the plant. During dry falls or winters, it's not an issue. But a blanket of fog creates ideal conditions.

If left to thrive, botrytis can cause twigs to die back and can damage new growth. The best solution? Trim out the problems.

The master gardeners recommend removing and disposing of fallen leaves and debris around plants. (Don't compost it; put it in the trash.) Also, prune out any dying twigs or blooms.

To help stop more fungal outbreaks, avoid overhead watering of roses. Prune to promote good air circulation around bushes. That's next month's job.

For more on botryits: or .


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Dig In: Garden Checklist

For week of March 19:

Spring will start a bit soggy, but there’s still plenty to do between showers:

* Fertilize roses, annual flowers and berries as spring growth begins to appear.

* Watch out for aphids. Wash off plants with strong blast from the hose.

* Pull weeds now! Don’t let them get started. Take a hoe and whack them as soon as they sprout.

* Prepare summer vegetable beds. Spade in compost and other amendments.

* Prune and fertilize spring-flowering shrubs after bloom.

* Feed camellias at the end of their bloom cycle. Pick up browned and fallen flowers to fight blossom blight.

* Feed citrus trees as they start to blossom.

* Cut back and fertilize perennial herbs to encourage new growth.

* Seed and renovate the lawn (if you still have one). Feed cool-season grasses such as bent, blue, rye and fescue with a slow-release fertilizer. Check the irrigation system and perform maintenance. Make sure sprinkler heads are turned toward the lawn, not the sidewalk.

* In the vegetable garden, transplant lettuce and kale.

* Seed chard and beets directly into the ground.

* Plant summer bulbs, including gladiolus, tuberous begonias and callas. Also plant dahlia tubers.

* Shop for perennials. Many varieties are available in local nurseries and at plant events. They can be transplanted now while the weather remains relatively cool.

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