Over-watered potato plants?

[anubeon]

Greetings All,

I have been lurking these forums for a while now, and having picked up a fair few useful tips I thought it wise to register and elicit some much needed advice about an issue I'm having with my container grown potatoes.

First a little background. This is my second year growing potatoes in containers (potato bags specifically) and this year I'm growing five varieties. Two varieties (Purple Majesty and Lady Balfour) in re-purposed garden compost bags, and three varieties (Charlotte, Mayan Gold and Vivaldi) in bonafide, store bought potato bags. This year I'm growing my potatoes in a mixture of loam, Pro-Grow™ soil improver, compost and Hertfordshire clay (we've renovating part of the garden and had a lot of this slight silty clay left over. Since I'd heard that potatoes are good at breaking down clay, I thought I'd mix some in). Last year I used a mixture of loam, compost, coarse perlite and fine vermiculite, but I thought I'd save myself the expense of bulk buying the later two this year.

Now on to the business at hand. I'm having some issues with the Purple Majesty (one of the varieties planted in the compost bags) which I initially ascribed to under-watering. Specifically, from approximately two weeks ago the plant began to decline, with increasingly yellow and rolled leaves (and more recently, wilting leaves). I responded by deep watering this variety when I deemed appropriate, but now I'm of the opinion that the original decline was related to over- rather than under-watering. One of the things which points to this is that I neglected to pierce drainage holes in the compost bag in question (as they do not come with drainage eyelets as do binafide potato bags). Whilst this doesn't appear to have affected the other compost bagged variety (Lady Balfour), I can only guess that it's a matter of time before it does. Anyway, I pierced the offending compost bag near the bottom and fingered the soil (Oo er!) and it's definitely saturated, and quite possibly beyond saturated. I also pierced a hole further up the bag (about 1 foot or ⅓ of the way up) and the soil their feels relatively dry. I wouldn't describe it as parched, but then I wouldn't describe it as saturated either.

So as you can fathom, as a relative novice and perennial bungler in the garden, I'm in a bit of a bind. I'm not yet certain that over-watering is the culprit (as the column of soil doesn't appear to be uniformly soaked) but assuming that this is the issue, what is the best course of action? I've pierced a number of holes around the base of the compost bag (approximately 1 inch above the base, as I can't access the base itself) so should I simply stop watering for a while or until the plant shows signs of improving vigour? Should I prune the plant a little to decrease water loss from the leaves? Any advice would be greatly appreciated.

I've included a number of photos, including one of a more recent volunteer Purple Majesty plant which demonstrates the decline rather nicely (prior to this decline, the main Purple Majesty plant was the greenest of all of the varieties I'm growing). Hopefully these will help with diagnosis and/or prognosis should there be other culprits.

The Main, declining Purple Majesty plant:



The tiny volunteer Purple Majesty for reference:


All five varieties with Purple Majesty on the far left, the slightly legger Mayan Gold in the middle, Lady Balfour on the far right and Charlotte and Vivaldi in between and near the rear:


Kind Regards,

Lee.

P.S. The only other (non-)issue I'm having is with the Mayan Gold variety. Specifically, the plant appears rather leggy and has smaller leaves. Other than than the plant appears perfectly healthy, so I don't know whether this is characteristic of this variety or something more worrisome. The Mayan Gold potatoes were planted in a slightly heaver mix, as the clay I mixed in to this bag (planted a couple of weeks later than the other varieties) was far less silty.

[teakdesk]

I've pierced a number of holes around the base of the compost bag (approximately 1 inch above the base, as I can't access the base itself) so should I simply stop watering for a while or until the plant shows signs of improving vigour?

Should I prune the plant a little to decrease water loss from the leaves?

The plants look ok. Don't worry about small brown patches on some leaves or yellowing of others; this is normal in plants subject to the wind, rain and sun of our climate.

Make sure you have enough holes to drain all excess water away and provide air into the soil.

Plant roots need bacteria to be able to take up water and nutrients properly and bacteria needs water and AIR so drainage is essential.

Assuming you can't re-hydrate the top of the bags by dunking them in water, keep watering from the top. Don't stop watering. Keep adding small amounts and letting it drain away then add more water until the top compost has got wet. It will take up a little water each time you add some.

You could help restore bacteria by adding a liquid feed or by dissolving some rotting compost in water and making that your final water.


You don't need to remove any foliage unless it is damaged. Wind-damaged or dead leaves can let disease into the plant.

[anubeon]

Thank you for responding teakdesk,

I hope you correct in your assessment. It's certainly true that as well as being younger, the volunteer plant mentioned above is comparatively sheltered. The main plant(s) do seem to have lost an awful lot of their colour, and I don't think those photos do the difference in colour justice.

I think I'll poke a fair few holes in the lower foot of offending compost bag, to allow for better drainage and aeration. What I wouldn't give for a device that can hand punch brass eyelets into bags like these.

You could help restore bacteria by adding a liquid feed or by dissolving some rotting compost in water and making that your final water.

Would a standard liquid feed like Miracle-Gro™ or perhaps a comfrey tea (as I happen to have one brewing as we type) do the trick? Also, three days ago I added a light scattering of slow release Miracle-Gro™ pellets and some sulphate of phosphorous to the surface of all of the bags. Is it a safe assumption that it'll take a while for those pellets to kick in, and that a light liquid feed wouldn't be overkill?

As regards compost, I did mulch two of the varieties (Lady Balfour and Vivaldi) with a mixture of garden compost and manure (store bought, and so I presume well rotted) a couple of weeks ago. Those varieties are doing well, but I ran out of compost and so was reluctant to mulch with manure alone. Having no compost to hand, but a full bag of manure, would a mixture of latter and water suffice as an inoculate?

I also happen to have epsom salts to hand. Would a foliar feed be overkill at this point. I've been meaning to give my tomatoes a bit of a treat with this for a while, so I would easy enough for me to pop on over to the potato bags and include them.

Again, thanks for your advice.

Regards,

Lee.

[Potstubsdustbins]

It is more or less certain that the initial problem was caused by the root system standing in water logged compost. You have to water potatoes well but good drainage is essential, in my dustbins I have 9 15mm holes in the bottom of each one.

It is very hard to say if the damaged roots can recover but it is worth the effort as you have nothing more to loose.

I wouldn't worry to much about the central part of the compost being dry at this stage it is down below where the roots are that is the problem. My first move would be lots of drainage holes and no water for a couple of days and then check how wet the lower compost is. As that dries out you can then start regular watering and feeding to try to get things back on track.

[teakdesk]

It is more or less certain that the initial problem was caused by the root system standing in water logged compost. You have to water potatoes well but good drainage is essential...

Absolutely!

I grow, with minimal interfence except watering normal done by my better half, in B&Q buckets and every year one or two buckets without holes get mixed up and used! Don't ask me how - if I knew I'd never have odd socks in my drawer!!!

Those buckets are only discovered when the plant keels over.

I wouldn't worry to much about the central part of the compost being dry at this stage it is down below where the roots are that is the problem.

Agree, the roots are the key. I don't earth up my buckets (not very tall) so the roots on mine are the central part. There is no point at this stage in slaving to wet compost that is not in contract with them.

My first move would be lots of drainage holes and no water for a couple of days and then check how wet the lower compost is. As that dries out you can then start regular watering and feeding to try to get things back on track.

That's put a little clearer than I did!

[anubeon]

The plant still looks a little dishevelled and the lower part of the soil column is taking a while to drain despite the plethora of drainage holes punched into it. I've taken a cautious approach of holding off watering for a while but of course we've had a fair bit of rain and none of this helps the plant recover in the immediate term. Do you think foliar feeding and/or watering would help tide them over until their root systems can recover?

Agree, the roots are the key. I don't earth up my buckets (not very tall) so the roots on mine are the central part. There is no point at this stage in slaving to wet compost that is not in contract with them.

I have been earthing up the larger compost bag containers (including the offending purple majesty) but I practised the the all-in-one technique advised by Thompson & Morgan on the smaller bags (i.e. fill up to ⅓ plant 2/3 tubers, fill up another ⅓ and plant the remaining 2/3 tubers, then fill up the final ⅓).

I think I can feel a rather large potato bulging out at the centre of the column, but I can't be certain as it could always be a clump of soil. All I know is that with these large bags, I didn't get much at all out of the lower ⅓ of the column last year (I didn't get much of anything due to blight, but the bottom of the column was conspicuously unproductive). I suppose that was probably down to drainage again (not as acutely obvious because last year wasn't as wet?)

I'm wondering whether this combination of soil/compost mix with these large sized bags isn't particularly conducive to good drainage regardless of how many holes I punch through. Hopefully I'm wrong and things will pick up in a while.