Meteorologists are warning that the expected El Nino climate pattern this year is going to be a "super El Nino" comparable with the 1997-98 year. For coastal British Columbia, that brings record heat waves in the summer. With unprecedented warm Pacific water now reaching our coast, combined with a strong El Nino, which also brings warm water across the Pacific, gardeners need to be on top of managing for high temperatures. It starts this coming weekend and Environment Canada has issued a weather alert for a prolonged period of hot weather for coastal British Columbia, starting tomorrow and continuing through early next week. Predictions are for 27-31 degrees C (80-90 F), with the higher temperatures further inland.
Managing for heat: Garden vegetables are most vulnerable to heat damage at this time of year because plants are still small, with shallow roots and young leaves.
Shade young plants and seed bed: Cover small plants, at least for the midday heat for a few days to help them survive. For this, anything can be pressed into service, from proper shade cloth to curtain material or other fabric, newspapers, latticework, seedling flats turned upside down--anything you have. Because soil can easily be too warm for seeds to germinate, cover them with opaque materials to keep them cooler and evenly moist until seeds germinate. If it is still hot after the seeds germinate, graduate to covering beds with shade cloth or latticework. This will still cool the soil while allowing in sunlight, which the seedlings must have to survive. If possible, remove the shade for the morning sun and replace it for the hottest part of the day.
Mulch everything: Use smaller particles for small plants (take care not to cover the leaves) and coarser, deeper mulches for larger plants. If you are short on mulch and have a lawn to mow, use clippings to mulch seedlings. Lawn clippings rapidly dry up so don't last very long, but will help right now until you can organize other mulches. Straw and reed canary grass are particularly good mulches for summertime to keep soil cool because they are lighter coloured. If you have leaves stockpiled from last fall, of course, use those. If not, remember that pulled weeds, any garden waste, rhubarb leaves or crop trimmings, fern fronds, even newspaper can be used for mulching. More on mulch.
Tip: If you have started seedlings (such as cabbage, beans, corn, etc.) to set out, I find it easier to mulch the whole bed first, then dig holes in the mulch for the little plants.
Leave more foliage on your tomatoes: The leaves help protect the fruit from sunscald, grey wall, blotchy ripening (all show up as various shades of gray, brown or hard white blotches on the skin or inside the fruit). It can also help with greenback (shoulders of the fruit stay hard and green; more on that. These disorders are all related to heat stress or bright, hot sunlight hitting the ripening fruit. So this year leave suckers and leaves on the plants to help provide shade. One of my tomatoes is a leggy, tall plant with widely spaces leaves and I plant to shade the clusters of developing fruit with pieces of white paper clipped to the stems. If your tomatoes are in a greenhouse, tunnel or sunroom, try to keep air temperatures from going over 35 degrees C (95 F), as temperatures in the range of 32-35 degrees C sterilize the pollen. This weekend it may be impossible to keep temperatures inside a greenhouse low, so consider using shade cloth or other shading in the middle of the hottest days. Tomatoes need full sun to grow, so you don't want permanent shades, but temporary shading will get the plants through the heat.
Be on top of watering. I am sure that goes without saying, but don't be surprised if cabbage, broccoli and leafy greens wilt a bit in midday heat. These are cool weather crops and when it gets too hot, they can't maintain enough moisture in their leaves even in well watered soil. This is a normal response to heat and they should recover in late afternoon. If plants are still wilted by evening, then they are not getting enough water--or there is a root disease or pest problem, which often become obvious when plants are under drought stress.
Control slugs: When it is hot and dry in the areas around your garden, the moist zones around your irrigated plants are even more attractive to slugs. Don't mess around with home remedies or trying to catch them: just go straight for the very effective slug baits that contain iron, such as Sluggo (approved for certified organic growers) or Safer's Slug and Snail bait. If you are laying down leaves from last year, it is a good idea to sprinkle some slug bait on the soil first before mulching. If you have already mulched, just sprinkle the bait on top of the mulch.
Oops, gotta run--I still have more mulching to do!
About Linda A. Gilkeson, Ph.D.
Linda earned a Ph.D. in Entomology from McGill University in 1986, then moved to British Columbia to work for Applied Bio-Nomics Ltd., a company that produces biological controls. From 1991 to 2002 she worked for the provincial government, promoting programs to reduce and eliminate pesticide use. She was head of the provincial State of Environment Reporting Unit for the next six years, then the Executive Director of the Salt Spring Island Conservancy until the end of 2011. Linda now devotes her time to writing, teaching and consulting.
Linda has co-authored pest management training manuals for the government and organic gardening books for Rodale Press. She has self-published two books: Year Around Harvest: Winter Gardening on the Coast and West Coast Gardening: Natural Insect, Weed and Disease Control. Her recent book, Backyard Bounty: The Complete Guide to year-Round Organic Gardening in the Pacific Northwest, has become a BC best seller.
As a private consultant, Linda is a regular instructor in the Master Gardener programs in BC and is busy year around giving workshops on pest management and organic gardening.
Linda has served as President of the Entomological Society of Canada, the Professional Pest Management Association of BC, the Entomological Society of BC and the Salt Spring Island Garden Club. She was awarded a Queen’s Jubilee medal in 2003 and an outstanding achievement award from the Professional Pest Management Association of BC in 2005.
Follow Linda's work at lindagilkeson.com