Eat your veggies! (But not the arsenic, or the chromium, or the lead…)

vegetables_jpg.jpgThe last few years have been a perfect storm for the resurgence of home vegetable (and fruit) gardens.  Grapevines are trellised along sidewalks, herbs replace the grass in parking strips, and tiny gardens of carrots and lettuce are shoehorned into any available spot.  It’s all good  – but we need to be particularly careful about what those plant roots might be taking up along with nutrients and water.

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1)  Contaminated soil.  Many urban (and suburban, and even rural) soils are contaminated with heavy metals, pesticides, and/or industrial wastes.  Lead is commonly found in soils near roads (from the old leaded gasoline we used to use) or from old lead-based paint chipping away from houses.   Arsenic is a very real problem in North Tacoma soils, for instance, thanks to the smelter that operated there for decades.   Overuse and incorrect use of home pesticides will leave residues in the soil for years.

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2)  Contaminated compost and soil mixes.  Many of the same contaminants mentioned above can be found in unregulated composts and soil mixes.  (More on this topic here.)

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3)  Treated lumber.  The old treated lumber (CCA = copper, chromium and arsenic) is no longer being sold, but it’s out there.  These timbers should not be used around vegetable gardens, as they will leach their heavy metals into the soil.  Vegetables vary in their ability to take up and store these metals.  (More on this topic here.)  Likewise, rubber mulches may leach unwanted chemicals into the soil and should not be used around food plants.  (More on this topic here.)

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What can you do to avoid these problems?  A few things are quick, easy and cheap:

1)  Have your soils tested.  I’ve mentioned this in an earlier blog on urban soils.  It’s the best way to find out exactly what you have in your gardens – the good and the bad.

2)  Use only certified composts and soil mixes.

3)  Plant in containers if your soils aren’t safe for food.  This is especially easy to do with perennial herbs, which can be kept like any other container plant on your deck or porch for years.

4)  You can also replace the soil in your vegetable garden.  This isn’t quick, easy, or cheap, but is a solution for some people.

Voles are Pickier Than You Think

…and it’s not just the scientifically-proven inverse correlation between the price of the mail-order perennial and likelihood it will get chomped within six months. The prairie vole (Microtus ochrogaster) is notorious throughout central and eastern North America for laying waste to many a well-tended garden. Much of what’s out there in regards to herbivory of ornamental plants (said chomping by deer, voles, bunnies, etc.) is simply anecdotal, yet repeated ad nauseum as fact. So it’s exciting to see some new research in that field, published in a recent HortTechnology journal.

Dr. William Miller’s research focus is bulbs, and his group at Cornell University set up feeding trials with thirty common garden bulb species to quantify the prairie vole’s preference thereof. Tulips topped the list as the colony’s favorite (but you knew that already). In fact, “the voles became accustomed to this feeding schedule, and would vocalize and get excited when we entered the laboratory to prepare the bulbs…”

The voles showed the least interest in daffodil (Narcissus), grape hyacinth (Muscari armeniacum), Italian arum (Arum italicum), ornamental onions (several Allium species) and snowdrop (Galanthus nivalis). These bulbs were evidently high in the sort of secondary metabolites that, among other things, cause plant tissue to taste bad. There were even preferences shown as to different cultivars within each species – they were wild about tulip ‘Apeldoorn’ yet ate half as much of the species Tulipa turkestanica. Note to the vole-ridden…the daffodil ‘Ice Follies’ registered barely a nibble.

Apparently voles love apples more than anything, so the researchers also mixed dried, ground bulbs with applesauce to make them even more appealing. The point of this slightly eludes me, but the take-home message was 1) voles will eat anything except onions when mixed with applesauce, and 2) don’t dip your bulbs in applesauce prior to planting. Now if only Dr. Miller would work on vole feeding preferences by price point…

Source: Curtis, B, D. Curtis, and W. Miller. 2009. Relative Resistance of Ornamental Flowering Bulbs to Feeding Damage by Voles. HortTechnology 19:499-503.

Fabulous Sporobolus!

“Where have you been all my life?!!”

Every once and a while, I come across a plant and simply fall in love.

I  am not alone on this particular species, and the bandwagon is getting mighty crowded.  Sporobolus heterolepis is the object of my affections…it even has an intriguing common name – Prairie Dropseed. It’s native to much of North America, short of the West Coast.  Though most widespread in the Midwest, there are isolated populations in Virginia, North Carolina, and Pennsylvania. It’s even hardy up in the Arctic North (where Jeff and Linda live).


Sporobolus  shows off some  fluffitude while Echinacea tennesseensis look on in amazement.  Author’s garden.

Now on to the juicy description: fine, green foliage forms fluffy mounds or tussocks up to one and a half feet tall and up to two feet wide.  I describe it to my students as “pet-able” – one just wants to run their fingers through the flowing locks… The tiny, fragrant  flowers appear in late summer form a fluffy cloud above the foliage and wave about on slender stems, even with the slightest breeze.  I think the flowers have a coriander scent, have also heard buttered popcorn and vanilla.  Seeds form and then drop to the ground around the plant (hence the common name), at which point the birds scarf them up.  There is very little actual germination; the species is in fact endangered or threatened in several states (USDA Plants Database).  As the weather cools, the fall color can range from bronze to orange to apricot – just gorgeous – and then turns to a tawny buff for the remainder of the winter.

Newly-planted in the Hahn Horticulture Garden at Viginia Tech – check out that fabulous fall color!

As with many prairie natives, this a very tough character once established – puts up with lousy soil,  little rainfall, and is definitely drought-tolerant. We’ve added more than 100 of them to our campus meadow garden.  At my favorite public garden, Chanticleer (Wayne, PA), they’re planted in huge drifts and are managed in the “natural” way, with controlled burns in the early spring.

Doubt you’d find it at a big box store, but it should be available at an independent garden center near you! Please note this one of those species that does NOT look very exciting in the pot, especially in the spring (green, grassy, that’s it).  But give it a season or two in your garden and…[cue romantic violins…].