Propagating or repotting a pond plant:
Get ready with a supply of new mesh baskets, aquatic compost, a sharp knife and scissors.
All pond plants should be propagated using aquatic compost and a mesh basket. Aquatic compost has no peat in it and often some clay to add substance to the soil that will be placed underwater but different species have different requirements.
A mesh basket is always used so that the pond plant roots can grow through the holes out into the water. Many roots will rot if they are confined in a tight congested space – they need to get out to take the nutrients they require for growth from the water.
Seeing the roots ‘escape’ from the basket is not a bad thing in a water plant but the sign of a plant that is rooting well and trying to extend its growth. Repotting a pond plant with roots outside of its basket should only be undertaken at the correct time of year for each different plant.
1. Propagating Caltha palustris species:
Divide soon after flowering ie: May:
1. Remove the plant from the basket and wash off the surplus soil so that you can see the separate crowns clearly
2. Divide a Caltha by easing the plantlets apart that make up a clump.
3. Remove the older, taller leaf growth and leave the fresh new leaves only
4. You may need to start the division process with a sharp knife between 2 crowns and begin the easing by wiggling the knife until the plant starts to open up.
5. Then pull the pieces apart. We do not advise cutting down between the crowns as you will find you may cut through a crown rather than between them. The roots are often overlapped and intertwined.
6. Trim the roots back to 4″
7. Repot each crown into a basket of aquatic compost with an aquatic plant feed tab to give it a good start.
8. Press the soil firmly around the crown and lower into shallow water – newly repotted plants should be encouraged to root by standing the base of the basket in water and when rooted the crown of the plant can be submerged under the water surface.
2. Propagating Iris species:
Divide soon after flowering ie: July:
1. You need to remove the Iris from the pond to work on it.
2. Cut down the leaf growth to a height of 6″ and then you can see where the divisions should be made with your knife.
3. Cut the plant into fans of rhizome containing about 3 – 5 shoots of leaf on each one.
Do not cut back to single shoots of leaf growth if you want to see flowers again next year.
4. Snap off any old rhizome that is furthest from the growth tip and has no fresh white roots on it
5. Trim back the good root growth to the same length as the height of the basket you will be using. You do not want too much root having to be curled into the new basket.
6. Repot each fan with 4″ – 6″ of fleshy white roots into a basket if you have a small pond or make up larger baskets using more fans but allow space for them to grow over the next 2 years.
7. Add an aquatic plant feed tab to aid the plants regrowth
8. Press the soil firmly around the crown and lower into shallow water
9. Ideally you would split an Iris clump every 3 years and we would recommend you do some one year and some next and keep doing them in rotation not all in the same year to keep a continuation of flowering plants.
10. Newly repotted plants should be encouraged to root by standing the base of the basket in water and when rooted the crown of the plant can be submerged under the water surface.
3. Propagating Oenanthe, Houttuynia and Veronica species:
Propagate all rafting plants whenever the runners have set roots:
1. All these plants will have sent runners out into the pond as they only use the basket as a start point for growth and do not remain restricted but travel across the water all around them.
2. Each rafting stem will produce roots at a node or leaf junction as it grows
3. To propagate divide this stem into sections so that each section has root growth and a shoot. You do not have to remove the plant from the pond to do this.
4. Put 3-5 sections of rooted stem as a bunch into each mesh basket and surround the rooted sections of the stems with aquatic soil with the shoots protruding from the basket.
5. The baskets we use for the rafting plants are the 9cm size as there is no plant height needing solid anchoring – the important thing is that the plant will grow horizontally and be able to have its stems in the water.
6. Newly potted plants should be encouraged to root by standing the base of the basket in water and when rooted the crown of the plant can be submerged under the water surface.
4. Propagating Butomus, Sagittaria and Hesperantha species:
Divide Butomus species in Spring:
1. Butomus umbellatus will not flower if the small shoots that grow from each piece of rhizome cannot reach the top of the basket. With a congested mass like the LHS image few shoots will succeed.
2. Break the lump apart – do not worry if you break the rhizomes – this will often stimulate it into further growth. Spread the rhizomes out and choose those with shoots.
3. Place a single layer of rhizomes with growing shoots in a basket of aquatic compost and cover with a further 2″ of compost and firm down.
Propagate Sagittaria species in August/September:
1. Sagittaria species plants reproduce by turions which seen above are like bulbs on the end of a fleshy stem back to the parent plant. This is as they look when growing in the summer but eventually the stem will rot away and the turion (bulb) will be free floating.
2. The bulbil needs to be collected and bedded back into a basket of aquatic compost (2 or 3 to a basket) placed deeply down to the base of the basket to avoid frost and ice.
3. The parent basket of Sagittaria may or may not flower again the next year but as each will have provided many turions it will not be lost to the pond but may not be in the same place as it was the previous year.
The best time to collect the turions is early Autumn before you do your annual maintenance or they may accidentally be removed.
Hesperantha also produce bulbils but they do not travel far from the parent plant but collect around the outside of the basket so can be removed and repotted at the same time as dividing the main plant clump.
Propagate Hesperantha species in Spring as they are a late flowerer in the pond or bog garden.
5. Propagating Pontederia and Typha species:
Divide in Spring when starting into growth:
1. Remove any old growth remaining over Winter but be careful – the outer dead leaf may be protecting new growth inside the sheath. Unwrap rather than cut back.
2. Divide an old clump into sections – breaking each crown off-shoot with its own roots into separate sections.
3. Discard old and leggy crowns with no shoots or soft, mushy crown pieces.
4. Trim back the roots so that they are not curled into the basket.
5. Repot each crown into a basket of aquatic compost with an aquatic plant feed tab to give it a good start.
6. Press the soil firmly around the crown and lower into shallow water.
7. Newly potted plants should be encouraged to root by standing the base of the basket in water and when rooted the crown of the plant can be submerged under the water surface to the correct depth for over wintering.
6. Propagating from seed:
1. Collect seed from each plant species as it is dropping from the parent plant as this is when nature intends it to drop and be resown naturally. Named varieties will not generally come true from seed so British Native plants are always reliable and some others can be achieved too.
2. Collect each species seed in a paper envelope for storage. We sow some immediately and some later in the year in a polytunnel so we have a succession of plants coming on.
3. Use seed compost in a tray or plug tray and sow lightly over the soil area. Some pond plant seeds should then be just covered with water – Alisma plantago aquatica and Pontederia cordata. Other pond plant seed trays are happy to be stood in water as long as they do not dry out.
4. Moist plant trays should be sown in the same way and kept moist with vermiculite to cover the seed tray surface.
5. Some seed trays can take a season to germinate so have patience and do not throw the tray away too early.