Over the past few weeks we noticed that our 2nd year research garden has a lot of missing plants and what looks like new seedlings emerging. However, when these seedlings were dug up, the roots were those of 2-year old plants. This is the same research garden that had a lot of wilting of newly emerged stems.
A few weeks ago I speculated that the wilting 2’s could be freeze damage from the April cold snap since straw cover was relatively thin in this garden over the winter. It appears that the same cold that damaged some of the emerging 2-year old stems must have also killed a lot of the developing buds as well. What look like seedling tops are likely a result of the primary bud on the root being frozen off and a secondary bud developing instead. When plants are frosted off in May, these secondary buds never develop until the following spring. Obviously when the damage is very early, these buds can develop in the same year. Because these buds are less developed, and more energy of the root is required to form them, they do not form a normal 2-year old top.
These damaged roots will likely continue to develop this year, but with much lower root growth than they normally would in a 2-year old garden due to much lower leaf area.
The same type of damage is likely occurring in commercial fields wherever straw cover was thin and the garden was able to warm up rapidly in March before the April cold snap. Variable top growth in an area of a garden could be mistaken for root disease. If you are seeing what appear to be a lot of new seedlings, dig up one of the roots to see how big the root is. If the root has any mass at all, it is likely a 2-year old root.
I have not had any reports of any other major issues over the past week. The typical pest issues for this time of year continue including Alternaria and slugs. The first foliar signs of root diseases like Cylindrocarpon may begin to show up over the next few weeks.
Due to the recent rains, drip-line chlorosis will also show up over the next few weeks. Drip-line chlorosis is yellowing of tops where the water drips off of the shade. A relatively light rainfall can lead to much higher amounts of water under these drip-lines that can leach nutrients like nitrogen out of the root zone. This can lead to disease issues in these areas that can then spread to the rest of the garden. Additional fertilizer in these areas may reduce the issue. For macronutrients like nitrogen, foliar application is not usually sufficient to correct a major deficiency because leaves are not designed to take up nutrients. Application of a granule fertilizer prior to a rainfall or fertigation through the drip irrigation line will be more effective in this case so the nutrient can be taken up by the roots. Bear in mind that research has shown that ginseng has a relatively low requirement for nitrogen (40 kg/ha), so it will not take much fertilizer to correct a deficiency.
