The 2015 Seattle Flower and Garden Show gave me the chance to hear presentations by some brilliant minds in the horticulture world. WSU professor and author Dr. Linda Chalker-Scott offered compelling science-based research dispelling garden myths and advised against some commonly accepted practices. Are we actually harming our plants by loading up their tidy beds with bonemeal and chicken manure? In the case of gardening with woody plants in non-agricultural soils, the answer may be yes.
Nearly all shrubs and trees and quite a few perennial plants have associations with mycorrhizal fungi. These relationships make plants more efficient at absorbing water and minerals from the soil. High phosphorus fertilizers including bonemeal inhibit the growth of these beneficial fungi. Root growth will increase, but it will be at the expense of other functions the plant needs to perform.
Lack of phosphorus is usually not a limiting factor of plant growth in urban soils. The only way to be sure is to get a complete soil test. Otherwise, look to other possible factors in determining why growth appears to be slow: available nitrogen, ph levels, temperatures.These are complex relationships and rushing to apply a commercial product could lead to other imbalances. I look for the quality of plant growth as an indicator of plant health, not the speed of growth. If the colors are true (not faded or unusually tinted for that variety) and the complexion is clear (not showing the ravages of insect or disease) then the plant is doing fine.
So how can we help plants struggling to overcome pest and disease pressure and be resilient in times of changing climate? Dr. Chalker-Scott is a big fan of mulch ( I am too!). My mulching guidelines are to match the type of mulch to the plants you are growing. While woody plants have their partnership with fungi, many annuals and vegetables thrive in soils where bacteria life is favored. Manure based compost works best in the veggie and flower garden and a mulch of leaves and wood chips will best nourish the soils around shrubs and trees. This is a grand paradigm shift: feed the soils, not the plants!
Some cautions about mulching from Dr. Chalker-Scott's presentation:
Sheet mulch (laying sheets of cardboard to smother weeds after mowing) may cut off the soil life from moisture and inhibit gas exchange. In my experience, watering the soil deeply and applying smaller pieces of overlapping cardboard seems to work well. Don't use this method where burrowing rodents are a problem and expect a temporary increase in the slug population.
Lasagna gardening may overload a bed with high nitrogen materials that leach nutrients. My advice is to keep the moisture content at a moderate level, as with any compost pile, by protecting it from heavy rain. Gardeners in our area have had great success creating fertile beds with a little initial effort and then have patience while the worms do the hard work.
Nearly all shrubs and trees and quite a few perennial plants have associations with mycorrhizal fungi. These relationships make plants more efficient at absorbing water and minerals from the soil. High phosphorus fertilizers including bonemeal inhibit the growth of these beneficial fungi. Root growth will increase, but it will be at the expense of other functions the plant needs to perform.
Lack of phosphorus is usually not a limiting factor of plant growth in urban soils. The only way to be sure is to get a complete soil test. Otherwise, look to other possible factors in determining why growth appears to be slow: available nitrogen, ph levels, temperatures.These are complex relationships and rushing to apply a commercial product could lead to other imbalances. I look for the quality of plant growth as an indicator of plant health, not the speed of growth. If the colors are true (not faded or unusually tinted for that variety) and the complexion is clear (not showing the ravages of insect or disease) then the plant is doing fine.
So how can we help plants struggling to overcome pest and disease pressure and be resilient in times of changing climate? Dr. Chalker-Scott is a big fan of mulch ( I am too!). My mulching guidelines are to match the type of mulch to the plants you are growing. While woody plants have their partnership with fungi, many annuals and vegetables thrive in soils where bacteria life is favored. Manure based compost works best in the veggie and flower garden and a mulch of leaves and wood chips will best nourish the soils around shrubs and trees. This is a grand paradigm shift: feed the soils, not the plants!
Some cautions about mulching from Dr. Chalker-Scott's presentation:
Sheet mulch (laying sheets of cardboard to smother weeds after mowing) may cut off the soil life from moisture and inhibit gas exchange. In my experience, watering the soil deeply and applying smaller pieces of overlapping cardboard seems to work well. Don't use this method where burrowing rodents are a problem and expect a temporary increase in the slug population.
Lasagna gardening may overload a bed with high nitrogen materials that leach nutrients. My advice is to keep the moisture content at a moderate level, as with any compost pile, by protecting it from heavy rain. Gardeners in our area have had great success creating fertile beds with a little initial effort and then have patience while the worms do the hard work.
What's Growing: Lonicera fragrantissima
Well, I just learned that this easy-going shrub with the sparkling, sweet smelling Winter blooms may have a dark side. In Tennessee it may be considered an invasive plant along with some of its honeysuckle cousins. So, if you are cautious, don't grow this one. But right now I am so grateful for this shrub from China by my front walk as it unfurls it's fresh green leaves and dangles a hundred flowers from it's arching branches. The perfume has a fruitiness that is refreshingly different from those Spring bloomers veering toward the cloying or musky scents. By summer the leaves have a blue-green tint and hold on until bitter weather cleans the branches. All this from a plant I have never fertilized or watered, growing in deep shade in heavy clay under a Black Walnut tree!
What's Cooking: Alliums at Every Meal
Onions, garlic, shallots, leeks, scallions, chives- all are alliums - and I grow them all. It seems cooking at my house always begins or ends with one or more of these. Now is the time to start allium seeds and plant "sets" or baby bulbs. (Garlic goes in the ground in October, and no later than mid-winter.) They are cold tolerant plants, and as soon as the seeds sprout in the tray I keep them in a bright and barely frost-free space to be planted out after about six weeks and a haircut or two. Setting out the starts as single plants is very tedious. I am grateful for the farmer who advised me that onions grow just as well in clumps of four. Even fistfuls of baby onions will make gorgeous scallions - they really grow like grass around here in the early Spring. Keep them growing fast and free from weed competition because when the days stop getting longer the alliums will plump up their roots in direct relationship to the vigor of the green tops. Mulching with compost, grass clippings and straw will feed the soil and shelter the plants.
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