Parsnips and Potatoes

by on July 19, 2015
in Vegetable Growing

 

I was quite a bit later than usual in sowing my parsnips this year, this was deliberate as I only needed them for my display at Malvern during the last weekend in September. I would normally sow them on or around the 7th February but as Victor is an early variety I thought that they might get too big. I sowed 5 barrels with four stations in each barrel of the new Victor F1 hybrid parsnip on the 23rd March and 3 barrels with four stations in each barrel of the sister and later variety Viper F1 hybrid. I have to say that they are growing really well with very strong and powerful looking foliage on them. I might have been worried with such tall strong foliage just in case there is nothing developing underneath. However having grown Victor, and won with it last year, I know that strong foliage does actually produce top quality roots.

 

One problem I have every year on my parsnips, particularly growing under cover, is an infestation of Red Spider Mite that can seriously damage and weaken the crop.

Parsnip leaf smothered with the fine cob webs of Red Spider Mite.

Parsnip leaf smothered with the fine cob webs of Red Spider Mite.

Parsnip foliage covered with RedSpider Mite

Parsnip foliage covered with Red Spider Mite

When I saw it for the first time it was nearly too late to do anything about it as it had appeared and spread so quickly through the upper foliage. I can now control it using SB Plant Invigorator which is so safe to use on so many crops that you can safely eat the produce the same day that you sprayed them. You must though use it on a regular basis, every seven to ten days to keep the pest at bay. This year, around mid July, I did find one of the Victor parsnips had some dark blotches on the foliage and a couple of leaves were yellowing as well.

 Brown blotches on parsnip leaf on the 8th July.

Brown blotches on parsnip leaf on the 8th July.

Alwyn decided to pull this one out as none of the others were affected and I was very pleased with it. Considering it was barely 15 weeks

Alwyn with Victor pulled owing to brown marks on leaves at only 15 weeks from sowing.

Alwyn with Victor pulled owing to brown marks on leaves at only 15 weeks from sowing.

old from sowing, it had certainly grown fast with the promise of some good roots to harvest with another 11 weeks of growth to develop before my final pull.

 

As with the parsnips I was later than normal planting my potatoes for the Malvern display, they were planted directly into my 20 litre black polythene pots on the 8th May and they were kept inside my polytunnel until they were planted outside during mid June. The bags were planted in trenches 6 inches deep which is deeper than I normally plant them and some plastic mesh material was erected around them to keep the haulms upright.

Potatoes in 20 litre polypots in rows ready to remove flowers to defray it from producing fruit and seed to continuous  tuber development.

Potatoes in 20 litre polypots in rows ready to remove flowers to defray it from producing fruit and seed to continuous tuber development.

I have 120 bags of six different varieties, so 20 bags of each kind should give me plenty of good sized potatoes to fill a minimum of six baskets. The varieties are Bute, Amour. Kestrel, Bonnie, Blue Belle and Red Cheftain. The latter isn’t going to be a top flight exhibition variety but I grow it for the beautiful red skin colour that sparkles when given a spray of water. The bags have been kept moist throughout and will be harvested this coming week after checking that they are up to size.

 

There’s a lot of research going on at the moment regarding the skin quality on potatoes, just as we want clean scab free skins for exhibition, so the pre-pack and processed commercial sectors have strict skin finish quality. Their most effective control measure is the use of irrigation following potato tuber initiation (when the small potato is starting to develop) Scab-forming Streptomyces can multiply significantly on developing tubers as well as in the surrounding soil in the 2-4 weeks after initiation, a key time to control common scab. It’s important to understand exactly when initiation starts as it’s the key to control particularly on susceptible varieties such as Maris Piper which is grown commercially in huge quantities.

 

The research says that Irrigation, in our case regular watering, should start in earnest when the plants first tuberize, this is normally around 2-3 weeks after the haulms have emerged. The researcher Dr Mark Stalham, states that it’s important not to underestimate the speed at which the pathogen gets into the crop. Commercially it’s very important on susceptible varieties grown for instance as Jacket potatoes to ensure that that the crop is free from common scab as well as to prevent excessive peeling losses. The best time to water therefore is between 1 and 3 weeks after initiation as this coincides with the most rapid phase of pathogen development on tubers.

 

What is worst is to actually water consistently for 2 weeks and then stop, this can then result in higher levels of the pathogen and worse blemishing. It’s therefore vitally important that for good quality exhibition potatoes we must keep the bags or containers moist, particularly during the initial tuber development. I have maintained this all along that keeping the bags moist, not saturated, throughout the growing period will allow you to harvest perfectly clean tubers with hardly any scab on them.

 

Comments

2 Responses to “Parsnips and Potatoes”
  1. Simon Smith says:

    Many growers are still convinced that scab is passed from seed spud to resultant crop even though it’s technically impossible of course. You were doing an experiment last year I seem to remember Medwyn, where you were going to plant a scabby spud in a polybag and see what the resultant crop looked like. I can’t remember reading what the results were so I must have missed it. What happened?

  2. Medwyn says:

    There is a reply to your question on my latest Blog.

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