A spring crop of Ranunculus in unheated walk-in tunnel
Carol, Carol's garden
Protected cropping, what are we talking about?
This section will be looking at how to get more flowers from less work, by using various forms of crop protection. The main ways to achieve this are:
Using protection to grow bigger, stronger plants with more flower potential.
Using protection to improve quality and reduce losses and waste from weather damage.
Using protection to extend your cropping season and to ‘smooth’ cropping.
Using protection to reduce damage and losses to pests.
But first we will recap on the different types of protection available to most of us.
Fixed Glasshouses, greenhouses and walk-in tunnels:
Large walk-in polytunnel in early spring
These offer the greatest amount of protection from weather and large pests. Glass structures offer the greatest thermal protection from cold weather, and best light levels in winter - so they will produce slightly earlier crops than plastic tunnels. They are expensive to build and maintain, so space is at a premium.
Walk-in polytunnels are much cheaper to erect and can be classed as temporary structures. The plastic covers need to be replaced as they deteriorate (usually 7-10 years).
Some walk-in tunnels can have adjustable or open sides (like the US hoop houses) and/or removable covers (often called Spanish tunnels)/ In both cases, the tunnel framework stays in place. Open sided Spanish tunnels offer protection from rain, but not wind, and are designed for summer use only, over summer crops, eg roses.
The dry conditions in all of these structures can be attractive to rodents, especially in winter.
Temporary plastic covers:
Icelandic poppies in a caterpillar tunnel
A much cheaper alternative to fixed tunnels and glasshouses are temporary plastic covers such as caterpillar tunnels, cloches. These are often designed to be moved around from crop to crop. All offer protection from wind and rain, and from many large pests, but can create cosy environments for small pests eg mice & voles. They are cheap and flexible, but cropping is more difficult and internal temperatures more variable, and they can be vulnerable to wind and snow.
If you don't have polytunnels, you can use low ‘caterpillar’ tunnels, or fleece tunnels to protect plants over winter - either to get bigger plants which you will need to uncover for flowering (orlaya, ammi, might benefit from this) or are high enough to allow some crops to reach full flowering height under them e.g. ranunculus, anemones.
Temporary netting type covers
Environmesh covers over newly planted dahlias to reduce sun and wind stress
Such as Environmesh, fleece, shade netting, bird netting - used to offer some protection from wind, hail, sunshine and larger pests, especially for vulnerable periods. Not usually designed to remain in place all the time, although permanent mesh and shade tunnels are commonly used in some climates to protect from hot sun, hail or strong winds. The greater the wind protection, the more likely they are to blow away or cause damage by blowing across plants. Plastic covers offer the greatest protection, but will need structures as shown above. Fleece too, will need to be over a structure, or pulled tight across plants and weighed down or it will blow away or drag across plants. Environmesh, shade netting and bird netting all offer less wind protection, but will generally stay put with just a few weights as in the picture above.
Structural wind protection
Walls/fences, hedges, windbreak netting - specifically designed to reduce damage from wind, especially across open sites.
Caterpillar tunnels erected within the shelter of high field hedges, to protect from wind.
How to allocate your protected space?
Not all plants do better with protection from wind, but the vast majority do. But most of us can’t just plant everything inside a lovely, airy well ventilated glasshouse - and even if we could, the operating costs would not justify the difference in flowering potential of many crops. So, the trick is to decide which plants ‘deserve’ to be in the best protected conditions. ie will give you the best return on the space you give them.
The answer to this will depend on your markets and customers, as well as your own conditions. So the answer is not simple. These are some of the issues to consider when working out your priorities for any protected growing you can offer.
Bigger, stronger plants with more flower potential
Some plants are significantly bigger and have many more flowers than those outside. Orlaya, for me is like a completely different plant if grown in a polytunnel compared to outside. It is big, strong, and produces at least 10-20 times as many flower stems per plant than those outside. The same plants, sown at the same time, taking the same amount of my time, but taking the extra cost of covered protection. For me, this is significant enough for Orlaya to earn its place in the poly tunnel. If you can grow great Orlaya outside, then your priority will be different.
Orlaya in polytunnel, with Barbara for scale!
Better quality flowers, with less damage caused by weather
Some flowers just don't stand up to wind and rain very well, and you will get much better quality flowers (and, usually, many more of them) if they are grown in a polytunnel. For me, this would include poppies and chrysanthemums. Others are prone to rain-borne diseases and are just healthier if grown in dry conditions. Roses are perhaps the best example of this. Paula grows in Southern Scotland, with plenty of wind and rain. She struggled to produce a reliable supply of roses for cutting until she moved them inside the poly tunnel. She now has perfect, unblemished blooms from End May to November. Same plants, different conditions. Other examples are sweet peas, stocks, antirrhinums (which often suffer from rust outdoors)
A perfect, just-unfurled Icelandic poppy, protected from rain
extending the cropping season
This is about using types of crop protection to grow flowers for a longer season and to ‘smooth’ out peaks and troughs - not strictly more flowers for less work, perhaps, but making best use of your resources. You can use all the means of protection listed above to keep plants warmer during cold weather, to reduce wind and provide shade from drying sunshine. Aside from assisting plant establishment and early growth, clever use of protection can help to bring flowering periods forward, and to carry on flowering later, creating a longer season of flower production.
Earlier flowers - I’ve trialled lots of flowers inside and outside tunnels of various kinds. Most will flower about 1-6 weeks earlier than outdoor crops. This also changes with the weather, so is hard to predict. A still, cold, cloudy spring means that tunnel crops are not much advantaged over outdoor ones. But a sunny, windy spring will mean they are much further on than outdoors. A 1 week advance is not significant enough for me, so those types will stay outside e.g cornflower. A 4-6 week advance may well be valuable eg Orlaya (so it's scoring on both counts so far!). Another example is tulips - by planting early cultivars in the polytunnel, and late varieties outside, I can have flowers from end March to end of May, a full 8 weeks of flowers, compared to maybe just 4 weeks if they were all planted in the same conditions..
Later flowers - Protection will allow you to keep your season going a bit longer into autumn. Half hardy annuals will often flower for longer if they are inside a polytunnel, compared to outside. The best example for me is Chrysanths - by selecting the right varieties (see blog post) I can keep flowers to early/mid November or beyond. If they were outside, they would certainly be damaged by rain, wind, maybe frost by then. The issue then is what to do with them through winter - if you have space, you can leave them in the ground. I will be replacing mine with tulips as soon as I have finished cutting them. This is why I don't want them flowering into late November as I don't really have a market for them then, and I want to get another crop in to replace them over winter, for valuable spring flowers.
Keeping out the big pests
If you've ever carefully nurtured a beautiful crop of plants, only to find that they've all be eaten by deer, or pulled up by a pheasant....you will know only too well what it feels like to have wasted all that time and effort. Many of the crop protection methods will keep these kind of large pests at bay. Fine nets, environmesh and fleece will protect outdoor crops. I even just keep horizontal support netting stretched across my beds all the time, even when plants are tiny or beds have been seeded, as they will deter cats, dogs and pheasants. They wouldn't stop a hungry rabbit or deer though!
Clearly, plastic covered tunnels and caterpillar tunnels will also protect plants from these large predators — though you may need to cover doors when they are open. We grow right next to a pheasant shoot. We can be over-run with pheasants, and they love the warmth and dry soil of a polytunnel. We have to keep either drop-down bird netting or even low pieces of trellis across doors with vulnerable crops in, to keep pheasants (and our own hens) out.
None of these methods will help much against small pests - rodents, slugs, aphids etc though!
Claire has produced a handy video explaining how she uses various materials to protect from, in her case, deer & rabbits.
So which plants give the best benefit from being in valuable polytunnel space?
Our site is open, south-facing, has a prevailing South Westerly air flow, slight maritime influence, black, free-draining soil (and we use lots of black municipal compost and black weed suppressing membrane) So it warms up early in spring. I do weddings and I sell to wedding florists. So April, May and June are very important months for me. I have invested in three polytunnels so I can make the most of this geographical advantage, and sell spring flowers to lots of customers - including other growers who don't have the same conditions as me. So I pack my tunnels and caterpillar tunnels with spring flowers - including fillers to go with them. This is why I haven’t, as yet, planted roses in my polytunnels, ....One solution isn't right for everyone.
Our top plants that really produce more and better flowers from being planted in a polytunnel:
Carol - Orlaya, daucus, stocks, wallflowers, annual scabious, antirrhinums, zinnias, chrysanthemums, Icelandic poppies. All to the extent that I hardly grow them outside the tunnels now.
Claire - Orlaya, colibri poppies, ranunculus, scented pelargoniums, dusty miller, jasmine, alstroemerias.
Paula - Roses, chocolate cosmos, ranunculus, anemones, foxgloves, gaura, wallflowers, annual scabious, stocks.
A final point about microclimates:
We have similar soil across our 2 acre site, but one field is slightly more elevated and exposed to Easterly winds. This field is significantly colder, windier and harsher than the other. We have not really improved the soil up there. We use this colder field for trees, shrubs and tough perennials. Basically, anything that will cope with it. We reserve the more sheltered and warmer field for plants which need more cosseting, - for annuals and for perennials needing more organic matter and water. This means we don't have to battle the harsher conditions in the colder field, but can focus our attention on the more intensive areas. Within your site, you will discover and can create pockets of shade, shelter, heat, etc - different little microclimates which will benefit some plants, and help them to be more productive. It’s the Right Plant, Right Place thing again. Trying to grow plants in a place they don't really like takes far more effort and work than finding a plant that likes that place. As a flower farmer, you cannot be spending a disproportionate amount of time on some needy or difficult crops unless you are certain it will pay off in the end.
Planning your protected space
Use the worksheet below to develop your own plan for all the types of protection you can offer, identify the priorities for you to give protected space to, and draw up a planting plan for any tunnels, caterpillar tunnels. Do you need to invest in more protected space?