Preparing potatoes for planting
PLANT SEED POTATOES IN POTS
My spuds have been chitting for a month, have sprouted nicely and are now ready to plant. In Lynda Hallinan’s Potatoes in Pots trial in the August issue of NZ Gardener, she recommends one seed potato per 10 litres of soil – or one bucket full.
Lynda grew her trial potatoes in 50cm x 40cm planter bags with drainage holes and reinforced rims containing a 40-litre bag of growing media. I grow mine in a collection of old recycling bins, terracotta pots, grow bags and a half wine barrel. I’m also using a PotatoPot for the first time. The instructions recommend three seed potatoes which seems a bit optimistic but I’ll give it a go. I’ve given up on ‘‘earthing up’’ because it’s so fiddly in pots and it’s easy to break the shoots. I cover the pot drainage holes with a piece of weed mat to stop the soil washing out. Then I place the seed potatoes on a layer of potting mix around 5cm deep and fill each container to 5cm below the rim to allow for watering.
Leafy sprouts show at the surface surprisingly quickly. I add potato fertiliser as I’m usually reusing potting mix that has already grown a previous crop.
SEEDS AND SOIL TEMPERATURES
There’s an old saying that the time to plant seeds is when you can comfortably sit on the ground with a bare bottom. I prefer to use a soil thermometer instead of shocking my neighbours! I have a nifty, dual-purpose one that shows the soil and air temperatures at the same time. In general, the soil in wooden raised beds is warmer than garden beds, and metal and terracotta pots are warmer still.
For example, one afternoon, when the air temperature was 15 degrees Celsius; the soil in a wooden raised bed was 12C; the soil in an old copper in full sun was 13C, but heavy, waterlogged clay garden soil only reached 10C.
Moisture and soil consistency affect the temperature too.
Light, aerated potting mix that’s well drained warms up much faster than dense, waterlogged clay. Interestingly, the soil temperature is much more stable than the air temperature. Early the following morning, the air temperature was 11C, the raised bed and the copper were 12C and the clay soil was still at 10C.
So why does it matter? Seeds need specific temperatures for germination.
You’ll have much better results if you wait until the temperature is in the right range before sowing spring and summer crops.
Beans, for example, need soil temperatures of 18-25C for reliable germination.
There are some soil warming techniques to speed things up.
Try covering a garden bed with a cloche or a sheet of plastic to warm up the soil for a couple of weeks before planting. I’m using the polycarbonate sheets to warm up my soggiest garden bed.
MADE TO MEASURE
Plant labels and seed packets usually include instructions for how far apart seedlings or seeds should be spaced so they can grow to their full potential. In display gardens like the Lost Gardens of Heligan in Cornwall, England, where Victorian walled gardens are meticulous recreated, they use marked measuring tapes to line up the vegetables in regimental ranks.I don’t bother to use a ruler as I went ‘‘digital’’ long ago. Nothing electronic, just my fingers, thumbs and whole gumbooted foot. My handspan is 18cm so I allow a tad over a handspan between seedlings that need to be 20cm apart. The width of my hand including the thumb is 10cm and that of my index finger is 1cm. From the tip of my index finger to the second joint is 5cm and my gumboot is 27cm long. Learn the measurements of your own hands and feet as a guide when sowing seeds or thinning out seedlings. When diluting fertiliser, it’s handy to know that a standard plastic bucket is 10 litres. For me, one handful is 75g, so I can work out how many handfuls of fertiliser or gypsum to spread.
CHOP DOWN GREEN CROPS FOR MULCH
If you’ve grown green manure crops over winter, chop them down before the stalks get woody
GET GROWING
This column is adapted from the weekly e-zine, get growing, from NewZealand Gardener magazine. For gardening advice delivered to your inbox every Friday, sign up for Get Growing at: getgrowing.co.nz. or they flower and set seed. It’s usually recommended to dig them in so they’ll break down over 5-6 weeks in time for planting spring crops. But soils are often too wet and puggy to dig.
Alternatively you can chop and drop – just let the cut foliage lie on the surface as mulch. I avoid digging altogether so the soil profile isn’t disturbed and I don’t have the space to let beds lie empty while the green crop breaks down. Instead I shred my green crop with whatever prunings are on hand and spread the lot as mulch around the next crop that’s planted.