Your Gardening Questions Answered

Topics this month

Editorial

Hello there,
Only two and a bit months for horticultural students to enter the gardening writing competition. A link is on the right. Go on - do it!

We have some great articles for you this month.
Heard about roof gardens and want to know more? Well Melanie saw a magnificent one in California and tells us about it in this issue.
Helen tells us how to make use of Winter to improve our garden.
David has visited a garden he loves north east of London and Alex talks about what his loved Australian plants are doing in his Yokohama garden.
In our Australian plant section this issue we look at a plant that contributes to the wonderful West Australian wildflower display and our landscaping section deals with the difficult question of what to plant under trees.
This is a June / July issue but do check back in July because parts of it will be updated including Planting Guide, Activities and the garden questions.

All this is online for your reading pleasure in our latest edition of Global Garden.

Happy Gardening

John & the Global Garden Team

John Gee
Co-founder & Publisher
Global Garden
 

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Your Gardening Questions Answered

Stumped? Need some gardening advice? Send your garden question to us by clicking here  and filling out our question form.

Before you send a question:
 
Check the  recent back issues
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  Check the Garden Basics section.
  Moving plants? Try here.
  Problems with lemon trees? Try here.
  Yellowing gardenias? Try here.
Passionfruit? Try here


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Question Topics This Month

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transplanting 4 m tall pencil pines WA
identifying bush WA
avocados NSW
hydrophobic soil VIC
Pruning NSW
naked ladies not flowering NSW
harpullia tree QLD

rejuvenating grass trees VIC
Planting gum tree VIC
passionfruit QLD
growing mint NSW
g
rowing Cabbages QLD
root identification VIC
Japanese Cedar - California

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Topic and Question

Answer

transplanting 4 m tall pencil pines WA
I am wanting to transplant several 3-4 year old pencil pines - 4 metres in height. Is it possible? how ?


BACK TO TOPICS

Winter is a good time to transplant almost anything. You need to make sure that the ground is moist before you dig up the root ball taking as much soil with it as possible. Wrap the root ball in hessian so the soil doesn’t all slip away. Have the hole where it is to go already dug. Place the tree in the new hole at the same level as the old spot and water in well with a seaweed solution. Don’t fertilise until the tree shows signs of new growth.

identifying bush WA
Love to know if you have a flowering bush index to identify mine as no nursery can help me?

BACK TO TOPICS

We don’t have a flowering bush index sorry. If you are having no luck getting plants identified at your local nursery, then try your nearest botanic garden. Staff or Friends groups are often very helpful and very knowledgeable about the plants that do well in their area. The major botanic gardens in each capital city also have plant identification services (usually for a fee).

avocados NSW
My son lives 20 mins inland from Queensland sunshine coast. He grows lovely big avocados but they never ripen - either on tree or in brown paper bag. They just stay unripe and eventually rot. What is wrong?

BACK TO TOPICS

I would contact your department of agriculture for advice or have a look at their avocado information website http://www2.dpi.qld.gov.au/thematiclists/1078.html
 

hydrophobic soil VIC
I have very hydrophobic (water resisting)soil in one of my garden beds. Today I dug up an area ready to put in a plant (about 500mm x 500mm) and I gradually added a whole bucket of diluted soil wetter and the water barely seeped in. I also added a large shovel full of compost. Am I doing the right thing for the long term improvement of this soil? The garden bed is about 10m x 2m. How do you recommend I treat the whole bed?

BACK TO TOPICS

My soil is also very hydrophobic. This is how I plant my plants. I dig a big hole (bigger than the pot) throw a good pinch of granular soil wetter into the hole and then fill the hole with water making sure the jet of water is strong enough to make the granular soil wetter foam up. I come back a couple of hours later when the water has soaked in and place a tsp of water crystals in the bottom of the hole before planting and backfilling with some homemade compost mixed in with the soil. I build a little moat around the plant to hold the water and I also sprinkle a tsp of granular soil wetter around the top of the soil before giving it a good soak. You could treat your bed by spreading granular soil wetter at the recommended rate, watering it in then spreading some compost over the top and digging it in but that is a lot of work!

Pruning NSW
Do you need to prune coleus and may bushes. If so when?

BACK TO TOPICS

Coleus benefit from constant pinching out of their tips to encourage bushiness and to remove flower stalks because it’s the leaves you want to enjoy. Use these tips to make cuttings for more plants in spring in case the mature plants don’t make it through the winter. May bushes (Spiraea sp.) can be pruned after flowering.
 

naked ladies not flowering NSW
I have bulbs of naked ladies (Amaryllis belladonna) which should have flowered months ago before the leaves come but did not. They are now forming their leaves. This is at least the second year in a row in which they have not flowered but have formed leaves. Any ideas to get flowers next year? Do I need to dig up and replant each year? More water? Less water? They do face the westerly sun.

BACK TO TOPICS

Belladonnas are usually foolproof and very tough bulbs (witness their flowering after the bushfires). Perhaps you are taking too much care of them! They do like to be planted in a hot dry spot with their necks poking out of the ground. Perhaps you gave them a fertiliser high in nitrogen which has encouraged leaves but not flowers. Possibly too much water is the problem at your particular location. Check drainage and planting depth. You do not need to dig them up every year.

harpullia tree QLD
I have planted an avenue of harpullia trees in my garden (3 down each side of garden). One of them seems to have an abundance of red seeds but the rest have none so it looks a bit odd. Any suggestions as to how to reduce the seeds on the tree?

BACK TO TOPICS

You don’t say which species of harpullia you have planted but it sounds like Harpullia pendula the Australian tulipwood. This tree is known for its attractive red/orange seed cases that contain black seeds. Only one tree bearing could just be a quirk of nature and maybe next year all of them will produce seeds at the one time. There is nothing you can do to reduce the production of seeds, short of cutting off the flowers when they appear.

rejuvenating grass trees VIC
What can I do to rejuvenate a grass tree which has been happy for 5 years but in the past month the foliage has browned and appears dead? I have heard about treating with a mixture of brown sugar. Would this or seaweed extract help? Would it help to remove the dead foliage? Help! I love that tree and would hate to have lost it. Thanks so much
 

BACK TO TOPICS

It could be a lack of water but it could also be a root rotting fungus. I would try watering the plant with a seaweed solution which acts like a general plant tonic. You could also try watering it with a fungicide/anti-rot treatment (there are a few on the market – ask at your local nursery). I have to say that if all the foliage has gone brown, it does not bode well for the future of the plant. I’m sorry.
 

Planting gum tree VIC
We had our hearts set on planting a large gum tree in our new backyard as the feature tree, but as the house also has a pool we have been warned that a gum tree is not a good idea due to tree litter and particularly staining of pool wall by gum leaves. We'd like a second opinion please before we give this idea away. Thank you!
 

BACK TO TOPICS

I do agree with what you have been told, particularly about the staining. However any tree will drop leaves; I would be more concerned about its roots. Also gum trees do not offer any real shade.

passionfruit QLD
I have 2 grafted black passionfruit growing about 1m apart they look very strong & have intertwined very well & now covering about 10m of fence line at times they grow lots of flowers but no fruit the flowers usually shrivel up & die. Any ideas?

BACK TO TOPICS

Getting passionfruit to set fruit successfully is a tricky task. Some references say plenty of food, well-drained soil and lots of water is all you need. Irregular watering (or too much water) may have stressed the plant and caused it to drop its flowers. Fertilising a plant without watering it is enough to stress a plant. If the flower is not fertilised it will fall off – perhaps plant more flowering plants around to attract the bees and ensure better pollination in the future.
Here are two helpful websites:
http://www2.dpi.qld.gov.au/horticulture/5524.html
http://www2b.abc.net.au/gardening/newposts/000/topic236901.shtm

growing mint NSW
I have grown several lush crops of common mint in a pot. Each time after reaching a luxurious stage (and looking and smelling great) it develops a leaf curl which browns then kills the leaves and it then dies back to ugly dead sticks. It then (if ignored) rejuvenates and the whole process begins again. I have twice removed all the roots and stems and replaced the mint with cuttings from other sources but to no avail. How can something as vigorous and easy to grow as mint be so hard?
 

BACK TO TOPICS

If mint is allowed to flower the leaves will stop growing and then they might be susceptible to rust and bugs that eat the leaves so this might be the problem. Letting the plant dry out even once might stimulate it to flower. I grow my mint in a pot sitting in a saucer of water in morning sun only and harvest as many of the leaves in spring as I can and freeze them. Then I cut the plant back hard and repot it in summer and it reshoots and goes through to autumn when I cut it back again and repot to take it through to spring.

Growing Cabbages QLD
I have an old cabbage that has sprouted smaller cabbages from the base. Can I cut them out (leaving some of the old cabbage) and plant them? Will they grow into a cabbage worth eating?

BACK TO TOPICS

You can leave them where they are and they might grow big enough to eat. Sorry but you can’t cut them off, replant and then hope they’ll grow roots – it won’t work.
 

 

root identification VIC
Can you provide me someone who is able to identify roots of trees in Melbourne. Many thanks.

BACK TO TOPICS

A qualified arborist would be able to make an educated guess as to root identification during an onsite inspection. Positive identification requires analysis of the root under a microscope. Dr Jugo Ilic runs a wood and root identification service that costs approximately $250, takes a couple of days and the roots have to be pencil thickness. He also needs a list of trees (no matter how small) in a 10-15m radius. He can be contacted on 0412786482 or knowyourwood@bigpond.com Also the CSIRO publish a pamphlet called “Plant Roots in Drains” available at a small cost at http://www.publish.csiro.au/pid/2992.htm  if this is what your problem is about.
Other tree root specialists:
Dr Neil Hallam www.Flindersconsulting.com.au
 

Japanese Cedar - California
After this winter my Japanese cedar has gone brown from the inside out with green on the ends of the branches and at the top. How can I help it.

BACK TO TOPICS

Both cryptomeria and the true cedars (Cedrus sp.) can suffer from a type of dieback which is present in California. It may also be some sort of rust (fungus) – I would be getting a local arborist to come and take a look or ring your local botanic gardens for advice. If you have had a particularly dry winter, then the tree might be suffering from a lack of water – check the soil. You might need to treat the soil with a granular soil wetter and give the tree a very thorough watering before summer’s heat sets in. And don’t forget to mulch the tree as this will help lock in moisture and keep the roots cool.

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