Replant Disease

Question :rose-on-yardI want to replace an old rose but one of my neighbours mentioned that I should never plant a rose where another has been. Is this just an old wives tale or should I listen to the advice. 

Replanting roses

Replant disorder or replant disease refers to the problem of re-establishing plants in soil where the same species was previously grown. Roses are particularly prone, though it can affect other trees and shrubs namely

Apple,Cherry, Peach,Pear,Quince,Plum and Cistus

It can occur quite quickly after planting even if the roots of the previous plant  have been in the soil for only a few months .

Symptoms                                                                                                          The new Roses tend to sit in the ground for a while and not put on any real growth and if dug up  you  find the roots have put on little growth and with the fine roots rotten away

The commonest conditions thought to affect the newly planted shrubs roots are

Allelopathy.

Where a plant release biochemicals into the soil called allelochemicals to either encourage other plants to grow with it or to stop other plants growing with it.

An example being  black walnut produces a biochemical called jugulone that stops most other plants from growing under it

Autotoxicity.

Established older plants releasing toxins into the soil and those affect  new plant’s  as the existing plant has an inbuilt resistance to the toxin as it builds up during the life of the first planting                                                                                                            Fungal root diseases and eelworms(a type of nematodes) are favourite suspects for this

 

The classic method of dealing with rose replant disease was to remove all the old soil and replace it with fresh soil which works perfectly if you have access to large quantities of new soil or an unlimited budget and time to remove large amounts of soil.

latest Practice

Now we have a more comprehensive understanding of how the conditions  affects the roots there is an easier way of overcoming it

It has been proven that roses treated with mycorrhizal fungi thrive in soil where roses used to be.

Mycorrhizal fungi have a symbiotic relationship with plants.  Essentially they help the plants take up water and nutrients over a much larger area  while also acting as a buffer against certain harmful microbes and pathogens that may have been left behind by the roses that used to be there.

By using mycorrhizal fungi at the time of planting there is no need to replace the old soil.

Application
Mycorrhizal fungi are applied by either coating  the roots before planting, adding them to the planting hole or by dipping bare root roses in a liquid form.

How you apply it will depend on if you are planting bare root or container roses and which method you feel is easiest

Whichever Mycorrhizal you  purchase its vitally important that it comes into contact with both the roots and the soil for it to be affective and allow a connection to be made between the roots and the exsisting mycorizal structures within the soil

Manure
The other thing you must do when planting roses in an area where roses used to be, is to add lots of well rotted manure or  garden compost into the soil that you backfill the planting hole with and generiously mulch the roses each Autumn to ensure strong healthy growth and to replenish the soil for the new plants

Heres a film on Mycorrhizal

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