Got a Gardening Question?

Meet Dr Bill

Dr. Bill Carlile is the Chief Horticultural Scientist with Bord na Móna since 2006. He has 45 years experience in the world of horticulture both professionally and as a hobby.

Being the author of numerous scientific papers, having 25 years experience in compost research and having written two books on plant protection Dr. Bill would be only too happy to answer any of your horticultural questions.

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Resolved questions and answers will be published on this page each week.

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Q: Tomato hanging devices

I notice in many supermarkets there are products on the shelves to grow your own tomatoes from hanging devices. Are these suitabale for my apartment balcony, which only gets direct sunlight for the first early hours of the day and is drenched in shade from about 10 am onwards?


Now, you have a difficult situation here: trying to grow tomatoes in a hanging basket with sun only in the morning. We think you might be able to grow in these conditions but need a good summer to help. You'll need a hanging basket with a good volume of compost- 10 litres or more, to avoid drying out especially when the plants are large. Use of Growise Multipurpose or Tub and Basket will help since it has a natural moisture retaining agent. We'd recommend using the tomato varieties Tumbler or Balcony Red. Plant firmly into the hanging basket : water regularly and start of feed with a standard tomato fertiliser when the tomatoes begin to form. Good luck: pray for a warm summer!


Q: Hibiscus

I got a potted Hibiscus in Woodies last week with impressive yellow blooms and numerous buds. I have it in a warm bright room. The original bloom fell off in full bloom. It appeared to go dormant for a day or two and then another spectacular bloom appeared, which also dropped off in the full of it's bloom. Temperature and watering are steady as per instruction. Any idea what's happening?


You bought a plant that whilst beautiful, needs care especially in an indoor environment. It's been used to a moist glasshouse-type environment & shifting to a drier (home) situation can trigger bud and flower drop: it's very common. Hibiscus like steady moist warm environments: keep the soil/compost moist but not overwet ie water little & often. You can tell if the compost is moist enough by lightly pressing a bit of kitchen towel on to the pot surface: it should come away damp: if not, water. You could also mist the plant with a fine spray of water from an atomiser (an old perfume dispenser is ideal). Try to avoid high/low temperature fluctuations.

In rare cases bud & flower drop may be caused by thrip insects: look carefully at the flowers: but if you just bought it, these should not be present.

Basically treat it like a loved one...


Q: Decking area

I am currently building a decking / patio area around my conservatory and was wondering if I should plant a hedge around it to act as a wind break and for privacy. The hedge will be grown on raised beds approx 400mm wide and 400mm deep. Would this be sufficient for a hedge. I am looking to grow the hedge to 5ft tall and as narrow as possible. I am concerned that a hedge will attract a lot of insects / birds etc? What would you recommend for a suitable hedge given the above information.


Thanks for this and the clear sketch enclosed. We feel that the space allocated for your hedge is limited, especially if you want to grow up to 1.8 metres ( 5 foot) and have it as 'narrow as possible'. You could use beech or hornbeam but both are slow growing: Cupressus of which I am not a fan would spread laterally.

Can we suggest an alternative?: Why not erect a trellis and grow an upright drought resistant species through it? One such would be Cotoneaster lacteus, an upright form of cotoneaster which is commonly seen as a ground cover plant. This would weave itself into the trellis and its bright red berries would provide interest during the winter months. They are generally the last berries to be eaten by birds! The Cotoneaster would provide refuges for insect life too. You would need to keep the cotoneaster cut to stop it spreading laterally, but it is tolerant of drought, which might occur in the narrow beds of soil you propose. Plants should be set about 1m apart.


Q: Plant life after Winter

After the most difficult winter in decades me plants are not the best- Please recommend the best compost in your new range for me. My House plants are starved. My Patio plants are dead but will buy new ones and my Vegetables are ruined!


You're not the only one! Some of my container plants froze through & have thus died. In future with strong frosts, protection might be the answer: up against a south facing house wall, or fleeced in a cold frame or glasshouse.

However, looking forward; for your house plants I'd use our Growise Multipurpose compost: it's got plenty of nutrients including trace elements from the added green compost. If your plants are pot-bound move them to a larger pot and pot up with Multipurpose. You could use the Multipurpose for your container plants too, but Growise Tub and Basket is specially formulated for containers. It's also rich in plant nutrients. For vegetables, you could use one of our range of planters: they have more compost than a conventional growing bag & thus need less watering & feeding. If you intend to grow in the garden, our Organic Living Peat-free compost is a useful addition to raised beds: it has slow release nitrogen and trace elements from the green compost.


Q: Cordyline Tree

We have a Cordyline Tree in our garden that has been severely damaged by the harsh Winter we had this year. Can it be saved or should we just cut our losses and cut it down?


Many cordylines, yuccas and canary island palms have suffered during the winter of 2009-2010. The extent of damage depends on the type you have & where it was grown. If it's been in a container & this has frozen through, then the plant, roots and all may be killed. If it is in the ground, its roots may have survived. If there is no growth showing at the moment, cut the foliage down to about a third & see if any leaves sprout by the end of May. If not, I fear it is probably dead. It may however, sprout away & recover when the weather warms up, although it may never gain its former appearance.

The green cordylines tend to be hardier than the variegated forms: if your plant is one of the latter & has died, you might want to replace it with a green type of Cordyline.


Q: Butternut squash

What do I need to do to grow butter nut squash. Could I use one of the growise packs and if so when do I transfer and what do I transfer? Do I transfer and what size pot do I put it into.


I assume you are growing the squash from seed: if so plant a couple of seeds in Growise Multipurpose compost in a 7.5 or 10cm pot and keep in a warm place; as soon as the plants have germinated remove one and keep the other in a warm well-lit place. Squashes do not like frost although I think the risk is just about over now.

You can grow the squashes like courgettes: once they get going they grow very quickly. After the roots begin to appear in the bottom of your pot, transplant into a Growise growing bag..just ONE plant per bag. If you need more, I'd recommend the Growise tomato planter where you can put one plant in either end of the planter. Keep in a warm well lit place; a cold frame or greenhouse preferably. If you intend to grow outdoors, try growing against (or even up) a south facing wall.

Even though Growise planters and growing bags have a good supply of nutrients, you'll need to feed the plants. You should feed as soon as the squash fruits begin to form. Use a tomato feed and once vigorously growing, feed twice a week at full strength. You will also need to water regularly; squashes take up a lot of water, especially in sunny weather. Remember these plants can travel...they can trail for up to 5 metres. Give them space.


Q: Window boxes

I live in a one bedroom flat in the city and therefore have no access to a garden or a balcony. I would love to have flowers and have a south facing window, are window boxes my best option? If so, could you tell me what flowers might be suitable for a small ledge?


You are quite right: window boxes would be the best option without a balcony. Make sure you have a sturdy box, about 15-20cm tall and obviously shorter in length than the window ledge. You'll need a tray under the box to retain any water straining.

I'd recommend Growise Multipurpose or Tub and Basket as the compost with its natural water retaining properties. I'd also recommend using plants that are fairly resistant to heat and drying out such as marigolds: especially dwarf French marigolds. These would be great on a south facing window. Buy a six pack from your local Woodies or other store, and space them about 6 inches (15cm) apart. Plant them firmly into the compost. They will give a lovely display for months if you remember to dead head them: take off the flowers once they have faded. Don't overwater; keep the compost moist: if you push a piece of kitchen towel into the compost with your finger, it should be slightly damp. After a month in the compost you'll need to feed: use a tomato feed at half strength once a week.

Finally one of the problems of growing on a window ledge is that the plants will lean towards the light. To get round this you can turn the whole tray round every two days, but a trick you might want to use is to put the plants in 4 or 5 inch (10-12 cm) pots and insert the pots into remaining compost in the window box. You can then turn each pot round every two days without the need to turn a whole (sometimes heavy) window box. Good luck!