Problems and Pests

Problems

All garden plants of any age can suffer from pests, diseases or other problems and seeds and seedlings are no exception.

Pests

Bean Seed Fly
In recent years poor germination of beans, and sometimes peas, has become an increasing problem and samples returned by customers have shown that this fly is very often responsible. The larvae of this pest, which are small white maggots, attack the growing point and seed leaves of the bean as it attempts to germinate. If these attacks don’t kill the bean then fungal rots which follow them often do and, in many cases, the seedlings don’t emerge from the ground.

Problems of this kind are most likely when beans are struggling to germinate in cold soil and are much less often seen when they are sown under glass of if sowing outside is delayed until a spell of warm weather has thoroughly warmed the ground. Attacks can also be prevented by a dressing of soil insecticide raked in before sowing.

Birds
Certain birds can be very damaging to some seedlings, particularly brassicas. Where they are troublesome, covering rows or beds with a fine mesh net raised a few inches off the ground will give good protection.

Cats and Dogs
Freshly made seedbeds are extremely attractive to these pets, particularly cats. Commonly their excavations will bury some seeds too deeply, expose others on the surface where they dry out and move still others to where they are not wanted. Young seedlings can be similarly buried or uprooted and the overall result can be large gaps and seedlings appearing all over the place rather than in the intended rows.

Various repellent chemicals and devices are widely sold but, in our opinion, the best method of preventing this kind of damage is to cover beds or rows with netting or chicken wire. Covering with cloches or fleece has a similar effect.

Cutworms
These are not worms but the caterpillars of certain moths which live in the surface layers of the soil and eat through the stems of seedlings at soil level. If they work their way along a row they can cause considerable damage. They are usually only a problem in the garden where control can be achieved by dusting drills with a soil insecticide when sowing. Where use of chemicals is not desired or if damage still occurs, a careful search of the soil near the damaged plants will often reveal the culprit.

Mice
These rodents are also very partial to pea and bean seeds and can quickly clear out a whole row, again making it appear as if germination has failed. Where mice are known to be troublesome an old remedy is to dip pea seeds in paraffin before sowing while beans can be raised under glass. Alternatively, careful baiting or trapping may need to be considered.

Slugs and Snails
These pests love the soft, juicy seedlings of many plants and will seek them out. A whole row of newly germinated cabbages or pot full of young lettuce can mysteriously disappear overnight if a large snail finds them. Problems are most acute in the garden but slugs, in particular, also enjoy conditions in the greenhouse and can cause much damage there too.

Various chemical baits and poisons are widely available but must be used with care as some are toxic to pets and other animals. Traps, such as those containing diluted beer and set slightly above soil level, will drown or collect many slugs which can be subsequently disposed of. In the greenhouse, good hygiene, particularly measures which reduce places where they can hide during the day, will usually keep them under control.

Diseases

Damping off
This is the number one enemy of young seedlings grown under glass where the air circulation is poor and is caused by various fungi which live in the soil. Affected seedlings rot off at soil level, suddenly collapsing and withering away.

Still healthy seedlings away from the edge of the affected patch can often be saved by quickly transferring them to fresh compost but, once this problem appears, it is almost impossible to cure and so it is important to prevent it occurring in the first place. The keys to doing this are, as already mentioned, clean containers, fresh compost and the use of tap water, not rainwater. Compost can also be watered with the fungicide, Cheshunt Compound, and this is recommended in cases where seedlings are known to be particularly susceptible. If the above rules are observed, however, and seeds are sown thinly and not overwatered, fungicide should not be necessary in most cases. It is certainly not a substitute for good hygiene.

Other problems

Abnormal growth or development
We sometimes receive reports of plants growing taller or less tall or maturing more or less quickly than stated on our packets. As living things, however, the performance of plants is very much subject to the conditions under which they find themselves. The notes on seedpackets are for guidance only as no seedsman can guarantee that a particular variety will perform in exactly the same way in all summers, on all soils and in all parts of the country.

Capping
On some soils a crust or cap forms on the surface after heavy rain or watering. This can make it very difficult for smaller seeds to germinate. If such a cap forms soon after sowing and before seeds have had a chance to start germinating it can be carefully broken up by very light cultivation. In vulnerable areas, however, it is best to avoid the problem by using general purpose compost rather than soil to cover seeds.

Weak, leggy seedlings
Seedlings which receive insufficient light will often become drawn up, thin and weak and this problem most often occurs when temperatures are also high. Most likely to be affected are those from early spring sowings, when light levels are naturally very low, and ones grown on windowsills, especially windowsills over radiators, where light is only received from one side. In so far as this is possible, the remedy is to move them to a position where they receive more light and to reduce the temperature if this is too high. When pricking out or potting on such seedlings the problem can often be corrected by planting them deeper than previously, as long as their lowest leaves are still above the surface of the compost.

Sunscorch
Even early in the year, sun shining directly through glass can have a burning effect on delicate seedlings. In an unventilated greenhouse, propagator, coldframe or cloche this can also result in injuriously high temperatures. The problem becomes more acute as the season advances and the sun gets stronger. Seedlings can then easily be scorched, particularly if they are actually touching the glass or have droplets of water on the leaves. For this reason, young seedlings under glass should not be placed where they will be in full sun, even for part of the day, and, in all cases, adequate ventilation must be given on sunny days to prevent temperatures rising to a damaging level.

Weeds instead of plants
Every year we receive a few letters complaining that weeds have appeared with or instead of the expected seedlings. The usual reason for this is contamination of the compost or seedbed rather than any problem with the purity of our seeds. With our good reputation at stake we wouldn’t supply weed seeds instead of the variety purchased!

Modern general purpose composts are not sterilised and can quite often contain dormant weed seeds. Such seeds are also common in most garden soils while other seeds can blow in on the wind or be introduced with compost or manure. The very act of preparing seedtrays or a seedbed can provide these seeds with the ideal conditions for germination. Rarely, these seeds may germinate while ours, for some reason, do not.  Occasionally the ‘weeds’ can be the result of self-sown seeds from other flowers, such as larkspur or poppies, making it appear as though we have supplied the wrong variety.