Last summer, instead of the soft, deep red fruit promised by my Malwina strawberry plants, I was confronted by the strange leafy overgrowth you see in the photos. Thank goodness for all my years of gardening experience; I knew instantly that something was Not Right.
Could it be proliferation?
Flower proliferation occurs when buds form in an already open bloom. Various plants are prone to it, including clover and plantain, and some cultivars manage to stabilise the effect to produce a “hen and chicken” version of themselves. The daisy Bellis perennis “Prolifera” is one, and the Opium Poppy “Hen and Chicks”. (Here are pictures of rose proliferation.)
But mine had leaves, not flowers.
Phyllody, a fascinating but rather repulsive affliction, is the development of small leaves from developing fruit. I was pretty sure this had to be it. Now, I just had to work out if it was terminal.
One cause is infection by phytoplasmas, bacteria-like organisms that are obligate parasites1 of both plant phloem tissue (responsible for circulation of food substances) and insects, usually of the sap-sucking variety.
Strawberries have some picturesque-sounding diseases such as Green Petal and Lethal Yellows and when I emailed Thompson and Morgan, from whom I received the strawberry plants at last year’s Garden Press Event, I was told:
“Phyllody…is caused by the Green Petal Mycoplasma2. It is carried by the Leaf Hopper that is on clover nearby and very occasionally turns up in the UK. Our supplier hasn’t seen it for the last fifteen years in Norfolk!
I looked guiltily at the lawn, bursting with clover. Had I infected my babies through eco-friendly gardening?
Research published in 2001 lists symptoms that may accompany phyllody in strawberry plants: chlorosis (yellowing of leaves), virescence (greening of petals), stunting, crown proliferation. And, apart from their weird fruit, some of which were long and thin as well as leafy, my Malwina strawberries positively burst with health—big, strong green leaves, fine thick runners (and you’ll note the petals were white).
A paper from the Third International Strawberry Symposium 1996 (I so hope they have strawberry-themed dinners) described Strawberry Phyllody on Cold-Stored (Frigo) Plants. Strawberry growers around Sydney found it appearing on plants lifted in mid-winter, cold-stored at -1°C and planted mid – late summer for an autumn crop.
The same year, Italian research investigated strawberries in Campania that had “pronounced foliaceous growth from the achenes” (those are the bits that we laymen thought were seeds).
And, in 2000, research published on Non-infectious Phyllody Disease looked at an epidemic in many strawberry-growing areas of Thailand.
None found any evidence of phytoplasmas and all came to the conclusion that physiological damage was the cause. Put all the research summaries together and you build a picture of phyllody occurring in the first harvest of certain cultivars grown from runners that have probably been cold-stored but may have been affected by weather prior to lifting or after planting.
Malwina prone to phyllody
In last November’s Kitchen Garden Magazine, a reader sent in a picture of his phyllodic strawberries:
“More than one variety has been affected and probably one in four plants has one or more deformed fruit. They have already fruited well this season and it is only in the last few weeks that I have noticed these fruit/plants forming (since the plants have been producing runners, in fact)."
So much for phyllody only occurring in the first harvest… But Bob Flowerdew replied:
“…I strongly suspect this complete rosette of leaves replacing the fruit entirely is not induced by the virus [oh, Bob! Phytoplasma! Ed] but by the weather. I have had many similar, all on the new superbly flavoured later variety “Milvana” (aka “Malwina”). These occurred on plants from cold-stored runners.”
Hah! Malwina! More information from Thompson and Morgan arrived last month after I reported my experience to Director Paul Hansord at this year’s Garden Press Event. He forwarded me the following unsourced snippet:
"Phyllody is a genetic fail from Malwina. But that’s been written into the variety description for years. Phyllody often comes in one year old plants or if you are planting a fresh plant late, in Germany. It’s most one flower on one plant. In the second year and on coolstore plants, there is almost no phyllody on the plants."
With its tortured English, this isn’t the easiest passage to comprehend and I haven’t traced any references to Germany elsewhere, but it sounds as if my phyllody might have been a one-off, induced by cold storage, and possibly the atrocious weather we had in 2012.
Let’s hope so. I’m not confident, though. A response in a StrawberryPlants thread reads:
“I’m reliably informed that the…[Malwina]…variety is affected by a genetic anomaly which will be transferred to any daughter plants.”
Wouldn’t you know it? The one year I was organised enough to pot up the runners…
So, it’s now a case of waiting and seeing. If a significant number of fruit exhibit phyllody again, then I’m afraid they’ll have to come out. If none or only a very few do, then, if they are as delicious as Bob Flowerdew says they are, it might just be the price one has to pay.
1Obligate parasites can’t complete their life cycle without a suitable host. 2 Mycoplasmas and phytoplasmas belong to the same bacterial class (Mollicutes).
NB Since writing this I have also come across a thread on Malwina strawberries on Grow Your Own forum, where several others have had this problem.