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All Past Questions and Answers Library | October 2008

This month's questions concern:

Apple Trees With No Fruit
Dividing Sedum
How to Extract and Start Seeds From Leopard Tree Seed Pods
Do Calla Lilies Make Good Cut Flowers
Disturbing Japanese Maple Roots
Collecting Seeds From Black-Eyed Susan 'Alba'
Planting Daffodils
Greenhouse - Use Glass or Polycarbonate
Organically Get Rid Of Imported Cabbageworm
About Mulch
Soda Ash On Soil
Should You Prune Digitalis

Please scroll down to read the answers.

Question #1:  Why Apple Trees Have No Fruit

Question:  I planted 2 apple trees last year along some that have been there for the past 40 years or so. Last year I had some nice fruit expecting that I would have a better crop this year but unfortunately I have none on the new trees and only a small amount on 1 of the older trees what might be the problem, do I remove the old ones and plant some new young trees?

 Derek Hetherton, Navan , Rep. of Ireland

Question:  I have a Hazen Apple tree and Honeycrisp Apple Tree. My Hazen only produces every other year, but in fact I was told it should bear fruit every year, is this true and what am I doing wrong? My Honeycrisp hasn't produced yet. It is 10 feet (3 m) tall. What's wrong with it? Thanks in advance.

 Patti Jagodzinski, Tomahawk, WI, USA


ANSWER:  Hi Derek and Patti! Since your questions are so similar, I am going to answer them together, I hope you don't mind!

There are several reasons why apple (Malus) trees fail to produce any fruit, and as I go over each one, they will answer all of your above questions.

1. Weather: When growing any type of crop, the weather always has a major influence. For apples, one critical time is when trees are in bloom, as poor weather conditions during bloom can have a devastating effect on apple production. Cold, wet, windy weather while many apples are in bloom reduces the activity of pollinating insects. So even if your trees were in full bloom, those flowers may not have been pollinated. Without pollination, there will be no fruit.

2. Age: New plantings will take some time before fruiting. The exact time will vary, but trees need to become established before they start flowering. Newly planted apple trees start to bear fruit anywhere from 2 to 5 years of age. Dwarf apple trees bear around 1 to 3 years old. So your newly planted trees, may not be old enough to start bearing fruit yet.

3. Apples Need Cross-Pollination: If an apple tree flowers every spring but never seems to produce much if any fruit, it could be there is no pollinating source. Most apple varieties require another apple variety or a crabapple for cross-pollination. So if only one tree exists, or an isolated group of the same variety, poor pollination means poor fruit production.

Plant at least two varieties of apple trees near one another. Golden Delicious, a self-fruitful type, is one of the few exceptions to this rule. Poor pollen-producing types, such as Gravenstein, Jonagold, Stayman, and Winesap, need to be planted with at least two other varieties to insure adequate pollination.

4. Pruning: Pruning on a regular basis is needed to keep trees productive. Neglected trees will decline in fruit production. For good fruit production, apple trees need branches that are horizontal in orientation. If all the branches on a tree are vertical in growth, fruit production is likely to be poor. Early spring is a good time for pruning apples.

Keep in mind however, that apples do produce fruit on old "spurs" so older wood is necessary for fruit production, but the trees need to be kept opened up and healthy with proper pruning.
See our story on How To Prune An Apple Tree

5. Health: Overall tree health is also very important. Water trees during dry periods. Avoid wounding the trunk or root system. Manage diseases and insect pests. Sound pest management helps keep trees healthy so they set fruit and also helps protect fruit once it has set.
See our stories on: Apple Scab and Codling Moth

So in closing, no, you don't have to get rid of your older trees, but you may have to prune them to get them producing again, and for the new trees, see that they are old enough and that you have pollinators nearby to help set fruit.

Good luck to both of you!

Question #2:  Dividing Sedum

Question:  Can I divide sedum? They are overgrown and was wondering if they could be divided and if so any advice. Thanks Rob.

 Rob Ingham, Lyme, CT, USA


ANSWER:  Hi Rob! I'm not sure which kind of sedum (Stonecrop) you have, there are dozens of them, but the good news is that all sedums are very easy to divide and propagate. Living in Connecticut, however, I would wait until early spring to dig them up and divide them.

Since most sedums are easy to propagate by stem cuttings, and even detached leaves will root and form new plants, I would carefully dig up the area, remove as much of the plant material as you want, or remove all of it, and then just plant back as much as you want. Succulents are not fussy about such things, just be careful not to crush the leaves or stems.

You'll be happy how easy it is to do and how well the plants will respond.

Question #3:  How to Extract and Start Seeds From Leopard Tree Seed Pods

Question:  We have a beautiful "Caesalpinia ferrea" (Leopard Tree) in our garden with loads of seed pods. Can anyone enlighten us on how to extract the seeds from the pods without damaging the seeds please? Thanks!

 Cheryl Lean, Gold Coast, Qld, Australia


ANSWER:  Hi Cheryl! When dealing with Leopard Tree (Caesalpinia ferrea) seeds, they are very similar to how you work with Acacia Seeds. The one big difference is the seed pod itself.

Acacia tree seed pods open by themselves, but with a leopard tree, the pods are quite tough. First when you gather the fallen pods, shake them. If they rattle, you have seeds inside, and the best way to get them out is by using a nut-cracker.

Now as for germination, some people say they are hard, other say they are easy, but my acacia seed that I germinated took some preparation first.

The seeds need to be "scarified" first by either nipping the hard outer coats with a nail clipper or you can abrade them with a bit of sandpaper or even rub a bit on brick or concrete to just weaken one side of the seeds. An easier way to "rough" up the seed coats is to poor hot water over them and soak overnight. Since I never had luck with the nail clippers or the sandpaper, because I took too much seed coat off, I use the hot water method.

Plant at about 1/4 inch (.6 cm) below the soil, water in, and place somewhere warm but not in hot sun, keep them moist so they don't dry out, and be patient.

Once they start growing, the seedlings do better if their roots are not disturbed so sow in small individual pots if you have them - like a 2 inch (5 cm) pot. Then you can plant your seedlings out when and where you want.

Have fun!

Question #4:  Do Calla Lilies Make Good Cut Flowers

Question:  Should I cut the flower heads from my Calla Lilies, and do they make good cut flowers?

 George Davies, Durham, UK


ANSWER:  Hi George! Calla Lily (Zantedeschia aethiopica) make terrific cut flowers and many brides use them in their bouquets.

It's up to you if you want to cut off the flowers or not, you don't have to, but it is a good idea to remove them once they have finished flowering. It keeps the plant looking better and healthier.

If you do want to treat the flowers as cut flowers here is what you do:

1. Calla lilies stay fresh as a cut flower for a long time if you treat them right. A calla lily cut flower will need its long stem so a rather high vase to begin with will be a perfect start.

2. Always cut fresh flowers with a sharp knife because scissors or a dull knife can crush the stem of a flower and reduce the amount of water that can reach the bloom.

3. When you cut the stem place the knife on an angle and slice through the stem. This creates a point at the end of the stem which maximizes the amount of water that can reach the flower.

4. Place the cut end of the flower stem immediately in water. I usually take my vase out to the garden with me so I can put the cut stems in water right away. Just fill the vase about a quarter of the way. You can fill it with water to the top when you go inside.

5. The water in the vase should be mixed with some flower food, and if you have none, add a little 7-UP or Sprite to the water because these drinks have citric acid which is one of the ingredients contained in a package of flower food.

6. Replace the water in the vase every other day, and also recut the base of the stem every now and then to keep it fresh, and only use a sharp knife to make the diagonal cut that is needed.

7. Try to handle the flowers as little as possible and keep them away from warm drafts such as from the TV or vent, because it could ruin the calla lilies in just a matter of hours.

Instead place them someplace out of full sun and in a cool area like on a table somewhere.

If you follow the above, calla lily flowers will last indoors for several weeks so it is well worth the small effort!

Question #5:  Disturbing Japanese Maple Roots

Question:  My son has a large spreading deciduous Acer palmatum bush it is now about 3 feet (1 m) high x 7 feet (2 m) across and over 30 years old. His problem is that the low wall which the Acer has spread over is unsafe and needs replacing. Are the roots of Acers deep, or are they surface roots that may get damaged? Could he prune it to be able to rebuild the wall and when would be the best time of the year? Hope you can help.

 Annette Holloway, Penkridge Stafford, UK


ANSWER:  Hi Annette! Wow, a thirty year old Japanese Maple (Acer palmatum), that is something you want to be careful with, isn't it?

Well, first of all, most Japanese Maple's root systems are shallow fibrous root systems, and they do not compete with other plants. It's what makes them such good patio and container plants.

The good news is that their fibrous root system quickly regenerates and spreads upon transplanting, or having been disturbed, so if your son is careful, very little damage to the bush will be done.

The best time to prune any deciduous tree or shrub is when it is fully dormant, so a good time is in winter or early spring before it breaks dormancy.

Sounds like your son is going to be super careful, no matter what, so the shrub will be doubly safe. Thanks for the question!

Question #6:  Collecting Seeds From Black-Eyed Susan 'Alba'

Question:  Can I collect seeds from my white black-eyed susan vine and if so where do I find them?

 Marianne Johnson, Kingston, Ontario, Canada


ANSWER:  Hi Marianne! Black-Eyed Susan Vine (Thunbergia alata) does come in white, some called 'Alba", 'Bright Eyes' and others.

The seeds are super hard to find, but it can be done. Thunbergia seeds form inside the leaves where the flower came out of it, and it has a sort of beak on it. They tend to fall off before they turn brown so gather them when they are green and let them dry in the house.

When you have them in the house, watch the areas where the flowers dried up. Soon a sort of a cone shaped pod will appear. When that opens a bit you will see the seed. It's quite small, about 1/4 the size of a pea.

Once you have the seed you will want to store it, and you can read our information about how to do that: How To Save Seeds

Good luck!

Question #7:  Planting Daffodils

Question:  Real beginners question here, but what way up do you plant a daffodil bulb?

 Sue Riley, London, England


ANSWER:  Hi Sue! Well we all start somewhere, and since bulbs are so expensive, it's definitely better to ask then to waste them. Plus, we have a lot of beginners here, and we all learn from each other, so never hesitate to ask!

Daffodil (Narcissus) bulbs are always planted with the pointed end upward and the broad base sitting on the soil.

The roots will form from the base of the bulb, as shown in the picture next to your question.

Good question!

Question #8:  Greenhouse - Use Glass or Polycarbonate

Question:  I am intending to build a greenhouse, 2.4 mtrs (8 feet) x 3.6 mtrs. (12 feet) Hobby use only. What are the relative merits, both pros and cons, of using either glass or polycarbonate? Also, what is the best method of constructing the base for it to stand on? I have seen greenhouses built on dwarf walls, which are built on concrete footings, and also ones built on top of timber bearers which are secured to the ground with long steel pegs. The second method seems relatively insecure, given that I live in a fairly windy area, 2 km (miles) from the ocean. All advice will be gratefully received.

 Clive Fletcher, Canterbury, New Zealand


ANSWER:  Hi Clive! First I have to tell you, I'm not a contractor, but my father is. He is a licensed contractor and architect so I will give you his information about the construction, and my information about the glass - OK?

As far as the construction of the greenhouse, because of your windy area, you are better off with the concrete wall footings. You should put the footings 12 inches (30.5 cm) wide by 18 inches (45.7 cm) deep. For tie downs to the concrete, use 2 x 4 plates with 1/2 inch (1.3 cm) diameter x 6 to 12 inch (15.2 to 30.5 cm) long anchor bolts, 4 feet (1.22 m) on center, and 6 inches (15.2 cm) from each corner. Use Number 4 rebar 6 inches (15.2 cm) from the top and 3 inches (7.6 cm) from the bottom with the bars wrapping each corner 6 to 12 inches (15.2 to 30.5 cm).

Tie down the frame of the greenhouse to the plate with appropriate Simpson tie downs. Simpson catalogs are available internationally at lumber yards. If your lumber yard does not have one, then they should be able to tell you which tie downs will be correct for your construction and wind factors.

I know that doesn't go over all the construction details you will need, but it will give you some solid information to start with and go from there, and it throws out the idea of using the timber bearers.

Now on to your glass vs. polycarbonate part of the question.

Overall most people prefer to go with glass, I know I do.

Polycarbonate can warp, drop out of the frames, and the panels can get sucked out by the wind, but it is lighter, safer, and less likely to be destroyed if it is attacked by vandals or hail stones than glass. My question to you is, do you have a vandal or hail stone problem? If you don't - use glass.

Glass has its advantages for better light transmission and heat retention, is more secure against the wind, and it's cheap to replace.

The bottom line is however, what is going to work for you. If the greenhouse is going to be in your yard, and vandals aren't likely, then I would go for glass, especially if its a wind exposed site, which it is. To me there's something about glass that polycarb doesn't deliver, but that's my opinion.

Hope this helped!

Question #9:  Organically Get Rid Of Imported Cabbageworm

Question:  Is there an organic method to keep the white butterflies from laying eggs on the broccoli, cabbage, or cauliflower?

 Tim, Reiles Acres, ND, USA


ANSWER:  Hi Tim! In a word yes! What you're probably talking about is Imported Cabbageworm. It goes after all kinds of crops. Here is the article we did on that a few months ago: Imported Cabbageworm

Thanks for the question!

Question #10:  About Mulch

Question:  I live in SE Lower Michigan and need to mulch for winter. How much should I use per plant and what is the proper technique? I live in a townhouse on an end unit and the wind is one of my gardening problems.

 Linda Melnik, Saline, MI, USA


ANSWER:  Hi Linda! This is a great question, because mulch is so important, but can sometimes be complicated.

That's why a few months ago, I did a "Complete Guide to Mulch." It covers everything you've ever wanted to know about mulch, it's free, and you're going to love it!

Here is the link: The Wonders of Mulch - A Complete Guide on How To Use Mulch

Enjoy mulching!

Question #11:  Soda Ash On Soil

Question:  I live in Casper, Wyoming. Here soda ash can be found on the ground surface in many places. At night it looks like snow in your headlights. Sooo, it's on the wind going everywhere I would assume. Does this high alkaline pose a problem with growing popular garden veggies?

 Joseph A Donais, Mills, WY, USA


ANSWER:  Hi Joseph! You bet it does. Interestingly enough, Wyoming produces more than 90 percent of the nation's soda ash (Sodium carbonate). So you have a lot of it there.

Most fruits and vegetables like a pH range of 6.0 to 7.5. In your case, with it being so prevalent, I would use raised beds and I would line the bottom of the raised bed with landscape fabric to keep any of the soda ash from migrating upwards into the raised bed.

Thanks for the interesting question.

Question #12:  Should You Prune Digitalis

Question:  Should you prune Digitalis if so "how do you do it" mine has leaves galore but only one flower stem.

 Rachael McCann,Glasgow, Scotland


ANSWER:  Hi Rachael! Well, I've grown Foxglove (Digitalis Purpurea) for years, and other then to remove the spent flowers, or to remove the plant after it has died back, I have never pruned it.

Some people will cut back the main flower stem after it has flowered in order to try and encourage a second bloom, but most people will leave the flower stems on so the plant will re-seed itself, which it does abundantly.

Pruning the leaves back won't encourage more flowering, but perhaps you can check your growing conditions, and, your plant might just be flowering late this year.

As for growing conditions, digitalis like partial to full shade, moist, well-drained soil that is slightly acid. If have fertilized your plants, check to see what the ratio is. Use either a balanced fertilizer like a 10-10-10, or one that is higher in phosphorus to encourage flowering like a 3-15-2.

Lastly, if the weather in your area has been as odd as it has been around the globe, your plants may just flower late this year and have nothing to do with you. This year, many people have reported their foxglove not flowering until late September, early October.

So review what you are doing, and hang in there!

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If you can, it is always best to water early in the morning. This allows the plant's leaves and flowers to dry off as the day warms up.

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