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All Past Questions and Answers Library   |   October 2010

This month's questions concern:

Using Rain & Wash Water in the Garden
Is a Maple Tree's Fall Color Genetic or Environmental
African Violets Refuse to Flower
Siberian Irises Are Flopping Over

Please scroll down to read the answers.

Question #1:  Using Rain & Wash Water in the Garden

Question:  I divert rainwater from the roof, and wash water into my garden. Is there anything wrong with this?

 Rachel Connally, London, England


ANSWER:  Hi Rachel! Well I congratulate your recycling ability, that's great.

You didn't say if your garden contained any edibles or if it is just ornamental plants you are watering.

It is normally recommended that "gray water" be used on ornamental plants only. Many studies have been done and researchers have found that bacteria common in human intestines survive in wash water. These bacteria don't get into the plants, but there is a "splash factor" when the water is put directly on the soil of the garden.

If you are going to continue to use this water I would recommend two things:

1. Water ornamentals and lawns only

2. If you must use this water on edible plants, grow crops that produce above-ground fruits and vegetables such as corn, tomatoes, broccoli, and trellised peas, beans and cucumbers.

Try not to apply gray water around low, leafy, or root-crop vegetables such as spinach, lettuce, cabbage, carrots, radishes, and beets.

If you are using any washing-machine water, don't use chlorine bleach in the laundry since moderate to large amounts of chlorine are toxic to plants.

Also avoid using detergents containing boron, since even small amounts can kill plants.

Most softeners and cleansers release sodium into the water so be careful of those as well.

Over a long period of time, minerals and sodium can collect and build up in the soil resulting in alkalinity and poor soil drainage, but if you get lots of fresh rain, as you do in your part of the world, that should help wash any problems away.

It would still be a good idea to use fresh water alternatively with the gray water and every year or so do a soil test to check your pH levels. A pH of 7.5 or higher may indicate a high level of sodium.

Applying some gypsum (calcium sulfate) will correct this. Just make sure your soil eventually tests to about 6.5 the preferred pH for most plants.

I hope this answer wasn't too long, but the question was a good one and the information will help a lot of other gardeners who are doing the same as you.

Thanks for the question!

Question #2:  Is a Maple Tree's Fall Color Genetic or Environmental

Question:  To what extent is the outstanding fall color of certain sugar maples genetic, and to what extent is it related to environmental factors?

 Ron E. Westingham, Alberta, Canada


ANSWER:  Hi Ron! Don't you just love sugar maples in the fall? Spectacular!

Actually, both of the causes you mentioned do factor into how much display a tree will put on in the fall.

Hereditary and genetic factors do determine which pigments are present in a tree's leaves. The red coloration of many maples, and trees that display red leaves, is due to a pigment anthocyanin, while yellow coloration displayed by beeches, birches, and sycamores is due to carotene and xanthophyll.

But we can't ignore the environmental conditions, however, because they influence how much of the pigment is actually produced. The amount of light, oxygen, nitrogen, and water a tree received all play a part.

Weather also has an effect. Fall color is always most showy and glorious when the days are clear, dry, sunny, and cool. If the weather is cloudy, the fall display is equally muted and not as brilliant.

I hope this answers your question. Go enjoy some of the wonderful fall color that is starting to appear right now!

Question #3:  African Violets Refuse to Flower

Question:  My African violets refuse to flower a second time. I have them under a grow light from 7 a.m. to 11 p.m., and I fertilize them monthly with a weak solution of 12-36-14. How can I get them to flower?

 Erin Guerssy, Victoria, Australia


ANSWER:  Hi Erin! Gosh, it sure sounds like your plants are getting excellent care, I can see why you are frustrated!

There are a couple of things you can do, however, so let's take a look.

First of all, check to make sure the light tubes are between 6 to 12 inches (15 to 30 cm) away from the plant tops. If the grow lights are too far away, they won't do much good.

You can also give your violets a bit more food. Some African violet growers feed their plants twice a month and use a balanced fertilizer of a 20-20-20 used at the rate of 1 teaspoon (5 ml) per gallon (4 liters) of water.

Make sure you have given the plants enough humidity too. African violets will not flower if the air is too dry. Misting is not a good idea for hairy-leaved plants because they can get leaf spot, but you can place the plants on pebble-filled trays of water, so the bottoms of the pots are sitting on the stones, not in the water. Or run a humidifier in the room if you have one.

African violets are also sensitive to cold and they do best with daytime temperatures between 72° and 75° F (22° to 24° C), and between 67° to 70° F (19° to 21° C) at night. If the plants get too cold, their leaves curl downward and flowering stops. They can take a long time to recover from being chilled, so warm up the room and protect them from drafts.

Lastly, make sure your plants are not overcrowded. A plant with too many crowns will not flower very well. Every second year, in the spring, you should divide your plants and repot them.

By following the above your African violets should be flowering like crazy very soon!

Question #4:  Siberian Irises Are Flopping Over

Question:  After my Siberian irises flower, they flop over and create a mess in the garden. What causes this and can I cut them back?

 Larry Delaides, Christchurch, New Zealand


ANSWER:  Hi Larry! Let's take a look at what Siberian irises need and go from there.

Siberian irises need full sun, well-drained, organically rich, slightly acid (pH 6.4) soil. They also like plenty of water from spring through flowering.

Now even if they get all the right conditions given to them, their leaves are inclined to flop all over the place as fall approaches. Although the plants will be stronger and flower better if the leaves are left intact, you can neaten them up a bit by cutting the leaves back in late summer.

Just make sure to leave 6 to 8 inches (15 to 20 cm) of the foliage.

Remove all flower stems at their bases within two weeks after completed flowering. Every third year or so, when the clumps get oversized, divide them either right after they flower or the first part of fall.

I hope this helps and your garden looks a little more organized from now on!

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