Gardening: Moths and white butterflies the enemy of the vegetable gardener

When sowing seeds direct into the garden ensure the ground is well dug over and broken down to a fine soil.

Vegetable gardens at this time of year are often a busy place. These summer months with warmer temperatures make planting to harvest time short and rewarding.

Growing lettuce for salads for lunches and dinners is so easy. They can be picked up from the garden centre in punnets of six plants and will be ready for harvesting in 3-4 weeks.

There are many varieties that outer leaves can be harvested from while the plant continues to grow. Some prefer the traditional Iceberg type varieties where you harvest a tight ball-shaped head.

Lettuce is well suited to growing in pots if you lack room in the garden and has a quite decorative effect as well.

Harvesting of tomatoes, beans, zucchini and cucumbers is becoming prolific for many during this midsummer period.

Carrots and parsnips sown in November and December are growing rapidly now. Finger size thinned-out carrots can be pulled out and eaten to leave more growing space for the others.

Onions should now be drying off prior to harvesting and storing away for the winter. Once the stems of onions have bent over, they need to be pulled and left to lie in the sun for a few days to dry and cure.

There are various ways of storing them including stringing (hang in the kitchen by the stems), on wire netting strung between garage or shed rafters, or in onion bags that can be hung up where air can circulate freely.

During this period of summer harvest it is time to think ahead to autumn and winter harvest.

Now is the time to plant leeks and brassicas.

Planting now will allow some fantastic growth and vegetables ready to harvest in May and June. Plant brassicas too late and they will not be ready until spring as the growth stops when temperatures get cold in winter.

When planting you need to be vigilant in the battle against the white butterfly caterpillars.

White butterflies are not as bad as other years at this stage due to a cooler summer. When present, the caterpillars will eat brassicas like cabbage, cauliflower, broccoli, brussels sprouts and kale. If something is not done to avoid or control the attack, your crops can be destroyed.

Protect your vegetables with bug netting.

Another pest that will damage brassicas, which is often blamed on the white butterfly, is the diamondback moth.

The caterpillars of the diamondback moth are similar to the white butterfly caterpillar but a lot smaller and are capable of more damage as they can drill deep holes into host plants such as cabbages.

The adult moths are very small but can be seen flying off the crop when disturbed.

Establishing a cloche and covering with bug net (available in the garden centre where it is sold by the metre off the roll) at the time of planting will prevent many insects gaining access to the plants and thus protect against damage.

There are some good sprays available if necessary for both of these pests. Derris dust provides some control but must be applied frequently for effectiveness, especially after rain or irrigation. Yates Mavrik is also very effective and is bee friendly.

An excellent control product is Yates Success Ultra. This product is derived from naturally occurring bacteria. It is very effective when applied about every 14 days over the white butterfly breeding season and is also effective against aphids, whitefly, codlin moth, psyllid and more.

It is time to make new sowings of carrots and beetroot for a tasty autumn/winter crop. I highly recommend the new Ican Chefs Best Seed Range.

This is a range of 15 of the best vegetable seed categories. The majority of these varieties are hybrids where there has been a focus on breeding for superior taste, improved pest and disease resistance, increased vigour and yield.

In addition, hybrids have the benefit of being consistent and reliable. A number of the varieties are also more compact, and faster maturing, which results in a larger range from less space, and the ability to produce more crops through the season. Many are ideal for raised planter beds and container gardening.

The following carrot and beetroot are in the range:

Beetroot Red Lightning: Sweet and tender. Strong and vigorous early maturing, upright grower, producing uniform size deep red globe shaped roots. The best variety available.

Carrot Europa: Strong, vigorous germination and rapid growth. Long straight carrot with good disease resistance and tolerance to 'bolting'. This is the best home garden carrot yet developed.

When sowing seeds direct into the garden, ensure the ground is well dug over and broken down to a fine soil.

Once germinated, thin out plants for a better crop and keep moist and weed free. Protect seedlings with slug bait and feed regularly with liquid fertiliser Ican Fast Food. Very few pest and disease problems are encountered when growing beetroot.

Carrots grow best in soil that is low in nitrogen. A soil too high in nitrogen may result in the carrot roots forking – a very common problem for home gardeners.

Carrot seed is very fine and difficult to handle. To get an even distribution, mix the seed with sand or similar fine organic matter to increase the bulk. Sprinkle this mixture along your marked rows 1cm-2cm deep with rows 15cm apart.

Keep moist until the ferny foliage appears. Thin 4cm-7cm apart, depending on how large you want your carrots to grow.

Some common problems with growing carrots are splitting, forking and a number of rots.

Carrots grow best in soil that is low in nitrogen.

Carrot splitting is caused through irregular water supply and by soil being over-fertilised or manured with excess nitrogen.

The general rule is higher nitrogen fertilisers for leaf crops such as silverbeet and lettuce; use Tui Potato Food for root crops such as potatoes and carrots; and potash for fruit and flower crops such as tomatoes and broccoli.

Plants do of course require some of each element and many other trace elements as well. A good general all-encompassing fertiliser is Ican Organic Vegetable Food.

Carrots are ready for harvest when they are around 2cm across at the top of the carrot.

You may need to carefully remove some soil from around the carrot to see this, or sometimes you will be able to see the carrot slightly above the ground.

Carrots are generally sweetest when they are slightly on the small side and will lose flavour if they get too large.

Don't store damaged carrots. Soft rot can be caused by growing in a heavily manured garden, particularly if there is poor drainage. Carrots prefer a deeply cultivated soil and can be sown any time from spring to autumn.

Have a good week.

•Gareth Carter is general manager of Springvale Garden Centre