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All Past Questions and Answers Library | September 2008

This month's questions concern:

How to Get Rid Of Thistle
Passion Flower Vine
Japanese Maple Turning Green
Overwintering Strawberries
Suckers on Plum Trees
Dodder Vine
Rotting Pears

Please scroll down to read the answers.

Question #1:  How to Get Rid Of Thistle!

Question:  My garden is over-run with thistle. It is everywhere. Will the frost get it, or should I do something else? Thank you.

 Joyce Weese, Owatonna, MN


ANSWER:  Hi Joyce! Good to hear from you, but I'm sorry you have such a thistle problem! The frost will help, but not get rid of it.

The problem is that it has formed flower heads and gone to seed. The trick to suppressing any kind of weed is to take care of them before they form a seed head, otherwise they spread seed everywhere,and the next season, the problem starts all over again.

Here is what I would do:

1. Either now or in the very early spring before it gets too warm, get rid of all the thistle. Pull it up and clear it out.

2. Now what you next depends on what you are going to do with the area. ** IF ** you are going to use the area to sow seed, like seed a lawn, or grow flowers or vegetables from seed, then do NOT put down a pre-emergent . A pre-emergent inhibits seed germination, so if you want to seed a lawn or put seed down to grow flowers or edibles, seeds won't grow there.

If, however, the area is to be used for landscaping, and trees, and shrubs, then DO put down a pre-emergent, because inhibiting seed growth won't bother established plants.

3. If you ARE going to use a pre-emergent, because the area is always going to have established plants and not be seeded, then a good organic to use is "Corn Gluten Meal", a chemical version is "Ronstar."

4. If are NOT going to use a pre-emergent in that area, because you DO plan to put seed down, then be very diligent about keeping the weeds down either by carefully spraying an herbicide, a good organic one is: "Concern" , a chemical one is "Roundup." Just be careful not to get any spray on established plants because non-specific herbicides kill anything they come into contact with.

5. The trick is to not let the weeds get stared growing again, and with thistle especially, you don't want to allow it to go to seed again.

6. Thistle is a tough plant and you will have to keep after it for a couple of years. The good news is that every year thereafter, you will see less and less of it as it dies out, and the seed is no longer in your garden.

Hope this helps and have a great weekend!

Question #2:  Passion Flower Vine

Question:  How do I overwinter my passion flower vine?

 Diane Dileo, Oshawa, Ontario


ANSWER:  Hi Diane! Passion vines, Passiflora, comes in evergreen semievergreen and deciduous forms. Up in your area, I would expect you have the variety that goes dormant.

Hopefully you have planted it in a warmer part of your yard like against a wall or beneath an overhang. When the colder weather hits it will die back to the ground.

The most you can do is mulch heavily around the roots during the winter to keep them as warm as possible. In the spring cut out any congested growth and it will come back quite nicely.

Enjoy those beautiful flowers!

Question #3:  Japanese Maple Turning Green

Question:  I have a Japanese Maple and the leaves have started to turn a green colour as opposed to a plum colour and the edges of the leaves have started to go a beige colour, as if it is dying. Could you please tell what the cause of this is and what to do to put it right. Thanks Donna.

 Donna Hartley, York, North Yorkshire, UK


ANSWER:   Hi Donna! Well, the good news is that in time your plant will change back to red, but the dying leaves is something we need to be careful about. Let's take a look at this.

Keep in mind that there are hundreds of varieties of Japanese Maple (Acer palmatum). Now, regular Acer palmatum has red color in the spring, green foliage in the summer, and scarlet, orange, or yellow foliage in the fall, and that's just how it grows, and it will do that every year.

I don't know what you bought, but if you purchased a variety that was supposed to hold its red color all year long, again, keep in mind that many varieties, when experiencing a weather, climate, or location shift, will revert to the green leaves.

This is because some varieties are more sensitive to weather shifts than others, and that's why you can see similar looking red maples holding their color while the one right next to them will be turning green. The red gene that they bred into the more sensitive one just won't hold its color as well. The plant will eventually turn back to red in the fall or when the stress is removed.

The browning of the leaves to me, indicates that the plant is either getting a warm wind on it, or it isn't getting enough water. Either one would be enough to stress the plant and have it revert to green leaves. Keep your maple's soil moist, but not wet.

To recap, you may just be experiencing the regular foliage color shifts of Acer palmatum, or you could be causing it by the plant being too dry.

I hope this helps.

Question #4:  Overwintering Strawberries

Question:  My grandchildren have been growing strawberries and tomatoes in pots in my garden, are we supposed to bring them indoors over the winter? We have never tried anything like this before.

 Helen Logan, Kilwinning, Ayrshire, Scotland


ANSWER:   Hi Helen! Well, since tomatoes are an annual, and they are supposed to die at the end of summer, you don't need to worry about trying to overwinter them. The Stawberries, however, are a different story.

There are two different things you can do to overwinter strawberries in containers.

1. If you have the space: dig a hole in the ground and sink the pot up to its rim, and fill in the soil around it. By doing this, you're giving the plant all the benefits of being in the ground for the winter, which strawberries that are planted out would have. Put some mulch around them, like straw, or compost, or even shredded newspaper to help keep them warm and not freezing.

In the spring you can lift the pot out again.

You can also help your strawberries by double-potting them. That's when you place your existing container inside a larger one and fill the gap in between the two with soil that will act like insulation.

2. If you don't have the space: you can over winter them in your garage, or if you have a garden shed, as long as they are in a cold spot that doesn't freeze. The ideal temperature would be between freezing and about 45°' F (7.2° C). If you choose to do this, just don't forget to give the plants a little water during the cold dry months.

Good luck!

Question #5:  Suckers on Plum Trees

Question:  I have a two part question:

Question 1. My Santa rosa plum is sending out hundreds of new starts from it's roots. I chop them down, but they come back even more. What can I do to stop this from happening?

Question 2. Is this true of the roots that come up from the ground? I know about the suckers that come off the limbs. My problem is coming up from the ground from the roots.

 Debbie Ingamells,Estacada, OR


ANSWER:  Hi Debbie, I answered your two part question with two answers!

Answer to Question 1: Lots of trees produce suckers every spring, and even though you cut them back, the suckers will continue to come back all summer long, which can be very annoying.

I think you should try a product called Sucker Stopper. It prevents suckers from coming back after you have pruned them back. All you do, is after you have cut the suckers back, cover where the sprouts have been removed with Sucker Stopper.

Try and treat the sucker area before the suckers get 10 inches long. The earlier you treat them, the better.

Make sure you read the label carefully, and don't apply during bloom or fruit set because fruit set reduction may occur. On woody ornamentals, this isn't a problem.

Control usually lasts about 3 months.

Answer to Question 2: I hate to be the bearer of bad news, but yes, suckers can come from the roots! You will have to dig down and see where they are originating from, cut them off, and then carefully use the Sucker Stopper.

When putting Sucker Stopper near the root area be super careful because you don't want to affect the growth of the plant. It is a lot of work, but with consistency you will get rid of them.

Hang in there!

Question #6:  Dodder Vine

Question:  I have a threadlike vine that is growing in my Verticillata. It is an orange-yellow and wraps around the stems and appears to grow out of no where. It has no roots and I have been pulling it off the plant. What can I do to get rid of it?

 Renae Learn, Denver, IA


ANSWER:  Hi Renae, it sounds to me like you have Dodder Vine. Does it look like the picture I have posted here? Let me know.

Dodder Vine (Cuscuta Sp.) is a parasitic plant that doesn't make its own food like most other plants. It steals all its food from other plants through suckers that grow into the other plants bark. The vine has no roots, no leaves, no chlorophyll.

Dodder is also called strangleweed, love vine, angel's hair and witches shoelaces and comprises a group of over 100 species.

Dodder seeds can lay dormant for almost ten years. Interestingly this parasitic plant has no connection with the ground. Once it starts growing it quickly looses any connection to the ground and relies totally on its host for nourishment, eventually killing it.

So how do you get rid of it?

Well, unfortunately, it isn't easy. All you can do is try to pull it from all affected parts of the host plants. Take care to get every fragment of it off your plants, then burn the dodder-infested plant remains.

If you have a really awful infestation or find it growing on plants you are willing to sacrifice, you can use a pre-emergent herbicide in the early spring or apply Round-up or Brush-b- Gone to kill both dodder and host plant.

Burning will kill the plants and seeds, but buried seeds will then germinate. Don't go off on a knee-jerk search-and-destroy mission every time you see a strand of dodder in the bushes, though.

Many dodders require very specific host plants and are therefore rare species themselves. If a dodder is in your garden or growing nearby among the weeds, then you should go after it with a vengeance.

If the dodder, however, is in a natural habitat growing on native vegetation, stop and think first. Watch it for awhile. If it seems be relying on just one or two kinds of plants and not attacking others or moving into cultivated areas, let it be!

Let me know how it goes.

Question #7:  Rotting Pears

Question:  My pear tree bore a tremendous amount of fruit this year. However, this is now all rotting from the middle out. Someone has suggested that the tree may have canker and must be cut down. I dread to do this - is there any treatment.

  Andrew Keegan, Dublin, Killiney, Ireland


ANSWER:   Hi Andrew! No don't cut your tree down, there is nothing wrong with it!

You simply are allowing your fruit to ripen on the tree instead of picking it while it is still green. Let me explain.

First of all I am assuming you have a European pear variety and not an Asian variety, and European pears divide into two basic categories: fall pears, that do not need a storage period before they are ready to use, and winter pears, that will not mature properly unless they are given a resting period in cold storage immediately after picking.

The fall pears are earlier ripening varieties such as Bartlett, Clapp Favorite, and Orcas, while those that ripen later, such as Bosc, Comice, and Highland, are winter pears.

In either case, both fall and winter pears still look "green" at the time they are ready to pick. If you wait to pick your pears until they look ripe, with yellow skin color, they will be soft and soon rot in storage.

In addition, since most pears ripen from the inside out, if left on the tree to ripen, many varieties will brown at the core--in other words, they are overripe in the middle.

This is variety dependent but is particularly common in most fall pears. The Orcas pear is one fall variety that has not been plagued with this condition and ripens fairly well on the tree. However, if you want to store pears for a month or more, letting them ripen on the tree won't work. The earlier harvested fruit on a pear also stores the best for a given variety, and like apples the later season varieties (winter pears) have the longest storage potential.

The best guide is this: when most pears are ripe, the stems will easily separate from the spur when the fruit is lifted up, not pulled down. If you have to tug and pull to get the pear off, it usually is not ready.

After picking, fall pears can be kept on a shelf at room temperature until ready to eat - when yellow color develops and the fruit begins to soften. Fall pears can be stored but usually do not keep for more than 4-6 weeks.

Many people use their fall pears for canning and drying.

Winter pears should be put into some kind of cold storage (33 to 40° F or .56 to 4.4° C) for at least 3 weeks. After that period, you can start to bring out fruit as needed to soften up at room temperature. At first it may take 5 to 9 days before the pears are ready to eat; later on a couple of days at room temperature may be long enough.

I was probably a little too long in my answer here, but pears are one of my favorite fruits, and they should not be wasted, so I wanted to give you enough information so you can enjoy your pears as much as possible.

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