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All Past Questions and Answers Library   |   May 2009

This month's questions concern:

How To Get Rid Of Dandelions
How To Care For Black Hamburgh Grape Vine
Understanding Soil Test Results
Mulching Mower Doesn't Mulch That Well
Problems Growing Freesia
Removing Tomato Leaves
What To Do With Tomatoes At End Of Season
Trees That Do Well In Containers In High Heat

Please scroll down to read the answers.

Question #1:  How To Get Rid Of Dandelions

Question:  What is the best way to get rid of dandelions please?

 Jean Cook, Romford, Essex, UK


ANSWER:  Hi Jean! This is a great question because it seems as though it would be easy to answer, but it isn't!

You're in luck in that this month's feature story is about this very topic. You can read it at: Control and Kill Dandelions Organically and Permanently

We stressed the organic method in our article because we are trying to get away from recommending chemical use unless it is absolutely necessary.

If you follow the steps that are offered in the article, you won't have any more dandelion problems. Thanks for the question.

Question #2:  How To Care For Black Hamburgh Grape Vine

Question:  Can anyone please tell me what, when and how to care for my grape vine. It`s a Black Hamburgh. The roots are grown outside, but the vine is in the green house. It is about three years old. I did have a gardener who cared for it but he is no longer available. Any help would be greatly appreciated. From a hopeful gardener.

 Elaine Firth, Kingston upon Hull, East Yorkshire, UK


ANSWER:  Hi Elaine! Black Hamburgh (also known as Frankenthaler) grapes are so good, and it sounds like yours is doing quite well.

Don't worry that your gardener is no longer available because luckily Black Hamburgh is very easy to grow and it is by far the best black grape for growing indoors because it will give a crop of sweet grapes that ripen in most summers, when other varieties would produce fruit that fails to ripen or develop any sweetness if there has not been enough sun.

The downside is that it is an older variety and it is susceptible to diseases such as botrytis and powdery mildew (for more about those diseases click on the underlined words).

The Black Hamburgh grape does well in an unheated greenhouse and will not be affected by frost. It is an early season grape but make sure it gets full sun. Give it regular water, and fertilize every spring with a balanced fertilizer like a 10-10-10 or a 15-15-15 using the amount recommended on the bag.

For its yearly pruning, cut it back to the main framework in the winter or early spring while it is still dormant and before the buds swell. Like other indoor grapes it is best planted in the ground, either in the greenhouse or outside the greenhouse with the main trunk trained to grow inside, which it sounds like yours is, so you're doing everything right.

The good thing about grapes is that once they get established they are relatively easy to care for and you should have no problems with yours.

Question #3:  Understanding Soil Test Results

Question:  We had our garden soil tested at the OSU lab. The results were: Bray-P 156, K 690, NO3-N 40.4, NH4-N 5.0. We have no idea what that means! Can you advise a resource that can give guidance on what to do about soil chemistry? Thanks!

 John Schulte, Dallas, OR, USA


ANSWER:  Hi John! I'm surprised they didn't include a documentation sheet explaining your results, most labs usually do. Here are what the numbers mean:

Bray-P 156: This is your soil phosphorous test used for acid soils and it tests available phosphorous in your soil. Medium is 20 to 40 ppm, High is 40 to 100 ppm, and Excessive is over 100 ppm. Your test suggests high levels and you should reduce your phosphorous applications.

K 690: This is your soil potassium. Low is less than 150 ppm, Medium is 150 to 250 ppm, High is 250 to 800 pmm, and Excessive is over 800 ppm. So your potassium is quite high too.

Nitrogen is absorbed from the soil as nitrate (NO3-) and ammonium (NH4+). Soil concentrations of NO3 and NH4 depend upon biological activity and can fluctuate with changes in temperature and moisture.

NO3-N 40.4: This is your soil nitrate-nitrogen. Nitrates can leach from the soil so if nitrate levels remain high, you need to reduce your nitrogen based fertilizers. Medium levels are 10 to 20 (surface foot ppm, High levels are 20 to 30, Excessive levels are over 30. So your nitrogen from the soil sample you sent it is quite high and you should reduce your nitrate levels.

NH4-N 5.0: This is your soil ammonium-nitrogen. This does not accumulate in the soil and concentrations between 2 to 10 ppm are typical. Yours look normal.

I'm no soil lab expert, but with results like yours I would follow up with OSU to get some definite answers. I don't know what you were testing for, but it sounds like farmland that has been over fertilized and needs some cover crops or other mitigating crops to level your soil nutrients out.

Let me know any other information you find out, I would be interested to know. Good luck!

Question #4:  Mulching Mower Doesn't Mulch That Well

Question:  My lawn mower is supposed to "mulch" the grass as it cuts, but I'm not sure it does a very good job at that. Should I bag (I'd have to buy a bag for the mower) or rake the cut grass? Is it OK to leave the cut grass on the lawn after mowing?

 Marcia White, Columbia, MD, USA


ANSWER:  Hi Marcia! Well different mowers do a better job of mulching than others. I have a really good mulching mower, but my grass is so thick and heavy that quite a layer of clippings is left behind so I put the bag on.

It really depends upon your type of lawn. If you have grass that tends to build up thatch easily and quickly like Bermuda and Zoysia grass, then you might want to get the bag.

Any lawn that builds up excessive thatch, which is anything over 1/2 inch (1.25 cm) creates an environment favorable for pests and disease and an unfavorable growing environment for the grass roots and should be avoided.

If you have no thatch problem and a lighter weight grass like a fine fescue, leave the clippings behind and watch your thatch levels.

If they begin to build, then you can either get the bag on your mower, or aerate your lawn every few years which we talked about last month: When Is The Best Time To Aerate A Lawn.

Basically, grass clippings are good. They have good nitrogen content and decompose quickly providing a good mulch but they do little to improve soil structure and they are best if they are weed free otherwise you are just spreading weed seeds all over.

If it were I, I would leave the bag off, see what happens and then go from there based on what occurs. The good news is that you're not really going to hurt anything and if you see no thatch building up then you don't have to rake, bag, or aerate and you'll have that much less work to do!

Question #5:  Problems Growing Freesia

Question:  I cannot succeed in growing Freesias. What am I doing wrong please?

 Marie Twomey, Cork, Ireland


ANSWER:  Hi Marie! I doubt you're doing anything wrong, but let's take a look at the basic needs of freesia plants and then you can take if from there - OK?

Freesia like full sun to partial shade, and they are hardy down to 20°F (-7° C). Plant them in the fall, setting the corms 2 inches (5 cm) deep and about 2 inches (5 cm) apart.

Freesias like well-drained loose soil and will rot if left in heavy wet soil. Give them regular water during their growing and blooming season, and then cut back on watering when the leaves start to yellow in the late spring. Don't water them during their summer dormancy.

In dry summer climates they can be left in the ground, but in wet summer climates, it's best to dig them up when their foliage begins to yellow and store the corms until it's time to replant them in early fall.

Freesia corms increase fairly quickly and you can dig and divide them when the quality and vigor of the flowers start to decline.

I hope this helps because freesia are wonderful to have in the garden and their fragrance is fantastic!

Question #6:  Removing Tomato Leaves

Question:  I've heard that by removing the right leaves on tomato plants that they will produce better tomatoes. Is this true and which leaves should be removed?

 Katie Coyle, Hodgenville, KY, USA


ANSWER:  Hi Katie! The best time to remove any tomato leaves is when you plant.

You want to remove all the leaves and branches and leave only the top growth. Then plant the tomato deep, stem and all and only leave the upper foliage above ground.

This is done so the tomato develops a strong and sturdy root system that will help it take up more water and nutrients which in turn will produce a better crop of tomatoes as well as to better withstand heat, drought, disease and pests.

For more information read the following articles, I think you will find them very helpful. Thanks for the question.

Growing Tomatoes & Tomato Growing Tips

How To Start A Vegetable Garden

Question #7:  What To Do With Tomatoes At End Of Season

Question:  What do I do with the tomato plant after fall? Just before the first frost? Do I cut it back and save it in the basement for next spring or toss it and get a new one in the spring? First time trying to grow them. Do they need lots of light during the day or can they have shade in the afternoon?

 Tracey, Ipsheim, Germany


ANSWER:  Hi Tracey! In the fall when the tomatoes are finished fruiting, just dig them up and toss them, or, if you have a compost pile, compost them.

They are annual plants and once they are done, they will die anyway. Tomatoes need full sun, but in super hot climates they can withstand some shade in the afternoon.

Like the previous question I think you would benefit from reading our more in-depth articles about tomatoes.

Don't worry about being new to gardening, just have fun and enjoy the process!

Growing Tomatoes & Tomato Growing Tips

How To Start A Vegetable Garden

Question #8:  Trees That Do Well In Containers In High Heat

Question:  I wish to ask you if I can plant a tree (flowering or fruiting) in a large pot and let it be for years. I want to have some shade at the entrance of my office, but there is no ground space for planting a tree. If you could advice me on this, and which trees would be ideal, I shall be highly obliged. I live in Delhi, India and the weather is primarily hot. Thanking you.

 Dr. Achala Agarwal, Delhi, India


ANSWER:  Hi Dr.Agarwal! Well I don't blame you for wanting some shade. For those not familiar with your climate, you can get some high heat there going up to 113° F (45° C) in the summer and then dropping to around 30° F (4° C) in the winter.

Those are pretty challenging temperatures for plants, especially in a container. Here are a few I think would work for you (and also please check out our content on flowers that survive in heat):

Cotoneaster lacteus
Evergreen with red berries to 8 feet (2.5 m) or taller

Pyrus calleryana (Ornamental Callery Pear)
Deciduous flowering tree to 30 feet (9 m) tall

Crataegus (Flowering Hawthorn)
Deciduous flowering tree to 20 feet (6 m) tall

Malus (Flowering Crabapple)
Deciduous flowering tree to 20 feet (6 m) tall

Gleditsia triacanthos (Honey Locust)
Deciduous shade tree to 30 feet (9 m) tall

Just remember to plant them in a large container, and that a tree in a container is going to depend upon you for regular water and care, so keep an eye on your tree, especially when you get your summer heat because you don't want the root ball to dry out.

Hope this helps, and let me know what you ended up planting!.

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Keep Some Birds Away

When you have worked very hard to grow your grapes, fruits and vegetables, it's hard to not be bothered when birds come in and take the best of everything!

A few tricks that work well are: netting over grapes, mylar strips tied to branches of your fruit trees, even blow up owls work.

If you use a blow up owl, or scarecrow, keep in mind to move them every few days so they appear to "move." Othewise the birds get wise fast and they are no good.

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