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All Past Questions and Answers Library | April 2008

This month's questions concern:

Should I Weed Before Mulching
When to shape a hedge
Colloidal Compost
Can Grapes Ripen Off The Vine
Getting Rid of Grasshoppers
Snails in Dense Ground Cover
Termites in Avocado Tree
Lilly Pilly Cuttings
When to Cut Lawn After Winter
Why Use Dry Moss For Pots

Please scroll down to read the answers.

Question #1:  Should I Weed Before Mulching?

Question:  I am finding it hard to keep weeding my flower beds. If I put mulch down do I need to weed the bed first please?

 Angela, Belfast, Northern Ireland


ANSWER:  Hi Angela! Yes, the best way to keep your flower beds weed free is to weed thoroughly first and then put down a good thick layer of mulch. Here are a couple of other things you can do in addition to that:
  • First if you do NOT intend to ever plant seeds in your flower beds, you can put down a preemergent. What you do first is to go ahead and remove any existing weeds, and then apply an organic preemergent like corn gluten meal (read about corn gluten meal) which will help prevent any future seeds from germinating, then apply your mulch.

  • Another trick that works well is after weeding your area, put down a couple layers of newspaper, then apply your mulch. The newspaper really helps smother any future weeds, and it breaks down adding organic matter to the soil.

  • A 2-inch (5 cm) layer of organic mulch is usually enough for weed suppression and moisture retention. Try not apply too thick a layer of mulch, because if the particles are small, like compost, it can keep oxygen from getting to the roots of shrubs and trees.

  • If you want to read about different kinds of mulches and how thick to apply each, read our story: Mulching - How Much And How Deep?
Keep in mind however, that while mulches can be very effective in reducing weeds, they can't stop them altogether. Due to wind blowing seeds in and other factors, weeds tend to appear. But if you pull them as soon as you see them, you can easily keep up with them, especially if you have done any of the above tips.

Once you get the hang of mulching, you'll never want to do without it again! Good luck Angela.

Question #2:  When To Shape a Hedge

Question:  I've been wanting to re-shape the hedge in front of our house for years now, but just have not gotten around to it. I recently went on long term disability, and can now afford the time, but don't really know when to do it. What time of year is best to do so, and why?

 Larry Gladstone, Calgary, Alberta, Cananda


ANSWER:  Hi Larry! You didn't mention what kind of hedge you have, so I am going to assume it is an evergreen hedge and go from there.

With evergreens, the main thing to keep in mind, is you don't want to feed them or prune right before very cold weather where a heavy frost or snow will damage soft new growth.

I like to prune hedges any time in the spring, provided it's not a flowering hedge of some kind. Then I wait till it flowers, then prune. I also will prune through summer, but not past then.

Since pruning triggers a plant to grow, I never want to risk getting a flush of soft new growth that will be killed back by cold weather.

Lastly, when you prune, try and shape the base slightly wider than the top (see picture next to your question).

What often happens is that people will prune hedges so the tops are wider than the base, and the lower growth doesn't get any sun and dies back. Then you get that weird lollipop look where the shrub is bare on the lower half and shrubby on top.

So get your pruning shears ready, because the weather is warming up and you'll be able to get out there soon and get that hedge shaped up in no time!

Question #3:  Colloidal Compost

Question:  What is colloidal compost, and how do you make it?

 Peter Steward, Erith, Kent, UK


ANSWER:  Hi Peter! OK - this is a really good question because there is a lot going on about this. First what is it:

Colloidal compost or humus is a step beyond compost. Compost is fibrous, dark and smells earthy. Colloidal humus can be rolled into a ball very easily and maintains its shape when formed like a piece of rubber or putty (see picture next to your question).

A colloid is a material that is a liquid but has a solid suspended in it firmly. A couple of examples of a colloid would be butter or jello.

The thinking is that regular compost is nutritious dirt that can have all of its nutrients washed away over time as it breaks down. Colloidal humus compost feeds itself and the nutrients do not wash away because they are suspended in a colloid.

In normal soil or compost, the water releases the nutrients and makes them available to the plant. Colloidal humus is available any time.

Now how to make it. I have to say I personally have never made colloidal compost, but here is what I have been able to find out. By the way, all humus or compost has colloidal properties...but this is different from the regular composting process.

Because I have never made it, I can't personally tell you if it is the wonder material some people are saying it is.

Making colloidal humus from raw organic material consists of a series of fermentations. As organic matter breaks down, it eventually becomes humus (well after the quick compost stage). These tiny bits will have a diameter of less than .002mm by definition. Their irregular shape, however, gives them a very large surface area compared to their size.

These nutrient particles, when combined with clay colloids can make a super enriched, water storing colloidal humus compost.


You will need to have a few square yards (meters) free and a reasonable amount of materials available. You don't need a bin, or a tumbler. Just some space.

Nitrogen materials are basically "green." Things like green leaves, green grass clippings, cow, horse, sheep manure, etc.

Carbon materials are basically "brown." Things like hay, straw, wood shavings (not painted or treated and the finer the better), dried out grass, etc.

Kitchen waste can be either depending on what it is but tends to be slightly on the carbon side and a little on the wet side. Soak up the extra moisture with some dry carbon type material.

To get a good compost, a rough rule of thumb is 50/50 of carbon materials to nitrogen materials as described above. So you can color code them to 50% greens and 50% browns!

If you have very fresh manure (and this gives the best results because of all the enzymes and things still in it) then limit it to around 30%.

The secret is to make the pile all at once with materials collected over time.

Then mix thoroughly at the correct moisture content (a wrung out sponge) and assemble into a heap all at one time. A core of straw or other fibrous material goes through the center to get the air in there.

It's a good idea to have fibrous stuff like straw in the mix as well to keep the air flowing without having to turn the thing. Keep it all at the same moisture content as it went together. (wet down when the weather is dry and put a cover over when it's pouring rain)

The pile works the best when it's over a cubic yard (meter) of volume as it heats more evenly and stays warm.

Don't let it get too hot though or else you will cook the nutrients out like a tumbler composter does.

Around 130° F or 54° C is as hot as it should go. Water the top if does get a bit too hot. Cover the heap with straw or such like to create a "skin" that breathes.

You're not supposed to turn the pile at all, just leave it, and in 6 months or so all the ingredients will turn into a rubbery putty-like substance called colloidal humus.

That's all I know about it, but if you or anyone else has more information, let me know! Thanks for the question.

Question #4:  Can Grapes Ripen Off The Vine?

Question:  My grapes are ripening, and when I'm out, my neighbors are picking the ripe ones and leaving me with the green grapes. So far I have not being able to have a nice sweet grape from my vines. Can I ripen the grapes away from the vines just before they sweeten up?

 Margaret H, Kaikohe, North Island, New Zealand


ANSWER:  Hi Margaret! I am sorry to hear about this. You must be very frustrated. Unfortunately, grapes do not ripen further once off the vine, and you can't ripen them like other fruit by putting them in a bag with apples or something.

Ethylene gas from apples can encourage ripening in avocados, bananas, and cantaloupe, but not grapes!

Plus, commercial growers will actually test the grapes before harvest because the sugar content changes throughout the day and throughout the harvest season, and they wait until grapes are as sweet as they want before picking them because, once off the vine, that's it.

So the only 2 things I can think will help is to first go over and talk to your neighbors about this.

If that doesn't work, then without sounding diabolical, the only thing I can think to do is put something bitter tasting, like an oil extract of some kind from the health food store that is edible so you won't hurt anyone, put that on the grapes and give them the old "sour grapes" right back!

I know it sounds so childish, but if they won't be adults about this, then at least they can't eat your grapes either! Let me know what happens!

Question #5:  Getting Rid of Grasshoppers

Question:  Last summer's growing season, my roses were invaded by grasshoppers that ate them down to sticks. They are showing promise of recouperation, and I'm hopeful of a healthy 2008 season of beautiful growth. Is there something I can do to get rid of these insects if they return this season besides call the exterminator?

 Monica Tobin, Chino Valley, AZ, USA


ANSWER:  Hi Monica! This is becoming more and more of a problem for people. Because of that, read our Disease and Pest Control Section this month. We highlight grasshoppers and a couple of methods how to get rid of them.

Here is a link: Grasshoppers

Question #6:  Snails in Dense Ground Cover

Question:  I loved your 12 ways to get rid of snails and slugs. My problem is that I have a hillside behind my house with dense ground cover. Each year the snails distroy portions of the hillside. I can't figure out how to set the traps close enough attract the snails since I think they are hiding somewhere in the middle of the hillside. I don't think throwing bait on top of the ground cover would do any good. Any suggestions?

 Marcia Borgman, La Jolla, CA, USA


ANSWER:  Hi Marcia! I'm glad you liked our tutorial. Snails and slugs are such a common problem that it was fun to get all the ways to control them into one story.

Try the Iron Phosphate baits, get the granular form, instead of the pelleted, and broadcast it over your ground cover. It will sift its way down and it will work great!

I have some very dense plants in my front yard, and I did this and all my snails are gone. If your local garden center only carries the pelleted form, have them order the granular for you, they can do that.

Do try it, you will be super happy you did!

For others who haven't read it here is a link: How To Kill Snails and Slugs - A Definitive Guide

Question #7:  Termites in Avocado Tree

Question:  I'm having problems with termites on an avocado tree in my backyard. What can I do?

 Francisco Rosa, Hatillo, Puerto Rico


ANSWER:  Hi Francisco! This can be a very serious problem in your part of the world, because termites can go from a tree, through the roots and under houses and dwellings, and cause huge problems.

First, for those who don't know, termites do not confine their attention to dead plant tissues such as wood.

In many parts of the world, species of termites are serious pests of growing crops including living trees. It is thought that termites are seldom primary pests, only damaging the plant, shrub or tree when it has already been affected by fire, a fungus or an insect of another order.

The fact however, that termites usually appear to be secondary pests, does not make them of less importance. The initial defect affecting the plant is often of minor importance, but after allowing the termites in, the effect may be the complete destruction of the plant or tree.

Cultivated plants in those areas of the world where termites occur can be divided into four groups: plantation crops - generally, these are woody perennials; field crops - generally, these are herbaceous annuals; young trees - in nurseries and plantations; older trees - mainly in forests, but including ornamental trees.

Ok, that said, what do we do about the problem?

Well the only thing that you can do is call a certified arborist or an exterminator who can help solve the problem. The good news is that, because of the seriousness of the problem, people have been working on this and have come up with a new "Fungal Foam" that kills termites.

You can read more about it here:

It is a fungus-filled foam that is being tested as a biological alternative to using chemicals to kill termites hiding inside tree trunks and other hard-to-reach places, and they are having really good results with it.

So Francisco, I'm sorry that in the short term, you'll have to call someone to help you, but in the long term, there will be better methods to help control termites.

Hang in there!

Question #8:  Lilly Pilly Cuttings

Question:  I have planted a young hedge of screen away lilly pilly - 20 plants in total - unfortunately our dog has broken several branches off one plant - I have kept the branches alive in water for several weeks - how can I replant these - someone told me recut branches and dip in honey before placing in potting mix - will this work???

 Claire Mouser, Burnside Hieghts, Victoria, Australia


ANSWER:  Hi Claire! Dogs are so wonderful but they can be rather mindless at times with the shrubbery!

Now you mentioned that you have kept your cuttings alive, but you didn't mention if they were starting to grow roots or not.

Lilly Pilly (Syzygium or Eugenia) is easy to propagate with semi-ripe cuttings, and it sounds as though that is what you have so far.

If no roots are starting, here is what I would do:

Semi-ripe cuttings are shoots from the current season's growth that is soft at the tip, but firm at the base, but not woody yet.

Using pruners, cut straight above a node, so you get a cutting that is 4 to 6 inches (10-15 cm) long.

In your case, you may just have to make a new cutting from what you have.

Then, remove all leaves except the two top leaves, and then cut those two leaves in half. This will reduce moisture loss and help a lot.

To help stimulate roots, you'll want to wound the base of the stem by slicing off a 1 1/4 inch (3 cm) sliver of bark from one side of the stem.

Now you can either dip the end in rooting hormone, which comes in powder or gel at 0.3%. The gel is better in some ways because it doesn't put too much on, but if you use the powder, after dipping the end of the cutting in, tap it firmly to remove any excess. If you get too much rooting hormone on sometimes it will inhibit growth, which is not what you want.

Now - having said that, honey is a hormone as well as a food. It is also a natural antibiotic, and some people do use it instead of rooting hormone, so if you have that instead, try it. Or try some with honey and some with rooting hormone and see what works better.

Stick the cuttings in well drained soil that is a mixture of equal parts of peat and fine bark. Make a hole and insert each cutting just deep enough for it to be able to stand up by itself. Firm the soil around the stem.

Put in bright indirect light and keep warm and moist until they have rooted. You will know they have rooted when you gently tug on them, and they feel firm in the soil.

So you can use what you have, just make some smaller cuttings and continue from there, and tell your dog to calm down!!

Question #9:  When to Cut Lawn After Winter

Question:  When should I give my lawn its first cut after winter?

 Mark Mccollin, Sunderland, Tyne & Wear, UK


ANSWER:  Hi Mark! Basically, as soon as your lawn greens up in the spring, let it grow to its maximum mowing height and then cut it. Keep in mind you never want to cut more than one-third of its length at any one time.

Being in the UK, you have more cool season grasses and therefore a good height to mow is around 2 to 3 inches (5 to 7.6 cm) and no higher.

So in your case, let it get around 3 inches (7.6 cm) and then cut it.

For more about mowing heights, see our Quick Gardening Tip Section this month. Here is a link: How High To Mow Your Lawn

Thanks for bringing this up!

Question #10:  Why Use Dry Moss For Pots

Question:  Hi, First I have to tell you that Murphy is as cute as Christmas! But, that's not why I'm writing. In the article on "Mossy Pots" why does the moss need to be dried out?

 Michael J. Healy, New York, NY, USA


ANSWER:  Hi Michael! I think Murphy is really cute too, and so does just about everyone else when I take her walking, and they stop me so they can pet her!

But to your question!

You want to dry out the moss so you get the moss spores. That way when you make your slurry, the spores are spread much more evenly, and you get better coverage and more even growth.

You can actually buy moss spores if you don't have real moss to use when making your pots.

For anyone else that wants read about making your pots mossy here is the link: How To Antique Your Pots & Add Fall Flowering Plants!

Meanwhile, I'll tell Murphy "Hi" from you!

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Keep Seedlings Moist

When you have just planted seeds, keep the soil moist until germination.

If the soil dries out, the seeds will die.

After germination, allow the soil to dry out a bit between waterings, but keep a close eye on the seedlings until they are well established.

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