Looking for annuals that can take hot weather? Isn’t that why you plant annuals — because they typically bloom all summer?
This is the time of year when I choose from the dozens of annuals and tropical plants in my garden that stood out as the ‘stars’ of the sweltering summer. You won’t find these frontrunners available now, but if you bookmark this article you can to refer to the list when the plant catalogs start arriving right after Christmas. Of course, you can also wait until next spring to seek out some of these beauties, but they may be in limited supply. Identifying sources for these plants in the next few months can be a great way to stay engaged with your garden as the weather turns cold.
Here is my list of eight annuals that can take hot weather —
Begonias usually are for shade, but a new group that is native to Bolivia loves to play in the sun. Hybridizers have been introducing named varieties into the marketplace, but one of the first — the Bonfire series — is still one of the best. It’s Begonia boliviensis, a tuberous species that loves good drainage, that contributes to these hybrids. I’ve seen this Begonia in plant trials growing in full sun, but it will also grow with just a couple of direct sun hours each day.
Light: full to part sun
Varieties: Bonfire, Bossa Nova, Encanto, Million Kisses, Mistral, Summerwings,.
Uses: in the ground, in a hanging pot or in a standing container.
Soil type: well-draining; this plant hates soggy roots.
Special information: Because begonias have brittle stems, care must be taken that they don’t get knocked off.
Cannas might not steal the show, but they’ll certainly inject a tropical presence. They grow from rhizomes that sprout as soon as they are subjected to enough warmth. One of the best for its health and flower production is the CannaCannova. I grew it in a large container with several other plants, and it reached no taller than five feet, which is short for a canna. Except for some leaf damage during Japanese beetle season, it looked good and bloomed all summer into fall. The Cannova series comes in a variety of flower colors. For dramatic leaves on a very large plant, try Tropicanna Black, a seven-footer with deep purplish-black leaves.
Light: full to part sun
Size: anywhere from four to 10 feet tall with a spread from two to five feet.
Uses: in the ground, or in a very large container.
Soil type: A rich, well-drained soil is best. Cannas are heavy feeders, so keep them fed with a slow release fertilizer like Osmocote.
Special information: For a good variety of unusual Cannas, check out Plant Delights Nursery in Raleigh, NC.
Commonly referred to as papyrus in its native Africa, this feathery beauty actually is a sedge that can grow up to 15 feet tall. Hybridizers have introduced it to American gardeners in a variety of sizes. Cyperus is considered an aquatic plant that doesn’t mind its roots in the water as long as its crown (the base of the plant at soil level) is not submerged. The beauty is that it will do just fine in a container with non-aquatic plants.
Light: full to part sun
Size(s): ‘King Tut’ is a 6-footer, while ‘Prince Tut’ grows to 4 feet and ‘Baby Tut’ ranges between 2 and 3-feet tall.
Uses: in the ground, or in a large container.
Soil type: A rich soil is best. Cyperus are not heavy feeders.
Special information: For more information about the ‘Tut’ family, visit Proven Winners.
A variegated version of Euphorbia — AKA Texas poinsettia — this cultivar was named for its patent-holder after he discovered it as a sport among a group of solid green plants. It is grown for its outstanding cream and green leaves and will develop a coral color at its tips in late summer.
Light: full to part sun
Size: (height by spread) 2 feet -3 feet x 3 feet – 4 feet
Uses: Grown for its attractive leaves, it can be grown as a houseplant or outdoors in warm weather in the ground, or in a large container.
Soil type: average drainage and fertility.
Special information: All Euphorbias contain a caustic white sap that seeps from the slightest wound. The sap is toxic, so wear gloves to avoid contact when pruning or taking cuttings. The milky substance evolved as a deterrent to herbivores.
This is a fuchsia that acts as a foliage plant, but then offers the bonus of the iconic dangling flowers that hummingbirds love. Leaves are tri-colored cream, grey-green and pink. Its upright nature (as opposed to the basket-types) makes it perfect as a mixed container accent, brightening up well-behaved grasses or a compact Sunpatiens (one of the sun-loving Impatiens). But when the blossoms arrive, you’ll have a multiple-weeklong windfall of bright red flowers.
Light: full to part sun
Size: (height by spread) 2’ x 1 ½
Uses: Upright fuchsias can be planted in the ground or in a container.
Soil type: rich but well-drained.
Special information: Visit the American Fuchsia Society for insight into the very wide world of Fuchsias.
It’s obvious why this plant is called firebush. Hamelia patens‘Lime Sizzler’ has vivid chartreuse leaves and bright orange-red flowers. The green-leaved version is commonplace in summertime Florida, but this hellaciously-hued hybrid has found a home in temperate gardens as well. Guaranteed to light up the landscape, it remains in bound during a shorter summer season, rarely reaching more than two feet tall and wide.
Light: full to part sun
Size: As an annual, will grow up to two feet tall and wide.
Uses: Firebush can be grown in the ground or in a container.
Soil type: Free-draining
Special information: Hamelia ‘Lime Sizzler’ was introduced in 2015 after being found growing on a plant with solid green leaves in El Campo, Texas in 2011.
There are thousands of Petunia and Petunia look alike cultivars on the market, but even with record heat, and humidity so high it might as well be raining, Petunia‘Paradise’ kept slogging away. Petunia‘Paradise’ is a deep pink, and one of the three colors in the Supertunia Vista The key to keeping modern Petuniahybrids in bloom is fertilizer—lots of it. At planting time, use a slow release fertilizer like Osmocote. Throughout the season, use a water-soluble fertilizer every other time you water.
Light: full to part sun
Size: (height by spread) 12” – 24” x 36”
Uses: Either in the ground or in a container.
Soil type: Fertile and free-draining
Special information: Proven Winners recommends pruning their Supertunia brand Petunias when the stems looks straggly, but by no more than about 20 percent of the plant.
The world of Salvias is huge, and this variety is less so. But you still need to give it room. Long stems that can reach three feet will cascade just enough to give its deep burgundy flowers even more drama. For more blooms on a more compact plant, it’s best to prune stems by about one third in mid-summer. Flowering will be delayed for a few weeks, but it will practically glow when they start to open.
Light: Although most Salvias require lots of sun, Salvia Vanhouttei will perform quite well in partial shade.
Size: (height by spread) 36” x 48”
Uses: Either in the ground or in a container.
Soil type: Fertile and free-draining
Special information: Hummingbirds love its blooms, so plant it where you can enjoy the show.
Other: My favorite place for rare Salvias for mail order is Flowers by the Sea, in Elk, California.
When purchasing your plants in April and May, you don’t know how hot the summer will be. That doesn’t matter if you go with one or more of the suggested plants in this article. Keeping your garden colorful during the hottest period is easier than you think. While some of the suggested plants may take just a bit of maintenance (and water!), summer’s short. You won’t be sorry with any of these selections.
This week’s featured article provides outdoor container ideas for season long color. Outdoor containers can be very satisfying additions to the garden, patio or deck because with a bit of planning they can be made to provide splashes of color from early spring to late fall.
At our house, pots and window boxes filled with colorful pansies, lobelia and daffodils brightened our cool spring for several weeks. But rather suddenly, in the Chicago area where I live, it’s finally become downright hot! Now, I’m looking to give my containers a make-over with heat-tolerant annuals and a few houseplants. Although some gardeners specifically plant their pots for a summer display only, I prefer to keep my containers looking great as each season changes by switching out the plants.
Just about anything can serve as a container for plants as long as it has drainage holes in the bottom. After drilling a few holes in a deep wheel barrow and filling it with potting mix, I packed it with all sorts of plants — from cool season lettuce and spinach in spring to ornamental grasses, coleus, dill and annual milkweed in summer. In the fall, the grasses are blooming so I switch out the other plants with ornamental peppers and tiny pumpkins.
Wheelbarrow Repurposed as a Container photo by Nina Koziol
No matter what you use as a container, a soil-less potting mix is a good choice — it’s lightweight and drains quickly. Don’t rely on bags of heavy top soil to fill plant pots. Instead, find out how to choose the right mix for your pots.
Thriller, Fillers and Spillers
I have a simple recipe for designing my containers — I try to use one each of three types of plants. I call the plant types, ‘thrillers’, ‘fillers’ and ‘spillers’. ‘Thrillers’ are plants such as ornamental grasses, large salvias or canna lilies. ‘Fillers’ can be calibrachoa, zinnias or begonias. ‘Spillers’ are trailing plants — bacopa, petunias or ivy. I like hot colors, so flowers or leafy shapes that grab my attention are preferenced.
I often start the season with pansiesbecause of the tolerance of cold temperatures. When it’s time to change them out, instead of consigning them straight to the compost pile, I prefer to transfer them to the edge of my shade garden where they often bloom again in the fall when the weather is cool. As a replacement, I look to one of my favorite long-blooming annuals, the Zinnia‘Profusion Cherry’. This compact plant blooms non-stop all summer and needs no care other than watering and fertilizing.
In some containers, I plant the lovely blue-flowered Salvia ‘Mystic Spires’as my ‘thriller’. The plant grows about three feet tall or more and attracts hummingbirds, bees and butterflies. Around the edge of the container, I pop in some Wave petuniasto serve as my ‘spillers’ by trailing over the sides. Both of these annuals are easy-care, long bloomers that take my containers right into September.
If I’m working on a container with edibles, Bronze fennelis a favorite ‘filler’ that I pop into large containers. Its dark, delicate and feathery leaves serve as a host plant for swallowtail butterflies, so that’s a real bonus. Tomato plants will fit into a few 17-gallon plastic tubs. Sow seeds of basil around the inside edge of the pots. It makes for an easy harvest in summer when I’m making salads or a pizza on the grill. Other herbs, such as dill and parsley make great ‘fillers’ in pots alongside flowers.
Color Combos
A gardener’s art lies in creating a colorful arrangement of flowers and foliage that harmonize and complement one another. A planting of beefy burgundy-leaved cannas, orange zinnias, red-leaved fountain grass, salmon calibrachoa and bronze-leaved coleus makes for a hot-colored tapestry that feels tropical and exotic. At the other extreme is a grouping of pale blue ageratum, pastel pink roses and white sweet alyssum, which creates a cool, soothing, classical English-garden combination.
Let’s consider the color wheel, which can help hone the hues in your container plantings. A very basic color wheel is composed of six colors: primary colors, which are red, yellow and blue, and secondary colors, which are green, orange and violet.
Complementary colors are those that are directly opposite one another on the color wheel, such as red and green, orange and blue, yellow and violet.
Combine complementary colors, such as yellow achillea or marigolds and violet salvia and both become more vibrant and intense than when they are grouped alone. Harmonious colors are those that appear next to one another on the color wheel such as green and blue, yellow and white, red and orange.
It’s often difficult to get great flower color in a shade garden, and that’s where a container (or two or three) set amongst hostas, ferns and other ground covers can create a splash. Red-flowered begonias or geraniums create a focal point because of the red-and-green color combination. Those complementary colors simply pop.
Caladiums in containers also look good in the shade garden. Set the containers up on a pedestal or bricks so the pots are up and above the ground covers. The large colorful caladium leaves in red, green, white and burgundy take the place of flowers.
Container Gardening Trends
One of the hottest trends right now are succulentsplanted in pots. Succulents, like jade plant and aloe, tend to have thick leaves that hold water and help the plant resist drought. Many types of Echeveriahave dusty or steel blue leaves while Aeoniummay form a rosette of chartreuse leaves edged in red. Agave also has a pale blue leaves edged in maroon or black with tiny spines. One of my favorites succulents is baby toes (Andromischus cristata), which looks like little plump feet. These plants need well-drained soil, indirect light and infrequent watering. At the end of summer, I bring them indoors.
Succulents photo by Nina Koziol
Using perennials in pots is another trend. Look for long-blooming perennials like Calamintha ‘Montrose White’. This low growing, well-behaved member of the mint family blooms for nearly two months and attracts butterflies. Each spring, I divide the Calamintha that grows in my perennial border and pop a few of the divisions into pots on the patio.
Ornamental grasses, like the native cultivar Panicum ‘Heavy Metal’,also look good in a summer container. Come fall, leave the grass but remove the petunias or other annuals and replace them with mums, tiny gourds and pumpkins. Changing some of the container plants takes the container well into autumn.
Smaller shrubs also can be used in large pots. Many of the compact panicle hydrangeas, like Hydrangea‘Little Lamb’have grown in pots around our patio during the summer. Come fall, I plant them in a permanent spot in my shrub border.
‘Apache Rose‘ switchgrass, Amsonia hubrichtiiand Hibiscus‘Cherry Cheesecake’are among the plants I like for long bloom, lasting form, good foliage or good fall color. Although it’s more perennial than shrub, Aralia cordata ‘Sun King’gets popped into a container in the shade garden because of its brilliant chartreuse foliage. It looks and grows like a shrub, and does well in dense shade to a half day of sun.
Choosing the Right Number of Plants
Use the diameter of the container to guide thevolumeof plants to buy. Divide the pot’s diameter by 2 to get the number of 4-inch plants you’ll need. For example, if the container is 14 inches wide, you’d need seven 4-inch potted plants.
Before removing the new plants from their pots, I position them in the container to see how they are going to look together. For perspective, focus on the area from the bottom of the container to the top of the vertical plant. A good ratio is for plant material to make up two-thirds of the total with the container as the remaining one-third. That ratio includes plants that cascade over the edge of the container.
Here’s another a simple design rule that bears repeating. Select one vertical plant, three cascading and three mounding filler plants to get the maximum impact.
Resources for Container Gardening
Check out the container gardening videosat PlantersPlace.com.
Some of my favorite books on container gardening.
Succulent Container Gardens: Design Eye-Catching Displays with 350 Easy-Care Plants by Debra Lee Baldwin.
Container Theme Gardens: 42 Combinations, Each Using 5 Perfectly Matched Plants by Nancy Ondra.
If you are new to container gardening, or you’d just like to brush-up on your gardening savvy, here are a few potting mix basics you may wish to consider.
In case you are wondering why I’m focusing on container gardening right now, it’s because I could use some flower power to regain my sanity after a very long winter. Hooray! It’s finally starting to warm up! I am eager to fill my pots and window boxes with fragrant pansies, Persian buttercups, sweet alyssum and other cool-season annuals.
Each year I plant about 40 containers, window boxes and hanging baskets. Although I buy plants and sow seeds, I don’t replace the potting mix from the previous year. That would be a very expensive endeavor. Instead, I simply add more potting mix and granular fertilizer.
Importantly, I never use garden soil or “top” soil in containers. Garden soil is far too ‘heavy’ (dense) for pots and window boxes, and it easily becomes waterlogged. When that happens, leaves turn yellow, the roots can’t get air or nutrients, plant growth slows, and the roots may rot. Instead, I use soil-less potting mixes, which are sold in bags at garden centers and chain stores. These loose, porous, lightweight mixtures not only make a container less heavy and easier to move, but they help get water, fertilizer and air down to the plant’s root system.
Selecting a Potting Mix
Soil-less mixes are made from a variety of organic and inorganic materials. The main ingredients likely include peat moss, composted pine bark, coir, vermiculite and perlite. These materials help hold water but also allow quick drainage. A plant’s roots seek out pockets around the coarse fibers where they can access nutrients and air.
Potting Mix Organic Materials
A typical soil-less mix may contain about 40 percent sphagnum peat moss, 20 percent pine bark, 40 percent vermiculite, perlite and fertilizer. Peat moss is part of the formula because it can hold many times its weight in water. That’s important when we have hot, dry weather in July and August. At that time of year, all of my containers get watered once a day. Composted bark from pines, and other trees, is one of the most widely used materials in soil-less mixes. While bark doesn’t retain moisture like peat moss, it’s spongy and permeable.
Coir is another organic potting mix material. It’s made from coconut hulls. Like peat moss, it has great water-holding capacity. Some mixes may feature only coir or a mix of coir and composted bark. Other potting mixes may include sphagnum peat moss, peat humus, shrimp shells, composted manure, seaweed powder, limestone, coarse sand, leaf mold or spent rice hulls. Some products contain granular fertilizers and / or mycorrhiza (my·cor·rhi·zee), a fungus that grows in or on a plant’s roots and helps the plant take in nutrients.
Potting Mix Inorganic Materials
Vermiculite and perlite are inorganic lightweight materials that help retain moisture and create a porous mix. Both of these ingredients improve the soil’s physical qualities. Vermiculite is a mineral that expands when heated. It is spongy and holds air, nutrients and water. Perlite is a volcanic glass that expands when heated at extremely high temperatures. It promotes good drainage while holding nearly as much water as vermiculite. Perlite and vermiculite are also sold separately in bags as soil amendments. If you have heavy clay garden soil in your beds, both products can help lighten and aerate the soil.
Some potting media includes plastic beads (polystyrene) and calcined clay (the type that’s found in cat litter products). The beads promote drainage and the clay particles improve the ability to hold moisture and nutrients in the soil.
Potting Mix Fertilizer
Soil-less potting mixes have little natural fertility so the manufacturer may include some slow-release fertilizer to get plants started. The fertilizer information can be found on the package. The slow-release granular fertilizers may feed the plants for up to three months. If the product does not have fertilizer, add it to the mix before planting. Material from Osmocote® Plant Food, this website’s sponsor, is included in some of the potting mix brands. If not and you want to add plant food to the potting mix, it is a safe and effective choice – even for edible plants.
When reusing potting mix, I always add some granular slow-release fertilizer before planting my pots. That’s because the plants that grew in the mix the previous year consumer most of the nutrition. Always follow label instructions so you don’t over-fertilize, which may burn the plant roots. It’s like vitamins — taking too much is not a good thing.
Potting Mix Water Retention
Some potting mixes contain crystal polymers to help retain moisture. They may be liquid surfactants or gel-forming granules. A potting mix with these ingredients can be helpful in keeping the mix moist in hot weather or when the containers are placed in sunny locations. If the potting mix contains extra “wetting” agents, that information is typically included on the label.
Planting in the Container
I like to open a fresh bag of potting mix and moisten the soil-less mix with a few cups of water. That helps prevent the dry fibers from floating up. I suggest using an inexpensive dust mask to prevent particles from getting into your respiratory system.
Place the moistened mix in the container about an inch or two from the rim. Next, water the plants that are going into the container. After I get them out of their pots or cell-packs, gently tease the bottom of the roots to loosen them. Be sure to place the plants at the same depth at which they were growing in their cell packs. Start fertilizing the plants with a water-soluble fertilizer ever two weeks or so, especially when they start to flower. Even though the potting mix may contain granulated fertilizer for roots and stems, don’t fear over-feeding the plants. Water-solubles work partially by feeding through direct contact with the leaves (called foliar feeding). Frequent watering of outdoor containers — especially in July and August when it’s hot — may result in some loss of nutrients as they drain out the bottom of the pots.
Recycling Potting Mix
I’m often asked in classes if it’s OK to reuse potting mix that was used in containers the previous year. Unless the plants were diseased, my usual reply is “yes.” There’s no need to throw out soil-less potting mixes. After the first fall frost, I empty each container onto a large screen placed over a wheelbarrow. Next, I brush off as much potting mix from the plant roots as possible. The roots go into the compost pile and the potting mix is returned to the containers or I may use it to top-dress my garden beds in fall. There’s always less potting mix than what I started with so there’s always a need to buy a few more bags each spring.
Photo: by Nina Koziol
DIY Potting Mix
Here’s my favorite recipe for making your own potting mix. This recipe makes enough to fill two 14-inch wide pots or five 12-inch hanging baskets.
Ingredients:
1 bucket (2-½ gallons) peat moss
1 bucket (2-½ gallons) vermiculite and/or perlite
1 half bucket (1-¼ gallons) screened compost or composted cow manure
2 cups coarse sand
Granular slow-release fertilizer
½ cup lime (to counter the acid of peat and keep the pH level near neutral)
Mix thoroughly.
One of the great things about growing plants in pots is that you can use them just about anywhere no matter how big or small your garden. Planted with flowers, vegetables or herbs, they add color to a deck or patio. A pair of pots flanking the front door is a warm welcome for visitors. And, for apartment and condo-dwellers with a balcony, a few pots or window boxes set on the floor help soften iron railings and brick walls and create that garden feeling.
Think of containers as accessories for your garden and outdoor living space. In small areas, they can be grouped together and staged for a sensational display. Because very few perennials bloom for more than a few weeks, I like to place large pots filled with annuals, such as red fountain grass, petunias, calibrachoa, nasturtiums, lantana and sweet potato vines in my long perennial border. There, they attract butterflies and hummingbirds and add interest until the first fall frost.
In my shade garden, most of the plants are green—epimediums, hostas and hellebores, for example. They all tend to carpet the ground at the same height, which can be monotonous. To draw the eyes upward, I set a few large resin urns filled with red flowering annuals like Dragon Wing begonias that serve as focal points. Red is a complementary color to green and when they are paired together, the combination is striking, especially in shade. On our patio, two shrubby panicle hydrangeas (Hydrangea paniculata ‘Limelight’) thrive in very large, lightweight “foam” pots that can be left out all year even though we are in zone 5 where winter temperatures can dip below zero. The hydrangeas have thrived for more than three years in the pots. Soon I’ll move them into one of my borders and replace them with something new.
It’s easy to design and plant a pot with stunning results if you follow a few essentials. First, choose pots that have holes in the bottom for drainage. That is critical. The containers need to shed excess water from the soil, otherwise the waterlogged roots will rot and the plants will die.
Let’s say you are on a garden walk and searching for inspiration, I look for containers that complement the style of the house. For example, a classic iron urn looks great with a Victorian home, while a tall, contemporary glazed pot can enhance sleek architectural lines. For me, this is a simple design principle that pulls the house and garden together. Another trick is using containers that are all made of the same material or the same style or the same color. It creates unity and consistency throughout the garden.
Many garden centers and big-box stores carry new lightweight, weather-resistant resin pots in a range of Crayola-like colors—red, blue, chartreuse, or purple, for example—and in many sizes. Pick a pot in a color that enhances your garden, patio furniture or the color of your house. Repeat it and it becomes a theme through the garden.
The size and material of the pot are important, too. Pots smaller than 14 inches wide will need frequent watering, so the bigger the pot, the better. In hot weather, potting mix dries out very quickly in a container that’s less than two feet wide and two feet tall. This will also stress plant roots and a stressed plant is more susceptible to pests and disease.
Terra cotta pots (made from clay) tend to dry out the fastest in our garden while glazed ceramic pots keep the soil moist much longer. However, ceramic pots weigh more and may need storing in winter. When buying pots, consider the weather. If you choose a ceramic pot but live in an area where the temperature dips below freezing, you’ll want to empty the container and store it off the ground in a garage or shed so it doesn’t crack.
I look for a good, all-purpose soil-less potting mix—one that contains slow-release fertilizer granules. To keep my pots of annuals blooming as long as possible, I also use a water-soluble fertilizer at one quarter the recommended strength every other week when I water. Picking off the spent flowers will also encourage prolonged blooming. If you have to move your pots, using soil-less potting mix makes the job much easier than if you use garden soil in them. Garden soil is typically too heavy for pots, doesn’t allow for good drainage and may contain pests or disease. You can find bags of potting mix at local garden centers and big-box stores.
Next comes the fun part—choosing the plants. Ray Rogers, author of “The Encyclopedia of Container Plants: More than 500 Outstanding Choices for Gardeners.” (Timber Press, 344 pages, $34.95), suggests ‘monopot’ and ‘combopot’ plantings. A monopot contains one type of plant while a combopot includes two or more different plants.
A monopot container filled with one type of coleus or an ornamental grass, such as Pennisetum ‘Prince’ (purple fountain grass), can create a very dramatic and contemporary look. Combopot plantings tend to have a thriller, filler and spiller. The thriller plant is typically upright and vertical, like grass. The filler could be a rounded plant, such as compact zinnias while the spiller, which trails over the edge of the pot, could be a vine.
Although petunias, coleus, sweet potato vines and grasses have been the mainstays of many container gardens, another popular trend is the use of succulents—plants with thick, fleshy stems that enjoy very well-drained soil and warm weather. It’s their leaves that create the visual interest with their rounded shapes and soft blues, greys and greens.
Herbs like basil, cilantro, parsley and oregano also do very well in a sunny location and are easily grown in pots. I group mine together so I can water them all at once without dragging the hose around.