Yesterday should have been “Spinach Day” in my garden, but it is far too hot to attempt to sow anything right now. I have had good results sowing spinach as late as the middle of August so will wait to until it cools down in a couple of days to plant seeds. The forecast for Saturday is for cooler weather, with a small chance of the ever-receding mirage of rain showers in some places. Gardeners along the outer coast and Strait of Juan de Fuca, where summers are cool and foggy should sow spinach right now to give it time to grow to a good size before winter.
Winter lettuce, arugula, salad radishes and winter radishes and other leafy greens, including leaf mustards, leaf spinach (‘Komatsuna’), leaf radish and Chinese cabbage varieties can also still be started from seed this week, but wait until temperatures drop in a day or two to sow these outdoors. Lettuce seeds simply won’t germinate if it too hot, no matter how carefully you keep them watered. Starting seeds in flats or pots works well because they can be kept indoors or in full shade until they germinate.
We are running out of time in the growing season to start larger plants from seed, such as broccoli raab, kale or Swiss chard, therefore look for seedlings at local nurseries and suppliers. At this time of year, even if it cools off in a few days, plan to cover the seed beds to cool the soil and keep it evenly moist. And if a heat wave comes back after the germination period, shade the seedlings, be vigilant about watering and get mulch of some kind around the tiny seedlings as soon as possible. If you are short on mulch for your seedlings, steal some from established plants that have deeper roots and a canopy of leaves shading the soil so are less at risk from hot sun.
Pest and disease update:
Slugs: Don’t forget to scatter around safe slug bait, especially where small plants are at risk. With so much of the landscape dried out, slugs converge on irrigated garden beds.
Spotted Wing Drosophila: I have been getting reports of this fruit fly throughout the region. As in past years, urban gardeners seem to find the tiny white maggots in berries and cherries earlier in the season than in rural areas. SWD populations will increase very quickly in this heat and numbers can be quite high by the end of August. While this fruit fly is capable of attacking any fruit except apples and pears, it is the later crops of everbearing raspberries and strawberries and wild and domestic blackberries that they are most attracted to. At the moment the best approach for home gardens is to cover fruit with insect netting, but this has to be done before the fruit flies start laying eggs. It is too late if SWD has found your garden by now, but if they haven’t, then covering everbearing strawberry beds works really well. I do recommend putting out a vinegar trap if you have berries or soft fruit so that you know if and when SWD arrives in your garden. This information will help you know when to cover your plants next year. For directions to make a simple vinegar trap.
Powdery mildews: This is the time of year that the white, dusty or chalky look of powdery mildew starts to show up on a variety of plants. Some powdery mildew occurred in the dry weeks of May so some plants might have quite a bit of mildew by now. Plants most commonly infected are squash, cucumbers and peas, while kale, chard, beets and tomatoes are sometimes infected. There are many different species of powdery mildew fungi, but they all thrive in dry weather and on older leaves. Vigorous new leaves have better defenses against infection, so keep plants producing lots of new growth with generous watering and weekly boosts of liquid fertilizer (e.g., fish fertilizer or manure tea). Growing lots of new leaves allows an infected squash plant to carry on ripening fruit even though the old leaves are covered with fungus. Don’t be in a hurry to pick off leaves, because leaves that are green under the fungal coating are still benefitting the plant (picking off infected leaves doesn’t help to control the disease since spores are everywhere). It is fine to put infected leaves and plants in the compost. Washing down the leaves with water every day or two can slow the spread of mildew on squash and cucumbers, because the spores can’t germinate in the presence of water (don’t try this on tomatoes as that invites late blight and other leaf diseases). For kale and chard with mildew, I don’t think it is a great idea to eat the leaves, but don’t take out the plants because when the rain starts in the fall the new leaves will be fine and plants should produce without mildew through next spring.
Tomatoes: During heat waves it can be so hot that it sterilizes the pollen of tomatoes and peppers (tomato pollen is killed by temperatures over 32oC/90oF, peppers are lower temperatures). Then flowers drop off and no fruit appears, which often goes unnoticed. Gardeners usually do notice that their plants don’t seem to have many fruit, but they don’t know why. This is more likely to happen to tomatoes growing in greenhouses, which in heat waves can be extremely hot even with shading. When the weather cools, new flowers set fruit normally.
Squash: Several people have asked about zucchini fruit that turns yellow and shrivels up from the blossom end when it is still quite small. This happens because the flowers were not pollinated, but because the little squash can grow a bit after the flower falls off, it doesn’t look like pollination could be the problem. To hand pollinate, pick a male flower from the plant, peel back the petals and tap the pollen on the centre structure in a female flower. Female flowers always have a tiny fruit just behind the flower, whereas male flowers have lots of golden pollen in the centre and a strait stem without the tiny fruit. A couple of questions came from people growing ‘Partenon’ zucchini, which is parthenocarpic (meaning that it can set fruit without fertilization). Not every female flower will set parthenocarpic fruit, however, so hand pollinate those flowers too, if you want to insure every flower sets fruit.
Upcoming Events: Saturday, August 25. Food Preserving workshops for Richmond residents. 9:30-11:30 South Arm Community Centre; 1:00-3:00 Ironwood Library, Richmond. Reduce food waste by learning how to store, freeze, dehydrate fruits and herbs, and find out about the best equipment to use for cold and hot pack canning. These workshops are free, but pre-registration is required.