I’ve noticed that my young tomato plants are covered in white nobbles all over, what are these and what can I do about them?
White nobbles on tomato plants are a relatively common issue for hydroponic tomato growers, they often appear when the plants are relatively young and immature, often they can be a sign of stress in the plants though and should not always be ignored.
In and of themselves the nobbles are not a problem, in fact they could end up being a positive benefit in certain circumstances. These nobbles are actually the beginnings of adventitious roots and left alone they will develop into a new root of their own, assuming that they find the correct conditions that is. The correct conditions for roots, as we all know, are dark and moist, any time that a root structure is in light or exposed to dry air it will automatically prune itself, a feature of plants that we take full advantage of by using our permeable fabric power pots. But if these new roots should happen to touch down in your moist coco medium for instance then they will keep right on growing and develop into an actual root. In the right circumstances this could well be a benefit to you the grower and also for the plant, if for instance the stalk was laying flat because of intentional training then the addition of new roots could add to the overall structural strength of the plant, helping it to literally root itself into the medium, and also the extra root would assist in the absorption of additional moisture and nutrients.
All this said, many times these white nobbles can be a sign of stress on the plant, it could for instance indicate that the plant is root bound and needs potting on, not an issue for user of power pots but if you are using traditional plastic pots then this could happen to you. It could also indicate an over watering scenario though, if this is the case then action needs to be taken to moderate the amount of water being given to the plants. Another thing to look out for is the humidity levels in your growing environment, when the humidity is too high plants increase production of certain auxins which will promote the growth of adventitious roots, this is essentially the same scenario that you would look to take advantage of when rooting cuttings.
Here’s the bottom line for white nobbles though, they are generally not much to worry about and most times they will go away on their own once the plants mature enough and also if the above stressors are removed.