Plants
   Vines
   Trees
   Shrubs
   Herbaceous perennials  

 Information
   Planting instructions
   Planting instr. (acid)
   Printable plant list
   Newsletter archive
   Ask the Chuckster

 Driving directions

 Chuck’s courses
 and consulting

 Driving directions

Ask the Chuckster...
Fertilizing plants that have already been planted

What fertilizer should I use on my plants?

It is always a good idea to do a soil test first before developing a specific fertilization program for your plants.  Soil test sample kits are available from the NC Agricultural Extension service.  Their recommendations are for non-organic fertilizers, but can be easily transferred for organics.

We need to talk about acid-loving and non-acid-loving plants separately. Let’s start with the acid-loving plants – that would be your blueberries, strawberries, cranberries, lingonberries, blackberries, raspberries, and tea camellias. We prefer organic or semi-organic fertilizers when possible, such as cottonseed meal (6-2-1) or Happy Frog (6-4-4). Another good one for acid-loving plants is coffee grounds (2-0.36-0.67).  The nursery uses Holly-tone fertilizer(5-3-4) on our acid loving plants.

Never use a fertilizer with high calcium content on acid-loving plants. This includes compost with eggshells, colloidal phosphate, bone meal, or agricultural limestone.  High soil calcium will cause Iron chlorosis (yellowing leaves) on blueberries and severely stunt their growth.

On all other plants you can use regular blended organic fertilizers, such as Plant-tone, Fertrell (5-5-3), McGeary Organics (5-3-4), or Harmony (dehydrated chicken manure). All of these are commercially available blended organic fertilizers.  Depending on your soil test results, you may need to raise (with agricultural limestone) or lower (with granular sulphur) your soil pH to meet your plants’ optimum pH requirements. 

Most of the soil tests I see are very low in phosphorus (P).  The best time to add phosphorus is at planting time by adding either rock phosphate or colloidal phosphate (never use this on blueberries due to its high calcium content) into the planting hole backfill soil.  We also add greensand at planting time for extra potassium and micronutrients.  See our planting instructions on the nursery website for more planting instructions.

When should I fertilize my plants?

Apply the first fertilizer just before the plant starts growing – late March to early April. If you missed that, it’s OK to fertilize in early May.  Make the second application around mid-late June. The fertilizer will last about six weeks.

Don’t fertilize heavily after early July. You need to leave plenty of time for the plant to harden off so they don’t go into fall in active growth. Too late of an application could leave the plant vulnerable to more winter damage. 

A December or January fertilizer application in colder areas can be beneficial in some cases.  Winter fertilization, after there is no possibility of the plant breaking dormancy will often allow plants to absorb those nutrients and produce strong spring growth.

What are those numbers after the names?

Those are the NPK ratios – the relative amount of nitrogen, phosphorus, and potassium in the fertilizer.

Nitrogen is vital for a plant’s vegetative growth. Plants deficient in nitrogen turn pale green or yellow. The demand for nitrogen is particularly strong in the early days of growing when the plant is flushing new growth.

Phosphorous has more to do with plants maturing than with growth. Phosphorous helps with photosynthesis and energy transfers within the plant, leading to good flower and fruit growth. It also helps with climatic stress, such as drought or cold, and strong root growth.  Phosphorous moves slowly through the soil, so for existing plants you’ll need to use a steel bar to dig 8-12” deep holes to get it down to the roots zone.  Poke these holes in a circle every two feet around the plants drip zone.  You can also add additional circles in circles two feet inside and outside the drip zone, depending on the size of the plant.  Fill the holes with a 50/50 mix of phosphate rock and compost or Michigan peat.  Plants deficient in phosphorus often respond well to an application of compost.

Potassium is critical for root development and cell division, it helps plants retain water, and helps with the manufacturing and movement of sugars within the plant.

What about using compost?

Well-made compost is great for feeding the life of the soil. It’s high in humates and has a wide range of macro and micro nutrients in a relatively easy to absorb organic form. And with compost you don’t need to worry about burning the plant. You just need a little at any one time – a few cups to the plant for small plants, more for larger plants.  Always water in compost or fertilizer well.

You can also make compost tea by soaking some compost in water for 24-36 hours and then applying the liquid to the leaves. In this form, the nutrients are readily available to the plants. You can also make manure teas. With animal manures you need to be careful not to burn the plant. Green manure teas are another option – soak plants with a lot of nutrients, such as comfrey, for three days in water and then use the water as a foliar feed or soil drench. All teas are fast acting and will provide immediate benefits to plants. Solid compost is slower acting. They work together.

What about seaweed concentrates?

We love seaweed concentrates as a transplant dip and occasional soil drench and foliar application when plants are in active growth. The nutrients are easily absorbed into new foliage. Our favorite is Nature’s NOG, which is manufactured in Clemson, SC, based on many years of research and testing by Dr. Senn, a global pioneer in researching the horticultural uses of seaweed. It’s a combination of emulsified cold-water seaweeds and humates.  For our customers’ convenience we now sell Natures NOG.

Seaweed is not technically a fertilizer, it’s a plant growth enhancer. It contains many micro nutrients, as well as plant stimulating hormones that stimulate new root and shoot growth following transplanting and during growth. Seaweed and humate solutions also stimulate biological activity in the soil, help plants overcome stresses from transplanting, drought, frost, freezing, and insect and disease pressure. I wouldn’t transplant a plant without a good dose of seaweed concentrate.

From the UPN May 2010 newsletter.