Gardening tips in May: what you need to know

It is shaping up to be a soggy Victoria Day weekend in Calgary and southern Alberta but that likely won't stop a legion of hopeful green thumbs from descending on garden centres.
May long weekend is often thought of as the beginning of gardening season, but gardening expert Kath Smyth warns it's still too cold out for many plants, especially annuals, to survive outside. (Courtesy Kath Smyth)

It is shaping up to be a soggy Victoria Day weekend in Calgary and southern Alberta but that likely won't stop a legion of hopeful green thumbs from descending on garden centres. 

The May long weekend is often seen as the start of the growing season so we asked horticulturalist Kath Smyth for some gardening advice at this time of year.

Kath Smyth is a horticulturist with the Calgary Horticultural Society. (Kath Smyth)

Q.  What can you plant in your garden or pots right now?

I think the long weekend is a little early this year. That being said, there is much a person can do in the garden right now. Perennials (plants that come back every year) are acclimatized to our cooler temperatures. Many are starting to show. If you are still planning your garden, you can put your new perennials in containers. Try grouping different combinations (sun or shade) together. That way, you can see how they look before they go in the ground.

As for annuals, I think it's still too early to plant. It's just too cool at night for many of them.

There are some cold-hardy annuals that are safe to put in your garden or pots right now. Annuals such as pansies, violas, primulas, and snapdragons would add some much needed colour this weekend.

Visit the garden centres to see what is new this growing season. The staff will be more than ready for a planning session with you.

Q. What about shrubs?

Deciduous shrubs can be planted now (the ones that lose their leaves in the fall) as can coniferous (junipers, pines). I would not try to plant a tree right now because it would be hard to dig the larger hole required in the heavy, wet soil.

Another thing you could do is pull up dandelions and thistles while the soil is wet. You stand a good chance of getting the taproot out whole. In dry soil, it invariably snaps off and then re-grows. Act now before the flowers set seed. 

And stir your compost bin! This is a great time to combine the wet and dry in your bin.

Q.  What vegetable seeds can be planted at this time?

It is time to sow peas, lettuce, spinach and chard. Sweet peas love cool soil to start with so they will do well now. Do not bury seeds too deeply. The smaller the seed, the less soil needs to cover it. Read the instructions on the seed packet. Do not forget to label the rows. I use plastic knifes and write on the blade part. There are also transplants available now for cabbages, broccoli and kale that can be planted now.

Q.  How can gardeners protect their new plants from heavy rain?

I have been known to use golf umbrellas to keep heavy rain from damaging my new plantings. I also will place cloches (transparent plant covers) over top to protect them. 

One important tip: do not put saucers under your newly-planted pots. Turn the saucer upside down and stand the pot on them. That way, the soil does not become too saturated.

Q.  What should you be doing now to prepare your lawn?

Don't rake your grass now! Do it when it's dry. Remove dead leaves and debris. We have seen a lot of snow mould this year. Be very careful when removing the mould. Wear a dust mask and gloves to take it off the lawn. A corn broom works well — but make sure you do not bring the broom into the house to use until you clean it off.

Q.  Can you give us one good tip for a novice gardener in Calgary?

Beginner gardeners are often too ambitious. For instance, they think that they can grow an eggplant. To do so successfully takes a lot of husbandry and babysitting. But, for a first-time gardener, there is no reason why they can’t grow a tomato plant or a pepper plant, especially when we have our long, hot summers with our wide open days.

Another major problem in Calgary is that we have to pay attention to the fact that our nighttime temperatures drop rapidly. You have to be ready to do a little bit of “cold work”, meaning that you have to make sure your plants are reasonably sheltered and protected. But really, the best thing to do is just stick to the basics when you first start out.

Kath Smyth teaches gardening through the Calgary Horticultural Society. For more information about classes, go to