FAQs from Plot Holders

This article covers a selection of frequently asked questions, usually but not exclusively from newcomers. Contact me if there are any particular topics that you would like to see addressed, or if you have any comments on the existing material. New topics are added at the end.

Article last updated on September 26th, 2021.

Raspberry Pruning
Compost Making
Sources of Manure
Potato Blight (also affects tomatoes)
Growing New Potatoes for Christmas Day
Honey Fungus
Powdery Mildew on Courgettes, Marrows and other members of the Cucurbita family
Storing Winter Squashes
Cultivating Asparagus
Use of Weed Killers
Blackfly
Pheasants and Beans
Flowering Rhubarb
Frost Damage
Borlotti Beans
Wasps’ Nest
New plot taken on in mid-season
Plants going to seed quickly
Soil Conditions at Sunningdale
Cultivating Tomatoes
Blackberries – White Drupelet
When to do my winter digging?
Blown Sprouts
Crop Rotation
Mice and Strawberries
Small Molehills
Hygiene

Raspberry Pruning. By far the most frequently asked question from newcomers seems to be “how do I prune raspberries?” The answer is that it depends whether they are summer or autumn raspberries. Summer raspberries typically fruit in June. The canes have a two year cycle. They grow from the ground up in year 1 and they fruit in year 2. When they have finished fruiting these canes are then cut out at ground level. Autumn raspberries tend to fruit from August through to early October. They have a simple one year cycle. All the canes are cut down to ground level in late winter. New canes will grow and fruit in a single season. If you do not know which type you have then just wait and see before doing any pruning.

After raspberries come questions on compost making. This topic is covered here on the Approaches to Cultivation page.

Sources of manure is another frequent question. Many plot holders on our site get their manure from Broomhall farm which is just next door. However, wherever you get your manure it is important to ensure that it is not contaminated with aminopyralid, a herbicide found in some manure which led to stunted and distorted growth in many crops across the country back in 2008. There are some growers in various parts of the country who reckon that they are still suffering. Here is a link which will give you a comprehensive background on the subject. We have been quite fortunate at Sunningdale. To my knowledge only one plot holder has received contaminated manure.

Potato Blight is usually more of problem on tomatoes which is in the same family as potatoes. It varies from season to season. In 2015 it was not a problem, not appearing until the end of September when crops had already been harvested. It appeared at the beginning of July in 2016, which is very early.

The ideal conditions for blight are high humidity, plentiful rainfall and a dayround temperature of 10C or more. Two consecutive days when the minimum temperature is 10C and there is at least 6 hours with a minimum humidity of 90% is termed a “Hutton Criteria”. The appearance of blight is more likely after a Hutton’s Criteria, though by no means definite. You can sign up with Blightwatch UK to receive email alerts when a Hutton Criteria occurs in your area (SL5 in our case). Older folk might be familiar with the term “Smith’s Period” which was used before Hutton Criteria. It had a slightly different definition.

Blight spores are carried on the wind. The leaves are usually (but not always) attacked first. The picture (below left) shows a diseased leaf. They are usually the size of a 10p piece. It is important that affected tomato leaves are removed immediately, taking them back to the main stem. In the case of potatoes, remove any suspicious leaves. If the blight spreads to the stem (see picture of tomato plant below right) then there is little that you can do. It will eventually move to the fruit and ruin them. It used to be possible to pre-emptively spray with copper sulphate-based preparations like Bordeaux Mixture that coated the leaves with a protective layer which prevented the spores from settling. However, such products are now banned.

blightonleaf
Blight usually first appears on the leaf

An increasing number of new tomato varieties have been bred for blight resistance (or should that be tolerance?). Mountain Magic and Crimson Crush are most frequently mentioned. They can both experience some blight on the leaves in years when the problem is particularly severe. However, they should shake it off and grow satisfactorily (Obviously remove the blighted leaves). Other varieties will be added here when further information is available. So far, there is no evidence of a blight-resistant cherry tomato. It is important to discover if your choice of blight-resistant variety, whether of tomato or potato, has any flavour.

blighton stem
Spreading to the stem and then to the fruit or potato

Early varieties of potato, particularly first earlies, are unlikely to be affected, as the plants are naturally dying off even if blight arrives in July. If maincrop potatoes become widely infected, cut the foliage down to ground level to prevent the blight from affecting the tubers, ranging from an inability to store them to outright destruction. You will almost certainly have a reduced crop, but better a reduced crop than no crop at all. Leave the potatoes in the ground for two weeks before digging them up, as this will allow time for a skin to form. There are varieties which are advertised with varying degrees of blight resistance, Sarpo Mira being one of the first that was available to gardeners. Do an internet search to find other varieties. My initial experience with Sarpo was that it had little flavour. I do not know if it has improved.

Under no circumstances should diseased material be composted or left lying around. Burn or otherwise dispose of it.

Here is a useful article on blight from the Royal Horticultural Society.

Growing new potatoes for Christmas Day. It is recommended that you grow them in large pots indoors or in the border in a greenhouse or polytunnel. If you attempt to grow them outdoors then the plants are likely to suffer from late blight and / or frost damage.

Honey Fungus is usually thought of as a disease of decorative trees and shrubs. However, two plot holders, including myself, have lost their strawberry plants by using the free wood chip on the site to stop the fruit from lying on the soil and rotting. In our cases the wood chip obviously included a tree or shrub that contained honey fungus. It is recommended that our free (untreated) wood chip should not be used on a strawberry bed, or indeed any other bed. Plant any replacement strawberry plants as far away as possible from the infected site.

Powdery Mildew on Cucurbita. Courgettes and marrows are mainly affected, although other members of the Cucurbita family may also suffer. Damp weather and poor air circulation (often because plants are too close together) are frequently the cause. The mildew can usually appear from early August onwards. The remedy is to remove diseased leaves as soon as possible. On one occasion I practically denuded an entire plant. It took about three weeks to recover and produce more courgettes. Spraying with a mixture which contains one part old milk and two to three parts of water is another approach.

Storing Winter Squashes. It is recommended that you leave a couple of inches of stalk attached when you remove the squash from the parent plant. Wipe each squash with a cloth which has been soaked in a weak bleach solution, paying particular attention to the point where the stalk is attached to the squash and to the underside where the flower was originally, as these are the places where rot is most likely to set in. Ideally, place the squashes on a sunny window ledge, conservatory or greenhouse for two weeks, turning them 180 degrees every other day. This process will help to harden the skin and hopefully lengthen their keeping qualities. Store the squashes in a cool place, e.g. a shed or garage. Beware that they do not like sub-zero temperatures, and so you may need to bring them into the house during any particularly cold spells when the temperature is around zero or lower during the day. Butternut squashes can keep until January, possibly February. Other types of winter squash can keep longer. I have eaten some in May.

Cultivating asparagus requires patience in the early years. It can be grown from seed, but I am only aware of one plot holder who has chosen that route. The majority purchase one year old crowns in early spring. Thorough soil preparation is recommended, i.e. incorporating lots of manure or other organic material before planting the crowns. See this RHS article for general advice. Do not pick any asparagus in the first year. The plants need time to build up their strength. Cut the foliage down to ground level in late autumn when the plants have died down, Pick a modest amount of asparagus the next year for (say) three weeks. From the following year onwards you can gorge yourself on the crop for six weeks each spring.  But no longer .. remember that the plants will still need time to recover for the following season. A mulch every winter or every other winter will be appreciated by the plants. If you look after your asparagus, the bed can last for twenty years.

Use of weed killers (assuming that you want to use them). The majority of weed killer sprays are applied to the leaf of the plant. The chemical(s) then travel down to the roots to kill them, and hence the entire weed. Such sprays will only work while the plant is actively growing, typically from late spring through to early autumn. Such sprays should only be applied to overgrown areas which will not be cultivated until the following season.

Blackfly can be a problem on beans (broad, french and runners). Autumn-sown broad beans are likely to suffer less than spring sown broad beans. The usual recommendation is to pinch the tops out of broad bean plants as soon as any blackfly is spotted. Ants are often the villains on french and runner beans. They farm the blackfly – wanting their honey-like secretions. The first step is to deter the ants. One approach is to apply a little ant powder to the base of any bean plant that ants are seen on. Blackfly can be rubbed out (between finger and thumb) early in the season (June) before there are too many of them. Companion planting is another technique. Some plot holders plant marigolds around the beans. The smell can deter the blackfly. If all else fails, you can use an insecticide. Pay close attention to the instructions on the tin, e.g. how many days between spraying and picking beans. Ideally, try to use any insecticide well before any beans are ready to be picked and just live with any residual blackfly that may subsequently appear.

Pheasants and beans. Over recent years, pheasants have taken to pulling up the seedlings of broad beans, runner beans and french beans. They are actually after the seed. Once the plants are 5 or 6 inches high they will leave them alone. So, either provide some physical protection initially or only put established plants out rather than sow seed directly in the ground.

Flowering Rhubarb has been a feature this spring (2017). The very dry conditions have obviously stressed the plants, encouraging them to reproduce. This is more likely to occur on young plants. It is important that the flowers are removed as soon as possible, otherwise the plants will simply throw their energy into reproducing rather than producing stalks.

Frost damage. A number of new plot holders have asked about the timing of sowing / planting, having experienced frost damage, most notably on early potatoes. Frosts can occur anytime up to the end of May. Having said that, there was one year when we had a frost in early June! Potatoes will recover from frost damage but they may lose some of their overall productivity. They should ideally be earthed up when the foliage appears. This will protect the plant from getting frost damage. Continue this process as the plant grows until you reach the point where earthing up is no longer possible. If frost is still forecast then you can cover with horticultural fleece to provide a degree of protection.

Any other tender plants will equally be at risk until the end of May. They include: runner beans, french beans, tomatoes, peppers, courgettes / marrows, squashes and cucumbers. Unlike potatoes, they are extremely unlikely to recover. Coping mechanisms include protection using cloches, cold frames and fleece. Note, however, that they may be insufficient to keep severe frosts at bay. Another approach is to use successional sowing so that if you lose the first batch then you still have the second sowing to fall back on. For example, you may sow some runner beans in late April, followed by a second sowing at the end of May, and even a third at the end of June. Obviously, this approach is only possible if there is sufficient time left in the summer for the crop to grow. This would not be possible with aubergines for example.

Borlotti Beans are a useful crop to grow. There are both dwarf and climbing varieties.  I think that the climbers ultimately offer better value for money. The picture below shows a range of pods. Pods are ready to pick when they turn a dark purple in colour (the ones in the centre and on the right in the picture) and they feel papery, i.e. they have lost most of their moisture. Beware that if you leave them on the plant for too long after they have reached this stage then the pods will burst open and scatter the seeds, the plant considering that it has done its work and now is the time to reproduce itself. Ensure that you dry the beans fully before you put them in jars for winter use. An alternative is to freeze them. You can find various methods of freezing them described on the Internet.

Wasps’ Nest. If the wasps are not particularly troublesome then leave the nest alone. The wasps will normally disappear at the end of the season. If you are allergic to wasp stings then obviously leave the nest alone, or get somebody else to deal with them. The majority of nests are likely to be found in compost heaps, although they might also be situated in sheds or storage containers such as keter boxes, particularly if they are seldom opened.

If you are unsure whether there are any wasps in the nest then prod it gently with the other end of a hoe, rake or long cane. Wasps detect vibration, and a bunch of defenders will quickly appear to confront the attacker. Hence using something long so that you keep your distance.

The best time to tackle wasps is in the early morning or late evening.

To get rid of the wasps you can use: ant powder .. puff a good wodge or two into the entrance to the nest and around it; an insect aerosol that can deal with wasps; water; or a mixture of these methods.

Check to see if there are any wasps on the following day. If there are, repeat the treatment. If you are certain that the nest is empty then it would pay to remove it, just so that any living wasps are not tempted to return.

You can always get a professional exterminator to come and do the job, although this will cost you.

New Plot taken on in mid-season. A frequent question from these new plot holders is what can I grow this season? Depending on the date that you got your plot ..

  • May and June. You can probably grow most crops and they will catch up
  • July. Runner beans sown at the beginning of the month should produce a crop. Leek plants can be put in during the first half of the month. Spring cabbage can also be planted for cropping early next season. If other vegetables are attempted, go for an early variety, e.g. peas, as they take less time from sowing to picking. Generally, aim for crops that will mature by mid-September at the latest
  • August and September. It is really too late to sow or plant anything for cropping this year. Avoid the tendency to grow new potatoes for Christmas Day, as they are likely to succumb to blight and/or frost. If you want to grow them then they are best cultivated in large pots at home in a greenhouse or conservatory.
  • October and November. Garlic, onions and broad beans can be planted in the autumn for cropping in early June the following year. Garlic is planted at this time by most plot holders on the site. Onions (from sets) and broad beans are usually planted / sown in late February or March by most plot holders.

Finally, a note on weeds. Beware that after you have cleared your new plot and possibly dug it that the weeds will continue to grow until the end of November. So, do not dig it in (say) August and expect that no further work will be required until next year.

Plants going to seed quickly. Quite a number of growers comment that certain vegetables go to seed quickly, too quickly. Spinach and Pak Choi are often mentioned. Late sowings, that is after the longest day, are much less likely to go to seed. Both vegetables grow quickly and will be cropping in August. This tip may possibly be applied to other vegetables. Some general advice on going to seed is available from the RHS. Obviously, extreme heat can cause inevitable bolting in some vegetables, e.g. lettuce.

Soil conditions at Sunningdale. New plot holders should be aware that the soil here is quite poor. Geologically speaking, we are on the Bagshot Sand, a very large area of sand that was left when the sea retreated many millions of years ago. To grow good crops it will be necessary to build up the fertility of the soil. This can be done by incorporating bulk material such as manure or compost, and by using a balanced fertiliser, e.g. Blood, Fish and Bone or Growmore. Particular crops will also benefit from other fertilisers, e.g. tomatoes, courgettes et cetera will thank you for the addition of potash in powdered or liquid form.

How to cultivate tomatoes seems to be a frequently asked question among new plot holders this year (2020). There are two types of tomato: determinate and indeterminate. The packet should tell you which type you have. Determinate are what I call bush tomatoes. They are the easiest to grow. Just leave them to do their own thing. No training is required. Indeterminate tomato varieties are grown as standards: that is you remove all side shoots that form between the main stem and a leaf. The plants will need to be staked. Presuming that you are growing them outdoors then you are unlikely to get more than four trusses in a British summer. Pinch out the growing point after four trusses (or around the end of July) to encourage the plant to put its energies into producing fruit. Tomatoes will appreciate periodic potash-based feeds. The problem with growing tomatoes – which puts many people off – is the likelihood of getting blight. See the notes on blight up above.

Blackberries – white drupelet. Blackberries are generally a trouble-free crop. However, one minor irritant can be white drupelet. A berry is technically called a drupe, consisting of multiple drupelets (or segments if you like). One or two of the drupelets may not colour up on some berries, being white, possibly turning to a tan colour. This is attributable to weather conditions, typically happening when a decrease in humidity is coupled with an increase in temperature. It tends to happen at the beginning of the fruiting period, being most prevalent on berries that are in full sun. The problem usually disappears as the fruiting period progresses.

When to do my winter digging? The short answer is whenever the weeds are not going to come up soon after you have finished digging, resulting in extra work. One plot holder was known to dig in late September, although she promptly covered her plot with weed suppressant material. Other people who dig during autumn use old carpet to keep the weeds down.

In a typical year, the weeds normally stop growing around the end of November. So, digging anytime from December onwards should mean that you will not be faced with any extra work from weeds in the early Spring.

Blown Sprouts. Sprouts require firm soil. This can be more problematic on the sandy soil that we have at Sunningdale. It pays to spend a good five minutes or so, trampling down the soil on the sprout bed before planting. Staking the plants will also help to reduce any incidences of blown sprouts.

Crop Rotation. Books talk about dividing your plot into three, sometimes four, equally-sized sections for the purposes of crop rotation. However, this can be difficult. Do you really have a third or a quarter of your plot set aside for (say) brassicas? Unlikely is the answer.

Each crop takes some goodness out of the soil, the precise details varying from crop to crop. It follows that a given crop will not grow as well if you keep growing it in the same ground. Hence, the need for some form of crop rotation, A pragmatic, alternative approach to that found in the books is simply to try move individual crops around your plot from season to season, and importantly to put back into the soil what you have taken out by the appropriate application of manure, compost, balanced fertilisers and, where necessary, trace elements.

Mice and Strawberries. If you see small piles of ripe / unripe strawberries, probably hidden beneath the foliage then it is likely to be the work of a mouse. After eating his fill, he will create a little pile ready to eat on his next visit, not realising that that will probably have started rotting by the time that he returns.

Small Molehills started appearing in one part of the site in 2020, becoming more widespread in 2021. They appear to be the work of voles or mole-rats, as they seem too small for moles. The molehills are more likely to appear on paths.

Hygiene. This question came up in the light of the blight attack in 2021. Badly diseased material, such as blighted foliage and fruit, should not be composted. It should be burned or put in your green bin from the Council, if you have one. As a general rule, not blight specific, it pays to disinfect items such as: pots, canes, stakes, plastic / glass cloches, garden tools et cetera before the season starts. It can be a winter job. Jeyes Fluid and Citrox are popular disinfectants for use on garden equipment.