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Past Questions and Answers | March 2007

This month's questions concern:

Pruning Crown of Thorns
Burnt Bird of Paradise
Legume Inoculant
Salt & Slugs?
Rubber Tree Leaves Falling Off
Old Apple & Pear Trees
Making Compost Tea From Kitchen Scraps
Sheep Manure
Move Adult Douglas Fir Trees
Flowering Pothos Plants
Planting Onions in Containers

Please scroll down to read the answers.

Question #1:  Pruning Crown of Thorns

Question:  I have a Crown of Thorns, mostly in the house, although I move it to an unheated (or uncooled!) greenhouse sometimes for a short time. It is getting pretty rangy. I'd like to prune it but my wife would crown me with the remains if anything drastic happened to it. Is there a special pruning protocol? Can the prunings be rooted reasonably easily? If so, short chunks? In any special medium - i.e., perlite, vermiculite, sand? Watering instructions for cuttings? (Maybe like cacti?) In sort, I'll appreciate whatever you can tell me.

 Bob Loveless, Shingle Springs, CA, USA


ANSWER:  Hi Bob! I totally understand your caution, once cut, a plant is hard to put back together again! The following should cover all your questions about Crown of Thorns (Euphorbia milii).

Pruning is best done during cool, dry weather to lessen the risk of stem disease, so I would wait until the spring. Since you are in California however, and we're not getting a ton of rain right now, you're probably OK doing it now, just be careful. Since it grows so slowly you won't have to prune it more than every 2 or 3 years, but Crown of Thorns will not only tolerate as much pruning as you want to give it, but it will actually become a much shapelier plant as a result of it. I have cut mine back to a stump in the spring and by mid-summer it is full and beautiful. Just make sure to give it a lot of light after cutting back so the new growth stays stocky and compact. To start you can take off a 1/3 up to 2/3 of growth.

A Word of Caution - if you don't already know this - as a Euphorbia, Crown of Thorns will bleed white sap when cut, which can be irritating to the skin to some people (I personally have never been bothered), so you may chose to wear gloves, and be sure to keep your hands away from your face until you've had a chance to wash well; better safe than sorry.

A Good Tip - When cutting, have a mister handy to mist the cut ends of the remaining plant (it will help stop the sap bleeding)

Since Crown of Thorns is a semi-succulent shrub, you can treat it very similarly to cacti.

Crown of Thorns is usually propagated from tip cuttings. Remove 3 inch stem tips. Place the cut end in water until the flow of sap stops. As soon as the sap stops bleeding, take it out of the water (don't let it sit in there too long, it will rot) and allow the cuttings to dry for 3 or 4 days. When a callus has developed, dip the ends in rooting hormone and place in a well-drained rooting mix. A good mix is a 1 : 1 : 1 ratio of sand, perlite and peat. Keep the mix slightly moist, but never wet. This Euphorbia doesn't like a lot of water. They will be rooted in 20 to 30 days and you can plant them out.

Crown of Thorns are drought tolerant, so when they are established, allow the top 1 inch of soil to dry out between waterings. It is very important not to over water, especially if the daytime temperatures are below 75 degrees. Around the middle of May and the middle of October, apply a light complete, slow release fertilizer, like a 15-15-15.

I think that covers all your questions. Good luck, and let me know how it goes!

Question #2:  Burnt Bird of Paradise

Question:  I have planted several birds of paradise and they never seem to look healthy. Some of them I think have been burnt because after a few hot days they just don't seem to recover. I have pruned dead leaves but left others that look as if they might come back. What do I need to do to get them looking healthy?

 Darren Lunny, Melbourne, Victoria, AUS


ANSWER:  Hi Darren! Yes, it sounds like they are getting too much direct sun. Bird of Paradise (Strelitzia reginae) require some light shade in hot climates, during the hottest part of the day, or they won't do well.

They can flower year-round, but they flower best in cooler weather. As they get older they do tend to flower even better because they like being crowded. They require regular water and are heavy feeders, so fertilize plants monthly with a complete fertilizer like a 20-20-20 or a composted manure.

Bird of Paradise do take time to recover from any type of damage. While they are growing back, you can either put some shade cloth over them, or move them to another area of your yard where they can get some shade. You might also consider planting them in containers, because they make a great potted plant.

They are such beautiful plants, and once you get them in the right spot, they will do really well for you.

Question #3:  Legume Inoculant

Question:  I am growing both peas and beans this year for the first time, and the company informed me that I should purchase a nitrogen gathering bacteria inoculant to better the plants. Do I really need to use an inoculant for these plants?

 Tony Bowden, Cold Lake, Alberta, CAN


ANSWER:  Hi Tony! Generally if you have never planted legumes before, using an inoculant will help. It isn't strictly necessary, but in order to help you make up your mind, here is a bit more information:

What does an inoculant do?
It inoculates the seed with nitrogen gathering Rhyzbium bacteria, which helps nitrogen fixation in the soil by the roots of legumes such as: peas, sweet peas, garden beans, snap beans and lima beans. It's a good non-chemical way of adding nitrogen to the soil.

Nitrogen fixation in legumes depends on the formation of nodules by Rhizobium (a common soil bacterium). Without enough nodule mass filled with the nitrogen fixing strain of Rhizobium, nitrogen fixation will be poor. Inoculation of legume seed makes certain that Rhizobium is in the soil.

Rhizobium is not toxic to humans, plants or animals, and some Rhizobium are specific and nodulate only specific legumes, while others may nodulate several legumes.

To help decide if you need to add an inoculant or not, here are a few things to consider:
  • If the legume to be planted was never grown, or hasn't been grown in the field for more than five years, the native Rhizobium is probably not enough to nodulate the crop, or may not be efficient in fixing nitrogen.

  • If the legume was previously grown, but nodulation or nitrogen fixation was poor (you had a poor yield and nitrogen deficiency symptoms), you should consider an inoculant.

  • Once Rhizobium is established in a field, it persists for several years between crops. There is no advantage to yearly inoculation of legume crops in fields,where well-nodulated legumes are grown.
What kind to buy?
There are several types of inoculany available: powder, granular, liquid and frozen concentrate. Pre-inoculated legume seed may also be available. The powder and granular inoculates are the most common, with liquid and frozen concentrate inoculates used for special purposes. Powder inoculates are the most common and most reliable.

How to apply it
It's easiest to pour the seeds and a powder inoculate between two clean containers to mix them thoroughly together. After mixing, all the seeds should be evenly covered with small specks of inoculate. Plant the seeds immediately, making sure the inoculated seeds are not exposed to sunlight. If the seeds become too dry, the inoculate will come off.

Overall there is no harm in using it, so let me know what you decide!

Question #4:  Salt & Slugs?

Question:  Can I use rock salt to scatter on my soil to combat slugs before I plant potatoes or will it harm the ground? Thank you.

 John Blackhurst, Gedling, Nottinghamshire, ENG


ANSWER:  Hi John! If it were I, I wouldn't put down salt. You can ruin your soil for a long time. After all, they used to salt the fields in times of war so people couldn't grow anything!

Acutally the timing of your question couldn't be better; I just wrote about how to use dry dog and cat food to help with your slug and snail problem in my blog this week. Click here to read the full blog

I'm glad you asked - good question!

Question #5:  Rubber Tree Leaves Falling Off

Question:  I'm very new to this gardening thing and was wondering if you could give me some advice about a rubber plant I have had for a couple of years now. The lower leaves keep going kind of brown in places. It always starts at one side of the leaf, in the centre, then it spreads and then the leaf falls off! I've no idea what I'm doing wrong, or right for that matter!

 Mary Jones, Shropshire, ENG


ANSWER:  Hi Mary! Well this is an interesting question because Rubber Trees (Ficus elastica) typically have a reputation for being somewhat problem free, but they can be very sensitive to a couple of things that can cause leaf drop. These few things are easily fixed, so don't be discouraged!
  1. They are sensitive to excess mineral salts, which can cause leaves to brown and drop

  2. They don't like sudden changes in lighting; that can cause leaf drop

  3. They need excellent drainage, so try not to let the plant ever sit in water, to avoid root rot, because that could cause leaf drop
I don't know what kind of water you are using to water your plant with, but from now on, I would use bottled water only. You may be in an area that has excess amounts of salts or minerals in the water, and your plant just isn't happy with it.

Also make sure you allow the soil to dry out a bit between waterings and make sure it has good drainage, or you could develop some root rot.

Make sure it gets good medium to bright indirect light, correct any of the problems I mentioned, and your plant should look great.

Good luck!

Question #6:  Old Apple & Pear Trees

Question:  Hi - We have moved to home with a lovely big garden which has in it a Pear tree and two Apple trees. We would like to know what time of the year we should prune them, and how to prune them, as we have never had fruit trees before. We know that the family who owned the house before us didn't pruned the trees for three years. Thank you if you can help us.

 Mr & Mrs Dyson, Conwy, WLS


ANSWER:  Hi Mr. & Mrs. Dyson! Congratulations on your new home. I hope you have many happy years there!

In regards to your questions, the best time of year to prune apple and pear trees are when they are dormant, which is from late winter into early spring before new growth starts.

Both apples and pears fruit and flower on old wood, so generally pruning them consists of removing any broken branches, crossing limbs, and any branches that grow toward the tree's center of grow vertically or downward.

Since your trees haven't been pruned in a few years, your goal will be to open up the center of each tree, just a bit, but thinning out enough growth to allow light to filter into the canopy when each tree has leafed out. If your trees are too tall, you can prune them down to the size you want, and then shape them to suit your tastes.

If the branches are loaded with spurs (the small stubby branches that bears the tree's fruit), you can thin those out a bit, so you will have less fruit, but what fruit you get, will be larger and healthier.

When you have older fruit trees like this, you mainly prune to keep the branching structure open, to limit size and shape, and to thin fruiting spurs if there are too many.

I will be posting a tutorial on how to prune an apple tree (which will apply to pears since you prune them the same way) in two weeks in the How To Section of this site and you may find it helpful, so check back. Here is a link for you: How To Tutorials Section

I hope your apple and pears are wonderful this coming year and you enjoy them to the fullest!

Question #7:  Making Compost Tea From Kitchen Scraps

Question:  I found instructions for a setup to make compost tea. It uses a garbage can as a container with gravel at the bottom, and a hole for a hose also at the bottom to allow the tea to drain. On top go compost scraps and worms.

I live alone and don't generate enough scraps for a garbage can. I have a plastic foam container (a shipping container for some meat ordered off the internet) and have foam packing popcorn. I'm wondering whether I can use the foam container in place of a garbage can, and the packing popcorn in place of gravel. My fear is whether there might be harmful chemicals that would leach out of the plastic into the compost tea.

What do you think?

 Robert Gilman, Albuquerque, NM, USA


ANSWER:  Hi Robert! I think I'm glad you asked before you made a smelly mess! Making compost can run a fine line between making a good quality compost and having fermenting refuse if it's not handled properly. I wouldn't use the foam containers for many reasons, but I think your concern about possible harmful chemicals is one of them.

If you can only generate a small amount of kitchen scraps for compost, and then eventually compost tea, you are better off using one of the small automatic composters that are made just for indoor use.

The good thing about these composters is that they have no odor, and they can be used with indoor waste alone like: paper, coffee grounds, egg shells, food scraps from the kitchen, etc. Depending on your price range there are two options: Once you have your compost, you can then make compost tea which is easy to do:
  1. You simply take some compost and put it in some kind of porous material like cheese cloth or an old section of pantyhose, just like you would a tea bag (see picture above)

  2. Then place the cheese cloth filled with compost and place it in a bucket full of water and allow it to steep for about eight hours. That allows a lot of the nutrients to leak out of it as well as many of the microbes

  3. Once it's steeped, take out the "tea bag" (your cheese cloth full of compost) and left behind is your compost tea. Water your plants with it for a great boost!
Rich compost is full of nutrients and microbes that really stimulate your soil and benefit your plants, and compost tea is just as good.

I hope you'll write me back and let me know what you ended up doing!

Question #8:  Sheep Manure

Question:  My neighbor wants to give me sheep manure, I'm afraid of a weed problem as it is not sterile. She said sheep manure has very little weeds, is this true?

 Keitha O'Toole, Crystal, ND, USA


ANSWER:  Hi Keitha! Well, I would be cautious of using any manure that hasn't been composted and aged for a couple of reasons.
  1. Sheep manure, like horse and chicken manure is considered "hot", meaning it contains soluble nitrogen compounds and ammonia that can burn plants and interfere with seed germination. Manure that is well composted, or has aged for at least six months is best - a year or more is even better.

  2. If you use fresh manure (less than 60 days old) in the garden, there is a small risk that pathogens which cause disease may contaminate garden vegetables. The risk is greatest for root crops, like radishes and carrots, and leafy vegetables, such as lettuce, where the edible part touches the soil. Careful washing and/or peeling will remove most of the pathogens responsible for the disease. Thorough cooking is even more effective.

  3. Lastly, as you mentioned, the possibility of weed seeds is a problem. Weed seeds are common in some manure. They may enter the animal with its feed and then pass through the digestive tract, still viable, or they may have simply blown into the feed yard where the manure was stored.

    Poultry droppings typically have fewer weed seeds surviving the digestive processes. However, other animal manure may contain numerous viable weed seeds if the original feeds were contaminated. Composting and stockpiling manure can reduce the number of viable weed seeds.
So if it were me and I wanted to use the sheep manure, I would compost it myself first, and then use it around my garden. Because to assume that there would be no problems using it fresh, would be a pile of ........ trouble!

Question #9:  Move Adult Douglas Fir Trees

Question:  I need to move 2 Douglas Fir trees (Pseudotsuga menziesii). They are 6 feet (1.8 m) tall and about 10 years old. Can I? and how if I can? I hope you can help since I can't find any answers!

 Dsiree Hruska, Boise, ID, USA


ANSWER:  Hi Dsiree! The only way I have ever seen full grown trees succussfully moved is using a tree spade. I have shown a tree spade in the picture for this question. It's a piece of equipment that uses huge blades to cut around and under the tree making clean cuts. They can then move the tree to a new home, or box it up to be planted later.

Before I did anything, I would talk to an arborist in your area and get some pricing and more information. A few things to keep in mind are:
  • Special considerations are necessary when moving large trees. If trees are over 3 inches (7.6 cm) in diameter, special equipment is often required to transport the tree. Depending on the size of the tree and the technique used, the equipment may include hand carts, winches, tree spades, or cranes. If trees will be transported on a truck, precautions must be taken to ensure that they will clear power lines, bridges, and other obstacles. Permits may be required to transport large trees on some public roads.

  • Only individuals properly trained in the maintenance and operation of tree spades should use them. Sharp blades reduce damage to roots during transplanting. Crushed or shredded roots caused by dull blades will develop more dieback than clean cut roots. Large trees should not be transplanted with root balls smaller than 12 inches (30.4 cm) in diameter for each 1 inch (2.5 cm) in trunk caliper (diameter).

  • Before moving a large tree, keep in mind that smaller trees of a particular species typically transplant better and catch up in growth to larger trees of the same species. A general rule is for each 1 inch (2.5 cm) in caliper (diameter), a year is required for transplant recovery; therefore, a 4 inch (10.1 cm) caliper tree may require four years to recover from the transplant procedure before normal, active growth resumes.
It is too bad you have to move them, but since you do, look into getting a reputable tree company that has a tree spade, make sure they are licensed and bonded, ask them for references, and get everything in writing before you allow anyone to move your trees. This is a big undertaking and you want to make sure it is done right.

Question #10:  Flowering Pothos Plants

Question:  Do Pothos plants produce buds and seeds?

 Deb Ferguson, Menifee, CA, USA


ANSWER:  Hi Deb! Pothos Plants, also called Devil's Ivy (Epipremnum pinnatum 'Aureum') are mostly known for their foliage. That said, however, the foliage does go through both juvenille and adult forms, with adult leaves of some species growing up to 24 inches (60 cm) long. They rarely flower until they produce adult foliage, so they don't often bloom in non-tropical areas.

Pothos does not flower in cultivation, since only the juvenile phase is grown as a houseplant, and flowering occurs only in the mature phase. In the wild, these plants produce a number of erect flower stalks together, each with a cream spathe (the spathe grows up to 9 inches or 23 cm long) marked with purple surrounding the spadix.

Even though we never see the flower, it's still one of the most popular houseplants around because of its outstanding foliage and vining habit, and its ability to easily grow in just about any condition.

Question #11:  Planting Onions in Containers

Question:  Hi, I 'm a beginner gardener. How do I plant onions in a container? Your video on potatoes was excellent. I can start my potatoes now. Thank you.

 Diane P. Allen-Lightsey, Chester, PA, USA


ANSWER:  Hi Diane! I'm glad you enjoyed the video. It is always so much easier when you can see someone actually doing it. I will be converting more of my videos to streaming format for the internet in the next several months, so check back.

To your question, it is very easy to grow onions, especially in containers where you can keep a close eye on them. Here is a quick list of what to do:
  • Onions can be grown from seed or from sets (baby bulbs). Sets are very easy to plant and grow, and escape many of the problems to which seedling onions are prone. I always recommend sets even though you have less choice of varieties

  • Plant between February and April, or as soon as the soil is sufficiently dry and warm in your area

  • Heat-treated sets (which have had their flowering potential suppressed, so are bolt resistant) should not be planted before late March or April

  • When selecting untreated sets, choose smaller bulbs over large ones, as smaller bulbs may be more resistant to bolting (they are less mature, so have less well developed flower buds)

  • Choose a container large enough to accomodate the growing blub. A half wine barrel or a pot that is at least 8 inches (20 cm) deep and wide

  • Soil should be loose, rich and well drained. In a container, any good potting soil will be just fine

  • Plant in full sun

  • When planting sets, push them in just under the soil surface so the point of the bulb is still visible

  • Space the sets about 4-5 inches (10-13 cm) apart. You can put them closer if you are going to harvest green onions

  • Water regularly, and keep evenly moist but not soggy; you don't want to rot them

  • Feed plants regularly, especially early in the season; the larger and healthier the plant, the bigger the bulb will get. Using a hydrolized fish fertilizer always works great

  • When most of the tops have begun to yellow and fall over, dig up the bulbs and let them cure and dry on top of the ground for several days or in a warm dry area out of the sun if you are worried they might get sunburned

  • When the tops and necks are completely dry, pull off the tops, brush the soil off the bulbs and store them in a dark, cool, airy place
That should get you started. I know you'll do great, enjoy your onions!

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Planting Depth

As a general rule, most bulbs are planted at a depth that is equal to 3 times their diameter at their widest point.

Tulips like to be planted about 6 inches (15.2 cm) deep and 4-6 inches (10.2-15.2 cm) apart.

Always plant bulbs as soon as possible after purchase to prevent them from drying out.

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