The days are getting shorter and with less than a month left until fall officially starts, it means it is too late to plant some things people have asked me about this week, including beans, peas, Brussels sprouts. We are out of time to grow chard, kale, spinach, or Chinese cabbage from seed before winter, but if you can find seedlings right now, they should succeed in gardens that are still getting a full day of sun. With the sun lower in the sky these days, gardens in forested areas or urban neighbourhoods where buildings and city trees cast shade, now have fewer hours of direct sun than gardens in wide open spaces with sun from sunrise to sunset. In gardens with more shade, planting earlier helps to compensate for the fewer sun hours this time of year.

There is still time to sow the small leafy greens (winter lettuce, corn salad, arugula). These can usually can be sown up to the first week of September in most gardens, but last fall was colder than normal so late seeding didn’t work as well as usual. The same may happen this year because the La Niña ocean circulation pattern, which gave us the cold, wet weather last fall, is likely to continue through this fall. SO, just in case we have lower than normal temperatures in September again, I suggest you sow these last greens sooner rather than later. If you are sowing in a greenhouse or tunnel, you can usually sow up to mid-September for successful crops.

For usable leaves by late September, sow leafy greens in empty garden beds or wherever there are empty spots. Keep the seedbeds well-watered and shade them from hot sun until plants germinate and, continue shading, if necessary, during the hottest hours of the day while seedlings are tiny. Alternatively, you can scatter the seeds under tomatoes, peppers, squash and other warm season plants (including those in greenhouses) that will be finished in October. First, pull back the mulch in places where you can do so without damaging the established plants and broadcast the seeds on the soil surface. Don’t disturb the soil around the growing plants in the process, but if you can get soil from elsewhere in the garden and sprinkle it on top of the seeds. I usually just fling the seeds under the plants and hope for the best. If the weather is hot, the shade from the older plants helps, but seeds may still not germinate until it cools off. By the time tomatoes, etc., are finished, however, the soil should be covered with small plants. Avoid disturbing the new seedlings by cutting the finished plants off at the soil line, leaving their roots in the soil. Under-planting works best with corn salad because, if germination is delayed due to warm weather, it doesn’t matter as much as it does for other greens. Corn salad is so hardy that it can grow slowly during the winter when it is too cold for other plants to grow.

One last reminder, with the growing days ticking down, check that carrots, beets and other root crops, new plantings of leafy greens and Chinese cabbage are thinned sufficiently. Plants that are growing slowly, including Brussels sprouts and cabbage, may benefit from a dose of liquid fertilizer, such as fish fertilizer, to provide a last growth spurt. This isn’t usually needed for overwintering varieties of broccoli and cauliflower because it isn’t an advantage to have large plants for winter; as long as these are around a foot and half high by late October, they will be a good size to get through winter and produce heads in the spring. Taller plants overwinter too, but they just need more looking after to brace them up against wind and wet snow.

Miscellaneous notes for late August:

Insect covers: I always get this questions so will head it off now: Yes, there are still plenty of adults of carrot rust fly and cabbage root maggot flying around attacking crops. Therefore, you do need to leave the insect netting or floating row cover on your carrots and radish beds for another couple of months. At the end of October you can remove the covers, clean and store them as the insects will be done flying then.

Stopping tomato flowers: Tomatoes in the garden won’t be able to mature fruit set after the first week of September so snip off the flowering shoots of vining (indeterminate) tomatoes in another week or two. Bush or determinate tomatoes probably have already stopped producing new flowers, but if not, pinch those out too. Tomatoes in unheated greenhouses can be left another month to set fruit and, of course, if they are in a heated greenhouse, there is no need to stop new growth until you want to change over the crop.

Powdery mildew: The white dusty coating on squash and pumpkin leaves, perhaps also seen on your peas and other vegetables, is a layer of spores of one of the powdery mildew fungi (there are several common species). Keeping plants growing well, with liquid fertilizer and extra irrigation will keep squash producing well as it outgrows the fungus.

Corn salad sown under squash plants