Garden Soil Preparation For A New Perennial Flower Bed

Soil Preparation

Let’s be clear right here at the beginning.
There are few shortcuts in the garden to making really good soil for perennials. Oh, magazines are full of plants to grow and wonderful garden pictures but the hard, oft-cold reality is that a great soil will grow a great garden. A good soil will grow a good garden and – you got it – a poor soil will grow a poor garden.
Our objective is to grow a great garden and for this we need great soil. I’m going to tell you how to do this quickly and I’m going to tell you how to do this slowly. It will be your choice on which method you use.

The quick method.

Note I didn’t say that this was the easiest method.
To make a great soil very quickly, you double-dig the garden. While I mostly use this for my annual vegetable and herb garden, I have double dug many of my perennial beds when I wanted fast growth and respectable gardens in a very short time. This system gives you a great soil to a depth of 18-inches and any plant will thrive in this soil because of the fertility and aeration of the soil.

Double Digging

Double digging means digging a trench 18-inches deep or double the depth of a single shovel blade. This trench is traditionally described as one foot wide but wider is fine. The length of the trench is the width of the flower bed in question. So the trench is dug across the flower bed as in the diagram. The dirt from this trench is usually put at the other end of the trench as in the second diagram.
The second step is to dig a second trench, identical to the first, right beside it. The difference is that the dirt from the second trench goes into the empty first trench, filling it up. I generally recommend that for every three shovels of soil you move, you add one shovel of peat and one shovel of compost or composted manure to the trench.
In this way, the entire 18-inches of the trench is made into well-aerated soil with organic matter and compost from top to bottom.
Trench #3 is a repeat of trench #2. Dig out the soil in the third trench and fill in trench #2 with it. Repeat until your garden or back is done.
When you get to the end of the garden bed, you’ll find the soil from trench #1 in a pile. Use this soil to fill in the last trench.
This is an old system of garden digging but it will give you the best garden soil you can imagine and you’ll be able to grow anything you want in this bed.
And yes, I do know there are a ton of garden writers who run down this system of garden bed establishment. Let me suggest you do one small bed this way and one small bed any other way you like. Then compare growth rates. Decide for yourself. I did. Which is why I suggest it to you. 🙂
But nope, never said it was easy. 🙂

The slow method

Now this method of building soil combines two separate gardening techniques that – when combined – work particularly well together. It does take a longer time – but it also takes a lot less back-work as well.
I’m talking about a combination of mulching the garden with a fast-decomposing organic mulch and applying compost every spring and/or fall.

A 3-inch layer of garden mulch will do this nicely assuming the garden is weed-free and grass-free. This amount of mulch will cut weeding work by approx 80% while going to 4-inches of mulch will decrease weeding by approx 90% (now you see why I like mulch)

A mulch (and I’m a great believer in garden mulch for all garden beds) does several things.

  • It evens out the soil temperature cycles – reducing the heat of the summer and increasing the heat of the winter. It also reduces the minor heat swings of a week of really hot weather in the summer – so that plant roots are not stressed by small fluctuations of air temperature (high or low).
  • It evens out the moisture levels of the soil. By reducing air circulation across the top of the soil, evaporation is reduced. An evenly moist soil produces a better perennial crop than a fluctuating one.
  • It decomposes. At the interface layer of soil and mulch – the mulch is full of soil bacteria breaking it down and making the nutrients in the mulch available to the plants. This is a good thing. A mulch such as straw that will break down in a single year if applied at the rate of 1-inch deep or leaves that will do the same applied at a 3-inch depth are wonderful soil builders. They feed the soil microorganisms and keep life going.
  • So while a mulch will not directly feed the plants, it will provide a home and food source for all the bacteria and fungi that will eventually feed the plants.


Other Mulch Thoughts

So you can mulch before planting, during planting or after planting your perennial gardens, but mulch will be the long term key to soil improvement. And the quicker this material breaks down, the faster your soil will improve.
This is why a three-inch layer of leaves is ideal while a 3-inch layer of wood chips (decomposing slower) will be slower to make a difference to perennial production.

Does a mulch make soil better?
Let’s be clear – it doesn’t change the “structure” of the soil except to add extra organic matter. So the amount of sand particles, and clay particles will stay constant – they won’t change. But what happens (in real gardening effects) is that as the percentage of organic matter in the soil increases, your perennials will grow better. Mulch adds organic matter to the soil.

Do I cover over all perennials?
In the beginning I used to do exactly that but as I gained some experience I started to see there was a difference in how different perennials respond to different layers of mulch. Some would shrug off 4-inches while some would only take 3-inches. Some would rot at the merest sign of mulch.
Now – I pull the mulch back from around the crowns of all perennial plants. I leave those crowns dry but surround them with mulch (pull it back 6-8 inches from around the crowns. It does make a bit extra hand-weeding but survival rates across the board are better on most plants.

Do I have to pull it off in the winter?
Are you kidding? 🙂 Nope – leave it alone

What about feeding compost? Do I have to pull it back?
Are you kidding? 🙂 Toss the compost on top of the mulch, the worms will thank you and pull it back down where it belongs. Either that or the first rainstorm will wash it down.

How Often Do I Have To Renew The Mulch
Some material – such as bark mulch will last for several years without any topping off. While straw or leaves may only last one year or two at most. So it depends on the material you use but generally adding bit every year is less work than a bunch all at once. Hint: Buy it in the fall when the sales are on. 🙂

Light Levels in the Perennial Garden

Light levels are set out in the graph below. You’ll find much more gardening success if you stick to plants that grow well in the light levels you have at your property. The good news is that by utilizing the four sides of your house, you’ll discover you likely have light levels for both sunny and shady plants. (That is of course unless you have a lot of shade from trees or other tall buildings; then you just have a shady garden.)

Full Sun

On the graph, full sun is represented by the distance between 10am and 2pm.
Add another section – any one and you have full sun.  So, if you have sun on your garden during that time either with sun before or after,(or both) you have full sun conditions.

Those mid-day sun levels are the most important.

Shade Garden

If you have sun in the morning but not the rest of the day, then you can consider yourself mostly shady.
With sun only in the later part of the day, you are definitely shady.
If your sun is before 10 and after 2 or even 4, then you definitely have a shady garden.

Part Shade

When you get sun in two of the time periods but NOT the noon period.

Having Said All That

There are regional differences. So what we consider “part shade” in Florida is considered full sun in Ontario, Canada.
These rules of thumb are guidelines rather than carved in stone.  Other factors such as variety choice will often make a difference when growing some plants in more or less sun than recommended.

The Single Best Way to Improve Your Perennial Garden

You can struggle all you like with designing perennial garden borders for timing and sizing and color but the single best way to make that border look better is to get the size right.

The rule of thumb I’ve always worked from is that a perennial bed has to have 1 foot of width for every 3 feet of length.

This means a 30-foot long border is 10-feet wide.

The maximum width imho –  is 10-12 feet.

After that, it becomes a visual problem in most gardens. This means a 60-foot long border still has beds that are only 10-12 feet in width.

Get the width right and you’ll be amazed at how much better your garden looks right away.

Get Outstanding Blooms Growing Your Fall Chrysanthemums This Way

Many folks assume the fall chrysanthemums normally seen in garden centers are hardy perennials and I’m here to tell you (unfortunately) that is just ain’t so.

Are Mums Annual or Perennial?

The fall mum normally found on benches is a tender perennial and in a USDA zone 4, you’ll rarely get it to successfully overwinter two seasons in a row. Having said that, your garden may have a warm microclimate next to a house or special spot that allows you success with growing fall mums but on average, they won’t.  (Note you can find other articles about perennial flowers (here)
There are hardy varieties / species and they are listed below along with their hardiness ratings. Normally these are found on the perennial benches of garden centers.

Growing Tricks

The trick to growing fall mums and getting them to flower heavily is to treat them in a specific manner.

  • They like full hot sunshine.
  • Give them shade and they get tall and leggy.
  • They like regular and deep waterings all summer long. Figure soaking them at least twice a week.
  • They like to be fed. Feed with compost in the early spring and then give a booster of fish emulsion every two weeks to really pump them along.

How Many Times Does A Mum Bloom?

The answer to this question is generally once a year.  The blooms are triggered by a reduction in light levels and this happens naturally in the fall.

One of the things I should point out about growing fall mums is that the spring is the critical time to succeed with this plant.  Dig the “babies” or offsets off the mother plant when they’re about 4-6 inches tall (late spring)  Don’t worry about trying to save the mother plant – the odds are it’s not going to survive the winter in very good shape anyway.  Get those babies!  If the mother did survive in my gardens, I’d dig it up and compost it anyway.  The best flowering seemed to come from those offsets.

It is also a very easy plant to propagate from cuttings. And a cutting taken in very early spring will grow out to a full blooming plant by fall if you grow them properly

Do not mulch this plant over top of the plant! It will rot out.  While it likes constant moisture during the summer months, (this is not a dryland plant) it absolutely hates it during the winter

Can I Get My Indoor Mum To Rebloom Outside?

If you get a fully grown and flowering mum for Mother’s Day, then yes you can get it to rebloom in the same year.  Cut it back as below (about one third in the case of potted mums in 6-inch pots) and replant in garden after danger of frost has disappeared. It will rebloom in the fall.

Will It Survive The Winter?  Probably not but hope springs eternal so leave it and grow it as below in the section Double Duty From A Fall Mum.

How Big Do Mums Get

Well, that’s a “depends” kind of answer.  If you prune them as I recommend in this article, they’re going to grow to “about” 12-18 inches (30-45 cm) and about 24 inches (60 cm) wide.

If you don’t prune them, they’ll tend to grow tall and leggy (falling over in a fall rain) and around 36 inches or 90 cm tall.  See below “The Biggest Growing Trick”

The Biggest Growing Trick

Here’s the major trick in growing fall mums! Let them grow in the early spring and when they reach 12-18 inches tall, cut them back by half so they are only 6-9 inches tall. This will force the plant to bush out and produce more shoots. (more shoots equals more flowers)
Allow leaves on the bottom shoots. In other words, do not cut back so far as to remove all leaves.

If you don’t cut them back at 18 inches tall, they will continue to grow to 3 feet tall and produce flowers on top of the plant. A reduced number of flowers I note.

Double Duty From A Fall Mum

If you want to get double duty from the garden, allow the fall mum to overwinter in the garden where you’ve planted it.  Assuming it survives do the following.

Dig it up in the spring. Divide off babies from the main mother plant to increase your fall display. Replant in the vegetable garden.

In the fall, move it back to the garden to fill in bare spots. And then allow it to overwinter there.



At this digging and moving time, you’ll see all the babies around the main plant.

These can be pulled off the plant and as long as they have a bit of root, they’ll grow into full mums by fall if treated well by keeping them watered.

I’ll often throw away the woody center in the spring (it’s often dead anyway) and only grow the surrounding babies into full flowering fall mums.

Mums can also be easily propagated in the spring from divisions and or tender tip cuttings.

Unsure how to take cuttings? Check out my Plant Propagation ebook

Hardier Fall Chrysanthemums

These are some of the tougher plants on the market.
The old style of mums such as

  • Chrysanthemum x rubellum ‘Clara Curtis’ and
  • Chrysanthemum ‘Mei-kyo’.

Chrysanthemums bred in Minnesota including:

  • ‘Inca’, light bronze-orange, double button, low, early
  • ‘Burnt Copper’, copper orange-bronze, double pompon, tall, midseason
  • ‘Centennial Sun’ bright golden yellow, double decorative,medium height, early
  • ‘Minnautumn’ reddish bronze, formal decorative, low, midseason
  • ‘Minngopher’ crimson red, decorative, low, late
  • ‘Minnruby’ ruby red, decorative,low, midseason
  • ‘Snowscape’ white with purple tips,semi-double decorative, low, early
  • ‘Mellow Moon’ cream, semi-incurved decorative, medium, midseason
  • ‘Minnwhite’ white, decorative,low, early
  • ‘Rose Blush’ mauve, decorative, low-medium, midseason
  • ‘Rosy Glow’ deep rosy pink, decorative incurved, medium, midseason
  • ‘Snowsota’ white with cream centers, pompon, low, midseason

You can find other perennial plant articles here.

You can find both seeds and plants of fall mums here at Amazon.

My Three Favorite Blue Perennials

When it comes to my favorite blue perennials, it didn’t take long to come up with the first one. The other two were a bit more challenging (there are so many great candidates) but I’ve selected several for you to try. 

Geranium ‘Rozanne’

This perennial geranium is one of the longest blooming plants in my garden and this alone gets it first place. Starting in very early summer, it springs into a mass of violet-blue flowers and continues with this pace of blooming right to the very bitter, cold end of fall when winter sweeps across my garden.

  • Grow it in the full sun or light shade for best blooming.
  • Grows 12-18 inches tall if left to sprawl by itself. Will grow taller if crowded. I grow mine on the edge of the garden allowing it to hang over the raised beds down into the pathways. It would be a perfect plant to hang down over a wall.
  • Grows 36-inches wide give or take a few inches.
  • Propagation is by division in the early spring just as it is starting to grow.


How could I talk about my three favorite blue perennials and not write about growing Lavender?
Between the fragrance and the delightful flower spikes for a very long blooming season, this plant deserves a place of honor in my garden (and it gets it right beside the front door).
Grow in the full, hot sunshine. The hotter the better for this heat-loving perennial flower.
Grows 8-30 inches tall depending on variety but generally you’re going to see an 18-inch flowering plant if left uncrowded.
Grow in a well-drained soil (no clay) and shear the blooms after they are finished to promote a second flush of blooms.
Do not feed or water other than a shovel of compost in the early spring. The fragrance is much better if left alone.
Propagation is by tip cutting

I had a lot of trouble deciding on the last one of three of my favorite blue perennials but had to finally pick the plant I’ve collected for a few years and the one that’s slowly taking more and more space in my garden as I add newer varieties.

Nepeta or Catnip

Ornamental catnip is again one of the full sun perennials that has to be included in this list. It’s a long-season bloomer that lasts from mid-summer until late fall in my garden. While I’m not overly fond of the fragrance, I’m enchanted with the blooming.
Grow this is the full sun or very light shade. It will get powdery mildew or botrytis if it doesn’t get enough sunshine.
Growth to 18-inches depending on variety and at least 24-30 inches wide.
You can propagate it by cuttings or an early spring division to get even more for your garden.
As a note – if your Catnip isn’t cut or bruised, cats won’t bother it at all. But as soon as you bruise a leaf or cut it to release the fragrance, you’re going to have visitors.

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