As our cool spring weather continues, everyone is asking about when to plant:
Soil Temperature: On the theme of testing, right now I am checking a soil thermometer out in a garden bed. It shows that the soil is far too cold to plant anything (and of course our soils are far too wet to be handled at all). As of today my soil temperature had come up to 4 degrees C by afternoon, but is lower in the mornings after overnight frosts. So we are a long way from the 12-15 C minimum for planting cool season crops! Bear in mind that the optimum germination temperatures for even cool season vegetables is minimum 21 C ; peas, for example, germinate best at 24 C. Which is why sprouting early peas indoors is such a good idea, giving them a nice warm germination period, after which they can go outdoors to cooler weather. To hasten soil warming, rake off any mulch on the surface and lay clear plastic on the soil to trap heat. Black plastic won’t heat the soil nearly as fast as clear.
If you have good growing conditions for seedlings indoors or in a greenhouse, you can start cabbage, cauliflower, broccoli, lettuce, spinach and other leafy greens now for later planting out. If you can provide warm conditions for seedlings (and very good light levels), then tomatoes, peppers and zucchini can be started now (some of you will have already started these, especially if you want to try for that first zucchini harvest in May).
Frost Free Dates? I discussed this a few years ago but thought it would be worth a reminder for new subscribers. Unlike in interior regions and areas with relatively flat landscapes, average frost free dates are meaningless here. On the coast there are big differences in frost patterns over very small areas because of our complicated geography. While some sheltered coastal gardens may see only a few days of below freezing in a typical winter, others in valleys away from the water or at higher elevations might see ground frosts into May. Since official weather records are only taken at a few sites around the region (often at airports), any calculations based on long-term weather records would only apply to those sites--if they apply at all, given our increasingly variable weather as the climate changes. Rather than going by particular dates for spring planting, I think it best to go with soil temperature and adapt to whatever each year brings. If you just moved here in the last couple of years, I have to break it to you that the last 2 springs were unusually warm, early and wonderful for spring gardens. While this winter was indeed colder than usual, a cold, wet spring is actually “normal” for the region. Interestingly, Environment Canada meteorologists forecast that we may be in for record-breaking heat this summer, but after a cold spring…
Soil tests: While waiting for things to warm up you could get a test of soil pH done. This test tells you whether you need to add lime to the soil before planting. You don’t need to test the soil every year (I test at 5-6 year intervals), but if you are starting a new garden it is always a good idea to test the soil first, before amending it. For established gardens, an indicator that you should check pH would be poor growth of beets, but a good crop of potatoes in the same garden. Potatoes do fine in acid soil, but beets are particularly sensitive to it. While ideal soil pH is in the 6.5-6.8 range for vegetables, another reason to test the soil is if you plan to grow blueberries as they need acid soil (pH 5.1 or so). Vancouver Island gardeners can send sample to MB Laboratories in Sidney, BC. See MB Labs for instructions on how to collect soil samples and where to drop off or mail samples. There are other labs, elsewhere, of course, including Pacific Soil Analysis, 11720 Voyageur Way, Richmond, (604) 273-8226, which strangely in this day and age still doesn’t seem to have a web site.
Note that the pH test kits and probes you can buy are not worth bothering with: Consumers Reports tested them a few year back and found none were accurate. Also, such tests can only show pH for the small bit of soil they are in contact with. This doesn’t tell you much, because soil pH naturally varies widely from one spot to the next, even over a small area. A properly mixed soil sample tested at a lab provides a more accurate reading of the average pH for the test area. The results from the lab include advice on whether lime is needed.
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