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All Past Questions and Answers Library   |   May 2010



This month's questions concern:

Will Soil Solarization Kill Fungus
Soil Solarization - Use Clear or Black Plastic?
Prune Forest Flame Bush?
Rhubarb Plants Are Flowering
Asparagus Plants Not Producing Spears

Please scroll down to read the answers.



Question #1:  Will Soil Solarization Kill Fungus

Question:  Will soil solarization with plastic tarps destroy any late season blight fungus that may still may exist in the soil from last year?

 Lisa, Cameron Mills, NY, USA

 

ANSWER:  Hi Lisa! Soil solarization can do amazing things and killing fungi is just one of them.

The trick is to leave the tarp on long enough, depending upon your climate, to do the job. So, very quickly, let's go over the steps to solarize your soil.

Overview:

1. Solarization consists of covering the soil with a clear plastic tarp for 4 to 6 weeks during a hot period of the year when the soil will receive maximum direct sunlight. When properly done, the top 6 inches (15 cm) soil will heat up to as high as 125 F (52 C).

Note: If you live in a cooler climate, you should use a black plastic tarp, not clear, because the black plastic absorbs more heat making the soil quite hot. Leave on for 8 to 10 weeks to give it more time.

2. Over several weeks, that's hot enough to kill a wide range of soil inhabiting pests such as; wilt and root rot fungi, root knot nematodes and noxious weed seed.

3. In addition, solarization stimulates the release of nutrients from organic matter present in the soil. It is especially effective for treating garden soils, where the intent is to plant vegetables, herbs, and flowers.

Here's What You Do:

1. Till the soil before you solarize it

2. Rake the soil smooth

3. Wet soil conducts heat better than dry soil, so water the soil until it's damp but not soggy

4. Cover the entire area with plastic - clear or black depending upon your climate as mentioned above

5. If you want, you can put a second sheet of plastic over the first, creating an air space between them with bricks. This will intensify the solarization process since the sun's heat will be trapped between the plastic sheets and push the temperature even higher

6. Hold the outside edges down with bricks, or by burying them in the soil securely

7. Now let the sun do its work! In hot climates, the solarization process will only take a few months. In more temperate climates, you may want to begin the solarization process in the fall soon after that season's crops are harvested, and leave the plastic until spring

8. You're now ready to plant. Avoid turning the soil up any more than necessary when it comes time to plant your flowers or crops because the solarization process only goes down from 2 to 6 inches (5 to 15 cm) and you don't want to turn up soil that may have weed seeds from underneath. That's one of the reasons we tilled the soil before we solarized it.

9. Lastly, keep in mind that soil solarization is most effective during the hottest times of the year. That's when it will kill disease, nematodes, pests, and weed seeds, but solarizing during cooler weather will still reduce weeds

Lisa, if you follow the above steps, your soil should be just fine to plant. Good luck!



Question #2:  Soil Solarization - Use Clear or Black Plastic?

Question:  Please explain the solarizing soil procedure for getting rid of nematodes. Should the plastic be clear or black? Thank you.

  Bill Parchman, Garden Grove, CA, USA

 

ANSWER:  Hi Bill! Good question and even though I talked about it in the above question, sometimes it's good to repeat information so that everyone understands.

What color plastic you use depends upon two things:

1. The time of year
2. How hot your area gets

If you live in an area with very hot summers, use clear plastic because the soil will receive maximum direct sunlight. Leave the plastic on for 4 to 6 weeks.

If you live in an area that never really gets hot, or you are doing this during a cooler time of year, say fall, then use black plastic. Black plastic will help absorb more heat and help the soil warm up. Leave the plastic on for 8 to 10 weeks.

In order to kill nematodes you'll need to solarize your soil during the hottest part of the year and perhaps use two sheets of plastic to help intensify the heat you generate. If you can do that, you can get rid of all kinds of diseases, pests, and weed seeds.

Thanks for the question!




Question #3:  Prune Forest Flame Bush?

Question:  Hello, can you prune a Forest Flame? I've been told you don't, but it's getting so big. Thank you.

  Margaret Taylor, Manchester, England

 

ANSWER:  Hi Margaret! Forest Flame (Pieris japonica 'Forest Flame') is an evergreen shrub that can get up to 8 feet (3 m) tall, so unless you want your shrub that big, yes, you can prune it!

For people that don't know about this wonderful evergreen shrub it has green foliage that starts off red, changes to pink and cream and finally becomes green. Panicles of small, cream flowers are produced in spring putting on quite a show.

They take care and growing conditions similar to rhododendrons.

When To Prune:

The best time to prune a 'Forest Flame' shrub is immediately after it has finished flowering. It's also good to pick-off the old spent flowers, because it not only improves the appearance of the plant, but it also reverts the energy of the plant to new growth and the development of next year's flowers.

So whenever your plant needs to be shaped or reduced in size, don't hesitate to do so! Good question.



Question #4:  Rhubarb Plants Are Flowering

Question:  One of my rhubarb plants (now 4 years told) is growing flower stalks this year - should I cut them off or pull them off or ignore them?

  Sylvia Woolhouse, Newport, Gwent, S E Wales

 

ANSWER:  Hi Sylvia! Actually, rhubarb plants will occasionally send up seed stalks with flowers in the middle of the plants. It's a natural maturity process of the plant so don't worry about it, but you will need to remove them.

The flower and seed stalks should be cut out (don't pull them, you can damage the plant) as soon as they start forming, and the plant may still continue to produce the flower stalks so keep cutting!

Some varieties of rhubarb are more likely to flower than others, and since flowering will reduce the vigor of the plant because its energy is funneled into the flower stalks instead of new growth for rhubarb you will need to remove them.

Other than that, your plants sound fine and if you make rhubarb pie - have a piece for me, it's one of my favorites!



Question #5:  Asparagus Plants Not Producing Spears

Question:  Hello. I have noticed this past week that the asparagus I have in the garden, is coming up and going straight to fern, it is tall and very thin, what could be the problem, I think it is the 2nd year for this planting as the first got tilled up accidently. We had it covered this past winter with leaves and such, was told by someone that this would make for a more tender spear.

  Karen Fulton, Huntington, IN, USA

 

ANSWER:  Hi Karen! My first notion about this problem is that your plants are still very young and they are still recovering from the damage of being tilled up last year.

The fleshy root system needs to develop and store food reserves to produce growth during subsequent seasons and if they didn't get that chance last year, (and it sounds like they didn't) they are going to get it this year by going straight to top growth.

Asparagus plants that have been damaged, or harvested too heavily too soon, often become weak and spindly and the crowns may never recover.

By putting on this top growth, your asparagus is trying to get more energy to the roots to get stronger and grow better. If it were I, I would leave these plants alone. Let them grow their ferns and put as much energy back into their roots as they can.

Next year if they do produce spears, if they are small again, I wouldn't harvest them. I wouldn't harvest asparagus until it is at least three years old and the spears produced are about the size and width of a pencil or larger.

I hope this helps and I hope your asparagus recovers soon!



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Gardening-tip:



Use Edgings

Nothing finishes off a flower bed like low, long flowering edging plants.

Alyssum, lobelia, and dianthus are great for just this purpose.

For good continual flowering, also fertilize every few weeks with a balanced fertilizer like a 15-15-15.


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