It is best to water first thing in the morning and later in the day

It is best to water first thing in the morning and later in the day

Goodness, as I write this, it’s hot out there!  Having watered already earlier today…I’m at it again, especially with my tomatoes, peppers and fruit bushes. Best to water first thing and again at the end of the day, hopefully standing pots on saucers or trays to try and keep as much water around the base of the pot. I usually water at the end of the day as this is great for reducing evaporation.  However, if a plant looks like it’s wilting and suffering from drought in the day, then water it immediately.

Using the right amount of water is the most important aspect of a plant’s survival in dry conditions. Bear in mind that it is not just hot weather that can cause soil to dry out, windy weather can also have a detrimental effect.  Try to avoid watering plant leaves in direct sunlight because they can become scorched, particularly when they have hairy foliage. Why not, if you haven’t already, install a water butt in the garden to conserve water.

For those of you enjoying yourselves away from home it’s worth investing in an automatic watering system with a timer, adjust it to take hot and dry weather into account. I’d also move container plants into the shade if you are going away on holiday and no one is watering your plants; your plants will thank you for it.

If you’ve got trees and shrubs that have been planted in the last couple of years on lawns or in areas of rough grass have a circle of clear earth around them – this must be kept clear or grass will prevent essential moisture getting through. Mulching with bark or compost will help.

Elsewhere in the garden consider cutting back early flowering plants such as foxgloves, snapdragons, lupins and penstemons as they go over, cut back just those sections of the flower spike that have faded, taking care to leave any secondary laterals that may be growing. You may get a second flush of flowers. Others worth doing this to are those lovely, fragrant catmints, hardy geraniums and any hellebore that escaped an early prune. With hellebores, as you cut back flower spikes, take a look at the base of the plant for seedlings. Don’t lift them now; come back in the autumn and pop them on into 9cm pots using a soil based compost such as John Innes Potting Compost No. 2. Grow them on by the back of the house, in a cold frame or unheard greenhouse and planting out next spring.

Lastly, be safe in the sun

It’s not only plants that can start to flag in dry weather, if you are working in the garden in hot conditions, it is important to take the following precautions:

  • wear suntan lotion or sun block and top up often
  • work in the shade if possible, out of direct sunlight
  • wear a hat or headscarf…they’re all the rage at the moment
  • take regular breaks and have frequent non-alcoholic drinks

Good luck and happy gardening!

For any gardening tips why not contact Tom Cole, Senior Horticultural Lecturer, Writtle College, Chelmsford, CM1 3RR by post (including a SAE) or by email at

Mixed borders can give year round interest

Mixed borders can give year round interest

The season is far from over.  At Writtle University College, the seasonal bedding is really at its best this time of year.

Over the last few years we have tried to make it a little more sustainable by using plants that are self-supporting, cover the ground and so block out weed growth that doesn’t require lots of deadheading.  The same can be said for our mixed borders around the campus.

A mixed border may contain trees, shrubs, herbaceous plants and bulbs.  Modern gardens tend to be small and may be better suited to a mixed border that can give interest throughout the year.

For me the advantages of a mixed border are many:

  • Labour is expensive and it may be difficult to afford to maintain large areas of herbaceous plants.
  • Herbaceous borders do not provide sufficient all year interest so trees, shrubs, herbaceous plants and bulbs are all grown together in a mixed border to provide extra colour and interest.
  • Shrubs are used to give structure.
  • Flowering and fruiting shrubs can provide interest in winter and spring.
  • Shrubs grown for their foliage colour can provide an effective foil or backdrop.
  • Herbaceous plants add to the seasons of interest especially in a small garden, by providing flowers and foliage at times when shrubs may be less interesting.

There are a few disadvantages of a mixed border such as:

  • Mixed borders can be difficult to plan
  • A range of skills is needed as trees and shrubs have to be pruned
  • Mixed borders may suffer from trying to look interesting at all times of the year

So if you want to add a new border this year why not consider a mixed one.  Consider the following:

  • The soil must be fertile, and well drained, with plenty of organic matter and moisture.
  • The area should be free of perennial weeds, pests and diseases.
  • The site must be sunny and open, away from overhanging trees; otherwise the plants become drawn and do not flower well. This is less important for foliage plants.
  • The site should be sheltered so that the wind does not damage plants.

Start planning now and preparing for planting out later this autumn or early spring.  If you’re sprucing up and existing areas these times are ideal for lifting up key plants and dividing them.  This simple technique enables you to keep young plantlets and discard and compost poor growth.

As far as maintenance goes check out my simple steps to success:

Fertilisation – an annual application in spring of a balanced fertiliser such as Growmore @ 100 g/m² or blood, fish and bone @ 70 g/m²

Weeding – regular weeding will be required, particularly in the spring and early summer

Staking – this is best carried out before required.  Materials used range from pea sticks, or lengths of hazel coppice, to bamboo canes and metal linking stakes.  Staking should be as unobtrusive as possible to allow the natural form of the plant to develop and should be 15-30 cm shorter than the ultimate height of the plant

Division – herbaceous plants require regular division to keep them floriferous and healthy.  This is carried out in the autumn or spring

Irrigation – irrigation may be necessary in prolonged dry periods or when plants are establishing.  Ground level irrigation systems such as porous pipes use water efficiently and do not damage flowers and foliage.  As with all irrigation a thorough soaking is preferable to a light sprinkling, in order to encourage plants to develop deep root systems

Dead heading – dead head where possible as this will encourage a longer flowering season

Pests and diseases – Monitor and treat pests and diseases accordingly.  Commonly occurring problems include aphids and powdery mildew.

Use this site for further information

Mulching – an annual application of a layer of leaf mould, well-rotted farmyard manure or garden compost helps to reduce weed seed germination and conserves soil moisture and improves soil structure.

Good luck and happy gardening!

For any gardening tips why not contact Tom Cole, Senior Horticultural Lecturer, Writtle College, Chelmsford, CM1 3RR by post (including a SAE) or by email at

Pricking out seedlings will give them more light and space to grow

Pricking out seedlings will give them more light and space to grow

If so it’s time to move them on to bigger and better things.  Once container-grown seedlings have germinated, it is usually necessary to prick them out.  This involves teasing out the seedlings and transferring them to a new container.

Why is pricking out necessary?
If seedlings are left to grow on in crowded conditions, they become drawn, with small leaves and long spindly stems and will never grow into good quality, sturdy plants. Pricking out will give seedlings more light, space and air making them less prone to fungal diseases.  At Writtle College most courses have been undertaking this task in readiness for summer bedding borders, vegetable plots and or trees and shrubs that were sown late last year.

The seedlings are transferred from a seed sowing compost to potting compost, which contains a higher level of nutrients than seed compost. Use a multi-purpose or a specific compost suitable for the plants you are growing on.

Broadcast seedlings may germinate erratically so that a range of sizes can be seen in the seed tray.  They can be graded during pricking out so that growth is more even.  Next time to avoid this try out modular trays – these contain cells of compost for individual seeds so there is no competition for water or nutrition.  As a result they can be left to grow for longer before moving to the next size pot.

Seedlings are spaced out so that they grow at a uniform rate.  This should mean that all the plants will be ready at the same time.

When should pricking out be done?
Basically as soon as possible! The seedling should have leaves that are large enough to handle and a simple, single, short root that will not be damaged by transplanting.  Another indicator is when seed leaves are touching.

Working area
Pricking-out should be undertaken either in a purpose-built, clean pricking-off shed or in the glasshouse beside the area where the containers of pricked-out seedlings are stood down. I haven’t any of these so I have ‘borrowed’ the dining room table and often use the draining board much to the consternation of my partner!

Gather all the necessary equipment and organise the workspace so it is both comfortable and efficient.

Choose a suitable potting compost such as loam-less potting compost (peat or coir potting compost) or J I No. 1 potting compost.  Never re-use potting compost for fear of disease.

Containers used range from seed trays to modular trays or pots depending on the seedling.  Today seed trays are less popular and modular trays are more common.  Containers must be clean to prevent the spread of fungal disease.

A striking off board is used to remove excess compost and boards that mark the pricking out stations are sometimes useful.  They may be bought but maybe made with two pieces of wood and nails spaced at regular intervals.

A dibber (a length of bamboo cane or a proprietary one) is used to tease out the seedlings.

Prepare the container by filling with compost and strike off the excess.  Modular trays should be tapped to settle the compost.

If pricking out into a tray an adapted striking off board may be used to mark out the planting stations.

Prepare the seedlings by watering in advance to ensure the compost is moist when you come to prick out the seedlings.  Ideally the seedlings should not be wet when you prick them out as this will make them more susceptible to damage.

Tap the tray of seedlings to loosen them from the sides.

Prick out the seedlings by:

  • Loosen the compost with your dibber and holding the seedling by the leaf gently tease it out of the compost
  • Make a hole in the compost using your dibber and insert the seedling into the hole.  Gently firm the compost around the seedling

Remember – never pick up a seedling by the stem, as this will cause damage.  Always pick up seedlings by the leaf using your thumb and forefinger.  Do not delay inserting the seedling into the compost as they dry out very quickly.

Most seedlings are pricked out individually but some seedlings such as Alyssum and Lobelia are pricked out in clumps of up to five seedlings.

Gently firm the compost around the seedling.  The seed leaves should sit just above the compost – if the seedling is left very tall it will not produce a sturdy plant.

Water the seedlings in, place the container in a warm environment to grow on (18– 20 °C), and protect from strong sunlight.

Keep a careful eye on watering and check regularly for pests and diseases.

Hardening off
Reduce the growing on temperature and eventually move the seedlings outside to covered cold frames.  Increase the ventilation during the day and eventually leave the lights (wooden framed glass panes used to cover cold frames) off at night.  Protect the seedlings by covering the lights with straw or newspaper should frost be forecast.

Good luck and happy gardening!

For any gardening tips why not contact Tom Cole, Senior Horticultural Lecturer, Writtle College, Chelmsford, CM1 3RR by post (including a SAE) or by email at

Hand-weeding is a practical way of removing weed

Hand-weeding is a practical way of removing weed

Weed control in horticulture generally falls into two main categories:

  • Cultural and mechanical methods
  • Chemical methods

Prior to controlling any weed it is important to establish whether it is an annual or perennial, as this will influence the control measure.

Annual weeds
It is important to prevent annual weeds from producing seed as the large numbers of seeds may germinate for years to come.

Effective control of annual weed seedlings can be achieved by hoeing on a dry, sunny day as they will shrivel on the soil surface, and need not be cleared away.  Larger weeds can also be treated in this way but it may be necessary to rake them off the soil surface.

A contact herbicide is sufficient for annual weeds.

Perennial weeds
Perennial weeds are more problematic as they can persist in the soil, re-establishing themselves from small portions of root or stem. Although they should also be prevented from going to seed it is the difficulty of ensuring that all parts of the plant are removed that is the main challenge.

Hand weeding is satisfactory for some perennial weeds such as Urtica diocia (perennial stinging nettle) and Taraxacum officinale (dandelion), but infestations of plants such as Convolvulus arvensis (bindweed) and Aegopodium podagraria (ground elder) may be made worse, as roots may be broken into several pieces, each piece capable of producing a new plant.  Mechanical soil cultivation will spread root fragments, allowing these weeds to further establish themselves.

A translocated herbicide may be required for control of perennial weeds.

However, there are other methods of controlling problematic weeds:

In early spring apply a mulch 10cm (4”) thick of weed-free, organic material such as leaf mould or processed bark to help prevent weed seeds germinating and to smother weed seedlings.  Do not use partially decomposed garden compost or manure as they often contain weed seeds… unless you’re happy weeding this to!

Established perennial weeds may grow through the mulch but as they tend to root into the loose material they are easier to remove.

Organic gardeners use a technique called sheet mulching – this involves mulching an area with material such as carpet for a year or more to control perennial weeds.

Why not try weed mats
This woven plastic sheeting can be laid directly over the soil.  It will prevent annual weeds from establishing and problem weeds such as Convolvulus arvensis (field bindweed) are both less likely to grow if the area is covered for at least two seasons.  Cover the sheeting with bark chip mulch to improve its appearance.  Weed mat is particularly useful in fruit and vegetable gardens.  Slits can be made in the sheeting through which the crops can grow.

Better still, hand-weeding and hoeing
Hand-weeding, hoeing and forking are often the only practical ways of removing weeds in flower beds, the vegetable garden and small patches of ground where weed killers cannot be used safely without risk of harming nearby garden or crop plants.

Small patches of perennial weeds may be forked out but great care must be taken not to leave in the soil sections of rhizomes, roots, or bulbils that will grow again.  Check a month or so later and remove any re-growth.

Hand-weed or hoe in dry weather, if possible, so that the weeds are easily loosened from the soil.  In wet weather remove uprooted weeds from the site to prevent them from rooting back into the soil.  Hoe only lightly around cultivated plants to prevent their surface roots from being damaged.

Mechanical weed control
Market gardeners often use rotary cultivators with hoeing or cultivating attachments for annual weed control between rows of vegetables but they may be unsuitable for perennial weeds, as they simply cut the rhizomes of weeds such as couch grass.

Back to chemical weed control
All chemicals used to control weeds are referred to as herbicides.  They are usually formulated as liquids, wettable powders or granules, depending on the product and its application.

Herbicides are categorised into two main groups:

Total herbicides
Total herbicides will kill all plants they come in contact with.  They must only be used where total weed control is required.

Selective herbicides
These are chemicals that have an ability to control certain groups of weeds e.g. broad-leaved weeds growing in turf, whilst at the same time leaving desired plants undamaged.

Mode of action of herbicides:

These products will kill the parts of the plant that they come into contact with.  They are effective at controlling weak rooted annual weeds.  However, perennial weeds with stronger root systems will re-grow.

These products will be absorbed by the foliage and translocated to the weeds’ roots, killing all parts of the plants.  As a result they are very effective at controlling perennial weeds.

Soil acting (residual)
These herbicides are applied directly onto the soil with the intention of preventing weeds from germinating.  For this reason they are often referred to as pre-emergence herbicides.

They form a layer of chemical in the upper topsoil, above the established ornamental plants’ roots but to a sufficient depth to control weed growth.

If using pesticides take care to read the label and follow instructions to the letter to avoid contamination of yourself, others and importantly the environment.

Good luck and happy gardening!

For any gardening tips why not contact Tom Cole, Senior Horticultural Lecturer, Writtle College, Chelmsford, CM1 3RR by post (including a SAE) or by email at

Over watering plants is a waste of time and money

Over watering plants is a waste of time and money

Plants have different water requirements which vary with their stage of growth.

Factors affecting water requirements:

• Size of plant • Speed of plant growth
• Stage in life cycle • Weather conditions
• Type of root system • Position in garden
• Size of leaves • Type of soil

Plants obtain the water they need from the growing medium, through their root systems or from the air. Many specialised plants such as those growing in tropical conditions have aerial roots or specialised leaves which absorb water from the surrounding air, storing it for use at a later date.

When plants are grown commercially or in amenity situations they often require more water than can be supplied by natural means. In such situations water has to be supplied by artificially to ensure good quality plants.

Before watering it is important to assess whether a plant requires irrigation to avoid wasting water and flushing plant pots of nutrients. Indicators include wilting, light coloured compost, a gap between the compost and the pot where the compost has shrunk as it has dried, and the pot being lightweight.

Water to the point of run off and stop, allow water to soak in and re-water if necessary. Large plants need enough water to allow soil to become wet to a depth of 15cm. A thorough soaking which percolates deep into the soil will encourage plant roots to grow deeper making them more drought tolerant. Irrigating little and often does more harm than good.

Equipment for watering plants
The type of equipment used for watering plants will depend on the number of plants requiring watering, the regularity of watering and cost of equipment.

Dipping plants
Used for watering individual dry container plants. Dip pot completely and leave until bubbles stop rising, remove and leave to drain.

Watering cans
Used for watering individual plants in the soil or container plants such as seed trays and pot plants. When watering plants in the soil the rose may be removed, however, you should make sure soil is not washed away from the root system.

Use a rose when watering seedlings, turning holes upwards for a gentler sprinkle. Stop once run off occurs and wait until water soaks in before continuing.

Hoses come in a wide range of sizes from 1.4 cm – 2.5 cm bores, with most nurseries using 2 cm hosepipes. They may be made of rubber or plastic, the most robust have a nylon braiding. Lay flat hoses are frequently used to irrigate growing areas. Hoses are used widely in amenity and commercial situations for watering plants; they can be used with sprinklers, roses or spray lances. Hoses can be permanently attached to taps using jubilee clips or be removable by using geyco or screw couplings.

To avoid scorching foliage never use sprinklers in hot sun

To avoid scorching foliage never use sprinklers in hot sun

Used to water large areas such as lawns. May be static, having to be moved periodically to a new area, or rotating when the head moves round, or from side to side. These cover wide areas but may still need to be moved if large areas are to be watered. The disadvantages of sprinkler systems are evaporation and overlapping spray patterns, leading to over watering within the overlapped areas.

Seep hose/porous pipe
Used for watering borders, beds, and within nursery areas for watering container plants. Seep hoses consist of a polythene tube with a sewn seam along its length, which allows water to slowly trickle out. This system is liable to blocking by calcium deposits, but causes less damage to soil media than many other systems.

Porous pipe is made from recycled rubber and allows water to slowly drip out onto the bed or border.

Both of these systems deliver water at soil level which avoids excessive evaporation. They may be covered with mulch or left on the top of the soil.

Oscillating spray lines
Consists of long metal or plastic pipes that clip to each other with a series of holes along their length. Usually mounted on stands, water pressure causes them to rotate back and forth. As with sprinklers, it is important to plan out carefully the position of spray lines in relation to each other, and therefore avoid overlapping spray patterns.

The following points should be observed to avoid damage to plants and soil, and accidents to members of the public.

• Never use sprinklers in hot sun, to avoid scorching foliage
• Do not over water plants – it wastes time and money and can cause disease problems
• Do not underwater – it causes checks in growth and poor quality plants
• Do not use watering cans that have contained chemicals
• Never water near electrical equipment, remember electricity kills
• Avoid leaving hoses and other irrigation equipment laying across walkways
• Outside taps should have an anti flowback device (to avoid contamination of water supply)

Good luck and happy gardening!

For any gardening tips why not contact Tom Cole, Senior Horticultural Lecturer, Writtle College, Chelmsford, CM1 3RR by post (including a SAE) or by email at