Heat Alert! Sowing Winter Brassicas

The recent cool weather is giving way to what is forecast to be pretty hot weather starting this weekend. This is a reminder that if you haven’t done so already, do finish mulching vegetables before it gets hot; it will conserve soil moisture and keep roots cool. Some people had quite a bit of rain, others not so much over the last week—but at least it was something after the driest May on record. It was so dry in May that powdery mildew showed up on a variety of plants (strawberries, kale, roses, etc.)--much earlier than we usually see it. On the other hand, some diseases of wet weather, such as apple scab, were noticeably absent.

Because it has been cool, young leaves of vegetable will be tender and prone to sunscald damage. Temperatures that could fry leaves this week wouldn’t likely damage plants later in the summer after leaf cells have had time to adapt to summer weather. Be ready this weekend to deploy some kind of shading for young plants and for cabbage family crops, which really do perform much better if they don’t experience a heat wave. Seedbeds should be shaded too to prevent the soil from getting hot enough to kill germinating seeds. You can buy horticultural shade cloth (products that provide 30%-50% shade are ideal) or use lacy curtain material, wooden latticework, plastic lattice seedling flats turned upside down. These all let in enough light that you can leave the shade material in place until the heat wave is over. If you use opaque materials, such as old bed sheets or fabric, then cover your plants in mid-morning and uncover them in mid-afternoon so they have some photosynthesis time in the cooler parts of the day. This is not the time to use floating row cover (e.g., Remay), since it is designed to let in as much light as possible and to trap heat—just the opposite of what is needed.

What to plant: Still lots of time left to sow a variety of crops and have harvests for late summer or September, including bush bean, peas, leafy greens of all kinds and root crops such as carrots, beets, turnips. For lettuce plantings, choose varieties that are described as heat tolerant or bolt resistant.

Sometime in the next week or two, sow purple sprouting broccoli and winter cauliflower for harvest from next March onward, also cabbage varieties that take less than 90 days to mature. The purple sprouting broccoli situation continues to confuse: up until a few years ago the only PSBs sold were winter varieties, but seed suppliers now sell summer PSB varieties too. However, the summer PSBs have been strangely inconsistent: some plants do produce summer crops, but others (from the same package!) don’t produce heads until the following spring. When you buy seeds or veggie starts, check variety descriptions to make sure you are getting ‘Red Spear’ (West Coast Seeds) or other PSBs specifically for overwintering (US gardeners: Territorial Seeds carries several varieties).

The winter cauliflower situation is simpler due to the loss of many varieties. For white winter cauliflower, you will likely only find ‘Galleon’ in Canada (West Coast Seeds); in the US, Osborne Seeds has half a dozen varieties and Territorial Seeds lists a blend of 4 varieties. For winter purple cauliflower, about all that’s left is Purple Cape (actually a ‘brocco-flower’). Salt Spring Seeds carries it, thanks to seed growers on the island that have propagated it. On Salt Spring, Chorus Frog Farm stand on Rainbow Road will have starts for the winter crops mentioned above in July and August. For other areas, be a savvy consumer and check carefully before you buy starts this summer because some seedling wholesalers are still selling summer varieties to garden centres for overwintering (and that doesn’t end well…).

Finally! insect netting for all: I am happy to see the sturdy knitted monofilament insect netting products are being carried by more gardening centres this year. These are a much better choice for keeping insects off of fruit and vegetables than floating row cover, which doesn’t last very long and tears too easily to be useful for keeping fruit flies out of berries, cherries and other soft fruit. Brands that you may see include ‘Bug Out’ (Foxglove Nursery, Salt Spring; Buckerfields and other Vancouver Island nurseries have it); ProtectNet (Russell Nursery, Sidney; Dinter’s Nursery, Duncan). You can also find these and other products, including ‘Environmesh’, online.

Happy Shaded Seedlings

On the subject of fruit flies, I would be interested in hearing from anyone finding the tiny white maggots of Spotted Wing Drosophila in strawberries, raspberries and other fruit (for what to look for, see). I am interested in how early and how widespread this pest is this year. Last summer, some city gardeners were plagued in early June by infestations in strawberries, while rural gardeners largely didn’t see SWD in significant numbers until late summer. I suspect this is because the very cold winter we had killed more overwintering adults in rural areas, whereas around city buildings more flies found warmer places to spend the winter. So, it will be interesting to see what happens this year. For how to make a simple monitoring trap to find out if SWD is in your garden this summers, see my June 14, 2016 message.

Spotted Wing Drosophil Laying Eggs On Raspberry

June 18, 2018 9:08 PM

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