April 20, 2008

urgent garden question: preventing mildew on phlox

Filed Under annuals & perennials, organics, tools & techniques, urgent garden questions

ON OUR NEW FORUMS, Dan asked a great question that reveals a tip you can use right now to prevent powdery mildew this summer on your garden phlox:

“The biggest problem I encountered was with the Phlox I planted,” Dan wrote. “The leaves developed a terrible fungus and it slowed its growth terribly. When I first spotted it, I did some research and decided to use an organic fungicide that I picked up at Storey’s. That worked alright, but the fungus came back. Then, I tried an organic remedy I found on the internet: spraying with a milk solution. That worked less well. The poor plants were so overcome with the black fungus that they eventually withered without flowering late in the summer. I finally cut them down. Now they are starting back with strong green growth and I’m pleased, but I wondered if you had any advice for treating Phlox fungus.”

THIN TO IMPROVE AIR CIRCULATION

One of the best non-chemical ways to deal with powdery mildew, I replied, which Phlox paniculata is so prone to in our humid summers, is to prevent it by improving air circulation in and around the plant.
Do this as shoots emerge by “thinning” the clumps—just use your finger (or a pruner if need be) to knock out like a third of the shoots, to space the remaining ones less closely together. The plant will breathe better, so to speak, and that will help prevent the fungus from overtaking it.
Another good preventive step is to spray starting before the outbreak occurs with a homemade anti-fungal like a solution of water, baking soda and horticultural oil. Rosarians do this with their roses to prevent black spot, another fungal pest; recipes vary but it’s approximately a teaspoon of baking soda and a teaspoon of horticultural oil (from the garden center) in a quart of water, or a tablespoon or so of each in a gallon. Other gardeners swear by horticultural oil alone.
Another truly preventive method: Grow mildew-resistant varieties, which give you the best shot of success. The Chicago Botanic Garden’s Plant Evaluation program is an excellent source for PDFs on the best cultivars of many kinds of plants, including Phlox (click on and download Issue #13 PDF at http://www.chicagobotanic.org/research/plant_evaluation/).

Ask, or answer, Urgent Garden Questions on any topic on A Way to Garden’s new forums. Look forward to seeing you there.

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Comments

4 Responses to “urgent garden question: preventing mildew on phlox”

Hilary on April 24th, 2008 8:19 pm

Phlox ‘David’ is a great cultivar that’s powdery-mildew resistant. Give it a try.
margaret on April 24th, 2008 8:27 pm

Yes, and a beauty–thanks, Hilary, and welcome to A Way to Garden. For those who have not seen it, ‘David’ is white-flowered, and maybe 3 to 3 and a half feet tall. Great suggestion.
M.
marina on June 19th, 2008 4:06 pm

I have PHLOX DAVID. about 30 plants also they are all infected with powdery mildew. i did not see them until all of the plants go mildew and now i spray it with Defender i don’t see any improvement but all the top part of the plant is nice and green i also have cut up all of the leafs that has mildew. i wonder if they are going to bloom this year.
any ideas
Thanks
marina
margaret on June 19th, 2008 4:14 pm

Marina, welcome to A Way to Garden. Wow–30 plants of a supposedly resistant variety all mildewed! Not so happy-sounding. If the tops are good and healthy and green, there’s reason for hope, however. Like so many things in gardening, one has to just wait and see. Keep them stress free from here on out if you can, watering when dry and so on.

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from martha to just margaret
I was so blessed to visit and document many of the nation’s finest homemade gardens for 15 years for ‘Martha Stewart Living,’ first as its garden editor and then as editorial director for the company. The list of places we were proud to publish included my own upstate New York home a few years back. Take a tour of how it looked then. Want to know more about me? Or read what Anne Raver said in June in The New York Times, calling A Way to Garden “the best (garden blog) I’d ever seen.”
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August Garden Chores

All based on my Zone 5B Berkshire/Hudson Valley location; adjust accordingly.

I SOMETIMES THINK THAT AUGUST, not April, is the cruelest month (though T.S. Eliot thought otherwise). Hazy, hot and humid…and plum tuckered out. But give up we must not. Every weed pulled now is a hundred you don’t have to deal with later (well, who knows the precise math of mama weed to baby weed, but you get the idea: prevention!). Don’t let them go to seed.

WATERING IS another major focus; don’t waste water on lawns, which will bounce back from brown in time when cooler, moister days return.

MAKE A PASS through each bed each week, since weeds are not just unsightly but steal moisture, nutrients and light from desired plants. Top up mulch in all garden beds if washed or worn away to help in the plight.

TREES & SHRUBS

STOP FEEDING woody plants. Promoting more soft growth in high summer isn’t good; time for them to start moving toward the hardening-off phase of their cycle. No more eats till earliest spring.

TREES ARE especially vulnerable to drought, particularly the oldest and the youngest (those planted in the last few years). Water deeply, as with a Tree-Gator. Ugly…but better than not watering the kids!

ALWAYS BE on the lookout for dead, damaged, diseased wood in trees and shrubs and prune them out as discovered. Ditto with suckers and water sprouts.

VEGETABLE, FRUIT & HERBS

AS AREAS COME EMPTY from harvest, build vegetable-garden soil by sowing cover crops: medium red clover now, or perhaps winter rye if you don’t do some areas till mid-fall. These “green manures” will be turned under to improve soil tilth and fertility.

SOW ANOTHER CROP OF PEAS right now for fall harvest (and perhaps freezing for offseason use!). Shelled peas from the freezer really make risotto in January taste like summer.

STRAWBERRY BEDS may appreciate rejuvenation now, if you didn’t get it done last month.

KEEP ASPARAGUS well weeded. Let asparagus ferns grow till frost to feed the underlying crowns.

DID YOU HARVEST GARLIC? Save the best heads for replanting this fall, the ones with the biggest cloves (or order more for fall delivery).

ANOTHER SOWING of chard, radishes, arugula, spinach, turnips, beets and lettuce means succulent fall crops. With salad greens, sow small amounts now and again in 10 days. Direct-sow one more row of bush beans if you don’t have pole beans to rely on for harvest now through fall, but do it fast.

DID YOU START MORE BASIL from seed? Young, fresh plants sown immediately will be better than woody old ones for combining with those fall tomatoes. Is there enough fresh dill coming for late pickles? For peak flavor, basil, sage, marjoram and oreganos, mint, tarragon are best harvested just before bloom. Harvest lavender, rosemary and chamomile as they flower, blossoms and all.

FLOWER GARDEN

DAYLILIES can be dug and divided as they complete their bloom cycle, right into fall, if needed.

PEONIES are best divided and transplanted in late August through September, if they need it. Remember with these fussy guys that “eyes” must not be buried more than an inch or two beneath the soil surface. Want more peonies? Now’s the time to order from places like Klehm’s (see Sources list).

MANY POPULAR ANNUALS can be overwintered as young plants if you take and root cuttings now rather than try to nurse along leggy older specimens. Geraniums, coleus, wax begonias, even impatiens (to name just a few common ones), if grown in good light indoors and kept pinched and bushy, will yield another generation of cuttings for next spring’s transplants. Probably best to expend this effort and space on things you really treasure—an unusual form of something, not the garden variety.

MANY PERENNIALS and biennials can still be started from seed if you hurry, then set out in the fall into nursery beds.

DEADHEAD FADED PERENNIALS and summer bulbs unless they have showy seedheads, or you want to collect seed later (non-hybrids only).

ORDER BULBS to get varieties you want (see Sources). Remember our “early, middle, late” mantra when doing so.

PREPARE NEW beds for fall planting by smothering grass or weeds with layers of recycled corrugated cardboard or thick layers of newspaper, then put mulch on top.

RE-EDGE BEDS to make a clean line and define them, and keep edges clean with regular fine-tuning with grass shears. A clean edge makes a big difference.

GENERAL

IF YOU ARE IN JAPANESE BEETLE territory, handpick (as with other obvious pests like tomato hornworms) in early morning and drown in a can of water to reduce infestation. Plan to try to reduce grub population with nematodes.

GARDENS NEED an inch of water a week from you or the heavens. Check your rain gauge to make sure they get it, and remember: soak deeply in the root zone, don’t spritz things with a sprayer now and again like you’re washing the car. That’s a garden no-no. Pots need extra attention, especially smallish ones in sun, and they also need regular feeding. Be alert!

HOUSEPLANTS

IF HOUSEPLANTS NEED repotting, do it now, while’s they’re still outside (less messy than in the house!). Don’t step up more than an inch (on small pots) or a couple (on large ones). Most plants don’t like to swim in their containers.

LAWNS

MID-AUGUST TO MID-SEPTEMBER is prime lawn-renovation and planting time in the North.

DON’T BAG OR RAKE clippings; let them lie on the lawn to return Nitrogen to the soil.

COMPOST HEAP

DON’T LET the heap dry out completely, or it will not “cook.” Turning it to aerate will also hasten decomposition, but things will rot eventually even if not turned.
Brief but Juicy

ultimate garden no-no’s
WHEN SOMEONE ASKED in a comment about my point of view on using landscape fabric, the fuse was quickly lit: NO! I said. NO! I’ve rounded up some no-no’s we’ve posted collectively so far, but I bet by now there are a few more things to bitch about. Grab a lawn chair and a cold drink, and we can fester together. Sure beats weeding (which ought to be a garden no-no).

lose anything lately?
THE SAYING GOES THAT a thing of beauty is a joy forever. I guess “forever” in this case is in the mind’s eye. My darling, oldest bottlebrush buckeye (Aesculus parviflora) went down for the count in July, or at least half of it did, and I had already seen the death knell for a couple of my 10 crabapples. Jeez.

true love, really
LOOK, I HAVE A THING for frogs. Call it my little fetish. An issue. Whatever. My general obsession notwithstanding, I’ve finally met THE ONE FOR ME.

hail the stewartia
I LIKE PLANTS THAT EARN THEIR KEEP. By that I mean they do more than a week or two of showing off; they look good in more than a single moment, or season. The small-ish to medium trees in the genus Stewartia are a good bet if that’s the kind of multi-season interest you are looking for. Sound good?

more, more, more clematis
WHEN I SEE ‘POLISH SPIRIT’ CLAMBERING up and through the golden Chamaecyparis in late spring-into-summer, I realize I have a serious Clematis shortage around here. Not in the Chamaecyparis, specifically, but in lots of other places where things look a little dull. I’ve got a penchant for growing vines up and over otherwise-dull shrubbery, you see.

can-do pruning
REPEAT AFTER ME: I can prune. I can prune. If you follow this simple method for starters, your woody plants will thank you.

the ‘other’ peonies
JUNE WAS PEONY TIME, the big raucous kind of peony time, but just before that another kind of peony you might want to consider adopting did its subtler, wonderful thing.

which lilac to plant?
SO MANY LILACS, so little space. Browse a glossary of some of my favorites before you shop—maybe you’ll like them, too.

non-blooming peonies?
Did your peonies not cooperate—was there not a good crop of flower buds, and you don’t know why? This came up on the Forums, and here’s the dish.

twist-off ticks
I AM COMING IN everyday with at least a tick or two on me; not embedded, thankfully, so far, but it's only a matter of time. But I am prepared. Are you?

anything but forsythia
I guess I have a thing against forsythia…even though I have several specimens of it along the fringes of my property. But there are better choices for spring color among shrubs.

surprise (avian) visitors
If you make a garden for birds, or even plant a crabapple or two (or ten), you never know who’ll show up.

magnolias to love
THEY’RE MEMORIES NOW but I couldn't garden without magnolias. Want to know more about the queen of the spring-blooming trees?

order in the garden
I AM LABELING my plants, I am. As memory fades, out comes the label machine, just in the nick. Saved by the Dymo. You can be, too.
Buried Treasure

I NOTICE THAT BLOGGING results in some rich but buried treasure: great stuff in a comment thread you may not see; interesting topics on the forums that perhaps you haven't visited.

Subjects ranging from feeding and pruning Hydrangeas and pruning clematis, to entertaining (read: ranting) lists and lists of garden no-no’s (not just mine!).

Pick a click, and enjoy. Better yet, CHIME IN yourself. Up in the nav bar…that's right, GO FOR IT: our Q&A FORUMS.