When people talk about perennials, they usually mean flowers that show up again and again, like clockwork. And while that's mostly true, there's a bit more to the story. In botanical terms, a perennial is any non-woody plant that sticks around for more than two years. But in the garden, a perennial flower is that trusted friend that returns year after year, through rain, snow, or drought, with a bit of help from you. Some are long-lived, thriving for decades. Others are short-lived perennials, bowing out after just a few seasons.
Perennials are the foundation of a lasting, low-maintenance garden. They help you build a landscape that changes and matures with time. But while they’re known for being reliable, they’re not completely hands-off. Without a little attention, even the hardiest plants can end up with tangled roots, fewer blooms, and tired-looking growth. A bit of regular care, like trimming, dividing, feeding the soil, and simply paying attention, goes a long way in keeping them at their best.
The Perennial Planting Calendar
Spring: Set the Stage
Spring and summer bring dreams of color, but early spring planting is all about getting your foundation right. Start by checking the soil, don’t dig when it’s soggy. Wait until it crumbles in your hand instead of squishing. This is your moment to divide mature clumps of plants like hosta, daylilies, and catmint before they shoot up. It's also a great time to sow cold-hardy perennial seeds, think Shasta daisy, columbine, or astilbe.
Work in compost, but go easy. Too much and you’ll get a jungle of leaves with hardly any blooms. Let the soil breathe. And definitely clear out old debris where pests and fungus love to hang out.
See our guide to starting flower seeds here.
Summer: Keep It Going
This is when new gardeners often step back, but summer is full of behind-the-scenes work. Deadheading keeps things blooming, stay on top of your coneflowers, black-eyed Susans, and salvia. Some, like catmint, can be cut back hard and bounce right back with fresh flowers. Stake floppy plants early, don’t wait until they’re sprawled all over. Keep an eye out for problems: rust on daylilies, powdery mildew on phlox, aphids just about everywhere.
If you’re planning to divide in fall, flag those overgrown clumps now while they’re still easy to spot. Waiting until the foliage fades just turns it into guesswork.
Fall: The Power Season
Fall planting is the gardener’s secret weapon. The soil’s still warm, the air’s cooler, and roots settle in without the stress of early summer heat. This is the time to divide perennials like iris, hosta, bee balm, and astilbe. Add mulch, but don’t pile it against the stems, leave a bit of space around the base so moisture doesn’t build up and cause rot. Then give your plants a final check before winter sets in.
Winter: Think, Plan, Start
You’re not planting, but winter is far from idle. Snow acts as insulation. Leaves give protection. This is planning season! Order seeds, review what didn’t do well, and if you’re starting indoors, get lavender or echinacea going under lights. Winter is when smart gardeners get ahead, or lose ground.
Understanding Microclimates and Hardiness Zones
Knowing your USDA hardiness growing zone is just the beginning. Every yard is its own ecosystem. You’ve got sunny corners, chilly pockets, slopes that drain too fast, and fences that either block wind or trap heat.
That sunny southwest spot against a brick wall? You might get away with growing a zone 8 plant there, even if your area is zone 6. Under that redwood? It’s not just shady, it’s damp, acidic, and full of hungry roots. Completely different story.
For example, lavender might thrive in gravel near a warm driveway but struggle just a few feet away in heavy clay under an overhang. That’s the power of microclimates.
Pick up a simple soil thermometer. Notice where snow melts first. Track how sunlight shifts across the seasons. Treating your whole yard the same way is a fast track to disappointment, or flowers blooming in all the wrong places.
Soil: The Living Foundation of a Healthy Garden
Soil isn't just something you buy in a bag. It’s alive, or at least, it should be. For growing perennials, it’s not about flashy fertilizers or quick fixes. It’s about texture, drainage, pH, and the life teeming below the surface.
Well-draining soil means water moves through it but doesn’t disappear in seconds. To check yours, dig a hole, fill it with water, and see how fast it drains. If it takes longer than an hour to drop an inch, you’ve got drainage issues. If it drops faster than four inches an hour, add organic matter to help it hold moisture.
Those “feeds up to 3 months” labels on bagged products can be misleading. A better approach is to understand what your soil actually needs. Is it acidic or alkaline? Clay-heavy or sandy? A $15 soil test can give you real answers, and save you time and effort in the long run.
Skip generic "garden soil" unless you know exactly what's in it. Many are just bark fillers that look nice but do little for your plants. What truly supports perennial growth year after year? A steady supply of compost, worm castings, and leaf mold..
One of the most common mistake is gardeners overfeeding with high-nitrogen products. It may seem like a good thing at first, but it often results in big, leafy plants that barely bloom. In perennial gardening, more nutrients aren’t always better, getting the right balance makes all the difference.
Perennial Planting 101
Planting a perennial isn’t just digging a hole and walking away. You’re setting that plant up for a long life, and a little thought now saves you a lot of work later.
Spacing and Airflow
Most perennials hate being crowded. It’s not just about roots fighting for space, tight plantings trap moisture and invite disease. Think powdery mildew, rust, and black spot. It’s tempting to cram things in so they “fill in fast,” but crowded plants are more likely to flop, rot, or struggle.
Sunlight angle matters too. Morning sun helps dry the dew. Afternoon sun brings heat. Put your sun-lovers like daylilies or coneflowers where they’ll soak up six to eight hours of direct light. Shade lovers belong in cooler, sheltered spots.
Dig Smarter, Not Deeper
The most common digging mistake is going too deep and too narrow. You want a hole about twice as wide as the rootball but no deeper. Perennials like sitting right at ground level, or even a bit above if your soil’s heavy. Before planting, check those roots. If they’re circling the pot like spaghetti, loosen them gently so they don’t keep spiraling.
Amend just the backfill with compost, not the whole hole. If the soil is too rich in that one spot, roots may stay put instead of growing out into the soil.
Mulch Like You Mean It
Skip the bark nuggets. They look tidy, but they don’t do much for your soil. Instead, use shredded leaves, well-aged compost, or arborist wood chips (often free from tree services). Lay it on about 2–3 inches thick, but keep it away from stems. Done right, mulch keeps weeds down, holds moisture, and slowly feeds your soil as it breaks down.
One thing to keep in mind though is too much compost can backfire. It pushes leafy growth over flowers. Remember, compost isn’t fertilizer. It’s soil food. You want just enough to spark life in the soil, not tip the balance away from blooms.
See more on the importance of healthy soil for a thriving garden here.
Companion Planting with Perennials
Companion planting isn’t just about picking flowers that look good side by side, it’s about creating a garden that works smarter. The right pairings can attract pollinators, keep pests in check, extend your bloom season, and even support healthier soil.
Think of bee balm and echinacea. Together, they bring in butterflies, hummingbirds, and native bees. They bloom around the same time, from late spring into fall, and help steady each other when the wind picks up.
Yarrow and lavender make another great match. Both love full sun, thrive in poor, well-draining soil, and once they’re established, they’re incredibly low-maintenance. Plus, yarrow reaches down for nutrients and can benefit neighboring plants with shallower roots.
If you’ve ever battled aphids on roses or Shasta daisies, try planting catmint nearby. It attracts helpful insects like hoverflies and lacewings, and its soft, purple blooms are a favorite with pollinators too.
Perennial Maintenance Through the Seasons
Deadheading
Some perennials, like coreopsis, coneflowers, and salvia, will bloom like champs if you stay on top of deadheading. Others, daylilies, for example, look better cleaned up, but won’t give you a second round unless they’re a reblooming type. So, know your plant and honestly, not everything needs to be clipped. Letting some seed heads linger, especially on coneflowers, adds winter interest and feeds the birds.
Division
Your perennials will tell you when they need to be split. If you’re seeing fewer flowers, smaller blooms, or a dead spot in the middle of the clump, it’s time. Lift the whole plant, slice it with a garden knife or spade, and replant the strongest pieces. Just remember, not every perennial appreciates this treatment. Peonies, for example, prefer to stay put. And for plants that spread aggressively, like bee balm or catmint, you can do root pruning instead by taking a spade and slicing around the clump’s edge to keep things in check without digging it up.
Natural Disease Control
Air circulation is key. Keep your perennials pruned, spaced properly, and mulched with care. If problems crop up, don’t jump straight to harsh chemicals. Lost Coast Plant Therapy can handle most pest and plant disease issues without wrecking your soil life. It's especially effective against soft-bodied bugs and common fungal problems.
Prune With Purpose
Some perennials bloom on fresh growth, others on last year’s stems. Cut back salvia and veronica midseason to spark a second bloom. But be gentle with shrubbier types like lavender, cutting too far into woody stems can do real damage.
See more on seasonal garden maintenance here.
Perennial Flowers That Bloom All Summer in Full Sun
If you want flowers that bloom all summer, choose sun-loving, drought-tolerant perennials that can take the heat and still show off.
Start with coneflowers. They handle drought, recover fast from storms, and keep blooming from late spring through fall. Add catmint, which sprawls beautifully, thrives in full sun, and brings in pollinators by the dozen. Shasta daisies offer classic cheer, while Salvia nemorosa delivers rich purple spikes that bounce back with a simple shear. Black-eyed Susans, coreopsis, gaillardia, and Russian sage all go the distance with little fuss.
To keep them flowering through the season, stay on top of deadheading, especially once early blooms start to fade. Give early bloomers a midseason trim to encourage fresh growth. A slow-release fertilizer at planting time is plenty, let the soil biology do the rest. And when you water, go deep rather than often. This helps roots grow down where they can find moisture, instead of hanging near the surface where they're more vulnerable to heat and stress.
Shade-Loving Perennial Beauties
Shade doesn’t mean boring. It just calls for a different kind of beauty, one built on texture, subtle color, and seasonal surprise.
Dappled Shade vs. Deep Shade
Not all shade is created equal. Hostas thrive in dappled morning light but scorch in afternoon sun. Astilbe loves moisture and won’t forgive drought. If you’re planting under trees, you’re not just dealing with limited light, you’re also competing with thirsty tree roots. In those cases, build up the soil gently on top rather than digging down into the root zone.
Designing for Shade
Think in layers, from low groundcovers to mid-height foliage to vertical interest. Brunnera brings delicate blue flowers in spring, followed by broad, heart-shaped leaves. Japanese forest grass adds graceful motion, while bleeding heart brings a softer texture. And don’t overlook toad lilies, they bloom late and bring unique, orchid-like flowers to the shade garden just when things are winding down.
Air and Moisture Matter
Shade gardens can trap moisture and limit airflow, which makes them prime real estate for slugs and powdery mildew. Keep air moving by spacing plants well and avoiding dense mulch. Use fine-textured mulch like leaf mold, and don’t water just because it’s cool out. In shade, soil dries slower, your plants likely need less than you think.
10 Easy Perennials to Grow in Your Garden
Iris (Iris germanica)
What other flower gives you vertical drama, early bloom in late spring, and sword-like leaves that hold their structure deep into summer? Bearded iris is the kind that steals the show.
The trick to success is in the rhizomes. Plant them shallow, half-exposed to the air. Bury them too deep, and you’re begging for rot. These plants prefer full sun, especially in cooler climates, and hate having wet feet.
Once the blooms are done and the leaves flop, give them a hard August cutback, not just a trim. Slice the foliage down to 6 inches, and you’ll see a fresh flush that keeps the bed looking clean through fall.
Daylily (Hemerocallis spp.)
A daylily flower lasts... you guessed it: a day. But the plant’s loaded with buds, and the scapes (flower stalks) just keep coming. Some varieties bloom for six weeks straight. Others throw a surprise encore in early fall.
If you want flowers bloom all season, choose a reblooming variety like ‘Stella de Oro’ or ‘Happy Returns.’ Others won’t rebloom but offer bigger or more exotic colored flowers.
When the first flush finishes, a tipd would be to shear the foliage back by a third and feed lightly. You’ll often get a second bloom window. Deadhead daily if you want things tidy, but they’ll come back year after year either way.
Echinacea (Coneflower)
Native, tough, and drought tolerant once established. Coneflowers aren’t fussy about soil, don’t need staking, and are magnets for butterflies, bees, and birds.
Most people get confused with them because they often won’t bloom much their first year. That’s normal. They’re building roots. But come the second year, boom, an array of colors from purples to sunset oranges and even green-tinged doubles.
Want strong color and plant health? Don’t feed heavily, and never overwater. Full sun, lean soil, and a little neglect bring out their best.
Coreopsis (Tickseed)
Coreopsis is the friend who’s always in a good mood. Long-blooming, cheerful, and almost impossible to kill, it delivers punchy yellow, red, or bi-color blooms for months with very little attention.
It’s one of the few perennial flowers that actually prefers poor soil. Overdo the compost or fertilizer and it gets floppy. Sun-loving, drought-tolerant, and deer-resistant, it’s perfect for garden beds, mixed borders, or mass plantings.
A tip with these is when the first flush fades, don’t deadhead one stem at a time. Take your shears and cut the entire plant back by a third. It’ll bounce back better and give you color into late summer.
Sedum ‘Autumn Joy’
Think of this one as your garden’s grand finale. Sedum ‘Autumn Joy’ shows up just when most perennials are fading out, bringing strong structure with upright stems, chunky succulent leaves, and flower heads that shift from soft pink to deep red as fall sets in. It’s a reliable, no-fuss standout when you need it most.
Pollinators love it too—especially in late summer when nectar sources are running low. It’s like setting out a final feast before the season ends.
This plant prefers a little tough love. Poor soil? No problem. It shrugs off drought and dislikes being fussed over. In fact, overwatering is the quickest way to disappoint it. Leave the dried flower heads through winter, they catch frost beautifully, and do your cutting back in early spring.
Black-eyed Susan (Rudbeckia fulgida)
If you’ve ever passed a patch of golden blooms glowing in the late-summer sun, chances are it was a Black-eyed Susan. These bright, daisy-like flowers bring a cheerful burst of color from mid-summer into fall, and they’ll do it in just about any soil without complaint.
They handle heat, tolerate neglect, and still manage to bloom beautifully. Yes, they self-seed, but not in a way that takes over. Deadhead if you like things neat, or leave a few seed heads for goldfinches to snack on, you’ve got options.
Make sure to give them a light trim around July. Not a full cutback, just a soft shearing to encourage fuller, bushier growth and keep the show going longer.
Woodland Sage
If you're looking for a plant that brings height, color, and energy to the garden, woodland sage is a dependable go-to. Its deep, spiky blooms start in late spring and, with a little encouragement, keep coming well into fall. The foliage has that rugged, slightly spicy scent that hints it can handle a bit of tough love.
It’s happiest in full sun and soil that drains well. Feeding it too generously, especially with nitrogen-heavy fertilizers, often leads to floppy stems instead of upright flowers.
One trick gardeners love is after the first flush of blooms fades, give it a solid cutback. It might look a bit drastic at first, but it bounces back quickly with a fresh wave of smaller, often more abundant blooms. Bees will be lining up.
Penstemon digitalis ‘Husker Red’
This one stands out before it even flowers. The rich burgundy foliage brings depth and contrast from early spring, and when the pale pinkish-white tubular blooms arrive, the pollinators show up too, especially hummingbirds and butterflies. Husker Red is a native cultivar, so it’s both beautiful and tough.
It does best in well-drained soil and doesn’t ask for much. In fact, too much attention, especially extra fertilizer, can make it leggy and reduce the blooms.
It works well in all kinds of spaces, from cottage gardens to wildflower meadows. If you’d like more of it next year, let some of the flowers go to seed. If not, a little trim keeps things tidy.
Heuchera (Coral Bells)
Some plants are all about the flowers. Heuchera? It's here for the foliage, and what a show it puts on. From deep purples to glowing chartreuse, even silvers with bold veining, these ruffled leaves add lasting color and texture all season long. And they don’t fade into the background when other perennials wind down.
The flowers are delicate and airy, and while they’re not the main attraction, bees and hummingbirds love them. It’s a nice little bonus.
Every few years, the crowns tend to rise up a bit in the soil. When that happens, it helps to lift and gently replant them right at the soil line. Just be careful not to bury the crown, that’s where problems can start. Treated well, Heuchera just keeps going.
Nepeta (Catmint)
Nepeta is one of those plants that quietly over-delivers. Clouds of blue to lavender blooms float above soft, gray-green foliage, and the whole thing looks like it took far more effort than it did. It’s heat-tolerant, drought-resistant, and generally unfazed by neglect.
Give it sun, a bit of space, and average-to-lean soil, and it will settle in happily. Humidity doesn’t thrill it, but it usually carries on just fine.
After the first bloom finishes, give the whole plant a gentle shear by about half. It regrows quickly and often blooms again even better than before.
As a bonus, it’s one of those rare plants that looks delicate but helps keep pests in check. Deer steer clear, aphids don’t stick around, but the bees will be all over it.
Troubleshooting Common Perennial Problems
Perennials don’t just fail out of nowhere. If something’s not right, yellowing leaves, stunted growth, no blooms, there’s almost always a reason. Nine times out of ten, it comes down to soil issues, poor spacing, garden pests or watering habits. Here’s how to figure out what’s going wrong and how to fix it.
Rot: Root and Crown
If a plant suddenly collapses while the soil still feels wet, root rot is probably the culprit. Crown rot shows up the same way, especially in plants like iris and heuchera that resent being buried too deep or sitting in stagnant air. Your move? Dig the plant up. Cut away any mushy, darkened roots or crown tissue. Then replant it higher, in soil that drains better. And change how you water, deep, infrequent soakings are much better than a daily sprinkle.
Overcrowding
Even the best-planned perennial beds can get overcrowded with time. Plants that once bloomed their hearts out might suddenly start sulking or shrinking back. It doesn’t mean the whole bed needs a do-over. Just pick a few overgrown clumps, dig them up, divide them, and replant the healthiest pieces where you see space opening up. This keeps your garden looking full and flowering evenly without starting from scratch.
Leaf Spot
Got blotchy leaves with yellow halos or spots? That’s a red flag for fungal or bacterial disease. First, remove and trash the affected leaves, don’t toss them in the compost. Then look at your spacing. If your plants are too close, airflow suffers, and that’s when disease takes hold. Thin out congested areas. If the issue sticks around, a natural and organic pesticide like Lost Coast Plant Therapy can help clear it up. It’s also a great preventative option, especially during warm, damp spells when leaf spot tends to show up in the first place.
Moving Mature Perennials
The best time to move established perennials is early fall or early spring, when the plant is still dormant or just starting to stir. Water it thoroughly the day before you dig. Then use a wide shovel to lift the whole root system gently. Trim back some of the top growth to ease the transplant shock. Replant right away in its new home, firm it in well, and water deeply. Resist the urge to baby it too much, letting the plant settle into its new spot without constant fuss helps it toughen up and get reestablished faster.
Watering and Fertilizing Perennials the Right Way
Forget the daily sprinkle. That kind of watering encourages shallow roots and fragile plants that can’t handle a dry week, let alone a full-blown summer heatwave.
Deep Watering
The real magic happens when you water deeply and less often. Give your plants a long, slow soak that reaches 6 to 8 inches down into the soil. Then let the surface dry out a bit. This encourages roots to grow deep, not linger near the surface, and gives your drought-tolerant perennials the kind of resilience that sees them through hot spells without drama.
Bloom Boosters
A lot of so-called "bloom boosters" are just phosphorus-heavy fertilizers. If your soil is already in good shape, they won’t do much except throw things off balance. In some cases, they can even stress your plants. Most of the time, a light application of compost in spring, maybe a splash of compost tea or fish emulsion, is more than enough. Think of it as a steady diet, not a sugar rush.
Reading the Leaves
Your plants will tell you what they need, if you know how to listen. Yellowing leaves with green veins often point to chlorosis, which might mean your soil’s pH is off. Purple leaves? That’s usually a sign of phosphorus deficiency. If everything looks pale green, they might need nitrogen. The key is to observe before you reach for the fertilizer jug. Most of the time, a lighter touch is better.
Creating a Bloom Calendar for Year-Round Color
If your garden explodes in June and fizzles by August, the problem probably isn’t your plants, it’s your timing.
Layer Your Bloom Times
Think of your garden like a relay race. You want one group to pass the baton to the next. In early spring, try hellebores and brunnera. By late spring, bring in iris and peonies. Early summer belongs to salvia, catmint, and coneflowers. Then hand things off to late-summer stars like black-eyed Susans, sedum, and daylilies. Come fall, asters, anemones, and ornamental grasses step up for the finale.
Foliage Carries the Gaps
When blooms fade, your foliage steps in to keep the show going. Shade lovers like heuchera, hosta, variegated carex, and ferns add texture and color that sticks around even when flowers aren’t front and center. These plants give your beds structure and softness, especially in those quieter weeks between blooms.
Sample Garden Layout
Picture a 10-by-4-foot backyard garden bed. In the back row, you’ve got Joe Pye weed and 'Autumn Joy' sedum anchoring the height. The middle is filled with coneflowers, Shasta daisies, and salvia. And up front, there's Catmint, low-growing coreopsis, and a few heuchera for color all year long. That little bed gives you six months of blooms with hardly a gap.
See more on how to design a stunning flower garden here.
Conclusion
Gardening with perennials isn’t about getting everything right the first time. It’s more like building a relationship, one season at a time. Some plants will do great, some won’t, and you’ll probably end up moving a few things around more than once. That’s all part of it.
What makes the difference is paying attention, seeing what’s working, what’s not, and making small changes along the way. Over time, you start to get a feel for your space. You notice which spots stay soggy, which ones heat up early in spring, and which plants seem to thrive no matter what.
It’s not about chasing perfection. It’s about building something that grows with you, season by season. Some years will be better than others, but every year teaches you something. And before you know it, you’ve got a garden full of stories.
FAQ's
What makes a plant a perennial, and do perennials come back every season?
A perennial is a plant that lives for more than two years and, yes, perennials come back each season with the right care. Unlike annuals, which complete their life cycle in one season, herbaceous perennials die back in winter and regrow from the roots in spring. With thoughtful planting and maintenance, flowers will come back year after year, adding lasting color to your garden.
Which perennials are low maintenance and bloom in summer and fall?
If you're looking for low-maintenance plants that thrive through summer and fall, consider coneflowers, Shasta daisies, black-eyed Susans, and Russian sage. These sun-loving perennials are easy to grow, resist drought, and bloom year after year with minimal fuss. Plant them in full sun, and you’ll have a summer garden that stays vibrant and welcoming to bees and butterflies.
Do hosta and astilbe come back year after year in shade?
Yes! Both hosta and astilbe are shade-tolerant perennials that reliably come back year after year, especially when planted in moisture-retentive soil. Hosta is prized for its bold foliage, while astilbe adds feathery texture and blooms in shades from white to purple flowers and pink. They're perfect for adding structure and color to a shaded garden or landscape.
Can I grow perennials like coneflowers and Shasta daisies in my USDA hardiness zone?
Absolutely, just check the plant’s label for your USDA hardiness zone compatibility. For example, coneflowers and Shasta daisies come in many varieties and are widely adaptable. When you choose plants that can survive winters in your USDA hardiness zone, you’re setting yourself up for success and summer blooms that return every season.
What perennials attract butterflies and pollinators?
To attract butterflies and other pollinators like bees, plant echinacea (coneflowers), bee balm, catmint, and lavender. These sun-loving plants not only fill your yard with color but also support local ecosystems. Their vibrant petals, strong nectar production, and long summer bloom season make them favorites in any cottage garden design.
How do I make sure my perennials bloom year after year?
Healthy perennials need the right start. Prepare your soil, plant them in full sun or partial shade depending on the species, and space them well for airflow. Regular deadheading, seasonal division, and deep watering encourage strong roots and repeat blooming. With good soil, compost, and attention, many sun-loving plants bloom on and off from late spring to early summer, and even into fall.
Can I create a garden that blooms in every season using perennials?
Yes, you can! By layering bloom times and mixing groundcovers to upright varieties, you can design a garden or landscape that offers interest every season. Try hellebores for early spring, peonies and catmint for early summer, sedum for late summer, and asters and grasses for fall. Add foliage plants like heuchera and carex to bridge the gaps when flowers take a break.
Why are my perennials not coming back?
There are a few common reasons, poor drainage leading to rot, overcrowding, pest infestations or planting varieties that don’t survive winters in your USDA hardiness zone. Some perennials also need time to establish before they bloom year after year. Check your soil conditions, watering habits, and whether your perennials are tolerant of your local climate. And remember to spray with our Natural Plant Protector to help prevent soft bodied pests and diseases from taking hold.
What are some great beginner-friendly perennials to try first?
Start with coreopsis, black-eyed Susans, coneflowers, and catmint. They’re easy to grow, tolerant of tough conditions, and bloom year after year with very little care. Many of them come in an array of colors, textures, and heights, so you can build a garden that feels full and dynamic from day one.
Additional Resources
Perennial Gardening - Colorado State University Extension
Perennials - University of Maryland Extension
Care and Maintenance of Perennials - Penn State Extension
Flowering Perennials: Characteristics and Culture - University of Missouri Extension
Perennials Selection - University of Wisconsin Horticulture Extension
Perennials - Cornell Cooperative Extension
Growing Perennials - Clemson University Cooperative Extension
Perennials for Continuous Color - University of Massachusetts Amherst
