CHOP DOWN GREEN CROPS FOR MULCH

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 tall 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, dualpurpose 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°C; the soil in a wooden raised bed was 12°C; the soil in an old copper in full sun was 13°C, but heavy, waterlogged clay garden soil only reached 10°C.

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 11°C, the raised bed and the copper were 12°C and the clay soil was still at 10°C.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 18-25°C 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 If you’ve grown green manure crops over winter, chop them down before the stalks get woody 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 (peas usually) with whatever prunings are on hand and spread the lot as mulch around the next crop that’s planted.

WEED WITH EXTRA CARE

Warmer weather and lots of rain means that weeds are romping away, but be careful with that hoe! Bulbs, perennials and annual seedlings are also poking up. These Siberian iris shoots (pictured) were hidden under a sea of chickweed and petty spurge. An upturned hanging basket stops me walking on them and will provide support for the leaves as they grow. Watch out for seedlings too. If you have grown coriander, dill, nigella, primulas, cerinthe and many other annuals, you’ll find babies like the violas popping up. They’re easy enough to move to a new spot or they can be grown on in a seed tray while you decide where to put them.