Gardening Guru: What’s on your mind?

Published on August 30, 2014

When I meet acquaintances and strangers in public they often ask me gardening questions, and inevitably follow with an apology for bothering me. 

‘Bothering me’ is, for the most part, a form of flattery. Your questions tell me that you prefer my answers to, say, those found on the Internet or from the eccentric neighbour with the giant dahlias growing at their front door. If it were not for your queries and questions about the garden, I would be out of work. Ask on, dear friends. This is what I do.

Here is what you seem to have on your minds these days.


1. How do I control snails and slugs? They love hostas, tomatoes and most anything that stands still long enough for them to ooze up the stem and munch on the leaves. Snails and slugs are the same pest, only one is dressed in a shell like a turtle and the other prefers to travel naked. Technically they are gastropod mollusks and there are literally thousands of species alive today and more than 200 that are extinct. We know that there were many that once roamed the earth as they fossilized during one prehistoric era or another. Don’t expect the remaining bunch to dry up and go away any day soon.

Getting rid of slugs or snails is not always easy, especially as they thrive in the cool, damp weather that has been featured this summer. Hand picking is recommended if you can stomach the job and have nothing else to do. I prefer to dust the area around valuable plants, like my prized hosta, with food grade silicone dioxide or Crawling Insect Killer. This works like a charm when it is dry. The mollusk moves over the dry powder, which is like microscopic shards of glass, and tiny cuts are created along the critter’s underbelly. They dehydrate and die as a result. There are environmentally friendly slug baits on the market that are safe around pets and children. Thank goodness, as the old metaldehyde bait was extremely poisonous.



2. My perennials have finished blooming. What now?  Don’t fertilize them. Rather, cut back the finished bloom to the green foliage and wait. With luck and a long, warm autumn, you may get a second coming of blossoms.



3. I have brown beetles with iridescent green markings on their back devastating my roses. What are they and how do I control them? Introducing Japanese beetles. Twenty-five years ago or so we only read about these in American gardening magazines but, thanks to global warming, they have moved up with the opossums and are likely here to stay. You don’t kill Japanese beetles, you manage them. You can control them by using a sex lure. It is not labeled as such, but that is what it is. Look for a Japanese beetle trap at your local garden retailer. They are pheromone-based and work like a charm. Be sure to empty of dead beetles regularly.

A second control option is to place wide, open containers with water and a few drops of dish soap beneath your affected plants. Go out regularly and scrape off the beetles into soapy water. If you don’t want to touch them, and I don’t blame you, get a spray bottle filled with soapy water and spray directly onto them. They will fall off and you can squish them. Leaving the dead beetles there will keep others from moving in.

There aren’t any sure-fire ways of getting rid of these critters but keeping your lawn grub free and not watered during the droughts can reduce next year’s population.



4. How do I get rid of wasps? Interesting, with all of the talk about honeybees and pollinators, the garden-variety wasp continues to be demonized along with snakes and bats. Well, listen to this: wasps are very important to the ecosystem. Each spring the queen in the wasp nest begins laying eggs, which hatch into larvae and the worker-wasps go looking for pollen and nectar to feed them. As they forage, they provide a valuable service to the plant world: pollination. As the larvae feed on the ‘meals on wings’ delivered by the worker-wasps, they secrete a sweet sticky substance that fortifies the workers and keeps them going.

As the summer wears on, the queen takes a break from all of that egg laying and the lava mature into adult wasps without any of the sweet stuff to eat. This is when they go looking for naturally sweet stuff like rotting apples and your unfinished can of coke.

If wasps are being a nuisance, you might want to trap some of them in a wasp trap using natural fruit juice [(not the diet kind) and water.  here are many great wasp traps out there. I can’t recommend one over another as they all seem to work if you use them correctly and empty them regularly.

Faux-wasp nests have been all the rage in recent years and guess what: they work. Wasps are territorial and do not like to set up shop in the neighbourhood of other wasps. If they think that a wasp nest exists on, say, your patio they will go elsewhere to build theirs.



5. When should I bring my tropical plants indoors? This is a question that most people with hibiscus, dipladenia and the like do not ask until it is too late. The answer is: any time now.

If the goal is to produce great looking tropical plants indoors year round, then bringing them indoors in the next couple of weeks will minimize the negative impact of changing their temperature and light dramatically. Moving tropical plants indoors after a summer vacation out of doors is always stressful for them. The high light of summer and the warm daytime temperatures is what makes their ‘garden performance’ so superior to their performance indoors during the balance of the year.

When you do move them indoors, be sure to wipe large leafed plants down with a clean rag and insecticidal soap. Small-leafed tropical plants enjoy a shot of insecticidal soap right out of the bottle. Be sure to apply to the underside of the leaves where most insects harbour.

The leaves on my oak tree are turning yellow and the veins are still green? This is a common case of chlorosis, a lack of magnesium and iron in the soil. The answer is to add chelated iron to the roots each month in the form of a water-soluble powder. You may need to order this from your local garden retailer as not many carry it as stock item.  Follow the directions. Also add epsom salts [magnesium sulfate] to the root zone. Dissolve one ounce into a gallon of water and slowly pour it on the root zone of your oak.  Do this three times per season if the problem persists. And it well might as chlorosis is a symptom of heavy, nutrient poor soil.



6. When can I thicken an established lawn and start a new one from seed? Now is the best time of year to do this. Cool evening temperatures, regular rainfall and heavy morning dew all assist in the development of quality grass seed into a young, handsome lawn.

Note that the seed needs a medium into which to put down a root: I recommend two to three centimetres of lawn soil or triple mix. And quote me any time: fast germinating grass seed is not a sign of quality but the opposite. If it germinates in less than a week it will die fast too.



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Mark Cullen is Canada’s best-known gardening broadcaster and writer. He is the spokesperson for Home Hardware Lawn and Garden. Sign up for his free monthly newsletter at and watch him Wednesday mornings on Canada AM. His column, which focuses on our growing zone, appears in the Hants Journal every two weeks.