Potting soil for Delphinums

How to grow delphiniums

Potting Soil for Delphiniums


John Innes Potting Compost

Seed compost:

2 parts sterilised loam
1 part moss peat
1 part sharp sand

The loam and peat is put through in 3/8 in (9mm) sieve.

To each bushel (8gal/36l) is added:

1.5 oz (42gm) superphosphate
3/5 oz (21gm) ground limestone

Potting Compost:

7 parts sterilised loam
3 parts moss peat
2 parts sharp sand

The loam and peat is put through a 3/8 in (9mm) sieve.
To each bushel (8gal/36l) is added

3/4oz (21gm) ground limestone
4oz (110gm) 14-14-14 Osmocote

This makes John Innes Potting Compost No. 1. For a richer mix simply double the quantity of John Innes Base to make No. 2 or treble it to make No.3




From Hobby Greenhouses in Alberta

Agdex 731-5

The Cornell peat-Lite Mix* is formulated for growing topical plants. The Foliage Plant Mix ** and the Epiphytic Mix** formulas are adapted specifically for their respective plant types and are modifications of the original peat-lite mix.

Cornell has used Osmocote 14-14-14 and Peters 14-7-7 fertilizers with the tropical plant mixes with good results. Other fertilizers are omitted with the exception of dolomitic limestone and 20 per cent superphosphate which are added to adjust the pH and to maintain adequate phosphorus levels. A trace element mix is added to assure a balance of minor elements. Trace element mixes can be purchased from specialty gardening centers.

* “Cornell Tropical Plant Mixes” by Russel C. Mott

**L.H. Bailey Hortorium, Cornell University, Ithaca, New York

Cornell Peat-lite Mix

Mix 1/2 cubic meter each of sphagnum peat moss and perlite or vermiculite. Add 6kg dolomitic limestone, 2.4 kg ammonium nitrate, 1.5 kg superphoshate, and 0.3 kg potassium chloride (omit if using vermiculite).

Cornell Foliage Plant Mix

The Cornell Foliage Plant Mix was developed for those plant that need a growing medium with high moisture-retention characteristics. Plants having a fine root system or possessing many fine root hairs are included in this group.

Material 1 cubic meter
Sphagnum peat moss (screened 1/2 inch
Horticultural vermiculite (No. 2) 0.25
Perlite (medium grade) 0.25
Ground dolomitic limestone 4.9 kg
Superphosphate 20% (powdered) 1.2 kg
Fertilizer (10-10-10) 1.6 kg
Iron sulfate 0.4 kg
Potassium nitrate (14-0-44) 0.6 kg
Granular wetting agent 0.9 kg

Cornell Epiphytic Mix

The Cornell Epiphytic Mix was developed for plants that require good drainage, aeration and have the ability to withstand drying between waterings. Plants having coarse, tuberous, or rhizomatous roots are in this category.

Material 1 cubic meter
Sphagnum peat moss (screened 1/2 inch
Douglas, red or white fir bark* (about
0.5 cm size)
Perlite (medium grade) 0.25
Ground dolomitic limestone 4.2 kg
Superphosphate 20% (powdered) 2.7 kg
Fertilizer (10-10-10) 1.5 kg
Iron sulfate 0.3 kg
Potassium nitrate (14-0-44) 0.5 kg
Granular wetting agent 0.9 kg

* Fir bark comes from Douglas fir, white or red fir, or redwood, ground and screened to a definite size. Finally ground bark (about 0.5 cm) has a dry weight of about 200 g per liter cube. Fresh bark has a pH of about 5.0. Upon weathering, it becomes slightly more alkaline. The bark contains some nutrients, but these will not meet the requirements of growing plants.

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