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Garden Help Desk: Autumn colors disrupted by unusual weather

By Uvu Extension garden Help Desk - | Nov 8, 2020
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Mixing bulbs with spring annuals and perennials will give a flower bed a full, fresh appearance.

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Annuals and perennials can be combined with spring-blooming bulbs if you take the time to keep track of where you've planted the bulbs. Having a plan or sketch of where everything should go makes it easier to plant.

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The hard freeze in late October left Ginkgo trees covered with dead, blackened leaves instead of buttery-yellow leaves that drop to the ground quickly.

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Shrubs like this Rose of Sharon will hang on to their dead leaves for several weeks until heavy wind or rain knocks the leaves off the branches.

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Mixing bulbs and perennials can keep a flower bed looking colorful once it's time to begin deadheading the bulbs but not yet time to cut back the foliage on the bulbs.

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If autumn leaves hadn't been killed by October's hard freeze, there could have been good fall color with leaves dropping naturally to the ground the way they did with this "Sensation" Boxelder last autumn.

Question: What happened to my shrubs? Some of the leaves were starting to change color and then suddenly the leaves were all curled and crispy. They never got any more fall color, and they haven’t dropped off yet.

Answer: You can blame last week’s weather for what happened with your shrubs. The hard freeze in the early hours of Oct. 26 interfered with the natural processes of color change and leaf drop.

Autumn leaf drop is a process that involves more than just a change in color. In the lower part of leaves, where they attach to twigs, there is a layer of cells that gradually begins to get corky and harden off when days get shorter, temperatures get cooler and sunlight begins to be less intense.

This area of special cells is called the Abscission Zone or Abscission Layer. Over the course of several days to a few weeks, the cells in this layer become weaker and the weight of the leaf will cause the leaf to separate from the twig. If the leaf dies before this layer is fully developed, the dead leaf may stay firmly attached.

Autumn color change is also a process. Yellow and orange pigments are already there in the leaf, but they’re masked by the green pigment chlorophyll.

When leaves get the autumn temperature, daylength and sunlight signals, they will make less and less green pigment, and the yellow and orange colors will be more visible. Sugars produced in the leaves can be trapped by the abscission layer that’s forming, and those sugars can produce the red colors we see in some leaves.

Color change can’t happen if the leaf dies before this process is complete.

In short, leaves need time to go through color change and leaf drop. The leaves on many trees and shrubs were killed by a few nights of hard freezes before they had time to go through a normal color change and leaf drop. There’s no need to do anything about the persistent dead leaves; they’ll eventually fall off.

Question: Is there a way I can mark where I plant my daffodils and hyacinth bulbs when I put them in this fall? I don’t want to plant a new plant next spring and accidentally dig up bulbs.

Answer: Many larger bulbs are actually planted deeply enough to safely plant shallow-rooted plants above them and for spring plantings, the green tops of the bulbs will let you know where your bulbs are.

When planting shrubs and larger perennials in the fall, there isn’t any top growth to mark the spot, so having some kind of reminder about your bulb plantings can be helpful.

There are a few simple ways keep track of where you’ve planted your bulbs.

Take a photo of the planting

Once you’ve prepared the soil and placed the bulbs, take a photo of the area before you cover the bulbs.

Stand far enough back to include a few other details in the photo-shrubs, sidewalk, driveway or anything else that will give you an idea of where the bulbs are planted. You can even lay a yardstick or tape measure in the photo.

This is probably the fastest way to keep track your bulb plantings.

Mark the spot

Once you plant your bulbs, you can mark the spot with a piece of yard art, a plant tag, sturdy garden marker or decorative rock. Make note of whether your marker is on the north, south, east, west or center of your planting.

This works well as long as pets or children don’t disturb your marks.

Make a measured sketch of your planters

Measure the dimensions of your flower or shrub bed, and make a sketch that shows the location of any edging, shrubs, perennials and yard art. Then measure your bulb plantings, and add them to your sketch.

This method involves the most work, but once you have your sketch, you always be able to go out to your flower beds with a tape measure and find a safe place to plant something new.

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