You may have noticed how all the plants started growing again recently after a few days of rain. Most vegetables benefit from a good soaking of the soil as water is taken up by the roots and then evaporated through the leaves. However, too much water can result in nutrients being washed out of their reach and encourages shallow, surface rooting. If you’re wondering if you’re watering vegetables or seedlings correctly, these tips might help.
Waterlogging can result in plants dying as their oxygen source will be cut off. Generally, however, more water is lost through evaporation than through bad drainage.
No. 1: As a guide water thoroughly and gently. Don’t be tempted to put the hose on full blast on each plant for a few seconds or you risk damaging seedlings and young plants. You’ll also notice if you check the soil (stick your finger in it) that the surface area might be wet but the area you’re trying to reach (where the roots are) is still dry so aim to keep the top 20 cm of soil moist.
No. 2: Soaking the soil with about 10 – 15 litres per square metre per week will really benefit Brassica crops if it’s dry. Water directly to the base of the plant – an upturned cut off plastic drinks bottle propped in the soil next to an established plant (especially squashes and tomatoes) is great for sending water directly where it’s needed.
No. 3: Watering in the evening is also the preferred method, as the plants will absorb the water rather than losing it to evaporation, however this may attract slugs. In the morning the soil will be soft making for easier weeding. Make sure that the leaves are dry before nightfall however.
No. 4: Germinating seeds need water so always sow into moist soil or compost.
No. 5: One of the biggest killers of seedlings is watering incorrectly. They prefer to be watered from the base so stand them in trays and water the trays if possible. Alternatively use a watering can with a very fine ‘rose’ to prevent swamping the compost or try using a mister. Once compost has dried out it’s very difficult to wet it through again.
No. 6: Fruit and flowering plants such as tomatoes, beans and cucumbers need water to encourage their fruits to swell so heavy watering at this stage will increase yields.
No. 7: Root crops need a steady supply of water – too much will result in more foliage rather than big roots so only water if the soil starts to dry out, increasing the frequency as the roots start to swell.
No. 8: Crops that are grown for their leaves – spinach, lettuce, cabbages, etc., need more water than root crops.
No. 9: Plants are more prone to fungal diseases if their leaves are watered rather than their roots.
No. 10: Dig in as much bulky organic matter (compost or well-rotted manure) to increase the water-holding capacity of the soil.
No. 11: strong>Mulch the soil surface after watering to prevent evaporation (add a layer of straw, compost or leaf mould on top of the soil and spread it around the plants).
No. 12: Avoid cultivating soil in dry weather, as it will bring moisture to the surface, which can then evaporate.
No. 13: Keep the soil as weed free as possible as the weeds will compete with the plants for water.
No. 14: Put up wind breaks. Wind dries the soil quickly, again increasing the rate of evaporation.
On watering cucurbits – unlike tomatoes they are happier if the ground is wet under their leaves – helps to prevent powdery mildew and spider mite which both like dry conditions. But the sunk bottle or flower pot is certainly better for tomatoes to keep moisture from the foliage and prevent blight. Isn’t it fun when you need opposite things in the same polytunnel?
The best resource I know on polytunnels – better than either of the books you mentioned – is Nicky Kyle’s blog – http://www.nickyklyegardening.com – her month by month polytunnel suggestions are absolutely excellent and I don’t know a polytunnel where the plants are happier and healthier or yield better. She also grows a wider range than anyone else I’ve come across and has an amazing array of butterflies, frogs etc living there. She’s also great at home made equipment – I’ve had plants from her in plastic drink cups that must be a dozen years old 🙂
Thanks for those tips and the link Kathryn, I’ll take a look 🙂 Yes, it can be awkward in a polytunnel… Keep it hosed down and wet as the spider mites don’t like it that way but if its wet and humid, mildews thrive! Just have to do our best to please em all.
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