I’m looking for advice to plant my N/W facing yard (in midtown Toronto)with wildflower seeding.
For many years I had self seeding corn flowers, field poppies and calendulas but they’ve failed for the past two years
1. I’m planning to add a layer of good quality garden soil (Sta-Green) is this a good idea?
2.Should I seed now or early spring ?
3. Should I also add bark mulch?
4. Also please advise a good source of seeds?


Thank you for your question. The failure of your wildflowers over the last few years is an important point to consider. Have conditions in your garden changed recently? Has the amount of sunlight on that area of the garden by altered by a neighbours tree- which has grown larger,  or a new building gone up nearby? Could it be lack of water? Did you notice discoloured or wilted leaves on previous years wildflower crop or did the plants fail to emerge in the spring?

It is possible that the cause of this change in growing habits will affect your new garden, so if you have an idea about the cause of your plants failure to thrive, you can avoid the same situation with your new plantings. If it is a case of more shade, then you will need to look for perennials that will thrive in shaded conditions. Calendula and field poppies both do quite well in part shade, so I would have expected them to have grown but with less flowers or smaller plants.

If shade isn’t the issue, soil conditions could be. Look at your soil type and texture. If you squeeze a handful of damp soil, does it form a doughy ball or fall apart? In both cases- of clay or sandy soils, you can improve your soil texture by adding organic material- like compost. Your plants need a freely draining soil that has enough organic material to hold some moisture. Amending your flower garden bed every year, or two, with a few inches of compost will improve your soil texture, allowing more water and nutrients to be taken up by your plants.

Sta- Green garden soil contains added nutrients and has been designed to hold moisture during the seeds germination and early growing period. This product is most effective when used for spring garden bed preparation as the levels of available nutrients will deplete over time. The higher the rainfall, the quicker the nutrients will be washed away. If you have stocked up with Sta- Green already, plan to sew your seeds in early spring (late March or early April).

Ontario wildflower seeds have to go through a period of cold weather before they can germinate, called stratification. It is important to sow the seed while the weather is cold. It is hard to predict what the weather in Toronto will be like next spring, so you can prepare the bed this fall, then add an inch of Sta-Green in the spring before casting you seed.

If you haven’t stocked up on garden soil, you can use the following method for preparing the bed for fall seeding:  Weed the bed to remove competition for the new seedlings when they emerge next spring. Rake the area with a stiff rake to till the top few inches of soil. If you have determined that your soil is lacking organic matter, add an inch or two of well rotted or garden store bagged compost.

Don’t be tempted to add more than two inches of compost. Too much compost can cause poor outcomes as your flowers may grow too quickly and become tall and straggly and fall over. If nutrient levels are too high it can block the nutrient uptake of the emerging seedlings, resulting in a poor crop.

To avoid nutrient overload, blend the compost top dressing with the existing garden soil. It doesn’t have to be deeply dug over- just the top few inches. A stiff rake or garden hoe can be used to mix the compost into the soil. This process reduces soil compaction and improves soil drainage- essential for healthy seedlings. The compost will improve your soil texture and allow for better oxygenation and moisture retention.

Cast your wildflower seeds over the prepared bed. This can be done from mid September until mid November. Over the winter months, rain and snow will wash your seeds into the soil and the cold will stratify them. If you have issues with birds or small mammals in your area, you can gently rake over the seed mixture. This will conceal some of the seeds, then you can sprinkle about half an inch of compost- that has been blended with the same amount of your existing garden soil, to cover any exposed seeds. Water very gently with a sprinkler so that the soil is evenly moist, but not washed away.

Its important to note that I have discussed Ontario wildflower seed planting- ie. perennials that are native to Ontario. These are seeds grow best in our climate and soils. If you choose a mixture of seed that contains non native flowers, check the growing recommendations. Wildflower mixes that are native to the United States, for example, may have come from warmer climates, so may not require cold stratification. Also, the emerging seedlings may not be frost hardy -so would need to be sown in late April to avoid frost damage.

Mulch is not necessary for seeded beds with good soil texture. I am not able to endorse any specific seed companies, but if you go to a reputable garden centre they will be able to show you what is available, and appropriate to your garden.


Sept 20, 2022