Bulb Season: Setting Up Your Garden for Colorful Spring Blooms

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In this episode, host Erin Hoover breaks down the best time to plant fall bulbs and why soil temperature matters more than the calendar. She discusses the differences between bulbs, corms, rhizomes, and tubers, along with practical advice on planting depth, drainage, and how to set your bulbs up for success next spring. Listeners will also learn which spring-flowering plants do best in the Pacific Northwest, including Daffodils, Tulips, Crocus, Snowdrops, and native favorites like Camas and Fawn Lily. The episode offers a clear, seasonal strategy for building a spring garden filled with colorful blooms.

As a modern homesteader, Erin has turned her property into a small, thriving farm. She grows veggies, tends to fruit trees and shrubs, and raises livestock, all while keeping sustainability in mind. Her focus these days is on finding new uses for native plants, finding ways to feed her animals from her land, and growing her own food.

When she’s not working on the homestead or recording The Evergreen Thumb, you’ll find Erin out exploring Washington’s mountains, forests, and beaches, bringing new ideas home to try in her own garden.

• Ag Weather Net
• Plant Spring Blooming Bulbs Now – Skagit County Master Gardener Foundation
• Plant spring-blooming bulbs in fall for years of low-maintenance color
• Growing Iris
• Bulb Planting Guide by RoozenGaarde
• Enhancing Plant Biodiversity for a Vibrant, Thriving Ecosystem

Erin Hoover (00:00)

Welcome to episode 80 of The Evergreen Thumb. It is mid-August right now, and fall is coming. So now is the time to start planning for your spring. Believe it or not, as the blooms start to fade on flowers like dahlias and zinnias, that is the signal that it’s time to start planting your bulbs.

What is a Bulb?

I used bulbs as a kind of generic term. In fact, what we typically refer to as bulbs is a group of plants called geophytes. Geophytes are a perennial plant that survives some of the more unfavorable seasons, including cold, heat, drought, and fire. They die back to an underground storage organ, then regrow from that structure when the conditions are favorable again. 

That storage organ holds energy and moisture, and everything in the plant needs to resprout and bloom. This is why geophytes can push up flowers so quickly once the season turns.

Bulb is kind of the everyday word we use for this group, but botanically it only refers to one of the four distinct structures that fall under the geophyte umbrella. And that would be a true bulb, which includes flowers like daffodils, tulips, and snowdrops. They are a layered structure built from modified leaf tissue, kind of like an onion.

The second form is a corm, which is a solid mass of stem tissue without layers, often a little bit flatter in shape. And some examples include crocus as well as native Triteleia and Brodiaea.

The third one is a rhizome, which is a horizontal stem that grows at or just below the soil surface and sends up shoots. The most common example of a rhizome is Bearded Iris.

Then the fourth type is a tuber or a tuberous root. And this is a swollen stem or root tissue that stores energy without the layered or cormous structure of the other types. So some examples are the Winter Aconite, Anemone Blanda, and Dahlias.

 The difference between these is important because the structure of the geophyte helps determine how and when it can be divided, how it needs to be planted, and how it spreads over time. So, understanding the different types of geophytes helps you make better planting decisions depending on what your goals are.

Some things to keep in mind. Not only is, you know, September and into October, depending on where you live, the time to start thinking about planting that spring color.

Selection matters too. So, you want to pick large, firm bulbs now while nurseries have the best stock, even if you hang on to them to plant a month from now.

So we’re going to talk about all these different types of geophytes, including native ones, some of the smaller overlooked ones, the different iris types, and all connect back to getting that spring color and planning for it.

When to Plant Spring Blooming Bulbs or Geophytes

So the best time to plant geophytes is when the soil temperature is below sixty degrees Fahrenheit, ideally in the fifty-to-fifty-five-degree range, measured about six inches deep in the morning and take an average over a few days.

There is kind of a rule of thumb about two weeks of 50-degree nights, and once nighttime temperatures have held in the forties to 50s for about two weeks, the soil has usually cooled enough at planting depth. So that’s a little bit easier than going out with a soil thermometer and taking the soil temperature.

Another option is the WSU AgWeatherNet.

They have weather stations all around the state, and they routinely measure soil temperature, so you can find your closest weather station and get a good idea of what the average soil temperature is at the time you’re getting ready to plant. Just keep in mind that most bulbs and all geophytes need a minimum of six weeks with soil consistently below 60 degrees to build a proper root system before a hard frost.

In western Washington, hardy spring bulbs are typically planted October through mid-December for March or April bloom, so they have at least four months underground in cool soil. So you have a little bit longer to plan for those tulips and daffodils.

The reason why waiting is important is that if the soil is too warm, it can trick the bulb into pushing up green shoots in the fall. And I’ve seen that happen before with daffodils that have been left in the soil to naturalize and they’ll come up in the fall or they’ll come up in January when it’s way too early if we have a warm January and then they’ll get a big freeze and then the bulbs either don’t bloom or they die because they gave away all their energy trying to sprout.

Cooler soil also suppresses fungal diseases like bulb rot, which are more common when bulbs go into warm, damp ground.

Ideas for What to Plant

So what to plant? Some of the classic spring bulbs are daffodils. This is a true bulb. It’s very dependable. It naturalizes really well, as I mentioned, because they just reproduce and spread. And a lot of times you’ll see them like in the median on a highway or a freeway.

And also daffodil sap contains a calcium oxalate, which deters deer and rodents, making it, you know, obviously very deer- and rodent-resistant, but also I’ve seen where you can plant daffodils in a ring, like at the drip line of a tree, like a fruit tree and that way those rodents they won’t typically get through the soil past those daffodils and make it harder for them to damage, if they’re chewing on the bark or the roots or anything like that of your trees, makes it harder for them to get to them.

 The second classic spring bulb is tulips. Tulips are also a true bulb, and they are beautiful, and there are hundreds, if not thousands, of variations of colors and styles, and they can be very spectacular additions to the garden, but they are less reliable long-term in Washington’s wetter winters.

Surprisingly, some of the largest tulip growers in the country are in Washington, because of our weather, but they also pull a lot of those bulbs out of the ground for the winter, whereas we as gardeners usually leave them in so that they’re in there in the spring and ready to bloom when the spring arrives.

So, Tulips often perform better when they’re treated as a replant each year. Like I said, that’s the way the professional growers do it. And they don’t really do well as a permanent perennial.

The next classic one is a crocus, which is technically a corm and not a true bulb, but they can be a great very early addition for some spring color.  They come in a lot of different shades: whites, purples, and yellows.  Crocus are planted much shallower than daffodils or tulips, roughly about three to four inches.

 The next classic bulb is hyacinths. Hyacinths are also a true bulb, valued for their fragrance and their structure. This is also one of the more deer- and rodent-resistant choices for spring color.

Alliums are also a true bulb. They bloom later in the spring, and they are generally the easiest of the classic bulbs to place since deer and rodents avoid them more than just about anything.

How to Plant Spring Blooming Bulbs

The general rule for planting these bulbs is roughly three times the bulb’s height. So, a two-inch bulb goes six inches deep. Smaller bulbs like crocus only need a few inches.

Bulbs look far more natural, planted in irregular clusters or by tossing a handful and planting where they land rather than straight rows. And as I mentioned, some geophytes return and multiply year after year. Crocus and daffodils are really good with that. Others, like tulips, are best treated as a seasonal display.

When to Plant Bulbs

So when to plant?

As I mentioned, you plant once the soil is consistently cool and the summer heat has broken. So don’t be looking at your calendar. Try to pay attention to overnight temperatures or soil temperatures, or like I said, use AgWeathernet to determine what your average soil temperature is closest to you.

You’re gonna get the best results if you wait until that cooler weather comes. And again, the depth rule: three times the bulb height, pointy end up if it has one. And make sure you’ve got well-draining soil so that they don’t suffer rot. When you plant them, water once at planting to settle the soil and trigger root growth, and then rely on the natural seasonal moisture.

How to Prepare Your Soil for Success

You don’t want to overwater. And like I said, with good drainage being critical, overwatering is critical to avoid because again, that invites rot. You can mulch after planting. About one to three inches of mulch will help moderate soil temperatures and moisture during a warm spell during the winter that we sometimes get in Washington to help prevent those bulbs from waking up too early.

Soil prep matters too. Loosen soil 8 to 12 inches deep and work in a little compost, especially in clay soils. And that will help both drainage and root penetration. And so this episode is going live about September 1st. So this is really the time to prep and plan for those spring bulbs. Buy bulbs now while the selection is best, while most of the actual planting still happens over the next month to six weeks.

Geophytes Native to the PNW

Now, there are a number of native geophytes in the Pacific Northwest,

So, these native geophytes fit into this same structure we’ve been talking about. Plant in the fall, let them root and grow during the winter and early spring to bloom in the spring. This is actually a different rhythm than a lot of garden bulbs bred for other climates. These species are specifically evolved to survive our wet winters and dry summers, and so they thrive here with very little fuss.

My favorite native bulb, and we’re fortunate to have a lot of it on our property, is Camas. Camassia Quamash there’s several native varieties in Washington. It is a beautiful purple, sometimes white. I’ve seen genetic variations on my property that are white. But they naturalize readily.

They pretty much cover just swaths of our acreage in the spring. Lewis and Clark described Camas fields of it as looking like lakes because it’s this blue, and with a breeze that comes through, it looks like waves on a lake. They are a true bulb. You want to plant them about four to six inches deep and about six inches apart. They are a fairly small bulb.

They like full sun; they will tolerate some shade, and they do tolerate heavy clay. These plants want moisture in the winter and spring, but they must dry out by summer. And that’s part of the natural cycle in the native meadows, like where we are in southwest Washington; they’ve evolved to thrive in our wet winter and dry summer.

 They have kind of a tall stem. The bees love them: the bumblebees, the mason bees.

 Around here they bloom mid-May, and it could be different in other parts of the state. The Quamash species is about one to two feet tall. There is a giant Camas that can get up to four feet tall if you want more height or drama, but they are long-lived, they naturalize easily, and the numbers can double within a couple of years if they’re really happy.

Another native geophyte is a fawn lily or a glacier lily. Erythronium species. It is a true bulb. It is a classic spring bulb, up out of the ground, blooms, and then vanishes by early summer.

It has mottled brown and green leaves. They give it the fawn name; genuinely pretty, even before the flower. They like part shade. Something under a deciduous tree is ideal because it gets bright spring light before the canopy leafs out, and then it’s shaded through summer dormancy. They need very well-drained soil. They don’t want to water them over summer once they’re dormant, or they will rot. It pairs naturally in the wild with Camas, Oregon Oak, Ocean spray, Sword Fern; those are all good companion planting ideas for Fawn Lily. They’re very slow to establish from seed, like three to five years. So buying in bulbs or starts can give you faster results if you are impatient like me and want instant gratification.

Another native bulb that is just beautiful in my opinion is Fritillaria Affinis, known as a Chocolate Lily. It is a true bulb; it’s a woodland and meadow native on both sides of the Cascades in Washington. It has nodding bell-shaped flowers; they’re sometimes brownish purple. They have a checkered look; the blossom actually almost has a checkered pattern on the petals. It surprised me the first time I saw one. I didn’t think it was natural, let alone native. Similar to Camas, they do like sun to very light shade, well-drained soils, and they are dormant by midsummer.

So a lot of these that we’ve mentioned for the natives fit together very well. And then Triteleia and Brodiaea these are corms rather than true bulbs, similar to a crocus.

But they are native to meadows and grasslands. They bloom a little later than the others, later in spring and into early summer. But they are a great choice for a naturalized meadow-style planting, especially paired with Camas, because then you’ve got kind of a succession of those blooms.

Non-Native Geophytes that Thrive in the Pacific Northwest

There are several nonnative geophytes that pair beautifully as under-plantings beneath these natives, since they share the same bloom and dormant rhythm. So now I’m going to kind of go into small geophytes and other structures that are beyond what we typically think of as the big bulbs. And one of my favorites is snowdrops, Galanthus Nivalis. It is a true bulb.

It thrives in Pacific Northwest conditions and naturalizes well under deciduous trees, especially vine maples. And they’re easy to combine with crocus, winter aconite, and similar geophytes for a layered effect.

Another one is Scilla Siberica known as Glory of the Snow. It is a true bulb, early blooming, and naturalizes like Snowdrops. These are one of the most reliable naturalizers alongside daffodils and crocus. Winter Aconite is an Eranthis. It is a tuber, not a bulb.

It blooms alongside snowdrops in late winter and is one of the very earliest bloomers. And then the last one I’m going to mention today is Anemone Blanda, also called Winter Aconite. And it is a tuber; it’s small, knobby, and is also a good naturalizer under trees.

A design note is to pair shorter, earlier blooms like snowdrops and crocus towards the front with taller mid- to late-season bulbs like daffodils, tulips, and iris behind. So you get a natural progression of blooms through your garden. So that is the small true bulbs and tubers.

How and When to Plant Rhizomes

I also want to talk about some rhizomes. Mostly iris, and why the timing depends on which type of iris. So Bearded Iris is my personal favorite. If you haven’t divided or planted your bearded iris, you wanna get it done quick because July to August is the best time to divide bearded iris.

And the best way to do it is to dig up the whole clump, cut the leaves back to about six inches, and pull out the woody center rhizomes. These are like they were the mother rhizome when you planted it the first time, and each rhizome only blooms once.

So keep only the healthy young ones with a fan of leaves and then replant. You want just the top of the rhizome sitting at the soil surface. You want to be able to see a little bit of the rhizome. Don’t bury it deep like a true bulb because it will rot.

Siberian Iris are more flexible than Bearded Iris. They can be divided late summer into fall or even in early spring. So, if you didn’t get Bearded Iris in time for this fall, Siberian iris are a good option. They multiply readily.

Another iris is Dutch Iris. It actually is a true bulb and not a rhizome, but you can plant it alongside other fall bulbs about six to eight weeks before a hard frost.

And then finally, there are Pacific Coast irises, native irises, including Iris Tenax that are actually different from all the others. You want to leave these until the fall rains return. You don’t want to divide them or pull them until after it has started raining. And so that’s another reason why it’s really good to know what kind of iris you have so you know when and how to propagate them or move them if that’s what you’re aiming for.

Garden Design Tips

Okay, now that we’ve talked about all the different kinds of bulbs, let’s talk about planting them for the most impact in your garden. The first thing to keep in mind is to plant them in clusters, not in single rows. The clusters look more natural.

And you get good pops of color in your garden. A second design tip, is to layer bloom timing. So, I kind of mentioned this a little bit, but from late winter, the earliest bloomers like snowdrops and Winter Aconite, to crocus, and then to daffodils and tulips and camas in mid to late spring.

And don’t forget to combine height for visual depth. Shorter bulbs towards the front or edges, taller ones behind, to help give you that visual angle. Containers are a great option for small spaces or for renters. You can even layer bulbs in a single pot. The largest, latest bloomers at the bottom, the smaller early bloomers near the top, for an extended succession.

Underplant natives with small geophytes like snowdrops for a layered look. And a cluster of twelve or more bulbs of one type tends to read as a show in the landscape versus scattered singles that can kinda get lost visually in your garden.

Common Mistakes when Planting Spring Blooming Bulbs

So, what are some of the common mistakes? And some of these I kind of mentioned, but I want to call them out to give you the best chance of success.

So the first mistake to avoid is planting too early when the soil is still too warm. Remember, it needs to be fifty to fifty-five degrees to get the best results. There are tools out there you can use to determine what your soil temperature is, but planting too early can make plants prone to rot, or it can cause them to put up shoots which will freeze and could kill the plant

Another common mistake is planting too shallow. And I know I’ve done this before because sometimes if it’s a big bulb, planting six to eight inches down can be a lot of work. Bulbs planted too shallow are more vulnerable to temperature swings and are more vulnerable to squirrel and rodent digging.

I know a lot of people get really frustrated when squirrels take off with their daffodils or their tulips. And so, it’s important to make sure that you’re planting them three times the height of the bulb.

So, if it’s a two-inch bulb or a two-inch corm, you plant it six inches deep. A third common mistake or tip is to not ignore drainage; especially in wetter areas, standing water is one of the most common causes of bulb rot. So, make sure you’re putting it in well-drained soil or in a pot for the best results.

I mentioned this one earlier on, expecting tulips to behave like permanent perennials. In our climate, they often perform best when treated as a yearly replant rather than as a naturalizer. Especially some of the more unusual varieties, not only will they do better if you pull them and replant them, but some of those can actually also revert over time.

Planting Tips

Let’s see, another tip is to avoid treating a rhizome or a tuber like a true bulb.

It’s really important to understand the differences between the different geophytes because you could be planting them at the wrong depth. Like a Bearded Iris needs to be right on top of the soil. And the timing is different for some of these as well. Again, the Bearded Irises, missing that division window-dividing after August doesn’t give enough time for root establishment before they go semi-dormant for the winter.

So if you miss the window for iris division, wait till next year. You’ll have, you know, probably a clump in the middle that doesn’t do anything, but that’s better than risking them not being established and being vulnerable to winter freezes and poor weather.

The final tip is don’t skip soil prep. Even a good bulb will underperform in unamended heavy clay. Loosen soil, add compost. Adding compost is almost always the answer to improving your soil texture. And it is gonna pay off in bloom quality and bloom size over time.

Final Thoughts about Geophytes

To wrap up, I want to talk about what late-season planting really represents. September, October, we’re planning for a season that we won’t get to enjoy until spring. So late summer and fall work shapes the garden as much as the effort in the spring does.

I’m also hoping that you now understand a geophyte and the difference between a bulb versus a corm versus a rhizome. I’ll admit when I started doing some research for this episode, geophyte was probably a term I’d heard, but it hadn’t really sunk in.

It’s common and easy for gardeners to refer to them all as bulbs. But understanding the differences can increase your chances of success with several of these plants. native and ornamental geophytes often share the same regional seasonal rhythm.

So, plant them in the fall, let them grow through the winter, bloom in the spring, and then go dormant in the summer. So, whether you prefer natives or ornamentals or a blend of both, there is a geophyte for just about everybody. Your mission is to buy your bulbs now while the selection is good.

If you haven’t divided your Bearded Iris, depending on when you’re listening to this, you either need to do it immediately or wait until next year. And finally, watch the soil and not the calendar. Look at your Dahlias and your Zinnias for the cues when they start to die off. Check your soil temperature either through AgWeatherNet or with a soil thermometer and make sure that you are giving those geophytes their best chance at a beautiful spring.

Thanks for joining me today, and we’ll see you in two weeks.