Re-pot old stock or throw in the skip?

Autumn is a time of year when growers look at tired Hardy Nursery Stock (HNS) and herbaceous plants to decide whether to re-pot, or simply throw in the skip. Before being too hasty, Steve Hughes − Technical Area Sales Manager for the Midlands − says there are several factors worth considering.

Steve Hughes, ICL Technical Area Sales Manager

• Is it a variety that sells well?
• Is it in good health, both foliage and roots?
• Do you know when it was potted and what was in the mix?
• Have you got the space to keep it for another season?

If the answers to the above are yes, then this stock could benefit from re-potting into a larger pot and generate a higher selling price next season.

Again there are several factors to consider, not least on-going vine weevil control and ensuring you get the nutrition correct.

If you have a vine weevil issue you need to consider on-going protection for the plant.  Of course, you may have previously potted the plant in growing media treated containing Exemptor. However, if this was more than 37 weeks ago and there are pest grubs present you need to take further action. 

We recommend applying beneficial vine weevil control nematodes, such as Vine Weevil Seeka (if the soil temperature is between 12-30°C).  If it is later in the year, and the temperature has fallen below 12°C, but not lower than 5°C, then we recommend applying cold tolerant nematodes such as Vine Weevil Seeka CT (active between 5-30°C).

You also need to consider nutrition, the choice of controlled release fertiliser (CRF) is important.  To ensure the plant will be ready for sale early summer next year go for an Osmocote 5-6month product, or for sale mid to late summer choose an Osmocote 8-9month product.

One common mistake when re-potting into a larger pot is failing to increase the controlled release fertiliser rates.

For example, take a 2litre herbaceous plant with 3kg/m3 (3g/litre) CRF added that has run out of feed.  If re-potting in to a 5litre pot to take it in to a second year, the new mix will require 5g/litre to compensate for the 2 litre of growing media that has run out of feed. You can simply re-pot into a 3kg/m3 mix but remember to add 1 x 5gram Osmocote 5-6month tablet to bring feed levels up to where they should be.

If you have 3litre HNS plants (originally potted with 4kg/m3 CRF) and are re-potting for the second year in to 10 litre pots, the new mix will require 6g/litre to compensate for the 3 litre of growing media that has run out of feed.  Alternatively, you can re-pot into a 4kg/m3 mix and add 2 x 5gram Osmocote 8-9month tablets to bring the feed levels up to where they should be.

Finally, if you don’t have the space for larger pots but want to freshen up tired looking plants, consider applying Osmocote Topdress FT at the appropriate rate for the size of pot in early spring.  Alternatively use Osmocote Exact Tablets at the appropriate rate.   Don’t forget to treat as necessary for vine weevil, using the appropriate Seeka product as specified above.