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All Past Questions and Answers Library | July 2008

This month's questions concern:

What's Eating My Clematis Flowers
What To Do With Bearded Iris After Flowering
Do Tomatoes Benefit From Straw Mulch
How Large Should A Zucchini Plant Grow
Do Old Lilac Flowers Need To Be Removed
Pink Florets On Cauliflower
Peony Buds Won't Open
Epsom Salts For Peppers
Sooty Mold on Trees
Suckers on Bay Tree

Please scroll down to read the answers.

Question #1:  What's Eating My Clematis Flowers

Question:  Hello, I'm not sure what is eating the flower petals of my once beautiful angelique clematis. All the flowers are gone now. The leaves, however, are beautiful and green, not one indication that these are being eaten. Is it slugs? Don't they just eat the green leaves? We have had so much rain this year and I have put a thick layer of cedar mulch in this particular garden where my clematis is. Please let me know if you think it could be something else or is it slugs or snails. I have attached some pictures for you. Thanks so much.

 Elaine Geauvreau, Canada


ANSWER:  Hi Elaine! Thank you for the photos, pictures are always helpful.

That isn't slug or snail damage, that is earwig damage. Earwigs are notorious for eating holes in buds and blooms of Clematis while leaving the foliage alone. Earwigs like to stay hidden in moist dark places during the day and only come out at night to feed.

You can trap them easily during the day by providing them with a damp, dark place to crawl into like a rolled up newspaper that has been soaked in water so it is damp when placed in the garden.

You can also make a trap by filling a flowerpot with damp crumpled paper; then turn it upside down, but keep it propped up with a stick. Earwigs will crawl into the newspaper.

Place the traps near damaged plants, or in mulched areas, among shrubs or similar habitats. Check your traps once a day to remove the insects you've caught and then get rid of them in the trash. I put them in a plastic bag before I throw them out so I know they won't be back!

You can also use a beer trap because earwigs are attracted to beer. Place some stale beer in small jars and set the jars on their sides. The earwigs will crawl right in.

It will take time, but once the earwigs are under control, you'll be able to enjoy future flowers once again.

Question #2:  Bearded Iris After Flowering

Question:  I do not know what to do with my bearded irises now that they have finished flowering. I often see the remaining leaves cut off at an angle; is this what I should do?

 Jenny Sprod, Ampthill, Bedfordshire, UK


ANSWER:  Hi Jenny! Well, actually your question has brought up two different ways you can deal with bearded iris after they flower. Let me explain.

Option 1:
After bearded iris flower, if it is a year you don't plan to divide them, all you need to do is give them some moderate nitrogen-based fertilizer like a 5-5-5 or a 10-10-10, and remove the spent flowers.

Leave the foliage alone and continue watering regularly for about 6 weeks after the flowers fade. This is the time that increases and buds for next year's flowers form, during the post-bloom period.

After the 6 weeks after flowering, and during the rest of the summer, the plants will need less water until the fall. At that time, and as the plants are going dormant, you can then remove the old and dry leaves.

Option 2:
Now what you are referring to when you see the cut back foliage has to do with the second way you can deal with bearded iris after they bloom.

Every 3rd or 4th year, bearded iris do better if they are divided; it rejuvenates them and is also the best means of increase. Dividing is best done just after flowering is complete, and no later than mid-summer, because at that time, the plant has a brief dormancy. You can also divide in early spring, but this can delay flowering until the following year.

When dividing, the rhizomes should be separated so that each division has one fan of leaves and several feeder roots. The leaves are cut back to 6 inches (15 cm) and usually at an angle, which is better for disease and pest prevention. When you see the remaining leaves cut off at an angle, most often, someone has just divided his or her bearded iris.

So it's really up to you how you want to deal with your iris this year.

If you want more information about how to divide bearded iris, read this past answer: How To Separate Overgrown Iris which can be found in our past gardening questions library

Good question, and enjoy your iris flowers next year!

Question #3:  Do Tomatoes Benefit From Straw Mulch

Question:  Your recent article on mulch finds few "pros" associated with the use of straw and generally recommends against it. But your earlier tutorial on tomato growing recommends its use, as do a variety of other sources I've seen. I've read claims that research shows that the use of straw mulch enhances tomato production. Which is right?

 Robert Wood, Cherry Hill, NJ, USA


ANSWER:  Hi Robert! Great question!

If you notice in our Complete Guide To Growing Tomatoes we recommend two kinds of mulch.

This is what we say, "If you need to mulch, it is recommended to use a 3-4 inch (7.6-10.2 cm) layer of compost or straw." So we do recommend either one simply to give people a choice. Not everyone has access to compost or straw, so we give a couple of options so you can use what is accessible.

To continue, yes, we do recommend against using straw in our Complete Guide to Mulching because there are so many other options, that given a choice, are better to use. Here is what we say, "Straw can be messy and if used as a winter mulch can attract mice, voles, and slugs. Can be full of weed seeds and often needs to decompose for a year before use to kill any weed seeds. Also, ineffective on its own since it is mostly carbon. Because dry materials like straw, drain nitrogen from the soil to break the straw down, it should be mixed with grass clippings, manure, or compost to add nitrogen to minimise temporary nitrogen loss in the soil."

To be clear, yes, tomatoes most definitely do benefit from any kind of mulch whether you choose to use straw, compost, decomposed leaves, etc. I don't really believe it matters what kind of mulch you use, as long as you use it.

The benefits are terrific, since mulch helps keep the soil cooler in the summer and warmer in the spring. It also helps to keep even moisture retention in the soil so water intake by the plant is regular, which helps prevent blossom end rot which comes from a calcium deficiency from uneven watering. Plus, depending upon what kind of mulch you use, you can add nutrients to the soil and improve soil texture.

Anyway, I hope this makes it clearer for you, I'm really glad you brought it up!

Question #4:  How Large Should Zucchini Plants Grow

Question:  How big should I let my zucchini plants grow? I've been told with tomatoes you should cut the tops after the 5th bunch grows. Is there a tip for Zucchini as well? Thanks.

 Kellan Boh, Dagersheim, Germany


ANSWER:  Hi Kellan! The only reason some people cut the tops back on tomatoes is if they are growing indeterminate varieties (meaning the plants keep growing, while determinate varieties stop growing at a certain height). This keeps the vine from getting too large and to concentrate the plant's energy into the existing fruit for ripening and more flavor.

As far as the benefits of that, I them find questionable, since I have grown indeterminate tomatoes for years and never had a problem with having good fruit production.

In addition, tomato vines need enough leaves to shade developing fruits to prevent sunscald. Also, the leaves conduct photosynthesis for the benefit of the whole plant. So it's up to you if you want to continue to prune your tomatoes, but it isn't necessary.

Now on to your zucchini plant question, the answer is quite simple, don't prune them.

Zucchini plants are very prolific in their vegetable production and if you remove the leaves, which, like tomato plants are working hard to provide the energy to produce the vegetables, plus provide protection from the sun, you will have reduced yields, and zucchini that get sunscald. Plus you can weaken the plant, which can make it more susceptible to disease and pests.

So, choose a good large area when growing zucchini, or grow them on a trellis to save space. Good luck!

Question #5:  Do Old Lilac Flowers Need To Be Removed

Question:  Do I have to cut the old lilac flowers off when they've gone over?

 Diane Comley, Oxfordshire, UK


ANSWER:  Hi Diane! Well, it depends upon what you want your lilac plant to do. Lilacs (Syringa vulgaris), tend do better with light pruning and that includes removing spent flowers.

Removing the flowers keeps the plants looking better, and encourages the plant to direct its energy into producing flowers for the following year, instead of continuing to send energy to the dead flower.

In addition, a light pruning helps keep the plants more open and allows air to flow through thus reducing the chance for powdery mildew, which most lilacs are prone to develop.

If you never prune your lilac, over time you may see it get stringy and flower production start to decrease. It's really up to you, but I would tend to remove them!

Question #6:  Pink Florets On Cauliflower

Question:  My husband has a wonderful vegetable garden and we enjoy all manner of vegetables throughout the year. Can you please tell me what causes the cauliflowers to go pink where they should be white? Is it safe to eat the pink ones or should I be discarding or cutting out the pink florets.

 Christine Murdoch, Brisbane, Australia


ANSWER:  Hi Christine! There are couple of things that can cause cauliflower to turn pink or purple. It can be due to poor leaf growth and the exposed head can discolor. It can also happen due to weather fluctuations. Cauliflower is sensitive to variations in heat and cold, so it begs the question, how has your weather been?

Pinking generally occurs in the interior branches of the head, and it is usually due to excessively cool temperatures at harvest time for the variety being grown. Some varieties are more prone to pinking than others. Snowball types are more resistant to this defect that others.

Conversely, long days and hot weather can cause cauliflower curds (florets) to develop a red-purple discoloration. Varieties differ in their sensitivity to purpling and can be aggravated by overmaturity, or poor leaf cover that causes heads, or portions of them, to be exposed to light. Sometimes when cauliflower is stressed, it won't grow the abundant leaves that are needed to cover the head and keep it white.

As to whether you want to eat the pink part or not, I tend to cut it off myself. It would be like eating the sunscalded portion of a tomato. It's not going to kill you, but you're eating dead tissue, so just cut it off and eat the rest.

Now in addition to the above, and I understand that this isn't your problem, but just for those reading, there are also cultivators with purple, green and even pink curds (florets) as shown in the picture next to your question. So next year you may choose to grow another color and see how it does for you.

Question #7:  Peony Buds Won't Open

Question:  Why do my Peony buds get the size of a tennis ball and then don't open? Then they just start rotting.

 Lois Niedermeier, Rock City, IL, USA


ANSWER:  Hi Lois! There are a couple of reasons your peony buds are not opening.

1. Weather: Every variety of peony can respond differently to weather conditions. The most common reason buds fail to open is due to a frost or chill at the wrong time for that variety. A sudden chill at a later stage of development may have damaged just the inner flower parts, but not the outer parts. This will allow the buds to swell, but the interior tissue to fail and not develop properly. Peonies can be frustrating because some years they can do terrific and other years they do nothing. Meanwhile, continue to water and fertilize and wait until next year.

2. Botrytis is a common problem for peonies in certain climates, especially where a cool damp spring can encourage this fungus. Botrytis causes a fuzzy gray coating on the flowers and often kills the buds. Botrytis thrives in humid conditions and can be avoided or minimized by making sure the peony is planted where it receives lots of sun and has good air circulation. Once the disease is noticed, it is too late to save the buds for that season. Diseased areas should be removed. The whole plant can be treated later in the season with a fungicide. In fact this month we talk about a good fungicide: Fungicidal Soap

3. Water: Too much water while the flower buds are developing may cause them to wilt and die, just like too little water. Try to keep the soil evenly moist and make sure the peony is planted in well-drained soil.

Overall, with the bizarre weather the entire world is experiencing this year, I would lean towards it being a weather problem. If this continues for several years, you may want to consider moving your peony to a warmer location. Peonies don't necessarily like to be moved, but you will have more success if your plant just is not in the right place, and is not happy.

Question #8:  Epsom Salts For Peppers

Question:  I was told that if I take Epsom salt and desolve it and then pour it aroud my pepper plants I will get larger and more peppers. True or False?

 Mark Foust, Wellsboro, PA, USA


ANSWER:  Hi Mark! I would say that it depends - don't you just love an ambiguous answer!

Here's why I can't commit to true or false: The reason you would apply Epsom salts is because you have a pepper plant that has foliage, but no flowers or fruit.

This usually happens because people tend to over fertilize peppers. Peppers don't like a lot of fertilizer. They only need about 1 teaspoon (5 ml) of 5-10-10 at planting time, and another teaspoon (5 ml) when flowers start to appear.

So if you do have a pepper plant with no fruit, cool it with the fertilizer, and spray the plant with Epsom salts at a rate of 1 teaspoon (5 ml) dissolved in an old spray bottle full of warm water.

By spraying the plants, you will give them a shot of magnesium which they need at blossom time. Spray the plants once more 10 days later and you will have a nice dark, green plant with glossy leaves and flowers will start to develop.

Now if your peppers are doing fine, and you have flowers and fruit, then there is no reason to spray them with Epsom Salts.

See, it wasn't really a true or false question - good luck!

Question #9:  Sooty Mold on Trees

Question:  I have Sapota tree on a 5 acres of land with about 100 trees. Ther are 10 years old. Trees are affected with Sooty Mold. Tried all methods for one year. Sprayed incectcide and fungicide. Please suggest some remedy.

 Subramanyam Ksv, Bangalore, Karnataka, India


ANSWER:  Hi Subramanyam! Well, the first thing you really need to do is find the type of insect that is causing the sooty mold. Sooty mold is only a by product of sucking-piercing insects like scale, aphid and mealybug.

It is their secretions of honeydew that provide the environment for the fungus sooty mold to grow. Get rid of the insects and you'll eventually get rid of the sooty mold.

If you don't know what insects you have, we have profiles on: aphid, mealybug, and scale that you can look at. Each profile also gives instructions on how to get rid of it.

If after reading about the above insects, they don't look like anything you have, then have an arborist come look at your trees, or take a sample into a local agricultural office if you have one. They can help you identify your problem.

Once the insects are under control, sooty mold can be controlled by washing the leaves off and also being sprayed with an anti-fungal like neem oil.

I wish I could give you a more definite answer, but without being able to see the trees, it makes it really hard. Hang in there, I know you will get rid of everything in time and you're trees will be healthy once more.

Question #10:  Suckers on Bay Tree

Question:  I have a Bay Leaf Tree in a pot at my door. It is lovely but I have noticed shoots growing out of the soil. My bay tree is like a standard rose with a long stem like trunk. Should I remove the shoots or leave them? Also should I feed or generally how to care for it? Thank you

 Anne Clarke, Dublin, Ireland


ANSWER:  Hi Anne! You're right, a standard bay tree (Laurus nobilis) also know as a sweet bay or Grecian laurel, is lovely.

Many standards are trained up to grow like a tree, but they have bushy tendencies. Just look at how a bay tree normally grows in nature. It's natural habit is compact, multistemmed, with a broad base. The plant usually looks like a tapering cone.

So naturally it is going to want to send out more growth at the bottom. Those are just suckers and all you need to do is clip them off. You will probably have to do this more than once, because when dealing with a bay tree trained as a standard, you are fighting the plant's natural tendency to put out basal growth.

As far as general care, they are very easy. They can take a lot of abuse and still look really good. All they need is good, well-drained soil, full sun or partial shade, and moderate watering. You can give it some fertilizer once in the spring, and again in the summer, with a good balanced fertilizer like a 10-10-10 or 15-15-15, and that's about it.

The only thing bay trees don't like is the cold. If temperatures drop to 20° F (-7° C) or lower, you'll need to move it indoors to a cool, well-lighted room, or to a greenhouse.

Enjoy your tree!

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