It finally looks like night time temperatures will be reaching the comfort zone (10oC/50oF) for planting out well-grown squash and tomato plants this week (don’t rush to plant small plants that can wait awhile). In some inland gardens it might even get hot enough by this weekend that seedlings and seed beds may require shading in midday. With forecasted highs of 25-27oC (up to 80oF), very young plants and seeds in the process of germinating could easily be killed by the hot sun because their tiny roots are so close to the surface. For temporary shade, use anything you have: upside down pots or latticework seedling trays, newspaper or lightweight fabric supported on stakes or hoops. If you are using opaque materials for more than 2 days, only cover plants for the hottest part of the day (11:00 to 3:00 or so) so they receive light in the morning and late afternoon. For a long term investment, you might want to buy horticultural shade cloth or build wooden latticework to shade plants. These let in enough light for growth so can be left in place for the entire heat wave. Also, try to work mulch around small plants to cool the soil. Lawn clippings are excellent for this because they are soft and fine enough to use around tiny seedlings.
Of course, there is no guarantee that a late frost won’t happen later this month, especially in valley gardens where cold air pools on a clear night. On such nights, higher elevations can actually be warmer than in valleys due to temperature inversions. If frost threatens, cover tender plants with floating row cover or lightweight plastic, cloches or tunnels. If you know you are in such a location, don’t plant squash or tomatoes yet: it isn’t really safe to plant these until late May in some gardens.
In short, May is a tricky month because anything can happen from frost to heat waves. The varied geography on the coast means that garden microclimates, even those quite close together, can be very different. Depending on where you are, some gardens are still at risk of frost, while others are warm enough for all but the most tender vegetables. Just be extra vigilant watching the weather forecast this month. If you keep your own temperature records you will know your microclimate and can adjust your planting schedule accordingly. A manual min-max thermometer works fine for this and there are any number of wireless weather stations available in any price range.
Despite what look like some warm days coming up, the soil is too cold and the weather is too unsettled to plant beans, corn, eggplant, pepper, melons, cucumbers, sweet basil and sweet potato plants outdoors. It really doesn’t work to plant seeds of bean in cool soil (less than 15oC/60oF) because the seeds often rot. Varieties of corn with sugar enhanced genes (e.g., labelled as SH2 or SE) are best germinated at 18-21oC (65-70oF). Once they are up and growing, bean and corn seedlings can handle lower growing temperatures: they just have to germinate in warm conditions. This week is good timing for starting beans in vermiculite and sweet corn in small pots indoors. By ‘starting indoors’, I mean germinate them in a warm place or on bottom heat, then keep the seedlings in a greenhouse, cold frame, sunroom or even move them outdoors on sunny days, but bring them in to room temperature at night. These will be ready to transplant in 2-3 weeks, when the soil should be warm enough for them.
As always happens, many people started tender plants too soon or purchased them too early. Some of those starts have languished in pots they have outgrown and are becoming seriously stressed as shown by leggy stems and discoloured leaves (such young plant should not have purple, orange, brown or yellowish leaves). Plant these in bigger pots with new soil to allow them to keep growing. Starts that were prematurely planted outdoors also might not be looking very good after this recent period of cool, wet weather. If they were big and robust before planting, they will probably be OK, even if they have not grown much or have discoloured leaves right now. Tomatoes with a purplish look to the stems and undersides of the leaves are usually suffering from a phosphorus deficiency caused by being in cool conditions and the leaves should turn green as the weather warms. But seedlings or transplants with drooping leaves (not attributable to dry soil) are showing signs of root damage, possibly from root rots, which are common in cold, wet soil. Such plants may not survive at all, but even if they do, they are likely to be stunted. Be prepared to replant or buy replacements for these. There is plenty of growing season ahead of us to get a good crop from the new plants if you have to start over.
Slugs are rampaging, as always in wet weather and I would like to remind everyone that the iron/ferric phosphate slug baits, which are widely available, are safe and effective (not like the old metaldehyde baits that were so dangerous to birds, pets, etc.). The baits work by attracting slugs to eat the pasta particles and take in the iron, which disrupts a mollusc’s ability to make slime. The bait is not a contact poison and doesn’t work by toxicity. I was horrified to hear a gardening ‘expert’ on a CBC program last weekend recommending spraying ammonia on the soil to kill slugs—not only is this actually illegal under Canadian pesticide regulations, but it is not specific to slugs and could harm non-target organisms. There are many slug predators out there (ground beetles, rove beetles, snakes, etc.) so stick with the safe slug baits.
If you are growing gooseberries, currants or Jostaberries, see my May 5, 2017 newsletter: http://www.lindagilkeson.ca/gardening_tips.html on how to prevent damage from two common pests: Imported currantworm, which eats leaves (http://www.lindagilkeson.ca/leaf_chewers2.html#36 ) and the currant fruit fly (http://www.lindagilkeson.ca/borers.html#93 ), which wrecks berries. Right now it is easy to see and remove the eggs of the currantworm laid on leaves. Around mid-May to mid-June is good timing to cover bushes with insect netting to exclude the fruit fly from laying eggs. After that, these plants are usually trouble free. Insect netting is now more widely available, with many garden centres carrying BugOut, ProtekNet or Enviromesh, all of which are sturdy, long-lasting nettings designed to keep even tiny insects from laying eggs on plants.
Help for New Gardeners: Efforts are going on all over the region, ranging from hotlines and Facebook groups to projects matching experienced gardeners to mentor new gardeners. For a listing of various projects and links in the region, including password to access my Year Round Harvest course materials on my web site see my April 20 message: http://www.lindagilkeson.ca/gardening_tips.html
Plant Sale: Saturday May 9th, 10am-2pm. The Victoria Compost Education Centre is holding their 17th annual organic spring plant sale with a smaller number of growers and special COVID protocols in place. At the CEC demonstration site at 1216 North Park Street, Victoria.