July 26th, 2012
How to Change Your Hydrangea’s Color

The hydrangea that was a gorgeous shade of blue when I bought it last year bloomed pink this year. How can I get it back to blue?

blog-dougThe flower color of certain types of hydrangeas depends on the amount of aluminum they draw from the soil, which in turn depends on soil pH. In general, they bloom pink when soils are alkaline or neutral, or toward the blue/violet end of the spectrum when soils are acidic.

Many of the beloved mophead and lacecap varieties of Hydrangea macrophylla respond to changes in soil pH by shifting their flower color. Gardeners have learned to manipulate the soil to take advantage. It’s too late to change the color of your hydrangea this summer, but here’s how to alter it by next summer:

To obtain blue flowers, increase soil acidity by adding sulfur, with your goal being pH 5.5 or lower. Sprinkle about ¼ cup (if the soil is sandy) or ½ cup (for clay or loamy soil) of garden sulfur at the base of the hydrangea and water it in.

For pink flowers, use dolomitic lime to decrease acidity; aim for pH 6.5 or higher. Start with about a pound of lime, scattered around the root zone of the shrub and scratched into the surface. Use half that amount if your soil is sandy.

It’s not an exact science. Some soils (and some hydrangea cultivars) are stubbornly resistant to change. You may need to repeat the application, and even then you may never get the color you want. And don’t expect immediate results; lime or sulfur applied in fall will affect the following summer’s blossoms. Some soils can maintain the color shift for several growing seasons while others will revert after a year.

I used to live in Kansas City, where naturally limey soils tend to keep hydrangeas pink, and gardeners go out of their way to achieve blueness. Now I’m in Pennsylvania, where blue hydrangeas are commonplace and discerning gardeners strive for pink. To my eye, they’re all beautiful.  —Doug Hall

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July 17th, 2012
Embrace Your Brown Lawn

With all the hot weather we’re having in Iowa, my bluegrass lawn looks kinda brown. Would a summer feeding help it to green up?

blog-dougWhen a lawn is stressed from heat, fertilizer is the last thing it needs. Cool-season turf grasses, including bluegrass, fescues, and perennial rye, slow their growth in response to hot weather. If the weather is dry as well as hot, you’ll notice a lot of brown blades among the green. This summer “dormancy” can last through Labor Day or until cooler weather and fall rains prompt a return to green.

You could keep the lawn green through summer with copious amounts of water. But I would argue against that sort of wastefulness. Instead, why not take a break from mowing and allow the lawn to go dormant?

There’s one caveat to letting the lawn brown out, and that is the chance that patches of turf will die if the weather stays dry for too long. A good soak every 2 or 3 weeks is all it takes to keep bluegrass alive. Depending on your soil type and how dry the soil is to begin with, it could take between one-half inch and one inch of water to soak the ground to a depth of 6 inches. If natural rainfall fails to provide this much, you’ll have to step in. Apply water in the early morning, when less will be lost to evaporation, and water slowly so every drop sinks in.

Other summer strategies for keeping a lawn healthy include setting the mower blade high—up to 4 inches—and using a mulching blade that drops finely chopped clippings back on the lawn.

Save the fertilizer for fall. Bluegrass and other cool-season grasses naturally regenerate in fall, when temperatures drop and soil moisture is more abundant. In fall, bluegrass will devote the extra nutrients to extending and thickening its root system instead of producing more top growth. Choose a slow-release organic product.  —Doug Hall

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July 6th, 2012
Growing Foxgloves From Seeds

How do I grow foxgloves from seed? I admired my neighbor’s foxgloves this spring and she offered me seeds.

blog-dougI’m a fan of foxgloves of all types but especially Digitalis purpurea, the common biennial foxglove. They’re easy to grow from seed; one packet yields a generous drift of plants, which is fortunate, because the tall, tapering spires tend to look best when there are lots of them.

Gather seeds from your neighbor’s foxgloves a few weeks after they finish blooming. Stalks that were not deadheaded after flowering will have turned brown, bearing a gazillion seeds each. The seeds shower out of the seed capsules in abundance as you clip the stalks. It doesn’t take long to fill an envelope with seeds, even though they’re tiny.

The only trick to growing foxgloves is the timing. They’re biennials, which means they produce a rosette of leaves in their first year and a vertical spike of flowers the following spring. Sow seeds now, in early July. Some gardeners grow the seedlings in a flat and transplant, but I’ve always found it easiest to sow them in the garden where I want them to bloom next year or in a partly shaded “nursery” bed. Dig the soil to loosen the surface, mix in some compost, and then sprinkle the seeds over the ground. Keep the bed moist while the seeds are germinating.

Eventually—sometime in September or when the seedlings are about 4 inches tall—you’ll need to thin the seedlings so they’re spaced about a foot apart in all directions. It’s tempting to leave more, but crowded seedlings tend to produce wimpy flower stalks. Fortunately, they are easy to transplant at this stage, so you can share the extras with your neighbors. The plants will go dormant when winter arrives, only to return for their grand show next May.  —Doug Hall

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June 28th, 2012
Toxic Ties

We want to plant some garden plots. Can we use railroad ties as the perimeter sides?

blog-dougRailroad ties have no place in an organic garden—or any garden where kids play and edible crops are harvested. Wooden ties are traditionally treated with coal-tar creosote, a nasty, tarry hydrocarbon brew that acts as a wood preservative and water repellent. Creosote is toxic and is thought to be carcinogenic to humans. Less-hazardous preservatives are sometimes used on railroad ties today, but even so, they leave the ties saturated with chemicals that you don’t want in your garden.

Instead of railroad ties, choose nontoxic materials to construct the sides of your growing beds. Untreated lumber, logs, stones, bricks, sheet metal, and cinder blocks are a few options.  —Doug Hall

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June 21st, 2012
The Trouble With Tree Guards

Rabbits were gnawing at the bark of my apple trees last winter, so I put spiral plastic tree guards around the trunks. I recently looked under the guards and was alarmed to see split, oozing bark and lots of ants. What went wrong?

blog-dougThe tree protectors you describe are helpful at keeping hungry critters away from tender-barked trees in winter. The white ones also help protect against frost cracking and sunscald by reflecting sunlight. Tree wraps made of burlap and paper are sometimes used for the same purposes.

But whatever style of tree guard you use, you should consider it a seasonal protection. Wait until the tree is dormant in fall to install it, and remove it as soon as the tree begins to leaf out in spring.

As you’ve discovered, these protectors trap heat and moisture around the trunk during the growing season, creating an environment that can attract insects, promote decay, or even foster fungal diseases such as canker. For similar reasons, it’s not wise to mound mulch against the trunk of a tree.

If gnawing animals are a year-round nuisance, fashion wide cylindrical guards from hardware cloth, which won’t trap moisture against the bark. Or use a stinky repellent, sprinkling or spraying it at the base of each tree.

Fortunately, many trees lose their appeal to rabbits as their bark becomes thicker and corkier.  —Doug Hall

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June 12th, 2012
Planting Beneath a Thirsty Tree

It’s difficult to plant anything under my maple tree because of the abundance of roots right at the surface. Can I add 6 inches of soil on top of the roots and plant in that?

blog-dougMost trees have limited tolerance for changes in the soil grade over their roots. Either adding or removing soil in the root zone can weaken or kill a tree. Six inches is enough to smother many trees; I don’t recommend it. Even if the tree survives the added soil, it will immediately send its roots upward into the new soil layer and you’ll be back where you started.

Shallow-rooted trees like maples are a special challenge for gardeners. One landscaping solution is to choose a drought-tolerant, shade-tolerant perennial groundcover to blanket the ground under the tree. Tolerance of dry soil is necessary because of root competition from the mature tree. Plant smaller specimens that can be tucked among the tree roots without damaging them. You can top the area with up to 2 inches of compost, or a mixture of compost and coarser mulch, to help the groundcover plants get established. Don’t forget to water regularly; even a drought-tolerant groundcover will need some help initially to complete with aggressive tree roots.

Another option: Spread organic mulch, like shredded bark, 2 inches deep under the tree, and then add a few containers for floral color. By giving the tree and the potted flowers separate root zones, you’ll ensure they don’t compete with each other.  —Doug Hall

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June 4th, 2012
Baby Vegetables

At the farmers’ market they charge twice as much for so-called “baby” vegetables. Is there a trick to growing my own?

blog-dougThere are two ways to achieve a miniature harvest: select vegetable varieties that mature at a diminutive size, or plant regular-sized vegetables and pick them before they get big.

In the first category I’d put things like tomatoes, peppers, and eggplants—vegetables that aren’t fully flavored until they achieve maturity. My favorite tiny tomato is ‘Wild Cherry’, about the size of a currant and available from Tomato Growers Supply Co. We’re trialing Burpee’s ‘Cherry Stuffer’ sweet peppers in the Organic Gardening test garden this year. There are tiny eggplants, too, like ‘Little Prince’ from Renee’s Garden.

Other vegetables, including many roots vegetables and leafy crops, develop their flavors at a young age. There’s no need to wait for carrots, turnips, beets, radishes, or onions to reach full size before harvesting them. Kohlrabi, zucchinis, cucumbers, and crookneck summer squash have a superior taste and texture when harvested small. The early thinnings of salad and cooking greens—think of them as microgreens—are deliciously tender. And don’t forget the wonders of new potatoes.

John Scheepers Kitchen Garden Seeds has gotten on the bandwagon with The Happy Baby Garden, a seed collection of kid-size vegetable varieties. Just remember to plant a few extra rows to compensate for the scaled-down harvests.  —Doug Hall

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May 24th, 2012
Deliciously Indeterminate

At the garden center I see different varieties of tomatoes described as “determinate” and “indeterminate.” Which kind tastes better?

blog-dougWhen in doubt, go for the indeterminates. The two terms describe general growth habits of tomato plants. The wild ancestors of tomatoes, as well as many older heirloom varieties, are indeterminate. Their stems continue to grow indefinitely, continually cranking out new flowers and fruits a few at a time, until they are mowed down by frost or blight. The tall, rangy growth of indeterminate tomatoes requires a staking system or cages to keep the “vines” and maturing fruits off the ground. Because the fruits are produced over a long harvest season, indeterminate tomatoes are a good choice for home gardeners.

Determinate tomatoes, on the other hand, grow to a genetically predestined height, then stop. Their harvest period is shorter and more intense, allowing commercial growers to harvest a crop all at once. Compared to indeterminate tomatoes, determinates are a recent innovation, often bred to emphasize the shipping and mechanical-harvesting characteristics needed by commercial farmers instead of the culinary qualities desired by consumers.

There are good reasons to include determinate tomato varieties in your garden. Some of the best early varieties are determinate, as well as certain varieties recommended for cool-summer climates. Small-space gardeners appreciate the compact habit of determinate varieties, which can even be grown in containers. But in general, you’ll find better flavor among the indeterminates.  —Doug Hall

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May 15th, 2012
Sowing Seeds in Hills

Excuse me, but just what is a flat hill? I read about a gardening expert who plants her squash in flat hills. I don’t know what that means.

blog-dougIn gardening parlance, “hill” refers to a cluster of plants—usually vining vegetables such as squash, melons, or cucumbers—that have been sown as a group. I suppose the term got its start in an exceptionally rainy climate where raised planting was necessary to provide drainage for such crops. In this situation, or in poorly drained soil, it’s customary to make a small mound of soil upon which the seeds are planted—a literal hill.

But in regions where soil drainage is adequate or rainfall is scarce, the mounds dry out quickly. In most cases it’s better to form a shallow basin in the soil and plant the seeds in the middle of it. The basin facilitates watering through the course of summer. And even though there’s no elevated ground involved, gardeners refer to this technique as “planting in hills.”

Seed packets for pumpkins and other sprawling crops often recommend planting in hills. The usual procedure is to plant 8 or 10 seeds in a circle about a foot across. Once the seeds are up and growing, select the most robust 3 or 4 seedlings and pull out the rest. Space the hills of rangy melons and squash up to 10 feet apart; those of compact cucumbers or bush-style zucchinis can be much closer.  —Doug Hall

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May 9th, 2012
Choosing Organic Fertilizers

Please define organic where using superphosphate is concerned. Also when using 10-10-10. Thank you.

blog-dougSuperphosphate is a synthetic chemical fertilizer that is not approved for use in organic agriculture. It is manufactured by treating mined phosphate rock with sulfuric acid. It’s toxic to the microbial life of your soil. Because it’s water soluble, it can also contribute to phosphorus pollution of waterways.

If your garden soil lacks phosphorus, it’s better to apply it in the form of bone meal, rock phosphate, composted poultry manure, or compost made from yard waste and kitchen scraps. These organic materials release phosphorus to the soil slowly as they are broken down by soil bacteria. Fish emulsion and liquid seaweed fertilizers offer a quick phosphorus boost.

The ratio 10-10-10 describes the quantities of nutrients within a fertilizer but doesn’t reveal whether or not it’s organic. That said, the vast majority of fertilizers with a 10-10-10 analysis are synthetic. The three numbers represent the percentages of available nitrogen, phosphorus, and potassium in the fertilizer.

Gardeners who are in the habit of regularly feeding their soil with rich compost often find that they have no need for additional fertilizers. If necessary, you can supplement compost with complete organic fertilizers that blend natural sources of nitrogen, phosphorus, and potassium, as well as micronutrients such as iron and calcium. You’ll know which products at the garden center are organic by their “OMRI Listed” label.  —Doug Hall

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