With some surprise I just realized that we are already at the last week of May and, with that, I need to remind everyone to start seeds of some winter crops (already!).
Winter crop: Good timing for sowing Brussels sprouts seed is the last week of May to the first week of June. This is early enough to ensure plants have time to form sprouts this fall, but late enough to largely avoid late summer cabbage aphid infestations in the sprouts. If you have already planted Br. sprouts, that’s fine, but you may find in August that the earliest sprouts to form may have aphids in them (later developing sprouts won’t, however). The most common reason for failure with Brussels sprouts is planting too late: although some sources still say to sow seed up to July, that is too late for most coastal gardens. So start seeds this week, either directly in the garden or in seed flats. With birds and slugs still about in my garden, I find it more reliable to start seeds in small flats that I can bring indoors overnight.
If you plan to grow the winter cabbages that take the longest time to mature, start seeds of those now as well. This applies to varieties such as ‘January King’, ‘Deadon’, ‘Danish Ballhead’, ‘Langedijker Red’ and others that take 110-120 days to harvest. Cabbage varieties that take 80-90 days to harvest can be sown later in June. Since you can harvest cabbages at any size, err on the side of planting early. If started too late, heads may be too small, or not form at all by the time winter arrives, whereas plant started early will just have bigger heads.
Also, remember to keep sowing small plantings of lettuce, radishes and your favourite salad greens to keep a steady harvest coming along all summer. And plant more peas for later summer harvest. Peas sown at the end of May and in June are no longer at risk from pea leaf weevil, but it is a good idea to choose varieties resistant to pea enation mosaic virus (seed descriptions may say “EMV” or just “enation” resistant). Several resistant varieties of each type are available: e.g., ‘Green Arrow’, ‘Aladdin’, ‘Maestro’ shelling peas; ‘Sugar Ann’, ‘Sugar Sprint’, ‘Cascadia’ snap peas; ‘Oregon Giant’, ‘Oregon Sugar Pod’ snow peas. The virus is spread by aphids and doesn’t usually show up until later in July so I don’t worry about sowing EMV resistant varieties in March and April, but do choose resistant varieties for May and June sowings. The resistant plants continue to produce well into the fall, even if a few virus-spreading aphids arrive.
Replanting? With the prolonged cool weather this spring, some people lost beans, squash, cucumbers, corn and other tender plants or had very poor germination of carrots, salad greens, etc. Many plants simply found it too cool and succumbed to stem rots and damping off (or were eaten by birds or other critters). So if you have gaps in any of your plantings, plant more seeds now. There is plenty of time left in the growing season to grow summer squash, cucumbers and beans starting from seeds this week. Or purchase plants now, which I would especially recommend if you need winter squash, tomatoes, peppers, because there isn’t enough time left in the season to produce much of a crop from seed.
Pest du jour: Tent caterpillars! TCs have been making sporadic comebacks here and there around the region for the last couple of years. The last big regional outbreak of this native species was in the years 2011-2013 and it was an unusually high population outbreak in some areas (Salt Spring was very hard hit in 2012). This cycle of boom and bust over a 7-11 year period is characteristic of this species and, while it is frightening if you haven’t seen it before, it is always temporary and caterpillar numbers always crash. The combined effects of disease (caterpillers are prone to virus and bacterial epidemics when they are crowded) and attack by parasitic flies and wasps eventually catches up and drives TC numbers nearly to zero. It take years for them to slowly build up again and the cycle repeats. While the years caterpillars are feeding are unpleasant, the important things to know are:
1) There is only one generation a year so when they are done feeding and wandering (around mid-June), they are over for this year; webbing stays in the trees, but there won’t be caterpillars;
2) Whether or not you do anything at all to control them, the eventual result will be exactly the same: they disappear and won’t be back again for years.
3) Attacked mature trees are not in danger; they grow more leaves and by the end of July will look fine. The trees at risk are very young trees, diseased or already failing trees that might be too weak to put out another set of leaves.
Fruit trees under heavy attack can’t be expected to produce a crop as well as re-foliate this season. Your options are to either remove the fruit or control the caterpillars. On dwarf fruit trees you can pull off the web nests with the caterpillars inside (use gloves—the caterpillars have hairs on them that irritate skin) and drop them in soapy water. On large fruit trees, you can clip out nests using pole pruners as long as you aren’t removing a significant amount of branches. Or use sprays of the caterpillar bacterial disease (Safers Biological Insecticide), this is effective and does the least harm to other organisms. Note that spraying trees with soapy water, pyrethrins or other insecticides will also kill pollinators and beneficial insects.
If there was enough food for the caterpillars in the trees where their nests are, then in mid-June, caterpillars wandering out of trees are only looking for a place to spin a cocoon. If, however, there were so many caterpillars in the trees that they didn’t get enough to eat, caterpillars crawl down the tree trunks and wander off to continue feeding on a variety of other plants. BTK sprays can be used to control caterpillars on blueberries, strawberries, and other garden plants if wandering caterpillars are still eating leaves.
Above all, remember that this too shall pass and in just a few more weeks. In the last outbreak on Salt Spring, a man died falling off of a roof and another person broke a leg attempting to control TCs so please let nature do a much safer and more effective job of controlling the caterpillars. When we see caterpillars wandering around in June with white dots on their heads (perhaps this year, but more likely next year), it signals the end of the outbreak. The white dots are eggs of parasitic flies and their presence shows the populations of natural enemies have caught up with the TCs. Don’t kill those caterpillars with eggs laid on them: they are dead caterpillars walking at that point and their role to be a living incubator for caterpillar parasites.