problem solver

Tobacco hornworm
Manduca sexta

IDENTIFICATION — These 3- to 5-in.-long giants of the caterpillar world have a large harmless spike, or horn, on their tails. Their green color blends into the foliage of tomato and tobacco plants, some of their favorite foods. They will also attack plants in the nightshade family, such as datura, petunia and nicotiana.

DAMAGE — In early to midsummer, caterpillars can quickly strip a plant of foliage and may sometimes even chew on green tomatoes.

CONTROL — If there are just a few caterpillars on your plants, handpick them. If numbers are larger, spray Bt on affected leaves only. Thuricide, which contains the kurstaki strain of Bacillus thuringiensis, works well on tobacco hornworm and is safe to spray right up to harvest, but be sure to wash fruit well before eating. Or grow alyssum, dill or Shasta daisy to attract braconid wasps, which lay dozens of eggs within each larva, parasitizing and killing it.

plant pick

Penstemon
Penstemon hybrids

Need a plant for that hot, dry spot? Also want hummingbirds? Choose a penstemon! Although these plants have a reputation for being finicky, all they really need to thrive is well-drained soil. (Although some, like Red Rocks™ (USDA zones 5 to 9), at left, tolerate a little more moisture and humidity than others.)

To give them the sharp drainage they love, plant penstemons in rock gardens or raised beds, or work some gravel or coarse sand into their planting area. You’ll know the texture is right when you squeeze a handful of damp soil and it doesn’t stick together. They do like a little extra moisture in spring and as new plants just getting established. Water them deeply and infrequently to encourage the roots to grow deep. Fertilize sparingly or not at all, as too much fertilizer will make the stems weak and floppy. Follow these simple rules, and your penstemons will attract hummingbirds for months!

TYPE Perennial SIZE 4 to 72 in. tall and 10 to 36 in. wide BLOOM Red, pink, purple, yellow or orange flowers early to late summer LIGHT Full sun SOIL Moist, well-drained PESTS None serious HARDINESS Cold: USDA zones 3 to 10; Heat: AHS zones 10 to 1

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problem solver

Heat stress symptoms

Summer heat can be as damaging as winter cold. Here are some symptoms of heat-stress damage and some strategies for surviving the summer.

WILTING AND STUNTED GROWTH — Plants that exhibit these symptoms, such as fuchsia, are in need of water and shade. If a plant is exposed to prolonged periods of heat stress, the new growth will be smaller than the old and eventually the root system will shut down.

DROOPING OR ROLLED FOLIAGE — Another mechanism plants employ to protect themselves from heat is to roll their leaves and let them droop. Commonly seen on rhododendrons, this allows the plant to reduce its leaf surface area that is exposed to the sun. If left under these conditions for a long time the plant will eventually die.

To prevent these types of heat stress, place plants appropriately in your garden. If you have plants that are sensitive to summer heat, put them in a location that receives morning sun and afternoon shade, like an eastern exposure. This placement is also good for plants that suffer leaf scorch, like hosta.

Keep plants well mulched; organic mulch shades root systems and retains soil moisture. Rock mulches tend to add heat to the root zone and don’t conserve moisture as well. Also keep plants well watered. Using drip-irrigation lines can increase moisture without requiring you to stand out in the heat.

shrubby st. john’s wort
hypericum prolificum

Sometimes it seems that all the best shrubs either flower in the spring or have fabulous fall color, leaving the summer bare. Here’s a shrub that’s showy in the summer. Shrubby St. John’s wort has bright-yellow fluffball flowers that bloom for four to six weeks in midsummer. The foliage is clean, dark green and sets off the flowers nicely.

Although this shrub is showiest in summer when it’s blooming, it does have some winter interest too. Brown seed capsules dot the plant and usually last until late winter. They’re a great addition to dried flower arrangements too.

Shrubby St. John’s wort may need to be pruned hard to tidy it up. It also tends to be short-lived, so you may have to replant it after four or five years. The blast of summer color makes it worth what little added trouble it is to replace occasionally. ‘Hidcote’, in the photo, is a popular, widely available hybrid that has large, slightly fragrant flowers.

TYPE Shrub SIZE 1 to 4 ft. tall and wide BLOOM Midsummer LIGHT Full sun SOIL Well-drained to dry, alkaline PESTS None serious HARDINESS Cold: USDA zones 4 to 9; Heat: AHS zones 9 to 1

moving a plant
in the heat

It’s not ideal. But sometimes you can’t avoid moving a plant in the middle of summer. However, this project doesn’t have to spell disaster (or crispy plants). With some careful planning and planting, your plant may not even know it’s taken a road trip! Here are six tips for a smooth move:

1. Water the plant the day before you move it — a well-hydrated plant tolerates a move better than a dry one.

2. Dig the new hole before you dig up the plant you’re moving. It’s best to minimize the time your plant’s roots are out of the soil. Make the hole large enough for the existing root ball.

3. Gather everything you need: a spade and a tarp or a wheelbarrow, and if you’re moving any distance, wet newspaper or a sheet of damp burlap. A friend might come in handy, too, if your plant is large. Make sure you move the plant during the coolest part of the day.

4. Tie up the foliage to get it out of the way if the plant is very large. To dig, slice straight down with the shovel rather than at an angle toward the plant, and encircle it with these cuts. Go down one spade’s depth. Pry a bit at a time in several places so you don’t rip the roots.

5. Drag the root ball onto your tarp or into your wheelbarrow. For a distance that will take more than a minute or two, cover the root ball with the wet burlap or newspaper and move quickly. Slide the root ball into the new hole and set the plant at the same level it was before. Fill in the hole with soil, pat it down, mulch and water.

6. Keep the plant moist for several days. If your plant struggles, give it some shade, such as an umbrella or a screen. But if you haven’t disturbed the roots much, it may not even miss a beat!

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what’s new

Wide-Brim
Braided Hat

Keep the sun on the plants and off your nose with our comfortable, sturdy hat…

starflower
pentas lanceolata

Once starflower starts to bloom, nothing stops it until frost. Like many butterfly plants, this one prefers, in fact needs, heat to bloom its best. So there’s no point setting it out into your garden until all danger of frost is past.

If you have limited space for your butterfly garden, maybe only room for a container or two, plant starflower in those containers. Prune it back if it starts to get too big — it’ll bloom again in just a few weeks. You won’t need to worry about keeping this plant tidy. The spent flowers turn green rather than brown so you may not even notice them against the foliage. And later the heads drop off all by themselves.

TYPE Annual SIZE 15 to 18 in. tall by 18 in. wide BLOOM Pink, red or white in summer LIGHT Full sun SOIL Well drained PESTS Occasional aphids and spider mites HARDINESS Cold: USDA zone 12 (treat as an annual elsewhere) Heat: AHS zones 12 to 1