In the garden today

Here are some new pictures you might enjoy:

Berries of cranberrybush viburnum, V. trilobum, look almost too beautiful to be real. Soon they’ll be bright red, but despite that attractive color, birds don’t eat them until winter.

A detail of the flower of nodding pink onion, Allium cernuum.

And a view of several flower heads. This is a great front-of-the-border plant, only about 18″ tall.

As orange butterfly weed (Asclepias tuberosa) finishes blooming, the Rudbeckias take over for the rest of the summer. This is R. subtomentosa, an indomitable plant if there ever was one.

Wild petunia, Ruellia humilis, is another great front-of-the-border plant. It’s perennial and well-adapted to poor, dry soil.

And let’s not forget about shade plants for summer color. Great blue lobelia, Lobelia siphilitica, blooms throughout the month of August and into September.

7/28/17: In the garden this week

This plant combinations says “the height of summer” in no uncertain terms. The Rudbeckia will be in bloom until September, but the Vernonia (ironweed) will only last a few weeks.

Who says there are only four seasons? To me, we are transitioning from early summer to what I think of as the height of summer: the brightest-colored flowers are blooming, native fruits are ripening fast, fall bloomers such as asters are showing buds, and some late-summer plants, such as great blue lobelia, are coming into bloom. And of course, tomatoes are beginning to ripen fast in the vegetable garden. Here are some not-too-strenuous garden chores for this hot weather (in addition to weeding, made necessary by a season of normal rainfall, in contrast to the past couple of years of drought.

— water new plantings: unless we get a decent amount of rain this weekend (and forecasts do predict rain), go ahead and water newly planted grasses, shrubs, and woody plants. Remember that perennials and woody plants that you planted this spring or last fall need supplemental water during dry periods throughout this growing season. The rule of thumb is at least an inch of water per week for newly installed plants. In dry weeks throughout the growing season (weeks 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’s time to remove early greens like lettuce and spinach. In fact, if you intend to plant a second crop of cool-weather vegetables, you should be buying seed. 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. Continue to remove the flowers from basil plants as they form; you should already have cut down the plants to make pesto.

— be sure to properly tie, stake, and prune your tomato plants. Most tomato cages are much too small: 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 too late to plant. Wait until the weather turns col in fall. Once the weather turns hot, plants put their energy into top growth and blooming rather than growing new roots. If you do continue to plant, water very thoroughly and keep an eye on those new plants. They will need extra water during dry periods, as explained above.

— 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 almost time to prune woody plants. You want to prune when the plant is relatively quiescent—when it’s not using a great deal of energy growing, flowering, and fruiting that it has little to spare to healing a wound. This will happen between now and leaf drop in fall. Basically, when you see that the plant has finished fruiting and that it has formed next year’s buds, but the leaf color is not fading yet, you have a window of time for pruning. Of course, you should prune diseased or injured plants at any time as well as remove any safety hazards, such as overeager shrub that block sidewalks or diseased trees that might fall down.

Enjoy the garden this week!

The first blossoms of Hibiscus moscheutos, rose mallow, opened this week in my garden. This native hibiscus is a short-lived perennial that self seeds readily, produces flowers of different colors, and is very easy to grow.

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.

Watering wisely

An exuberant summer border should not require any watering once it’s established–if the plants were sited correctly in the first place. These plants are all perennials. This border is never watered or fertilized.

All horticulturists know that the main reason that plants die is improper watering. I see examples of this all the time, both insufficient watering and overwatering, and in this post I’ll explain some ways you can avoid it. But please refer, first of all to the watering guidelines page, which sets out general principles and explains the concept of “establishment.”

The first step is to pick the right plant for your site. If you place a wetland plant in a dry site, you may have to water it pretty much forever (although some wetland plants do quite well in dry sites, once properly established). A bigger problem is the opposite one: placing a plant adapted to dry conditions in a wet site, or in a site that’s watered continually. The plant is quite likely to rot away.

Many people start gardening by planting annuals, and when they go on to perennials, grasses, and shrubs, treat them like annuals. Annuals are plants that live for a single season. They include all vegetables and many ornamentals such as impatiens and marigolds. Because of their short lifespans, they do not develop large, deep root systems, so they do need continual shallow watering. (This is a big reason that I discourage clients from using annuals as ornamentals–growing them is just not sustainable.)

Most ornamentals, certainly almost all native ornamentals, are perennials: their lifespan ranges from several seasons to pretty much forever. These plants develop large, deep root systems. They put down roots that can mine the soil over a large area for minerals and moisture. To encourage them to develop these deep root systems, water infrequently, if at all, once they are established. A little drooping on a hot afternoon will not harm them. Recent research shows that stress is good for plants: it encourages them to grow deep, strong roots.

What does this mean for the average gardener? It means the following key points:

— during establishment, perennial plants need supplemental watering during dry periods only.

— once established, properly sited perennial plants do not need supplemental water except perhaps in periods of extreme drought.

— the rule of thumb for newly planted trees is one year of supplemental watering per inch of trunk diameter. So, for example, a tree with a 2-inch diameter should receive supplemental watering during dry periods for two years.

— established lawn grasses, which are perennial, do not need supplemental water, and if treated this way, they will go dormant during hot, dry periods but green up again with cooler weather or rain

— if you cannot tolerate a dormant lawn, provide deep but infrequent watering to encourage the development of deep roots

— for annuals such as vegetables, deep watering once or twice a week is better than daily shallow watering, which can lead to rot and all kinds of fungus diseases

Optimal watering for a vegetable garden, made up of annual plants, is deep rather than shallow watering. Monitor rainfall and water only when it’s needed.

7/14/17: In the garden this week

A luxuriant summer border–a bit too luxuriant this year. With all the rain, I have to keep cutting plants back.

Despite all the rain and warm temperatures throughout this growing season, when I look back at photos of past years’ gardens it’s obvious that many things are blooming 10 days to two weeks later than usual. Normally Rudbeckia subtomentosa begins around July 4; right now the first flowers are  opening, as you see in the picture above.

Over 4 inches of rain this week, and still counting! (It’s raining hard as I write this.) If you have a rain garden, or a spot that might become one, it’s probably been dry for the past 3 years, but it’s most likely nice and wet now. I’m seeing more powdery mildew than in recent seasons, and if it keeps raining, ripening tomatoes may crack on the vine. But all the rain is really good for our poor forest and street trees, which have had a thirsty time recently.

When it stops raining, here are some things you might do in the garden this week:

— water new plantings: NOT! Rainfall for the week is well over 4 inches, so nothing should need watering. BUT keep monitoring: perennials and woody plants that you planted this spring or last fall need supplemental water during dry periods. The rule of thumb is at least an inch of water per week for newly installed plants. In dry weeks throughout the growing season (weeks 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’s 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. Remove the flowers from basil plants as they form, and cut down the plants to make pesto as soon as you have enough leaves for a batch.

— be sure to properly tie, stake, and prune your tomato plants. Most tomato cages are much too small: 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 during dry periods, as explained above.

— 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 or diseased trees that might fall down.

It’s supposed to stop raining sometime tomorrow! get out and enjoy the garden this week.

Rudbeckia flowers are enchanting as they open.

Ripening fruit

Fruits of cranberry bush viburnum, V. trilobum, are just beginning to show color. Soon they will be bright, shiny red, but the birds won’t eat them until winter.

If you’ve read this blog for a while, you’ve probably realized that I’m obsessed with fruit. I noticed today that two of the many fruiting shrubs in my garden are “in that delightful state, when farther beauty is known to be at hand, and when, while much is actually given to the sight, more yet remains for the imagination.” Jane Austen always said everything best.

Look carefully amongst the leaves–fruits of black chokeberry, Aronia melanocarpa, turn reddish before they turn black. As soon as they’re ripe, birds will devour them.

7/7/2017: In the garden this week

Culver’s root (Veronicastrum virginicum), beloved of pollinators, is in full bloom now.

Refer back to last week’s post for some specific suggestions; not much has changed. I can see out my window that we received at least 1 1/2 inches of rain so far today, so no need to water this week. With this much rain, you need to be vigilant about fungus diseases, so carefully prune or pinch out the suckers on tomato plants to allow for air circulation.

Verbena stricta, or hoary vervain, is one of the strongest bloomers in my summer garden. It starts blooming in late June and continues through the summer.