Tag: acidic soil

  • How to grow lupines

    How to grow lupines

    Lupines like acidic soil and lots of drainage, so heavy clay soil just won’t do. These lupines are happily growing in hard-packed gravel.
    Lupines like acidic soil and lots of drainage, so heavy clay soil just won’t do. These lupines are happily growing in hard-packed gravel.

    Lupines are a perennial I always notice and admire, but I’ve had no luck growing them in my own garden. They grow abundantly on the east coast and in other places (some may say too abundantly), but they do have a few “special requests.” I decided to ask a friend of mine who has grown from seed for years in her Ontario garden for a few tips on how to grow lupines.

    1) Lupines like acidic soil. Sphagnum peat moss, conifer needles, oak leaves, coffee grounds and ground sulphur will lower the pH of soil to some degree and help make it more acidic. However, I know gardeners in Ontario who have had great success growing lupines without ever purposefully lowering the pH of their soil (though they do add compost, which probably helps).

    2) Lupines don’t like to be transplanted or have their roots disturbed. When growing  from seed, try biodegradable pots, like the ones made from peat, that can be planted with the seedlings inside, or try a tactic that my friend uses. She sows her lupine seeds in big, six- to eight-inch (15- to 20-cm) deep trays. When they’re ready to transplant, she scoops under the seedling to avoid disturbing the soil and plants them quickly in a hole that has been thoroughly soaked and has sand and/or gravel in the bottom. Which leads me to the next important tip….

    Lupines like acidic soil and lots of drainage, so heavy clay soil just won’t do. These lupines are happily growing in hard-packed gravel.
    Lupines like acidic soil and lots of drainage, so heavy clay soil just won’t do. These lupines are happily growing in hard-packed gravel.

    3) Lupines need good drainage. Try planting them on a high site so water drains away and doesn’t sit around their roots, or add gravel to the bottom of the planting hole. They won’t survive in heavy clay soil that retains water, but they can grow in hard-packed gravel. When starting seed, some people use sand as their growing medium, or you can try a thick layer of vermiculite in the bottom of the pots or trays.

    4) Lupines send out a long taproot, anchoring itself to where it’s planted. When a seed is started in a pot, the first thing it will do after sprouting is send a taproot out the drainage hole and form a knot, which you can’t disturb without potentially killing the plant. You can try starting seeds in deep trays with no drainage holes and lots of vermiculite and gravel to improve drainage around the roots, or try cutting the container off from the taproot before planting.

    5) Tip #4 means that growing lupines in containers can be tricky. However, I like to tell myself that you can grow just about anything in a pot if you overwinter it properly, and after seeing it done successfully in the past, I placed my lupine in a deep pot this year, with lots of drainage.

    6) Lupines will self-seed, and you can divide them in the spring, but not in the fall. If you wish to save the seeds to sow at another time, wait for the green seed pods to turn brown and dry out. You can then pick the pods and save the seeds within. If you wait too long, though, the pods will explode and release the seeds themselves.

     

     

  • Acid soil for mountain laurels

    Acid soil for mountain laurels

    ‘Minuet’ mountain laurel (Photo from Park Seed)
    ‘Minuet’ mountain laurel (Photo from Park Seed)

    Many years ago I spent some weeks in the Adirondack Mountains as spring-blooming mountain laurel (Kalmia latifolia, Zone 5) spread delicate pink blossoms across broad slopes as far as the eye could see. It was a gorgeous sight, and I cut armloads of flowering branches for every room. I was so enthused with the beauty of these plants that I planted several in my garden at home. Sad to say, they languished and died, victims of my alkaline soil. Had I taken time to research the plant’s soil requirements, I would have learned that it’s an ericaceous plant like heather and rhododendron, and these all require acid soil.

    There are dozens of named Kalmia cultivars, and I want to try again. But this time, I’m going to acidify the soil so that these beautiful plants will stay healthy and bloom lavishly each May. This is definitely not low-maintenance gardening.

    The acid or alkaline register of soils (referred to as soil pH) is dictated by underlying bedrock. Limestone sections of bedrock will be covered with alkaline (high pH) soil; granite bedrock will be covered by acidic (low pH) soil. Soil pH can be changed for brief periods of time, perhaps four to six months, before the true pH register returns.

    The addition of lime will raise the pH of an acidic soil; and the addition of sulphur will lower the pH of an alkaline soil. A soil-testing service will tell you how to take soil samples, and provide detailed analysis of pH and mineral content. But it’s not really necessary to know your soil’s exact pH. A simple home pH test purchased from a garden centre will provide a basic evaluation of soil acidity or alkalinity. My garden soil registers as slightly alkaline, and that’s bad news for growing mountain laurel.

    I’ll dig in sulphur to acidify the soil when I plant the shrubs, and at least once every growing season. The amount of sulphur required depends on soil quality. Clay soil and soil rich in organic materials have a natural buffering ability and will require more sulphur; sandy soil requires less sulphur (follow package directions for application rates).

    The ability of sulphur to lower soil pH is accomplished by microbial activity. Soil microbes are less active in cold soils, so the best time to dig in sulphur is in late spring through summer. Botanical grade, quick-release powdered sulphur is available in small amounts at garden centres. Farm-supply stores stock both powdered and slow-release pelletized sulphur in bulk bags.

    Mountain laurel is an ideal companion plant for rhododendrons, requiring the same cultural conditions — part shade to sun, and consistently moist, acidic soil in the range of pH 5 to 6. It has similar foliage to rhododendron, but unlike rhododendrons, which carry their flower buds through winter, mountain laurel shrubs don’t produce their flowers buds until spring. The flowers are formed in dense corymbs, and are in the pink to raspberry, deep red and cinnamon-maroon shades (often with fancy white markings).

    I wouldn’t want to alter the pH for more than a plant or two, but the showy flowers of mountain laurel are worth the additional maintenance effort. I’ve ordered the pretty new cultivar K. latifolia ‘Kaleidoscope’ (hortico.com) with dark red buds opening to cinnamon-red flowers with white edges. In my Zone 6 garden it could possibly grow to four feet (1.2 m) high and wide, although in warmer climates the shrubs can be much larger. There are several dwarf cultivars available, and I wouldn’t mind finding ‘Minuet’ (K. latifolia ‘Minuet’, Zone 6), 40 by 40 inches (1 by 1 m).

    If you see any of these beautiful mountain laurel shrubs for sale, I’d be glad to know about it!

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