Bulbs up? Put fertilizer down!

Slow release fertilizer is one of the best greetings you can give emerging bulbs. You can use any type of slow release fertilizer... if money is no object! Here's help picking the best without emptying your wallet.

Slow release fertilizer is one of the best greetings you can give emerging bulbs. You can use any type of slow release fertilizer... if money is no object! Here's help picking the best without emptying your wallet.

When to fertilize

How much to use

How to apply fertilizer

Which product to choose

The University of North Carolina conducted a four year study for the Netherlands Flower Bulb Institute to determine which bulbs might be most reliable as perennials in the U.S.

In addition to developing a list of bulb species and varieties that perennialize in the eastern U.S. -- perform well for at least 3 years -- the researchers discovered that longevity was greatly influenced by fertility. In a presentation of this study, chief researcher and native Michigander Gus DeHertogh stressed that the best time to fertilize was just as the bulbs broke the surface in spring.

Perennial gardens, shrub and tree beds also appreciate fertilizer now. Slow release organic fertilizers are best since their nutrients become available as the soil warms, right in step with plant development.

So break out the fertilizer. Spread it in all your beds.

When?

We fertilize gardens in fall (October or November or whenever we finish work in that bed) and early spring (April; or whenever we start working in that bed). Slow-release organic fertilizers have done the best job for us, so that's what we use. The amount we spread is what will provide 0.2 to 0.3 pounds of nitrogen per 100 square feet of bed.

How much?

For the 80-square foot garden you're about to see, we need just under 1/4 pound of nitrogen. (We figured that this way: We scaled down the 100-sq.-ft. max. rate of 0.3 lbs to suit an 80-foot bed: 0.3 X 0.8 = 0.24)

Please don't let your eyes glaze over. In short, we chose to use 6 pounds of Holly Tone by Espoma as it was the best buy.

For how we arrived at that decision, read on.

First step in spring: We cut back woody perennials like this butterfly bush (loppers at work, foreground) and cut down spent perennial stems such as those of the  threadleaf coreopsis (lapping onto the walk just beyond the butterfly bush).

First step in spring: We cut back woody perennials like this butterfly bush (loppers at work, foreground) and cut down spent perennial stems such as those of the threadleaf coreopsis (lapping onto the walk just beyond the butterfly bush).

Next, we remove the cut debris from the garden, then spread a slow release organic fertilizer.

Next, we remove the cut debris from the garden, then spread a slow release organic fertilizer.

How far back do you cut butterfly bush (Buddleia davidii)? Since we like the clean lines and slightly delayed bloom period of brand new wood, we cut it all the way to the ground. Look for the stubs in the circled area. What we cut out was one year's growth by a dwarf butterfly bush.

How far back do you cut butterfly bush (Buddleia davidii)? Since we like the clean lines and slightly delayed bloom period of brand new wood, we cut it all the way to the ground. Look for the stubs in the circled area. What we cut out was one year's growth by a dwarf butterfly bush.

Step by step to apply the fertilizer

The most efficient sequence we've found for spring work in a mixed border -- where perennials, bulbs, annuals and woody plants grow together -- is to:
• Prune the woody plants,
• Cut down spent or unwanted parts of herbaceous perennials,
• Remove that debris from the bed and then
• Spread a slow release fertilizer.

We apply the fertilizer before edging, weeding, dividing, planting and mulching because these follow-ups eliminate any need to "scratch in" the fertilizer.

Working this way means taking fewer steps, so we're all for it!

Choosing a fertilizer...

...is a two part process. First, select a product that will correct deficiencies in the soil. Either you have a fertilizer test result with a prescription, such as 4-6-6 ratio of nitrogen - phosphorus - potassium, or you are using a complete, reasonably balanced product such as 5-5-5 or 4-5-5.

Second, you evaluate the fertilizers that will meet the need to determine which is most economic.

Scroll down for what we found in considering four slow-release organic fertilizers currently on the market. For those who are handy with math, we've "shown our work" and know you can take it from there. For everyone else, we've prepared a fertilizer chart that includes even more types of fertilizer and how much ground each will cover, for which types of bed.

Download that fertilizer chart here. Read more about spring fertilizing in What's Coming Up #212 and Growing Concerns 559.

Here are the four slow release organic fertilizers we looked at when it came time to fertilize the 80 square foot bed you just saw.

Wow, $91 per pound of nitrogen!

Wow, $91 per pound of nitrogen!

Best buy at $34 per pound of nitrogen. Nearly balanced and adds acidifying sulfur but contains some quick-dissolve nitrogen.

Best buy at $34 per pound of nitrogen. Nearly balanced and adds acidifying sulfur but contains some quick-dissolve nitrogen.

$83 per pound of nitrogen, and not balanced.

$83 per pound of nitrogen, and not balanced.

$44 per pound of nitrogen, all of its nitrogen is slow release. Nearly balanced.

$44 per pound of nitrogen, all of its nitrogen is slow release. Nearly balanced.

Read on for how much we would need of any one product to cover the entire bed, and how much the nitrogen in that product cost us.

Dr. Earth Flower Girl Bud & Bloom Booster

3-9-4 in a 4-lb. bag. Since it's 3% nitrogen (N), we would need 8 pounds. That's two bags at $10.98 each. (.25 pounds N needed ÷ 3% nitrogen = just over 8 pounds of fertilizer.)

The nitrogen in this fertilizer comes to us for $91/pound.

Espoma Holly Tone

4-3-4 in an 8-lb. bag.

It's 4% nitrogen (N), so we would need 6 pounds: 3/4 of this 8-lb., $10.98 bag. (.25 pounds N needed ÷ 4% nitrogen = just over 6 pounds of fertilizer.)

The nitrogen in this fertilizer comes to us for $34/pound.

Miracle Gro's Nature's Care Rose & Flower Plant Food

3-4-1 in a 3-lb. bag.

It's 3% nitrogen (N), so we would need 8 pounds: nearly 3 bags at $7.48 each. (.25 pounds N needed ÷ 3% nitrogen = just over 8 pounds of fertilizer.) The nitrogen in this fertilizer comes to us for $83/pound.

Pennington's Alaska All Purpose fertilizer

6-4-6 in a 3-lb. bag.

Since it's 6% nitrogen (N), we would need 4 pounds: one+ bags at $7.98 each. (.25 pounds N needed ÷ 6% nitrogen = just over 4 pounds of fertilizer.)

The nitrogen in this fertilizer comes to us for $44/pound.

Our choice: Holly Tone

It's least expensive per pound of nitrogen, nearly balanced, plus it contains some sulfur to help acidify the soil --- almost always a good thing in our home ground, alkaline Southeast Michigan. A bit more than a third of the nitrogen in it is fast-dissolving which is not ideal for use in cold soil. That portion of the fertilizer may dissolve and drain away before the plant is ready to use it.

For the economy and the sulfur, we choose Holly Tone for this bed.