Peter Cundall: How to protect rhubarb plants from soaring summer heat
- From: The Weekly Times
- January 22, 2014
NOW the weather has settled, summer has finally arrived and the heat is on.
The amount of moisture now being lost from the soil due to evaporation is massive - far greater than that taken up by plants.
Some plants can't get enough water at this time of the year. Celery and celeriac for example. They cannot be over-watered. Freshly sown seeds, especially carrot, parsnip, spring onion and many annuals will need to be watered several times daily.
All tiny seeds are sown close to the surface, so are vulnerable to drying out. When this occurs after germination has started, they die. So keeping the soil constantly moist is difficult during this crucial stage in hot weather, but has to be done.
Rhubarb is easily taken for granted and is often an ignored clump on the fringe of the vegetable patch. Right now these clumps need all the water they can get. In fact, they also need all the nutrition we can shove into them.
I always give our rhubarb clumps a very heavy soaking at least once every week in summer and apply a thick, deep-feeding mulch well tucked in to the base of each clump. This is nothing more than straw, grass-clippings and wilted weeds, soaked in a weak solution of liquid manure, fish emulsion and heavily laced with well-rotted animal manure.
Keep in mind that some varieties of rhubarb produce green sticks while others produce red sticks.
It's impossible to make green rhubarb turn red.
Most green rhubarb fully dies down during winter, while red-stemmed forms usually continue to produce plenty of tasty picking almost all year round.
During summer, rhubarb clumps often send up great flowering spikes, even while still supplying plenty of sticks.
There are several reasons for this.
When a clump gets too old and overcrowded - more than five years after planting - it lets us know by sending up a distress signal in the form of powerful flower spikes.
Rhubarb clumps also begin to flower if they are not getting enough water, so are under stress. All flowering spikes can be cut off or even tugged out, but new flowers will appear within a week or two.
During hot sunny weather, many large, thick rhubarb stems flop over the ground. This is a clear indication that an extra-deep soaking is urgently needed. Do the job in the evening so the water soaks down to below the roots overnight. The best time to divide and replant an old rhubarb clump is during July. The roots can be massive and with very old plants, many original, deeply probing roots will have turned black and died. These are cut free and discarded.
Mulching all parts of the garden is one of the most significant ways of preventing moisture loss from the soil.
The best materials for the vegetable patch are always soft forms of organic matter, such as straw and grass clippings, because they rot down rapidly.
In the ornamental garden, pine bark and woodchips are best, because they rot very slowly and help smother weeds while sealing in moisture over many years.
At one time, black plastic film was used beneath mulching materials.
Not any more though, because this unnatural material not only caused soil to turn sour and infertile, but prevented rain or irrigation water from soaking in. This attracted ants on a huge scale and areas beneath plastic film, being bone dry is a perfect environment and cover for ants to build nests and multiply.
The only solution is to first remove all plastic from the surface of the soil and get rid of it. Next, deeply water the newly exposed surface to create a moist environment.
This gradually brings the soil back to fertility and at the same time destroys ant nests. All without the use of poisons.