What to Watch for After a Cool, Wet Spring

by | Jun 4, 2024

Normally, when we edge our way from spring to summer, the weather gets a little warmer, a little drier, and out come the shorts and T-shirts. Well, this year was a little off normal!

The many days of cool, wet weather that we have had are bound to cause a few problems in our gardens. Some issues may be readily apparent, while others may not show themselves for a little while yet. With a bit of careful attention to your plants now, many will bounce back without many issues. In the meantime, nip these problems in the bud to prevent more severe problems later in the season


Slugs and snails may start to make many gardeners feel defeated, but don’t give up. There are coarse materials that can be used to create a barrier around your plants. Lava rock and coarse bark mulch are surfaces that slugs tend to avoid because it takes too much of their slime to propel them through it. Dry eggshells can be helpful, but regular rain can reduce their effectiveness. Centipedes are your friend – they are a natural predator for slugs, so if you see them in your garden, let them be!

Tomato Plants Turning Purple:

This is to do with the cooler temperatures we’ve had. Once warmer days return they should start to perk up, but you can help them out by giving them a bit of 14-14-14 fertilizer. It will help feed them through the summer too!

Yellowing Foliage:

Lack of nutrients generally cause yellowing foliage, and excess rain/irrigation can leach essential nutrients out of the soil. Feed your plants with a liquid feed and top dress with a slow-release fertilizer. A 10-15-19 formula is a great all-around choice for vegetables, perennials and flowering shrubs, while 14-14-14 is ideal for containers, hanging baskets and rhubarb. You should start to see them green up in about 8-10 days.


Many plants are susceptible to developing mildew when we’ve had a spring like this. In periods of cool, wet weather, moisture sits on foliage instead of having sunlight/warmth or sufficient airflow to help it dissipate. Mildew comes in a few forms, but you’ll likely recognize it as grey ‘fuzzy’ spots on leaves. Unfortunately, sage and squash get mildew quite readily. To treat, remove the affected foliage and put it in the garbage (the new growth will come out clean) and give your plant a spritz of Safers’ Defender, which is a good general fungicide. Be sure to watch for those grey spots throughout the summer to catch future mildew issues early. To help prevent mildews and other fungal infections:

Try to position plants where they’ll receive less overhead water (if you can)

When you water, be sure to water early in the morning at the soil level and not on the foliage

As appropriate, selectively prune plants to improve airflow.

Roses can be preventively sprayed with garden sulphur or a mix of 8 mL baking soda to 1 litre of water to help prevent Black Spot.

Pin-holes in Cherry and Plum Foliage: 

Cool, wet weather can cause ‘Shot-hole fungus’ in cherry and plum trees, which looks like something has poked little holes throughout the leaf. Not much needs to be done to help your tree; new foliage will grow-in cleanly when summer weather prevails.

‘Wilting’ Plants in Containers:  

Check the weight of the container before you water! Oddly enough, plants that are overwatered may look like they need a drink, but check the moisture level in the soil before you water them again. Containers that have been in the elements, perhaps with insufficient drainage in the pot, could be holding too much water, depriving the roots of oxygen. To fix, pull the container under cover and let it dry out lightly. Once the excess water is gone, feed with liquid 20-20-20 fertilizer and top-dress with slow-release 14-14-14. The excess water may have leached many nutrients out of the soil, so your plants will appreciate the boost.

Underperforming Plants:  

Some folks have been upset that their flowers and plants just aren’t doing much. The colder days and nights have caused many heat-loving summer plants to essentially stall out, but they should pick up steam when warmer days return. Until then, keep them sufficiently fed and watered (but not overwatered), pinch back finished blooms, pinch back stems on leggy plants (by about 1/3) to encourage them to fill out. Finally, be patient—summer doesn’t officially arrive until June 20, so we’ve got lots of time to enjoy our plants yet!