In this newsletter you will find all information that is currently relevant to the crop of peonies. We trust that this information will help you in achieving a successful crop. Feel free to contact us for questions and remarks!

For a long time now you are receiving this newsletter from us. With information regarding the cultivation of peonies. Because we are always looking for ways to improve ourselves, we would like to hear from you how relevant this information actually is. What are things you would like to see differently and are there topics on which you would like to receive more information? We greatly appreciate any feedback, so please let us know!

Watering

After a period of little rainfall, it is advisable to water the soil. Because a moist soil and the right organic matter content are very important to promote the absorption of fertilizers.

Botrytis control

Because of its fast growth, the peony is hardly resistant to climate change. One of the resulting damages is almost certainly Botrytis. The fungus will especially keep causing problems when the peony doesn’t get protection during growth. In that critical period extra sprayings of the peonies are absolutely necessary. Good and effective resources in that case are Teldor, Kenbyo, Luna Sensation and Switch. The best result is obtained when the buds are wet with dew. The fungicide then flows around it more easily. You can also use a good spreader. And spray from both sides.

When Luna Sensation is being used just before the flowers start to bloom, it means that there will be a very low percentage of Botrytis in the flower buds. But it also ensures a remarkably low failure in the holding cell.

In terms of a weak crop, don’t spray for two days after night frost.

The so-called flower bud-Botrytis is the same Botrytis that causes collapses in your crop. Therefore it goes without saying that plots which have had many collapses are most prone to flower bud-Botrytis. It is very important that enough calcium and silicon (provides stronger leaves / cells for better protection against fungi) is available.

A major problem every year is bud loss with peonies. Although Botrytis grows most quickly during wet and warm weather, the biggest problems arise during cold and wet conditions. Just before flowering. In that case the flowers do not ripe off and will be on the plant too long in a fragile state.

And the fungus will grow into the flower bud from the little leaf underneath the flower. If the weather conditions become warm and humid, the flower buds will collapse in large numbers.

          

Two examples of Botrytis in a flower bud

Phytophthora

A quite new infestation in peonies is known as Phytophthora. An infection which takes place through injuries under humid circumstances. The fungus can survive in plant tissue and in the soil for years. The first infestation can be recognized through black and weak leaves in the crop. When there is an infection by Phytophthora in the spring, brown to gray black spots will arise on the stem parts. In that case the branches will come up like some sort of black brackets and they will not grow further than ten centimeters. After infection it is almost impossible to remove. Places of infection will most of the time feel spongy and soft, where the marrow will be dark brown and wet rot. Kansas and Duchesse are examples of species who are sensitive to Phytophthora. To prevent this, from the moment the flower rises till the mulching, you have to spray with, for example, copper, Axidor (works systematically), or the new fungicide Ranman Top (only works preventively).

It’s easy to confuse Phytophthora with damage from night frost. In both cases the head of the flower dies, a black brownish color arises, the flower dries out and the head will start to bend down. With damage from night frost, on the brink of diseased and healthy tissue, a cavity in the stem arises. The difference between Phytophthora and night frost can therefore easily be determined. With a serious infection, leaf nematodes can also be the cause of dead flower heads, with the difference that the head doesn’t bend. In that case, small, half-formed leaves can be seen. To prevent the unnecessary use of expensive pesticides, it is wise to test suspicious plants on the presence of Phytophthora.

Measures:

  • Use healthy starting material
  • Care for a good soil structure
  • Avoid a soil that is to wet and ensure adequate drainage
  • Avoid a high salinity of the soil
  • While spraying against Botrytis, occasionally add a Phytophthora agent

Nematodes

The so-called ‘predator’ nematodes are predatory nematodes. These are the direct natural enemies of the harmful species. Saprophages are nematodes which do not damage the plant, but they do break down dead organic material, for example. The higher the numbers of these saprophages, the better the soil life of a plot. On top of that, it is more likely that the good and harmful soil life will balance each other.

Free-living nematodes: only prick the roots of the host plants superficially. The nematodes occur on sandy and silty soil. These free-living nematodes got a lot of host plants. Economically speaking they are the main cause of problems. All free-living nematodes are capable of transferring the so-called tobacco rattle virus (TRV).

Root knot nematodes: make sure that, when buying or processing, you are alert of infestation by root knot nematodes. A highly branched root system or visible nodules are symptoms of this. Root pruning offers some possibilities, but remaining nematodes spread rapidly across the young roots which grow in the spring. Our Green Works International Care™-treatment does offer results.

Leaf nematodes: an infestation of nematodes is clearly visible because of the deformity of the leaf. In that case the tissue looks misformed and the leaves are half grown. The growing point can sometimes dry out by young shoots.

It is also possible that bud dehydration (bud abortion) occurs. Clearly identified by black, rotten flower parts with healthy petals around. The flower buds can dry out in every stage. Sometimes the flower bud will come into bloom, but the flower is misformed.

Nematodes need water so they can spread in the crop. The nematodes move to other parts of the plant through water which stays on the leaves after irrigation or at a high humidity. During crop activities spreading also takes place. It is important not to walk or spray in the crop, because wet leaves causes spreading. Spraying should be done from the spraying beds.

The nematode causes damage the season after infection. Still the infection is recognizable in the first year. In that case the leaves show blue, tight through the veins bordered spaces. After rain this expands to the next vein space.

Nematodes hibernate, amongst other things, in a dead leaf on the ground and in the young growth points of the peony. In the spring these nematodes come up with the crop growth or they crawl upwards through a film of water on the plant. They suck on the plant for nutrition. During the puncturing and deflating of the cells, the nematodes transfer a toxic substance in the cells. This results in deformation in the growth points, drying-out of the flower buds and total growth inhibition.

Nematodes are also capable of ‘hitching a ride’ on weeds so that they can infect the plot.

Measures:

  • Keep the plot free of weeds
  • Remove dried-out flower buds from the field
  • Spray three times with Vertimec Gold in the evening when the leaf is wet from dew. Because the nematodes will then be on the outside of the leaf
  • Mow the crop in mid-August and remove all crop residues. Only do this with dry weather conditions

Common swift (moth)

Root borers are ground-dwelling larvae of butterflies. These caterpillars are very harmful to various horticultural crops, because they eat at the roots of plants underground.

The caterpillars hatch between May and mid-July. And in the greenhouses often before that period. They are about 6 to 7 mm long when the eggs hatch and they can grow up to a length of 4 cm. They are transparent to white in color and the gut contents can sometimes be seen as a black streak through the insect. Caterpillars of the common swift (moth) have a brown head and large jaws. They are very mobile; if you put them on the floor or on your hand, they squirm to get away. Depending on the temperature, the caterpillars pupate between March (greenhouse) and mid-June.

Before pupating, the caterpillars make a path to the surface of the soil. That is an exit from which the butterflies can fly out later. In an affected plot, this can be seen as neat round holes in the ground. These can be confused with the corridors that are created by earthworms, with the difference that there are often piles of strings of soil next to them. If the soil with a hole from the root borer is dug out and if you break open the root ball with the hole, then the caterpillar or cocon of the pupa can easily be found.

         

In the greenhouses, the first butterflies have now flown. Which can be recognized by the empty husks on the ground around the peony.

The butterflies themselves are orange-brown in color and they are about 3 to 4 cm in size. They fly from April to late July, at dusk and in the dark. When flying low above the crop, the females drop their eggs above the host plants. In total about 300 eggs. When it rains during the flight of the common swift or when there is irrigation, the butterflies hide under the crop. They then lay eggs close to where they hatched from the pupa.

Due to the large number of eggs and the hidden way of life, a small infestation can quickly develop into a large pest.

Root borers prefer to stay in clay soil or in loamy soil. The possible reason for this is that they can make their exits better in fattier soil than in sandy soil. Sometimes we also find them in pots containing tree nursery crops.

         

Control

Control can best be addressed on taking on these young larvae. About 3 weeks after the first flight of the common swift (moth), the larvae emerge from the eggs. Concerning the control, it is important to start with Botanigard 3 weeks after the first flight of these butterflies.

Advice: 1,5 kg Botanigard WP, then repeat 2x with 5-10 day interval. It is of great importance that Botanigard is being sprayed on moist soil and that sufficient raining in is happening after that. To get the Botanigard in a proper way in the top layer of the soil. The minimum temperature for a good germination of the spores is 15 degrees C. Botanigard is available in both liquid and powder form. The caterpillars of the root borer can also be controlled with insect-parasitic nematodes.

                    

Leaf nutrition Peonies as an addition to soil fertilization due to low soil temperature and high soil pH. Peonies grow from nothing to a full grown plant in a very short time. Which cost a lot of energy. The plant needs a range of main and spore elements to make this possible. These elements are not always as readily available through the soil. Because of the low soil temperature and/or high pH value of the soil, or because they are simply no longer available in the soil. It is very effective to provide the crop with these elements through leaf nutrition. Starting with leaf nutrition is possible when the crop is 15 cm high.

Click here for all information from KaRo.

Leaf roller

Leaf rollers owe their name to the fact that the caterpillars string themselves between the leaves. And that causes the leaves to roll up. In the case of peonies, this little black caterpillar eats its way to the flower bud of the plant. This roller isn’t only hard to find, but the creature also causes damage directly to the flower bud. Therefore controlling regularly on leaf rollers is necessary.

Mole crickets

Mole crickets are digging insects with highly developed forelimbs. They can get about 5 centimeters big. They live of larvae (cutworms and leatherjackets) and other soil insects. Supplemented with plant material. The color of mole crickets varies from brown / red-brown to yellowish. To create corridors just beneath the soil surface, these mole crickets use their forelimbs as excavator. These corridors are used more than once. When digging, they bite off roots of a variety of crops. With all its consequences. These creatures are good at flying. Often on warm evenings. They occur in wet meadows, peat soil, plots and gardens bordering ditches.

The mole cricket (Gryllotalpa gryllotalpa)

From late April, adult mole crickets become active. They are most active in May. The number of eggs in a nest-hole varies from a 100 to sometimes 300 eggs. Around the nest they make the same corridors, but also drainage corridors. It takes at least 2 years for a mole cricket to become all grown-up. Mole crickets can live almost 3 years. Because the plants on the surface most of the time are dried-out or dead, nests are usually easy to track.

Control

Control of the population is only necessary when you have to deal with a lot of mole crickets. This can be done by enabling your own natural enemy. The insect parasitic nematode Steinernema carpocapse is a nematode which reduces mole crickets and cutworms in an effective way. These nematodes search for a place in the corridors of the mole crickets to wait for them to pass. Thereafter they hook on to the mole crickets, enter them and separate a bacteria which is lethal to mole crickets. After that a new generation of nematodes arises in dead mole crickets who will search for new mole crickets to infect. These nematodes cannot live very long without a ‘host’. Is there no prey available, then they die.

When planting peonies in fall 2022; benefits of investing in 3-5 eyes compared to 2-3 eyes:

Number of stems/flowers per plant (2-3 or 3-5 eyes):

Variety Year Amount of stems Amount of stems
    2-3 eyes 3-5 eyes
Sarah Bernhardt Planting in fall: 2022    
  Spring              2023 0 0
  Spring              2024 0 3
  Spring              2025 4 7
  Spring              2026 6 8
  Spring              2027 7 9
  Spring              2028 7 9
  Spring              2029 8 9
    32 45

In the following link you will find our extensive and updated peony assortment of 2022 – 2023:

Peony Catalog 2022 - 2023

Green Works also supplies other summer flower starting material, like: Ranunculus Butterfly™, Ranunculus Romance™, Scilla peruviana and Asclepias Beatrix®.

Also, follow Green Works on TwitterFacebookInstagram and LinkedIn for more relevant information about our Peonies, amongst other things.

Green Works is the grower specialized in young planting material for Peonies, Ranunculus, special pot plants and summer cut flowers. Green Works also is a large grower of peonies for the successful cultivation for cut flower and trade, in the Netherlands and abroad. We supply within the Netherlands and globally to professional growers and (export) traders. With support in cultivation, promotion and sales, Green Works offers a total package to put an unique and healthy product on the market: www.green-works.nl/en
Green Works can never be held liable for any cultural information given and only to be used as a guideline. The grower is at all times responsible for his own action and to read the label of the chemicals being used.

Have a look at our product pages for more information regarding our cut flowers, pot plants and peonies.

For more information about our products, please contact: