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Sunday, May 22, 2016

Wedding white

Dear friends,
I apologize for infrequent posts. I’m absorbed with a happy event, my son’s wedding next weekend. I’ll be back with another post in June. Here’s something I hope you’ll enjoy for the end of May:

White flowers signify innocence, purity, honesty, perfection--and weddings. Whatever the occasion, May’s white flowers are especially beautiful. 

    Before we assume that flowers are white for a biological purpose, we have to bear in mind that from the plant’s point of view, human vision is beside the point. Flowers evolve mostly to attract pollinators. 

    Bee vision, for example, differs from ours. Bees can’t see at the red end of the visible light spectrum, but they see ultraviolet light that’s invisible to us. A flower that looks white to us could show a bee ultraviolet runway stripes (nectar guides) or bullseyes to mark the landing area, holding up a sign that says “Get your nectar and pollen here!”

Visible nectar guides--stripes on this iris--guide bumblebees to pollen. Photo by Al Schneider

    Each of my white flowers has a different strategy for getting its flowers pollinated and reproducing itself.

    Sweet woodruff (Galium odoratum) is a hermaphrodite pollinated by bees, flies, or itself—no wonder it spreads so fast. 

    Double-file viburnum (Viburnum plicatum var. tomentosum ‘Shasta’) has been fooling visitors this spring into thinking it’s a dogwood because of its horizontal rows of glowing white flowers. These attract insects and humans first with larger, sterile flowers that resemble the “petals” on flowering dogwoods (in fact those are adapted leaves called bracts).

The inner fertile flowers of the viburnum open a few days later.  

    Lily-of-the-valley (Convallaria majalis) is flowering profusely this week. Last year must have been a good one for this plant, because as its leaves emerge this spring, I’m finding it has expanded into new territory. The tiny bells on its flower stalks are pollinated by honeybees and bumblebees.

Each lily-of-the valley needs to cross with a genetically distinct plant to make fruit, one red berry per plant. But anyone who lives with this determined shade grower knows it does plenty of vegetative spreading even without fruit.

    The flowers of dwarf fothergilla (Fothergilla gardenii) have both male and female parts but no petals. I read that they’re pollinated by honeybees. Offering such easy access to nectar, they must attract other insects too. 

Bottlebrush flowers of dwarf fothergilla

    Bleeding heart, a member of the poppy family (Papaveraceae), offers pollen but not nectar to visiting insects. 

White bleeding heart, Dicentra spectabilis 'Alba'

Once the seed develops, bleeding heart has an interesting method for spreading it around. Each seed is attached to an elaiosome, a white fleshy blob rich in lipids that ants like to eat. 

Bleeding heart seeds with attached elaiosomes

Ants carry the seed back to their anthills and eat the elaiosome without damaging the seed. In return, the seed gets a free ride to a location farther from its parent plant than it could otherwise travel.

Sunday, May 8, 2016

Quick and dirty

This weekend I potted up my tender perennials using homemade non-peat potting mix. I store dahlias, cannas, elephant ears (Colcasia esculenta), and South American anise-scented sage (Salvia guaranitica) in the basement through the winter and wake them up in spring to flower another season. 

Salvia guaranitica 'Black and Blue'

They’re plants from warmer latitudes that can’t tolerate New England winters outdoors. Because of their large fleshy roots, they can survive out of the ground until spring.

Dahlia tubers after a winter in the basement

     Making this happen is supposed to be more complicated than I’ve found it. For example, my old copy of The Reader’s Digest Illustrated Guide to Gardening prescribes many steps for winter storage of dahlia tubers. The reader is instructed to wait until frost blackens the foliage, cut off stems at 6 inches, carefully lift the roots from the soil without damaging them, use a blunt stick to clear loose soil from the tubers, hang the plants upside down for two weeks to dry, dust them with sulfur to prevent fungal infections, and store them in trays of dry sand or peat moss in a cool greenhouse or dry cellar at 40 to 45 degrees.

    This idea that houses contain rooms or outbuildings that stay at 40 to 45 degrees during the winter seems to be a throwback to English gardening. With central heating and effective insulation, I can’t imagine there are many houses in the northeastern US that offer these special conditions for plant storage.

    I tried the Reader’s Digest authors’ approach one winter (admittedly leaving out the sulfur sprinkling). By spring my tubers had dried up, shriveled and died.

    Instead, I stumbled on a much simpler approach for over-wintering tender perennials. In late fall I cut the stems and dig up the plant, leaving plenty of soil around the roots. I place each plant, soil and all, in a brown paper grocery bag. I enclose this in a plastic drawstring kitchen-size trash bag, tie the top closed, and store it in the basement on wire shelving. There the plants go dormant in darkness and cool-enough temperatures.

    Cultivating dahlias for the biggest, showiest flowers is a special skill that I haven’t acquired. However, I can count on my stored dahlia tubers and other tender perennials to stay hydrated enough to sprout indoors when I replant them in pots in May. I let them grow indoors for a month.

Potted and ready to go inside to sprout in a sunny spot

As the weather warms, I move them outdoors during the day and back inside at night. After Memorial Day I can plant them in the garden or in large containers, where they flower again for another summer.

Elephant ears in July
Dahlias in September

I used to consume many bags of commercial potting mix for this process. Now I get good results with a peat-free mix of half coir (coconut fiber) and half screened compost from my compost piles. I’m glad to leave the peat in its bogs, where it sequesters carbon.

I mix screened compost and coir right where I'll pot the stored plants

Monday, May 2, 2016

Lawn grass--threat or menace?

Why do some plants grow well only where you don’t want them? Lawn grass in my garden keeps reminding me of this question.

    A few years ago, the water department replaced our old cast iron main water pipe, leaving a big trench in the front yard that city contractors thoughtfully filled with topsoil. Apparently they didn’t notice that the shady area they’d dug up was not lawn—it had already been converted to a bed of periwinkle (Vinca minor). 

Periwinkle replaced our sorry front lawn

Following standard practice, they sprinkled grass seed on the new soil.

    I was amazed at how well that grass grew. I tried to scoop the seed up immediately and replace it with more periwinkle seedlings, but grass still sprouted. It was several seasons before I could weed it out, plant by plant. 

    I noticed the same with grass that showed up in a perennial bed in the backyard. It migrated from the lawn by sending out underground stems toward the bed, and once it established a foothold, it was quite hard to pull out.

Wandering lawn grass  peaking from under a meadow rue

    In contrast, the grass seed I planted in the backyard barely made an effort. Each spring and fall I’d hopefully over-seed my lackluster lawn with expensive seed mixes. To help the new grass plants along, I watered frequently with a hose or rotating sprinkler. One year I even put down a wet slurry of shredded newsprint, fertilizer, and grass seed that was supposed to keep the seed moist until it could sprout in bare patches of the lawn. 

    Each time I planted, a few young blades of grass would sprout, only to die away in the heat of the summer or disappear by the next spring.

    Why was this happening? Was it just my lack of diligence in caring for the young grass? If lawn grass could co-exist happily with periwinkle and coreopsis in planting beds, why couldn’t it also compete successfully with other species in the lawn?
    First, nature abhors a monoculture. I’d watched neighbors completely remove their lawns and reseed. After a year or two, unless they used weed-killers, they were back to the same mix of crabgrass and other weeds that made up my lawn.

The view from our deck--more weeds than lawn grass

    Second, my lawn’s soil is not hospitable. I don’t pamper it with compost or shredded leaves, we compact it by walking on it, and new grass sprouts don’t have the luxury of shelter from taller plants in their early days. They have little chance to establish a root system before investing energy in leaves.

    Lawn grass is the hardest plant for me to grow. I’m ready to give up. Moss thrives in our acidic soil in the shadier parts of the lawn. It looks quite nice. 

Moss is taking over a shady section of lawn

Bluestone pavers and low-growing perennials would look even better. 

In future I see more bluestone, less grass