Tricky May Weather vs. Eager Gardeners

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.

Upside Down Seed Trays Shade 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.

Floating Row Cover Protects Early Seedlings

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.

Salt Spring Beans Get a Head Start Indoors

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.

Pest notes

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.

 

May 7, 2020 9:43 AM

Community Comments

  • Avatar w101 says:

    A breath of fresh air.. Thank you for posting some News that has nothing to do with you know what... It's time to get on with life.