17 April 2009

To mulch or not to mulch

I'm speaking of winter mulching, I always figured, the more mulch the better, and that mulch over perennial or biennial plants acted like a blanket against the harsh freezing of our Northern winters. But I was surprised this week as I uncovered mulched plants and saw the results. Perhaps in zones 5 and 6 where there are enough mid-winter melts to expose the ground to hard freezing, or in arid zones with little snow cover and damaging sub-zero winds, mulch would be the rule, not the exception. But in our humid zone 4b, we generally have snow cover at least a foot deep, if not usually 3 or 4 feet deep, from December through April. And I have come to appreciate the insulative value of snow. Most years, the snow will fall even before the ground has a chance to freeze more than a few inches down, and the soil will stay soft and dormant all winter, even when we have week-long cold snaps below -20C. In zones where the frost permeates the ground 3 or 4 feet deep, mulch is required to keep the plants or garlic bulbs from being heaved up out of the ground come thaw. But we have not noticed any effects of heaving in the three years we've been farming here, leading us to realize that we live in a unique climate, very humid and cold. A new combination of gardening conditions for us.

The hardiest of our perennials and biennials are left un-mulched, and completely un-bothered by the snow and cold. I am always amazed to see green leaves appear from under all of that snow. Thyme and oregano are some tough little herbs.

This mullein plant was started last spring, and needed no mulching. The spine covered leaves are like a fur coat.

Parsley is another hardy herb, it is a delight to see this bright shade of green poke out of the snow.

The comfrey, also started last spring, is another new perennial in the garden. It's profuse leaves died back and left their own mulch around the plant, and it is still alive and well and ready to grow. The stinging nettle and alfalfa did equally well. I chose most of these herbs as my introduction to caring for perennials and biennials specifically for their hardiness, as well as their usefulness.
One herb that I experimented mulching was sage. It comes out of spring a little less green than the other herbs, so I lightly mulched over one bush in the row. Surprisingly, the mulch may have killed it, encouraging decomposition instead of protecting it from the cold. It may still come back, but the un-mulched sage bushes will certainly be ahead of the one I mulched.

I left a few tender biennial vegetables heavily mulched in the garden, as an experiment to get both early greens and to produce seeds. I used spoiled hay, propping the compressed biscuits around the plants, with at least 2-4 inches of insulation from all directions. When the snow melted this week, exposing my mulched plots, I found a lot of mold on they hay, not surprising, but unfortunately, again encouraging the decomposition of the plants. The kale stems are rotted, and not likely to sprout. We used our wheat straw over the garlic, which to be honest, I don't think really needs to be mulched in our climate. But the straw did not promote decomposition and mold, like the spoiled hay did, so next winter I will try both an un-mulched plot of late planted kale, and a plot mulched with straw.

I also mulched around four leeks with the spoiled hay biscuits, with not much success. One of them still has a firm crown, and looks like it will sprout. Again, I will try the straw and see if that makes the difference.
I also covered a row of chard with biscuits of spoiled hay, with better success. It is perhaps the low growing habit of the chard that made a difference. The kale and leeks are tall and awkward to mulch, but with the chard I could simply lay the biscuits of hay over the row, like a tipi, and not surround the stem with the moldering hay, which encouraged the stalky plants to rot. The leaves of the chard died back, but the crown is still alive, and will probably provide us with our first vegetable greens of the season.
I also had a pleasant surprise when we walked over our newly uncovered garden. I tried planting some two year old parsnip seed last spring, and it did not germinate well, by the time I got around to re-planting it, I knew it was a little too late, but decided to re-plant anyway. They did germinate, in their own slow fashion, but the little seedlings were then overshadowed by the exuberant carrots in the neighboring row, and never grew past the 4 to 6 leaf stage. When I dug up the carrots in the fall, I left these little parsnip seedlings in the ground, curious to see if they would survive the winter, but not expecting much. Well, they are all there, a whole row of parsnips, already a month of growth on them, and a month ahead of our usual planting date. My parsnip disappointment of last year has turned into a lucky accident. This year we are going to plant a late crop of carrots, parsnips and perhaps turnips, beets, and even onions, let them get a month of growth, and then put them to bed under a blanket of snow. We have a short, cool and wet growing season, leaving us about 120 days to grow as much as we can, but we are learning how to take advantage of the heavy snow fall over the winter, and it's ability to protect the ground from freezing.

And of course, we couldn't tour the garden without digging our hands into the soil. The garden soil is really beginning to show qualities of health, humus and vitality. The small plot we turned our first year will be going into it's third season, and is shown in the left hand below. The clump on the right is what we started with, and the soil we are growing our grains in, as the vegetable garden expands in the 2 and 3 year old ground. The soil shown below was heavily amended last year with compost from the horse's barn, and still had plenty of sawdust, stalky hay, and straw when we turned it in the soil. Every bit of that compost has been broken down and turned into humus as can be seen by the dark color and crumbly texture. We also amend the soil with crushed egg shells for calcium and wood ashes for potash.


Anonymous said...

rodents are also a consideration when deciding to winter mulch or not.

I would not draw firm conclusions based on only one years experience. Keep on trying different things. Last years failure may be this years success. Gardening is always change.

ChicagoMike said...

That first fist full of earth. The feel. The smell. Yummy.

Now you have options for mulching taller plants around in my mind.


ChristyACB said...

I live in zone 7b but not really since my riverfront wetlands area is quite unique, hence I don't have your snow issues. I also much pretty heavily in summer with wheat straw to keep my stuff growing in the broiling heat. This past year, I mulched the comfrey and some parsnips (2nd year for seed) and couldn't believe the difference. It just seems the straw works so much better than regular hay. Love the progress on your dirt! Amazing!

Freija and Beringian Fritillary said...

Anon, we have primarily voles here, very few field mice and no rats. Rodents have not been a problem in the garden, especially not in winter, our mulch is too sporadic for them to prefer nesting in the garden over nesting in the neighboring pastures. We see the remains of their tunnels and nests in the pastures when the snow first melts. They will occationally nibble at our squash and roots, but only when I have placed those crops against the edge of the garden or next to a grain crop where they have some coverage. So I have learned how to plan out the garden to discourage them.

Chicago Mike, yes it is great to feel the soil again. Nothing like solving a problem in the garden to get the creative and innovative juices flowing.

Christy, I would imagine that summer mulch would make a big difference in your garden, we mulch in the summer, but only after the soil has had a chance to fully heat up. I prefer the spoiled hay for summer mulching because it breaks down and can be worked into the soil the following spring, but the straw mulch worked out better for over-wintering tender plants. Isn't that picture great, for showing the difference in the soil we started with? It amazes me too.