Where | Deliberate Mechanical Defoliation of Perennials

Now that Marlene knows WHEN to cut her asters back, she needs to know WHERE to make the cut so she can accomplish her goal of keeping the asters shorter without losing the blooms.

Quiz

Question

Question: Where is/are the growing point(s) for most broadleaf perennials located?

A. There is one growing point at the apex (tip) of the shoot.

Incorrect: Chrysanthemums are an example of a broadleaf perennial that has an apical meristem at the tip of the main shoot. In addition to being a location of cell division and elongation, the apical meristem produces hormones that circulate through the plant and suppress branching from lower axillary buds. The axillary buds, also known as lateral buds, are located in the leaf axil (the area created between the stem and leaf). The axillary buds are undeveloped shoots, leaves, or flowers.

B. There is one growing point at the base of the shoot.

Incorrect: Chrysanthemums are an example of a broadleaf perennial that has an apical meristem at the tip of the main shoot. In addition to being a location of cell division and elongation, the apical meristem produces hormones that circulate through the plant and suppress branching from lower axillary buds. The axillary buds, also known as lateral buds, are located in the leaf axil (the area created between the stem and leaf). The axillary buds are undeveloped shoots, leaves, or flowers.

C. There are many growing points along the shoot.

Incorrect: Chrysanthemums are an example of a broadleaf perennial that has an apical meristem at the tip of the main shoot. In addition to being a location of cell division and elongation, the apical meristem produces hormones that circulate through the plant and suppress branching from lower axillary buds. The axillary buds, also known as lateral buds, are located in the leaf axil (the area created between the stem and leaf). The axillary buds are undeveloped shoots, leaves, or flowers.

D. There is one main growing point at the apex and many others along the shoot.

Correct: Chrysanthemums are an example of a broadleaf perennial that has an apical meristem at the tip of the main shoot. In addition to being a location of cell division and elongation, the apical meristem produces hormones that circulate through the plant and suppress branching from lower axillary buds. The axillary buds, also known as lateral buds, are located in the leaf axil (the area created between the stem and leaf). The axillary buds are undeveloped shoots, leaves, or flowers.

Looks Good! Correct: Chrysanthemums are an example of a broadleaf perennial that has an apical meristem at the tip of the main shoot. In addition to being a location of cell division and elongation, the apical meristem produces hormones that circulate through the plant and suppress branching from lower axillary buds. The axillary buds, also known as lateral buds, are located in the leaf axil (the area created between the stem and leaf). The axillary buds are undeveloped shoots, leaves, or flowers.

Question

Question: Why is the amount of green tissue (leaf area) remaining important?

A. The more leaf area that is removed, the more the plant must regrow.

Incorrect: The amount of residual leaf area remaining after defoliation must be adequate for continuing photosynthesis in order to get significant re-growth. Photosynthesis can be greatly inhibited with the removal of leaf tissue because green tissue is required for photosynthesis. This directly affects the source-sink relationship in the plant. Without the green tissue to perform photosynthesis there is no production of carbohydrates to supply the sinks with energy. Also, the more leaf area removed, the longer it takes for the plant to re-grow back to the stage it was at before it was cut back. This can delay flowering.

B. Flowering could be significantly delayed.

Incorrect: The amount of residual leaf area remaining after defoliation must be adequate for continuing photosynthesis in order to get significant re-growth. Photosynthesis can be greatly inhibited with the removal of leaf tissue because green tissue is required for photosynthesis. This directly affects the source-sink relationship in the plant. Without the green tissue to perform photosynthesis there is no production of carbohydrates to supply the sinks with energy. Also, the more leaf area removed, the longer it takes for the plant to re-grow back to the stage it was at before it was cut back. This can delay flowering.

C. More leaf area means more potential for photosynthesis.

Incorrect: The amount of residual leaf area remaining after defoliation must be adequate for continuing photosynthesis in order to get significant re-growth. Photosynthesis can be greatly inhibited with the removal of leaf tissue because green tissue is required for photosynthesis. This directly affects the source-sink relationship in the plant. Without the green tissue to perform photosynthesis there is no production of carbohydrates to supply the sinks with energy. Also, the more leaf area removed, the longer it takes for the plant to re-grow back to the stage it was at before it was cut back. This can delay flowering.

D. All of the above

Correct: The amount of residual leaf area remaining after defoliation must be adequate for continuing photosynthesis in order to get significant re-growth. Photosynthesis can be greatly inhibited with the removal of leaf tissue because green tissue is required for photosynthesis. This directly affects the source-sink relationship in the plant. Without the green tissue to perform photosynthesis there is no production of carbohydrates to supply the sinks with energy. Also, the more leaf area removed, the longer it takes for the plant to re-grow back to the stage it was at before it was cut back. This can delay flowering.

Looks Good! Correct: The amount of residual leaf area remaining after defoliation must be adequate for continuing photosynthesis in order to get significant re-growth. Photosynthesis can be greatly inhibited with the removal of leaf tissue because green tissue is required for photosynthesis. This directly affects the source-sink relationship in the plant. Without the green tissue to perform photosynthesis there is no production of carbohydrates to supply the sinks with energy. Also, the more leaf area removed, the longer it takes for the plant to re-grow back to the stage it was at before it was cut back. This can delay flowering.

To review these concepts click on the link: Perennial Plant Response to Defoliation - An Overview: Defoliation of Grasses and Broadleaves.

Quiz

Question

Image by UNL, 2005. Cut on dicot near ground level

Question: What would happen (how would new growth occur) if Marlene cuts the plants back below all growing points as indicated in the picture?

A. New buds and leaves would develop along the internode of the remaining part of the shoots.

Incorrect: All future growth would occur from crown buds growing new shoots.

B. Growth of the current shoots would cease and new growth would have to occur from dormant buds at the crown.

Correct: All future growth would occur from crown buds growing new shoots.

C. The plant would resume growing at the cut on the top of the shoot, developing new buds and leaves.

Incorrect: All future growth would occur from crown buds growing new shoots.

D. The plant would die because all of the growing points were removed and no new growth could occur.

Incorrect: All future growth would occur from crown buds growing new shoots.

Looks Good! Correct: All future growth would occur from crown buds growing new shoots.

Question

Question: Would cutting back the plant this amount result in a shorter plant and prevent it from flopping over the sidewalk?

A. Yes

Correct: Yes. Plant height would be significantly reduced. All future growth would occur from crown buds growing new shoots. It would take a long time for these to grow, and if conditions were not ideal, the plant could die.

A. No

Incorrect: Yes. Plant height would be significantly reduced. All future growth would occur from crown buds growing new shoots. It would take a long time for these to grow, and if conditions were not ideal, the plant could die.

Looks Good! Correct: Yes. Plant height would be significantly reduced. All future growth would occur from crown buds growing new shoots. It would take a long time for these to grow, and if conditions were not ideal, the plant could die.

Question

Question: Would cutting the plant this amount negatively impact flowering?

A. Yes

Correct: Cutting the plant back this severely (below all above-ground growing points) would cause the plant to have to initiate new growth from dormant crown buds. Since no leaf area remains for photosynthesis, carbohydrate reserves would have to be used to fuel new growth. Also, the amount of regrowth that would have to occur to achieve flowering would be significant and take a lot of time. As a result, flowering would be significantly delayed.

A. No

Incorrect: Cutting the plant back this severely (below all above-ground growing points) would cause the plant to have to initiate new growth from dormant crown buds. Since no leaf area remains for photosynthesis, carbohydrate reserves would have to be used to fuel new growth. Also, the amount of regrowth that would have to occur to achieve flowering would be significant and take a lot of time. As a result, flowering would be significantly delayed.

Looks Good! Correct: Cutting the plant back this severely (below all above-ground growing points) would cause the plant to have to initiate new growth from dormant crown buds. Since no leaf area remains for photosynthesis, carbohydrate reserves would have to be used to fuel new growth. Also, the amount of regrowth that would have to occur to achieve flowering would be significant and take a lot of time. As a result, flowering would be significantly delayed.

Question

Image by UNL, 2005. Dicot cut near top of the plant

Question: What would happen (how would new growth occur) if Marlene cuts the plants back “here” (about 1/3 of the mass of the plant or pinching back)?

A. New branches would grow from remaining axillary buds.

Correct: Broadleaf perennials, such as chrysanthemums, have many growing points all along the shoot. The main growing point is at the tip of the shoot. When the main growing point is removed, it can no longer produce hormones that suppress the growth of branches at the axillary growing points. As long as at least one growing point is still intact, new growth will occur in the form of branches at that the axillary growing points. As a result, plants that have been pinched back have a shorter, more bushy form.

B. The plant would resume growing at the cut on the top of the shoot, developing new buds and leaves.

Incorrect: Broadleaf perennials, such as chrysanthemums, have many growing points all along the shoot. The main growing point is at the tip of the shoot. When the main growing point is removed, it can no longer produce hormones that suppress the growth of branches at the axillary growing points. As long as at least one growing point is still intact, new growth will occur in the form of branches at that the axillary growing points. As a result, plants that have been pinched back have a shorter, more bushy form.

C. Growth of the current shoots would cease and new growth would have to occur from dormant buds at the crown. (which would take a long time?)

Incorrect: Broadleaf perennials, such as chrysanthemums, have many growing points all along the shoot. The main growing point is at the tip of the shoot. When the main growing point is removed, it can no longer produce hormones that suppress the growth of branches at the axillary growing points. As long as at least one growing point is still intact, new growth will occur in the form of branches at that the axillary growing points. As a result, plants that have been pinched back have a shorter, more bushy form.

D. The plant would die because all of the growing points were removed and no new growth could occur.

Incorrect: Broadleaf perennials, such as chrysanthemums, have many growing points all along the shoot. The main growing point is at the tip of the shoot. When the main growing point is removed, it can no longer produce hormones that suppress the growth of branches at the axillary growing points. As long as at least one growing point is still intact, new growth will occur in the form of branches at that the axillary growing points. As a result, plants that have been pinched back have a shorter, more bushy form.

Looks Good! Correct: Broadleaf perennials, such as chrysanthemums, have many growing points all along the shoot. The main growing point is at the tip of the shoot. When the main growing point is removed, it can no longer produce hormones that suppress the growth of branches at the axillary growing points. As long as at least one growing point is still intact, new growth will occur in the form of branches at that the axillary growing points. As a result, plants that have been pinched back have a shorter, more bushy form.

Question

Question: Would cutting back the plant this amount result in a shorter plant and prevent it from flopping over the sidewalk?

A. Yes

Correct: Yes. Plant height would be reduced from trimming, and removal of the main growing point would encourage branching (rather than one tall shoot). This would result in the plant having a shorter, bushier form.

B. No

Incorrect: Yes. Plant height would be reduced from trimming, and removal of the main growing point would encourage branching (rather than one tall shoot). This would result in the plant having a shorter, bushier form.

Looks Good! Correct: Yes. Plant height would be reduced from trimming, and removal of the main growing point would encourage branching (rather than one tall shoot). This would result in the plant having a shorter, bushier form.

Question

Question: Would cutting the plant this amount negatively impact flowering?

A. Yes

Incorrect: Removing this amount of tissue may delay blooming, especially if it is done later in the season. However, if it is done earlier in the season, the bloom delay will be minimal if any and the improvements in overall habit and appearance is worth it.

B. No

Correct: Removing this amount of tissue may delay blooming, especially if it is done later in the season. However, if it is done earlier in the season, the bloom delay will be minimal if any and the improvements in overall habit and appearance is worth it.

Looks Good! Correct: Removing this amount of tissue may delay blooming, especially if it is done later in the season. However, if it is done earlier in the season, the bloom delay will be minimal if any and the improvements in overall habit and appearance is worth it.

Question

Image by UNL, 2005. Dicot with flower parts cut off

Question: What would happen (how would new growth occur) if Marlene deadheads the plants?

A. New branches would grow from remaining axillary buds.

Correct: (if she waited until flowering occurred to trim the plant, it would get too tall. Already...too late to cut back for height savings.) Deadheading doesn?t take off enough of the plant to make a height difference?just encourages more blooms.

B. Growth of the current shoots would cease and new growth would have to occur from dormant buds at the crown.

Incorrect: (if she waited until flowering occurred to trim the plant, it would get too tall. Already...too late to cut back for height savings.) Deadheading doesn?t take off enough of the plant to make a height difference?just encourages more blooms.

C. New blooms would develop at the remaining axillary buds.

Incorrect: (if she waited until flowering occurred to trim the plant, it would get too tall. Already...too late to cut back for height savings.) Deadheading doesn?t take off enough of the plant to make a height difference?just encourages more blooms.

D. The plant would die because all of the growing points were removed and no new growth could occur.

Incorrect: (if she waited until flowering occurred to trim the plant, it would get too tall. Already...too late to cut back for height savings.) Deadheading doesn?t take off enough of the plant to make a height difference?just encourages more blooms.

Looks Good! Correct: (if she waited until flowering occurred to trim the plant, it would get too tall. Already...too late to cut back for height savings.) Deadheading doesn?t take off enough of the plant to make a height difference?just encourages more blooms.

Question

Question: Would dead headind the plant result in a shorter plant and prevent it from flopping over the sidewalk?

A. Yes

Incorrect: Removing only the spent flowers (deadheading) would not reduce the height of the plant. And since many broadleaf perennials do not re-bloom, including chrysanthemums, this technique will not encourage more flowering.

B. No

Correct: Removing only the spent flowers (deadheading) would not reduce the height of the plant. And since many broadleaf perennials do not re-bloom, including chrysanthemums, this technique will not encourage more flowering.

Looks Good! Correct: Removing only the spent flowers (deadheading) would not reduce the height of the plant. And since many broadleaf perennials do not re-bloom, including chrysanthemums, this technique will not encourage more flowering.

Question

Question: Would cutting the plant this amount and in this way negatively impact flowering?

A. Yes

Incorrect: No. Flowering is already finished at this point in the season.

B. No

Correct: No. Flowering is already finished at this point in the season.

Looks Good! Correct: No. Flowering is already finished at this point in the season.

Question

Question: Based on the previous questions, at which height should Marlene cut her asters?

A. Below all growing points.

Incorrect: Perennial plants need energy stored in the form of carbohydrates in their crown and roots. This energy sustains them during their winter dormancy, as well as fuels new growth in the spring before there is enough leaf area for photosynthesis to produce the energy. Cutting back perennials during the growing season can affect carbohydrate reserves, so timing is critical to make sure the plant will still bloom (before frost at the end of the growing season) and be able to maintain its health over the winter.

B. Cut off the top 1/3 of the plant.

Correct: Perennial plants need energy stored in the form of carbohydrates in their crown and roots. This energy sustains them during their winter dormancy, as well as fuels new growth in the spring before there is enough leaf area for photosynthesis to produce the energy. Cutting back perennials during the growing season can affect carbohydrate reserves, so timing is critical to make sure the plant will still bloom (before frost at the end of the growing season) and be able to maintain its health over the winter.

C. Deadhead the flowers.

Incorrect: Perennial plants need energy stored in the form of carbohydrates in their crown and roots. This energy sustains them during their winter dormancy, as well as fuels new growth in the spring before there is enough leaf area for photosynthesis to produce the energy. Cutting back perennials during the growing season can affect carbohydrate reserves, so timing is critical to make sure the plant will still bloom (before frost at the end of the growing season) and be able to maintain its health over the winter.

D. It doesn’t matter.

Incorrect: Perennial plants need energy stored in the form of carbohydrates in their crown and roots. This energy sustains them during their winter dormancy, as well as fuels new growth in the spring before there is enough leaf area for photosynthesis to produce the energy. Cutting back perennials during the growing season can affect carbohydrate reserves, so timing is critical to make sure the plant will still bloom (before frost at the end of the growing season) and be able to maintain its health over the winter.

Looks Good! Correct: Perennial plants need energy stored in the form of carbohydrates in their crown and roots. This energy sustains them during their winter dormancy, as well as fuels new growth in the spring before there is enough leaf area for photosynthesis to produce the energy. Cutting back perennials during the growing season can affect carbohydrate reserves, so timing is critical to make sure the plant will still bloom (before frost at the end of the growing season) and be able to maintain its health over the winter.

To review this concept view the: Perennial Plant Response to Defoliation Animation.

Quiz

Question

Question: How could this affect the health of the plant next spring?

A. hurt it

Correct: This could hurt the plant. The carbohydrate reserves will be depleted from fueling new growth. With little time left in the season to replenish the carbohydrate reserves the plant would go into dormancy and winter with low reserves. As a result, there would be reduced reserves available to supply new growth in the spring, weakening the plant.

B. help it

Incorrect: This could hurt the plant. The carbohydrate reserves will be depleted from fueling new growth. With little time left in the season to replenish the carbohydrate reserves the plant would go into dormancy and winter with low reserves. As a result, there would be reduced reserves available to supply new growth in the spring, weakening the plant.

C. no affect

Incorrect: This could hurt the plant. The carbohydrate reserves will be depleted from fueling new growth. With little time left in the season to replenish the carbohydrate reserves the plant would go into dormancy and winter with low reserves. As a result, there would be reduced reserves available to supply new growth in the spring, weakening the plant.

Looks Good! Correct: This could hurt the plant. The carbohydrate reserves will be depleted from fueling new growth. With little time left in the season to replenish the carbohydrate reserves the plant would go into dormancy and winter with low reserves. As a result, there would be reduced reserves available to supply new growth in the spring, weakening the plant.

To review this concept click on the link: Perennial Plant Response to Defoliation - An Overview: Carbohydrates and Defoliation.