Fall garden tips: Don't wrap cedars, how to harvest slug eggs and more

While Monday seemed a perfect fall day, warmer temperatures are predicted to rebound later this week, leaving time to clean up the garden.

Rob Sproule, co-owner of Salisbury Greenhouse in Sherwood Park, joined Edmonton AM to take questions from listeners Monday as part of a special Labour Day gardening call-in.

Here are some of the best questions and responses.

How should I care for cedars in the winter? To wrap, or not to wrap?

Many gardeners associate cedars with the West Coast and the warmer temperatures and humidity that comes with it, Sproule said. So, it's common to see cedars wrapped with burlap to add a little extra warmth during the Edmonton winter.

However, "wrapping them tight, like a cigar" can do more harm than good, as it cuts off air flow to the cedar.

"Wrapping is absolutely not necessary," he said. "It's just more work, and who needs that?" 

Slugs! What can I do now to prevent slugs next season?

By now, slugs have probably laid their eggs, under or near the leaves of the plants they have been feeding on all summer. This makes it a good idea to clear away leaves in any slug-prone areas. Aim to remove leaves and debris in a two-foot radius, around problem areas, Sproule said.

"If you pull up some leaves, you might see some slug eggs, they look like caviar," he said. (Do not spread on mini toast rounds.)

Instead, toss the leaves, and you could have fewer slug babies in the spring. For slugs in garden pots, clear leaf litter, move the pot to a new location, in case the slugs were under it, and cover with mulch for the winter.

Is now the right time to plant bulbs?

Labour Day weekend is usually the earliest time you should plant bulbs like tulips, crocuses and even garlic in the Edmonton area, Sproule said.

"I'd probably wait a couple weeks yet," he said. "You want enough time for the roots to get established in the ground, but not enough time for the plant to actively start growing." 

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A little investment in bulbs now can provide a much-needed boost of colour when the snow melts in early May. 

Should I rake all the leaves off the lawn?

Take heart, even Sproule doesn't have a leaf-free lawn. For a small amount of leaf cover, a lawn mower should do the trick.

"Mulch it right into your lawn," Sproule said. "The nitrogen in the leaves will actually break down and give a bit of a boost in the spring."

Of course, a thick blanket of leaves will need to be raked, but it doesn't have to be perfect.

And, here's a gardening tip from Edmonton AM host Mark Connolly: save some of the leaves from raking to add, slowly, to your compost into the fall and winter.

When can I transplant rhubarb to a new area?

Now, or even a couple weeks from now, is the time for "garden surgery," such as transplanting and dividing, Sproule said.

"The plant isn't actively growing anymore, so when you transplant it, it will be less of a shock to its system," he said.

For all dividing and transplanting jobs, it's a good idea to dig up as many of the roots as possible and do it as carefully as you can, without ripping the roots.

When moving the plant to its new location, dig a larger hole than you think you need, add some good soil and water the transplant well. This will anchor the plant for the winter and give it the best chance of growing in the spring.

Should I prune my trees now?

In most cases, the answer is no.

"If you prune them now, giving a prune is like an espresso shot, it wakes them right up," Sproule said.

Pruning now might encourage a lot of new growth in the warm days ahead, which will be killed off by the first frost.

For fruit trees, the buds are already set for next year, so don't chop now, or you could have fewer blooms, and fruit, next spring and summer.

The exception is elm trees, which you can only prune from October to March, when the sap isn't running. Do not prune elm trees during the summer, said Sproule.

What should I do with tomatoes still on the vine?

Alas, the time for vine-ripened tomatoes is pretty much over in Edmonton. Once nighttime temperatures get below 10 C consistently, they're not really ripening anymore, Sproule said. 

"Any mid-sized tomatoes and above, take those green tomatoes off," he said.

Put them in the basement, or in another dark place in a single layer, and they should ripen into the fall.

Are there any flower seeds I can plant right now?

You can plant some perennial seeds now or even give some of your existing flowers a little hand. Poppy seeds, for example, can be harvested and hand-spread right about now.

"Wait until they dry. They have to be really dry," Sproule said. "And then just sprinkle them where you want. Some of them will come up, some may not, but this is the natural time they would be spreading their seeds."

Is this a good time to mix compost into the garden?

Fall is a great time to mix in compost, so supplement that soil now, Sproule said.

"It's kind of like making your bed in the morning, so you come back in the evening and it's already made and you feel better."

In the spring, the ground will be frozen and compost can be difficult to fork into the soil. So, do a light dusting now to set the stage for stellar summer veggie crops in 2021, especially high feeders that need more nitrogen in the soil, like corn, peppers and beets.