Ask an expert

YOUR GARDENING QUESTIONS THIS MONTH

Q

SICKLY SEEDLINGS

The lower leaves of my tomato seedlings start going pale at the stem end and eventually the whole leaf turns yellow. They are heritage varieties growing in compost in a greenhouse. Could it be herbicide spray drift from nearby? MARY HARRIS, INVERCARGILL

ATomatoes are highly sensitive to weed sprays. Most herbicide sprays cause curling of the foliage and glyphosate also causes yellowing. The roots will also be stunted in the case of glyphosate spray drift.

However there are other possible causes for sickly looking seedlings.

Another possibility is a virus. Heritage tomatoes don’t have quite the same level of resistance as hybrids do to virus infection, but can still produce well when healthy. As the plants get bigger they may outgrow the tendency for the lower leaves to be affected.

Iron deficiency can cause leaves to turn yellow too. Straight compost is great for adding humus to the soil but may not have enough nutrients for healthy tomato growth. Goodquality potting mix which contains slow-release fertiliser will have a good balance of nutrients. There are even special potting mixes for tomatoes with the N:P:K ratio they prefer.

Don’t overfeed until the first truss has set fruit and then feed plants at least weekly with a suitable liquid feed or fertiliser formulated for tomatoes.

Tomatoes in glasshouses can overheat, risking fruit set failure or blossom end rot. Keep plants evenly watered and allow ventilation by keeping the windows open. Barbara Smith

QAN APPLE FOR ME

I’d like a good, all-round eating and cooking apple to grow in a small space with afternoon sun all year (less in winter). It’s damp in winter and frosty. Any suggestions? SHARON GUTSELL, TIMARU

AHere are three varieties I recommend as suitable for a cooler, damper spot. ‘Fairbelle’ or ‘Belle Bonne’ is a mid-season ripening from late March to April. It’s large and rosy red, an excellent dessert apple and cooks to a pulp. A healthy, disease-resistant tree. ‘Kentish Fill Basket’, an 1820 variety from England, is a mid-late season variety. It’s a large, pale green apple with red streaks that’s excellent for dessert or processing. Also a vigorous, disease-resistant tree.

‘Sturmer Pippin’, an 1800s Suffolk, is a late season variety with blushed, green-bronze skin and acidic, aromatic, sweet juicy flesh that is very firm. This variety makes excellent cider and is great cooked. The fruit is very high in Vitamin C. The tree is compact with low vigour, meaning it needs little pruning. It tolerates cold and was very popular in home orchards pre-1970s.

The main thing is to buy a heritage variety (pre-1940s) as modern commercial ones are not suitable for home gardens.

A list of other heritage apples can be found by searching for scion wood on sces.org.nz. Most are available through Waimea Nurseries and other specialist nurseries. Robyn Guyton

QWEEDY COMPOST

I have an old pile of grass and weeds that has gone to seed – nasties like cleaver, couch and thistles that have pretty well rotted away. Should I use this as a mulch? DI BROWN, SEDDON

AThe heap could be used as mulch but it will contain a lot of weed seeds and maybe perennial weed roots too. Here’s some ways to deal with them.

One: use as mulch somewhere where it doesn’t matter too much if weeds sprout. Perhaps under fruit trees or somewhere you can mow or strim them down.

Two: cover the rotted material with black plastic and let it heat up in the sun to cook the weed seeds. This works best if the pile is in full sun, the weather is really hot and the rotted material is less than 10cm deep. Perhaps you could recycle part of the heap by putting some in black plastic rubbish bags. Not too full – just enough so the material is 10cm deep when the bag is laid flat on its side. Put the bag in the very hottest spot you can find – perhaps on a path or against the side of the house.

Three: actively sprout the weeds. Spread out the pile thinly and cover with a cloche or clear plastic. Let the first batch of weeds sprout. Hoe them down when they are still small, and again several times till the number of weeds sprouting is at a manageable level. This might not work for couch which tends to rise from the dead with a vengeance. Barbara Smith