Powdery mildew


Powdery mildew, a harmless fungus infection, on leaves of beebalm (Monarda fistulosa). Notice that the plants bloomed heavily despite the infection and that neighboring plants of unrelated species are unaffected. Beebalm almost always gets powdery mildew.


Powdery mildew on coralberry (Symphoricarpos orbiculatus). Again, despite the infection, this vigorous shrub is quite healthy and about to bloom on schedule. Coralberry rarely gets powdery mildew, but we’re having a rather wet growing season.

Powdery mildew, like most of the diseases that infect plants, is caused by a fungus, or rather a large group of related fungi in the order Erysiphales. It unsightly but completely harmless.

What should you do about powdery mildew? Absolutely nothing. It is a cosmetic problem and will not harm your plants. To prevent it or reduce the incidence, you can use some commonsense horticultural practices, such as preventing overcrowding or watering in the morning only. If you feel you must treat it, a mild spray of milk, diluted 1:10 with water, has been shown to be effective. But remember that almost everything you do in the garden may have unintended consequences, such as changing the pH of the soil or killing butterfly eggs.


6/23/17: In the garden this week


June is bustin’ out (couldn’t resist) in a perennial bed glorious with yellow sundrops (Oenothera fruticosa), orange butterfly weed (Asclepias tuberosa), and bergamot/beebalm (Monarda fistulosa), plus grasses and numerous species that have finished blooming or not yet bloomed. This border gets full sun and was originally planted over 20 years ago. The soil, which is very sandy, has never been amended in any way.

During the past few years of drought, I had forgotten what a gardening season with normal rainfall looks like. I had forgotten how the plants grow so exuberantly that I have to keep cutting them back along paths, in front of patio chairs, near the air conditioner, how quickly tomato plants grow (more on that below). And what it’s like not to have to exhort clients to keep newly-installed plants well watered until they’re established. It’s a pleasant change.

As I write this, the predicted rain has just started. Can I confess that given a choice between a dry weekend and a good soaking rain, I’d vote for the rain in most cases? But the thing about gardening is that we don’t get a choice.

Here are some things you might consider in your garden this week (after the rain stops, of course):

water new plantings: We received about 1 1/2 inches of rain in the past week, so no watering should be necessary this week. However, you should always water well after planting to settle the new plants in the ground. In dry weeks (those with less than an inch of rainfall), you need to water all plants installed this spring or last fall. How do you know when we’ve received an inch of rain? You can make a highly sophisticated rain gauge–an old plastic container or tin can placed among the plants. I total the weekly rainfall and decide whether to water my new trees or my clients’ new plantings each week.

— all vegetables, including tender crops like tomatoes and peppers and corn, should be planted out by now, and it will soon be time to remove early greens like lettuce and spinach. Water deeply during dry periods, particularly when the weather is hot, and watch carefully for pests and diseases. Removed diseased plants promptly to prevent spread.

— be sure to properly tie, stake and prune your tomato plants. Most tomato cages are pretty useless: the plants outgrow them before they start to bear fruit. And unless tomato plants are properly pruned, by pinching out the suckers, they will be so bushy that they’ll be especially susceptible to fungus infections like verticillium wilt. You’ll find general guidelines for growing tomatoes here and specific watering instructions here.

—  It’s a bit late to clean up the perennial garden or to divide and replant. Once the weather turns hot, plants put their energy into top growth and blooming. I would no longer move or divide plants, but if you continue to plant, water very thoroughly and keep an eye on those new plants. They will need extra water.

it’s too late to fertilize your lawn or to reseed bare patches, no matter what your lawn-care service tells you. Here’s a suggestion: don’t feed at all this year. The lawn will look just fine. Or wait until around Labor Day and use one application of a slow-release organic fertilizer. Avoid pesticides, fungicides, and herbicides. Pesticides kill butterfly and firefly larvae and native ground-dwelling bees as well as “bad” insects. And garden chemicals are not so great for kids or pets either; common herbicides, in addition to killing butterfly host plants like violets, are carcinogens. Best to avoid them.

— it’s also a bad time to prune woody plants. The plants are using so much energy growing, flowering, and fruiting that they have little to spare to healing a wound. There will be short window of time later in the summer. Of course, continue to prune diseased or injured plants at any time and to remove any safety hazards, such as overeager shrub that block sidewalks.

And don’t forget to count the fireflies! The more you see, the healthier and more sustainable your garden is.


We moved the patio chairs forward to get out of the way of the raspberries. The elderberries (white flowers in background) are especially tall and vigorous this year.

The Lamiaceae

Beebalm (Monarda fistulosa) began to bloom this week.

Beebalm (Monarda fistulosa) is an easy-to-grow native plant that belongs to the Lamiaceae, or mint family. The square stems, strongly opposite leaves, and lipped flowers are family characteristics.

The Lamiaceae (the “-aceae” ending, pronounced “A-C-A,” always denotes a family) is a large and widespread plant family that includes over 230 genera and 7,000 species, mostly forbs (non-woody flowering plants) or small woody plants. It is commonly referred to as the mint family, and it includes most of our common culinary herbs, including the mints, basil, thyme, marjoram and oregano, rosemary, sage, and lavender. It also includes many familiar garden plants: in addition to beebalm (bergamot, Monarda), these include Agastache, Ajuga, Callicarpa, Caryopteris, Coleus, Glechoma (a weed), Lamium, Nepeta (catmints), Physostegia virginiana (obedient plant, a native perennial), Salvia (ornamental sages), and Stachys.

The aromas and flavors that make many members of this family pleasing to us as culinary herbs make them displeasing to animals. Most furry pests, like deer and rabbits and woodchucks, avoid all members of this family, which is why you can plant most culinary herbs (with the exception of parsley and dill, both members of the Apiaceae) in an unfenced garden. Although some insects do attack mints, most critters leave them alone.

Which leads us to their greatest benefit in the garden: they are distasteful to most four-footed garden pests, so if you scatter them throughout the garden, they protect or hide the more appealing plants. For example, Asters, Coreopsis, Phlox, and Echinacea are extremely attractive to deer and rabbits.But it you place these plants among members of the mint family, and they are much less likely to be eaten.

There are numerous native family members. Best known are several species of Monarda: M. fistulosa, shown above, blooms in shades of pink and lavender; M. didyma has bright red flowers. Both are about 3-4′ tall, perennial, and very easy to grow as long as they get at least half a day of sun. M. punctata, dotted mint, is an annual, although it self-seeds easily. It’s about 2′ tall, also a sun-lover, and is in bloom right now.


Dotted mint (Monarda punctata) is in bloom now. Notice the beautiful flame-shaped milkweed pods behind it. There’s some late-blooming M. didyma to the right.


M. punctata’s flowers are the small, lipped, dotted structures. The large curved white “petals” are bracts, or modified leaves.

Also in bloom now is Agastache foeniculum, or lavender hyssop, a biennial (but easy to keep going with seed). This plant has an anise, or licorice scent, and the edible flowers make a refreshing addition to salads (in small amounts only–the taste is very strong). It’s about 3′ tall and like its cousins needs a sunny spot.


Agastache foeniculum (blue flowers to the right), which rabbits and deer don’t like, serving as a sentry beside Rudbechia triloba, which they do, very much.

7/10/15: In the garden this week


This is the same part of the garden I showed you last week. Orange butterflyweed is almost finished blooming, and culver’s root (white) dominates for a short time while we wait for Rudbeckia to take command.

The garden changes so quickly in midsummer that I thought you would enjoy seeing the same views for a couple of weeks in a row. Compare this photos with last week’s—there’s not quite as much yellow as I expected, but the Rudbeckia is certainly primed to take over. In the shadier garden, the sweet joe pye weed that was in bud last week is in full bloom.


This garden gets only half a day of sun. The sweet joe pye weed (Eupatorium purpureum) is at its peak as the orange butterflyweed fades.

Here are some chores you might attend to in the garden this week:

water new plantings: we got well over an inch of rain this past week, so no watering is needed now, but keep watching. Any week in which we receive less than an inch of rain, water all woody plants installed this spring or last season. Perennials planted last spring should be well-established, but those planted last fall and this spring need supplemental watering during dry spells. How do you know when we’ve received an inch of rain? I use a highly sophisticated rain gauge–an old yogurt container placed on the ground among the plants. A tunafish or catfood can works equally well.

finish harvesting early greens such as lettuce, spinach, arugula, mustard greens, and mesclun mix, plus peas and radishes. As greens bolt, or go to seed, pull the plants and plant something else. A row of beans, perhaps?

practice good horticulture with warm-season crops such as tomatoes, peppers, squash, eggplant, beans, corn, and cucumbers: Monitor for insect eggs and larvae and remove them before infestations become serious. Throw out badly infested or diseased plants to prevent the spread of disease (do not compost diseased or infested plant material). Cucumber vines are showing signs of wilt: remove them immediately to prevent the spread of this fungal disease.

— As tomatoes ripen their fruit, cut back on watering to avoid split fruits. Keep removing suckers all summer long. Look at this post, this one, and this one for basic information about growing tomatoes.

— it’s not too late to extend a garden bed or start a new one, and it’s always a great idea to eliminate some lawn: spread a 3-4 inch layer of cedar or hemlock bark mulch over the area to kill the grass. In the fall, you’ll be able to plant right through the dying grass and mulch. I mulched an area of lawn about a month ago and am scattering perennials seeds there as they ripen. Columbine is almost finished ripening seed, and coreopsis seed ripens nearly every day.

— it will soon be a good time to prune woody plants. Once all growth, flowering, and fruiting are done, the plants are relatively dormant, giving you a window of time to prune before they get ready for their next critical task: leaf abscission (shutting down for the winter). I do most of my pruning in winter, but I also prune back shrubs as needed after they have ripened their fruit.

— follow a sustainable lawn care regimen: if you feel you must fertilize your lawn, best practice is to give it no more than two applications of slow-release organic fertilizer each season, around Memorial Day and Labor Day. It’s too late now to reseed bare areas: wait until early fall. Better still, if you have a place where grass won’t grow, plant something that will, like shade-loving native perennials. Let the grass grow at least 3″ tall for maximum photosynthesis. Lawns do not need water now (or ever), but if you do water, do it infrequently and deeply to encourage deep root growth. One inch of water once a week is much better than a few minutes each day. But remember: the more you water, the more you’ll have to mow!

Enjoy the garden this week!


Culver’s root (Veronicastrum virginicum) does well in any sunny site. It attracts pollinators by the score and makes a nice backdrop for more colorful plants. Beebalm (Monarda fistulosa) has been in bloom since late May and won’t stop anytime soon.

6/27/14: In the garden this week


The garden is becoming colorful! In this picture you see yellow sundrops (Oenothera fruticosa), which has been in bloom for a couple of weeks, and pink beebalm (Monarda fistulosa), and orange butterflyweed (Asclepias tuberosa), which have just begun to bloom–a bit late this year. The very tall plant on the left is sweet joe pye weed (Eupatorium purpureum), which will be in bloom very soon. Usually my garden turns pink around June 10, when the beebalm, queen of the prairie, coneflower (Echinacea purpurea), and red milkweed (Asclepias incarnata) all come into bloom together. Everything is still a bit late this year.

keep newly installed perennials and woody plants well-watered throughout the growing season. The recommended amount is 1 inch per week during dry spells. The storm on Wednesday night brought between 1 and 2 inches of rain to my garden, so there should be no need to water this week. Established plants should not need supplemental water.

do not do any pruning except removal of dead or diseased material while woody plants are in active growth. They are using all their energy to accomplish the vital tasks of blooming and setting fruit. They have no energy to spare for making scar tissue. The next window of pruning time will come in midsummer.

– for better bloom next year, remove the flowers of spring-blooming shrubs such as lilacs and mountain laurel after they finish blooming. The exception, of course, is fruit-bearing shrubs such as native dogwoods and viburnums.

monitor the vegetable garden for pests and diseases and take action immediately. In particular, remove plants affected by borers and wilt, and hand-pick to keep pest populations low.

water tomatoes deeply (up to 2” per week) until fruit begins to ripen, then cut back to 1” per week. Remember to take rainfall amounts into account when determining how much to water. Water in the morning, and water deeply. Continue to stake and tie tomato plants and to remove suckers.

– pick peas while young; cut down basil plants to  make pesto before plants begin to flower, remove early spring greens and lettuce when they bolt. Most vegetables taste better young.

– perennials should need no care except pinching to promote bushy plants and keep plants short when necessary

— lawns should not need watering this week because we’ve had ample rain, and they need no fertilizer until early fall, if then. Mow with a mulching mower and leave the clippings on the grass. Remember that the more you water, the more you have to mow.

Here’s the red or swamp milkweed (Asclepias incarnata) in full bloom yesterday:



The garden in snow

More snow yesterday–snow on top of snow, and the temperature hasn’t risen above 20 degrees for what seems like two weeks. The garden was particularly pretty yesterday afternoon while the snow was still falling.


Bergamot (Monarda fistulosa) is holding its seedheads high above the snow for the birds to take advantage of. Although most of the most nutritious seeds (such as sunflower) and berries (such as dogwood) are long gone, plenty of winter food remains for the birds we see everyday.


Coralberry (Symphoricarpos orbiculatus) should be called pinkberry. The berries remain bright pink all winter. So please, please consider this small, carefree native shrub instead of the invasive beautyberry.


If your garden isn’t feeding the birds all winter, check back soon for a list of plants you might consider for winter food.

6/28/13: In the garden this week


Late June is always the pink season in my perennial gardens–the place is lousy with bergamot/beebalm (Monarda fistulosa and M. didyma, two closely related native species). Rudbeckia is showing buds, so within a week or so, there will be lots of orange to enliven the scene.

In summer my perennials and woody plants require very little work; my attention is focused on the vegetable garden. Here’s a list of things to attend to this week, in between restful sit-downs in the garden to admire your handiwork:

– keep the grass long (3″ or more) to reduce mowing times. There is no need to fertilize or water. As the weather heats up, the grass wants to go dormant, so let it.

– start to collect perennial seeds: columbine, heuchera, and other spring bloomers are ripening seeds, even as they continue to bloom

— as perennials finish blooming, leave the dead flowers on the plants. The seeds will feed the birds next winter (and you can always collect some seeds later on yourself)

– if you have not already done so, pull out early spring greens, such as arugula, spinach,  and lettuce; pull out pea plants after they finish producing; compost all these plants unless they are diseased

— harvest basil and make pesto to freeze for the winter (see preceding post)

– continue to plant beans, kale, chard, and other members of the brassica clan if you have room; harvest peas, young squash, and beans before they get large and tough. Peas are finishing their brief but delicious run in my garden right now.

– continue to stake tomato plants firmly and remove all suckers

– monitor the vegetable garden carefully for pests and diseases

Happy summer weekend to all!