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All Past Questions and Answers Library   |   April 2010

This month's questions concern:

Flower Beds
Guiana Chestnut Tree Care
Wormy Cauliflower
Sick Oleanders
Kill Ivy
Tomato Blossom End Rot
Shamrocks Out Of Control
Pruning Clematis
Buying A Good Rototiller
Dormant Cyclamen
Lemon Tree Seedlings

Please scroll down to read the answers.

Question #1:  Flower Beds

Question:  I have a flower bed that is in direct sun for most of the day, but is at times overshadowed by a large evergreen tree will this tree take all the nutrients out of the soil near it so I can't plant anything next to it?

Also, I was hoping to put planters on the concrete area, which is in the shade for most of the day. I am aiming to grow flowers and shrubs (hopefully!) My friend has given me a small lavender plant too, where would be the best position for it? So many questions, but I am learning! Thanks again for your time, it is very much appreciated.

 Laura Walch, Bedford, UK


ANSWER:  Hi Laura! Sounds like you have a lot going on there. As to your first question, you should be just fine planting under your evergreen tree, there won't be a problem with sharing nutrients.

Having said that, there are a couple of things you will want to keep in mind. First of all, what kind of evergreen tree is it? If you don't know, take a sample of the leaves to your local garden center and have them identify it for you. It's important to know if the tree will be able to take the extra water that it will be receiving when you start watering your flower bed.

Some trees will be just fine, others don't like to be kept too wet. If it turns out to be a tree that doesn't like to be kept too wet, then plant outside its drip line. To determine the drip line, just look up, and where the widest branches end, draw an imaginary line from their tips down to the ground. That area, inside that imaginary line, where the main tree roots grow, is called the drip line. Plant outside that imaginary border.

If the tree turns out to not mind the extra water, plant whatever you wish. Just work in some compost or top soil, about 3 to 4 inches (7.6-10 cm) deep into your soil to give your new plants some good organic matter.

To your second question, putting planters in your concrete area is always a great way to garden. You can fill them with good compost or top soil and you can create the perfect growing environment for them.

Some good shade loving shrubs and flowers for your area, Zone 8 (10 to 20 ° F or -12 to -6.7 ° C), would be:
  • Summersweet (Clethera alnifolia)
  • Rhododendron or Azalea
  • False Spiraea (Astilbe)
  • Bergenia
  • Helleborus
  • Hosta
  • Many spring, summer and fall flowering bulbs
  • As well as many of the plants mentioned in my story about winter color perennials that you can read at: Plants for Winter Interest
As to your lavender plant, that is an evergreen perennial, and depending upon what variety it is, should be able to tolerate your climate. They like full sun and do best when fed with an organic fish fertilizer, because it really brings out the oils in the flowers.

In the fall, simply trim back the spent flowers, if you haven't cut them for indoor enjoyment already, and put down 3 or 4 inches (7.6-10 cm) of mulch to help it through the winter months.

I hope that answers all your questions, good luck!

Question #2:  Guiana Chestnut Tree Care

Question:  How do I care for a Guiana Chestnut Tree, does it need to be pruned and / or repotted at some point?

 Pola Florez, Duarte, CA, USA


ANSWER:  Hi Pola! Guiana Chestnut (Pachira Aquatica) - is a really great specimen tree. I am assuming from your question, you are growing your Guiana in a container.

They grow very well in containers, so I wouldn't worry about repotting it. This tree seldom needs pruning, but it usually grows more like a large shrub in cultivation. The only time you may want to prune it is for shape and form, which is a personal choice, you don't need to prune it to keep it healthy. It should, however, be fertilized frequently during the growing season.

For people who are not familiar with this tree here is a bit more information:

Guiana Chestnuts are evergreen trees that can vary in height from 15 feet (4.5 m) to 60 feet (18 m). They like moist soil and full sun, and a tropical climate. They come from tropical Mexico to parts of South America.

They're grown for their unusual, very large, fragrant flowers and fruit. The fruit pod's nuts are harvested when the seed pods burst and are eaten raw, roasted, or fried, the way sweet chestnuts are, and they taste sort of like peanuts.

Young trees grow with a single trunk for a long time, and don't seem to want to start branching until they're over about 8 feet (2.4 m) tall, then branch moderately. It can take years before a full canopy develops.

In the wild, Pachira aquatica is a wetland tree that grows in freshwater swamps associated with tropical estuaries. It often grows alongside rivers, where its branches arch out over the water.

Thanks for the question Pola, and good luck with your tree!

Question #3:  Wormy Cauliflower

Question:  Worms come up through roots on my cauliflower and ruin the whole califlower head, what can I do to prevent this?

 Larry Wilson, Viola, IL, USA


ANSWER:  Hi Larry! Sounds like you have Cabbage Root Maggots. These are nasty little bugs, but there are a few things you can do to slow down their destruction of your cauliflower crop.

First, let's take a look at the problem:

The Cabbage Root Maggot does most of its damage in Canada and the northern U.S. It feeds primarily on crucifers such as cabbage, cauliflower, broccoli, brussel sprouts, collards, kohlrabi, radish, and turnip. Cabbage maggots eat small fibrous roots and tunnel in stems and large fleshy roots.

The problem is that infestations can be difficult to detect because the tunneling of maggots in these large-rooted crops does not always cause the foliage to wilt, but wilting during the mid-day heat can be an indicator.

Cabbage Root Maggots do overwinter as pupae in the soil, and as the soil warms in spring, adult flies emerge from cocoons, feed on the nectar of flowers, and mate. Appearing as early as April, females soon begin depositing eggs in the soil at or near the base of host plants starting the problem all over again.

  • Don�t plant these vegetables where you had them last year. The reddish-brown, quarter-inch, football-shaped capsules that harbor the pests through the winter are lying in wait in the soil. Instead, grow these vegetables in another part of the garden this year, then use stem collars (see next bullet point) to keep the adult flies from laying eggs at the base of the young plants.

  • Put tarpaper collars 1 inch (2.5 cm) above and 1 inch (2.5 cm) below the soil around the stems to prevent egg-laying.

  • Unfortunately, insect-attacking nematodes have been fairly unsuccessful against cabbage root maggots, and there is no chemical control available at this time.
Just be diligent with your methods and you will eventually rid yourself of the problem.

Question #4:  Sick Oleanders

Question:  I have a problem with my Oleanders. One side of the yard they are doing fine, but the other side all the leaves are turning brown and falling off. I water both sides the same with soaker hoses. What could be the problem? Any ideas?

 Chris Koester, Lexington, TX, USA


ANSWER:  Hi Chris! I was trying to come up with a good news, bad news scenario for you, but all I have is bad news! Sorry!

It sounds as though you have Leaf Scorch, which is a bacterial disease that is spread to Oleander (Nerium) by the Glassy-winged Sharpshooter.

The disease is already very serious in Southern California, and parts of Arizona and Texas.

Leaves of infected plants turn brown and drop and the plant quickly declines and dies. No cure is known at this time, but you can slow it down by pruning out the infected portions of the plant. Just make sure you dip your pruning shears in a bleach-water mixture between each cut so you don't spread the disease further.

If they were my plants, I would consider two options:
  1. I would prune out as much as I could, just as I mentioned above, and then I would try spraying some neem oil. I know it's not listed as a cure, but neem oil has many properties, one of them being an anti-bacterial. I would spray every two weeks for 3 months and then monthly for 2 more months and see what happens.

  2. If pruning and the neem oil didn't work, I would then consider new plants.
I don't mean to be Ms. Doom and Gloom, but when there is a bacterial problem that is sweeping through, sometimes it is better to just replace the susceptible plants.

If you do try the neem oil, let me know what happens so I can pass it on to everyone. Hang in there!

Question #5:  Kill Ivy

Question:  This might seem like a strange one! But, I have got ivy climbing all over my house and I have been told by buildings surveyor that it needs to be removed! I don't know where to start! Can anyone give me any ideas? Do I poison it before I remove it, or do I just cut off at the roots?

 Sonia MacArthur, Lincolnshire, UK


ANSWER:  Hi Sonia! You have a serious problem! Ivy (Hedera) can be very destructive, and it is a very tough plant to get rid of because of the way it attaches itself firmly by aerial rootlets. When left unchecked, ivy can grow to 90 feet (27 m) with stems up to 1 foot (30 cm) in diameter. In many areas the plant has been banned because it is so noxious.

In your situation I would start on one side of the house at a time. You will want to cut the ivy off, don't pull it off. Pulling ivy off a brick, stucco, or wood walls can pull away mortar, and boards, and loose bricks as well.

Chemicals may stain the bricks or mortar. Immediately after removing the ivy use a stiff brush and laundry detergent to remove the pads that hold the ivy to the masonry. If you let them dry they will be nearly impossible to remove.

Once you have the plant cut back to the ground, pour undiluted Brush-B-Gon on the stems to kill it. Remember, any bit of root left in the ground will grow back, so, if you see any new ivy leaves starting to grow, pour on some more Brush-B-Gon.

Lastly, never let any ivy mature to produce seed, because the birds will spread it and you'll have an entirely new battle on your hands!

You may want to call a landscape company to do this for you, because this will take a lot of work and perseverance to get all the ivy off your house!

Question #6:  Tomato Blossom End Rot

Question:  I want some advice on my tomato plants. The leaves seem to be drying off and the fruit have has a brownish colour at the bottom of it. The tomatoes have not yet ripened, but are near. Any advice on what and how to treat the problem would be most appreciated.

 Daniel Nash, Canterbury, UK


ANSWER:  Hi Daniel! Sounds like you have good old Tomato Blossom End Rot. Normally you see a water-soaked, and sometimes sunken brown spot on the blossom end of the fruit, which can enlarge and turn into a leathery brown or black patch. If it gets severe, the fruit can have a flattened or concave bottom end.

The whole problem is caused by the plant having a calcium deficiency. There may be plenty of calcium in the soil, it's just not getting taken up by the plant.

This can be caused by:
  • Excessive nitrogen fertilization
  • Extreme variations in watering
  • A hot, dry spell
How to fix it:
  • Maintain even moisture with regular watering and mulching. Don't let the plants get too dry, then too wet, then too dry again, etc.
  • Avoid over-fertilizing with nitrogen
  • Test your soil to see if there are any nutrient imbalances
At the fist sign of blossom end rot, always pay very close attention to how you are watering and mulching. Make sure you are doing it evenly, since 90% of the time, that is what is causing the problem.

The good news is that tomatoes out grow the problem later in the season when the conditions are corrected, so you get a second chance!

Question #7:  Shamrocks Out Of Control

Question:  How can I get rid of the evasive plant shamrock it has taken over everything?

 M. Walker, Leeds, UK


ANSWER:  Hi M. Walker! Shamrocks (Oxalis sp.) are spread by bulbs, and it can be invasive, as you know, when given its ideal growing conditions which are: moist, rich soil in partial shade. The plant does go dormant in the summer, only to come back just as strong in the winter.

It will take some perserverance, but you can get rid of your shamrock problem.
  • Use a strong herbicide like Round-up or Brush-B-Gon.
  • Unfortunately you can't just dig them up, because if you leave one bulblet behind, it will start growing all over again.
So in the fall when it starts to actively grow again, give it a good spray. Wait a week or so, and if you see any more growing back, spray it again. This may take several months.

I don't know of an organic soltution, so you'll have to use the herbicides I mentioned above.

You'll have to keep after it, but in time, you will win the battle!

Question #8:  Pruning Clematis

Question:  How do you prune Clematis? I have never cut them back before but recently I was told that they should be cut back to approximately 1 foot (30 cm) every spring.

 Margaret Storrs, Boise, ID, USA


ANSWER:  Hi Margaret! The goal, as you well know, when pruning clematis vines is to get the best display of flowers on the plant as you can. The type of pruning you do depends on when your plants flower. If you don't know which kind you have (spring, summer or twice-blooming), watch your vines for a year to see when they flower, then use one of the following methods:
  • Spring-Flowering Clematis
    These produce flowers on stems produced the previous year. After the vine has finished flowering, thin out any weak or tangled stems, remove any dead or damaged growth, and cut stems back to the first (or topmost) pair of healthy leaf buds. So a very light pruning overall because you want to keep the older stems for more flowers.

  • Summer and Fall Flowering Clematis
    These flower at the ends of new stems that were produced in the spring of the same year. These vines should be pruned when their leaf buds emerge - this can be anytime from late fall to early spring depending upon your winter climate. In Idaho, it's probably early spring. Cut all the stems back to 12-18 inches (30-46 cm) above ground level, making each cut just above a pair of healthy leaf buds. So overall a very heavy pruning to encourage lots of new growth.

  • Twice-Flowering Clematis
    These flower on the previous year's stems in the spring, then again on the current year's shoots in summer and fall. In late fall, or early spring, prune lightly to thin out excess shoots or untangle stems. You want to keep that older growth for the first flush of flowers. After first flowers have faded, prune more heavily so that new shoots will develop for the second round of flowers. These clematis are a bit more work, but you get twice the show.
Always give clematis regular water and a good, steady supply of nutrients. Try not to let them dry out, and apply a complete liquid fertilizer monthly during its growing season.

I'm glad you didn't just whack your plant back, because knowing when they flower can make all the difference between lots of flowers and none!

Question #9:  Buying A Good Rototiller

Question:  I am a first time gardener and need to buy a tiller. Can you give me any suggestions as to what to look for in a tiller?

 Debra M. Mason, Fairburn, GA, USA


ANSWER:  Hi Debra! There are many things to consider when buying a large piece of equipment. Here are some suggestions:

First, think about how heavy or large a unit you want. Will you have to use it yourself, or move it yourself, or will you have help?
  • Small portable: where a person can literally lift and carry the unit to another location such as a raised planter area or gardening bed. These are convenient, but, make sure it is heavy duty enough for what you need to do.
  • Front tine style: A larger unit with the motor generally over the gearbox and tine area to add needed weight.
  • Rear tine units: A larger unit that has some sort of a drive train applied to propel the unit for the operator.

Differences between the types:

Front tine tillers are a nice way to keep the soil tilled up but will generally shake a person to pieces while operating them unless the soil is tilled more often. The self-propelling is done by use of the tines digging and pulling the machine along. Because the motor is usually on top of the tiller tine area it is subject to a lot more dust and dirt ingestion. Make sure to service the motor and air filter more often.

Rear tine tillers are the most comfortable to operate, but usually cost more because they have so many more parts needed for the propelling, and to separate the tiller operations, from the drive system.

Several companies offer counter rotating rear tine tillers. These are used to break down the soil as the rototiller is driving into it. These units wear tires out sooner, as well as putting an unneeded amount of wear on gears, and shafts. Look instead for a faster more controlled tine speed in a standard rotation. Geared seems preferable rather than chain or belt systems which may tend to slip or wear.

Things to think about when shopping for a rototiller:

When shopping for a tiller (like you would a lawnmower or string trimmer) make sure that parts are available and not just sold in an assembly; like a gearbox assembly, or a transmission assembly. Many times the gearbox assembly cost makes the repairs exceed the replacement cost of the complete unit.

If when looking at tillers, you can look beyond the soon-faded glitter and paint, make sure that the unit that is grinding through the dirt and debris is built to withstand years of abuse. This will save you from repurchasing another unit in a short period of time.

Look for enough dependable horse-power and ask how the drive is built as well as if the tiller is supported by bearings instead of bushings. Are there individual pieces or is the transmission sold as an assembly? How long has this company been around? Does the person selling this product service what they sell? Can they give recommendations of satisfied customers?

Hopefully, has given you a few things to think about, and I hope the product that you chose works well for you for years to come!

Question #10:  Dormant Cyclamen

Question:  I bought some corms end of Jan 07 planted in the borders and expected some growth by now to be seen. However I can say that having seen no sign of life I dug one up and it bore no roots or shoots the inside body was clean and hard like a potato, no decease and so should I throw them out or wait and see?

 John Wheeler, Elgin, Morayshire, UK


ANSWER:  Hi John! Cyclamen are great, and can last forever. I have a potted cyclamen on my front porch that I have brought with me from house to house for 20 years now, and it still looks great!

If I were you, I would wait a bit more. Cyclamen usually flower in the fall and spring, but with all the weird weather around the globe lately, your plants might be taking a bit more time to get established.

Before you rip anything out, let's go over a few things, just to make sure we covered any potential problems.

Cyclamen are perennials grown from tubers and it sounds like you have good, healthy ones. They are traditionally planted during the summer months when they are dormant, but you may have purchased a Florist's cyclamen (C.persicum), which can be planted out anytime.

If you purchased Florist's cyclamen, make sure the the upper half of the tuber is protruding above the soil, since they don't like to be covered completely.

The majority of other cyclamen species should be planted with the top of the tuber at, or just below the soil surface and always water around the tuber, not directly on it.

They like slightly acid soil, and a cool climate, and full sun to partial shade.

It sounds as though you are doing everything correctly, so just give them a bit more time and see what happens. Let me know, I'm always so curious as to the final outcome!

Question #11:  Lemon Tree Seedlings

Question:  I have several small lemon tree seedlings.I need info on taking care of them,and what kind of plant food they need.

 Johnnie Reed, Pleasant Grove, AL, USA


ANSWER:  Hi Johnnie! Just about any kind of citrus needs:
  • Full sun
  • Steady, moderate heat - although lemons have the lowest heat requirement of all the citrus
  • Mild winters with little to no frost
  • Well drained soil
  • Regular, even moisture - fluctuating soil moisture can lead to split fruit
  • Use a fertilizer formulated for citrus and avocado - and feed monthly throughout the growing season (spring - summer)
If you follow the above, your lemon seedlings will thrive and you'll have more fruit than you'll know what to do with!

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If you water at night, the plant stays wet for hours in the cool, which are prime conditions for fungi and other problems to set in.

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