Spring bulb reminder

When spring bulbs have finished flowering, don’t forget to allow the foliage to die back before lifting bulbs. It is important to leave the foliage because the yellowing and fading occurs as the plants withdraw nutrients from the leaves to store in the bulbs for next season’s growth. Depriving spring bulbs of this essential part of their growth cycle will result in poor, or no, flowering next spring.

Frangipani trees from seed

I often receive e-mails with questions about growing frangipani trees, and some readers may like to try growing them from seed. Paula Pugh Schipp of the Frangipani Society of Australia says that frangipani trees grown from seed grow much faster than those grown from cuttings because the root system starts to form when the seed germinates. Another advantage of propagating these lovely (Plumeria) trees from seed is that trees grown from cuttings will always be the same as the parent tree, but trees grown from seed are, like children, not usually exact duplicates of their parents. You may grow a tree with flowers with an entirely different colour combination if you have a variety of frangipani trees in your area.

Frangipani flowers do not always produce seed as the self-pollinating flowers do not always release their pollen. You can try hand-pollinating flowers with a piece of thick fishing line. Place the end of the line deep into the flower and wriggle it very gently to release the pollen. You have to be gentle as it is easy to knock the flower from its stem.

Seeds develop within a pod, often a double pod in a ‘T ‘ shape, which looks rather like two thin 17 cm zucchini in the early stages – changing over time to brown/black when mature (see photo, lower left). Pods can take up to 8 months to mature depending on the local microclimate.

When the seeds are mature, the pods become brittle and begin to split open revealing up to 60 seeds in each pod. Collecting the seed takes a bit of good timing because each of the seeds has a small ‘wing’ attached and, when the pod completely opens, the seeds can be spread far and wide on the breeze (see photo, below right). If the pod is in a position where you can easily observe its development, when the pod is just beginning to split, place a large basin under the pod structure and carefully cut the adjoining stem from the tree. If the pod is high in the tree and hidden by foliage, then when the pod starts to change colour, make a bag from nylon netting large enough to hold the pod structure with some room to spare. The will prevent the seeds from blowing away when the pod opens.

 

 

 

 

If you would like to try growing frangipani from seed, for best results sow them soon after they are collected.

This excellent Frangipani website provides a detailed guide to propagating frangipani, including an interesting method of germinating seed in paper towels: Frangipani Society of Australia

One of our readers, Sam, has shared some photos of his very successful efforts.
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Frangipani stem rot


A New Zealand gardener is having trouble with her potted frangipani. I am posting my reply separately as other gardeners may have had a similar problem:

I live in Auckland NZ. I have white frangipani over 1.5m tall in a large pot. It last flowered about 4 years ago which was it’s first year in the pot. Now we are getting good leaf growth and new stems in the summer but the new stems rot in the winter and we have to cut them off.

There are several reasons why new growth on frangipanis can rot in winter – (1) water-logging of the mixture while the tree is dormant. (2) Lack of nutrients, such as potassium, which strengthens cell walls as well as promoting flowering. Have you given the tree any fertiliser? (3) Its position in winter is too cold for a tropical tree.

Remedies for (1) and (2): If your tree has been in the pot for 4 years, it is quite possible the roots have blocked the drainage hole/s, and that is causing the softer, new growth to rot when the tree is not using the moisture in the pot. Or, perhaps the holes have become blocked if the pot is in direct contact with the ground. Frangipanis form lots of roots and they must have good drainage.

As their roots are rather brittle, if you can’t remove the root ball from the pot easily, lie the pot on its side and hose out the potting mixture. Then carefully re-pot it into a larger pot with fresh potting mix that contains some complete fertiliser, and gently water it to settle the mix around the roots. If you can’t find a larger pot for the tree, trim the longest roots (so that they will have to grow about 5 cm to fill the pot) and re-pot in fresh mix in the same pot. Sit the pot on some pieces of tile so that the drainage holes remain clear of the soil.

Remedy for (3): Even the white frangipani (which is the hardiest) will not do well if temperatures are too low or they are in windy positions. When growing frangipanis in temperate zones, on the north side of a wall is a good position for them. A brick or concrete wall is best because the wall absorbs heat during the day and releases it slowly at night, keeping the air around the tree slightly warmer.

New concrete near trees

I have received an e-mail from a reader who is concerned about her neighbour’s plan to put a screen fence about 35 cm from the base of her beautiful frangipani tree, because the fence posts must be set in concrete and doesn’t know the size of the tree’s root ball or if it will damage the tree.
As new concrete near gardens is a common problem for gardeners, I am posting my answer on my blog rather than merely giving a private reply.

Generally, the feeder roots of shrubs and trees are located under the outer edge of the plant’s foliage in what is called the drip-line. Nature designed plants this way so that rain (and bird droppings, mineral dust etc.) running off the foliage falls where water and nutrients can be taken up quickly by the feeder roots (see diagram).

There are some exceptions to this rule as roots of umbrella trees, figs, crepe myrtles and liquidambers, for example, can wander all over the place in search of water. Usually, when trees or shrubs are severely pruned back, they will produce new feeder roots below the new drip-line and this can be helpful in preparing to move large shrubs and small trees.
New concrete contains lime that makes it alkaline, and hydrated lime (brickie’s lime) that is used in concrete will burn plant roots and should not be used on gardens that contain plants. If you are unable to avoid using concrete for walls or footings near established trees or shrubs, you can ask the builder to line the hole with strong plastic sheeting to prevent the new concrete coming into contact with plant roots. Plastic degrades in light but not in soil.

Adding plenty of mature compost to topsoil before planting trees and shrubs will help protect plants from the adverse effects of new concrete as one of the functions of compost is to buffer plant roots from unsuitable pH levels in surrounding soil. Where plants are established before concrete is used, adding a 5 cm layer of mature compost to the drip-line area, and covering it with 5 cm of organic mulch will help your plants. Remember to keep compost and mulch well clear of the trunk.
A more serious concern is where the concrete is to support a wall or fence close to established plants and the trees and shrubs need to be pruned on the side closest to the wall, as timing is important. Some plants, including frangipani, bleed a lot of sap if pruned when they are not dormant. The very best time for this type of pruning to reduce “bleeding” sap, is to prune during Last Quarter phase of the moon. For these plants, the wall or fence should be constructed during winter when the affected trees and shrubs are completely dormant. However, if a shrub or small tree requires a lot of sunlight or warmth for good growth, and the proposed structure will prevent this (i.e. the plant will be on the south side of the structure), it may be best to move the plant during winter for deciduous plants, or in autumn for evergreens, to a more suitable spot or into a large tub, if space is limited.
In the case of frangipanis, these lovely trees are often seen growing against north-facing walls of houses. Once concrete has seasoned, it does not seem to bother them, and they love the warmth that is stored in the wall during the day and slowly released at night.

Frangipani in Victoria

Now is the perfect time of year to take Frangipani cuttings

frangwht1 Bill has e-mailed me about growing Frangipani in north-west Victoria – and his question may be of interest to other readers.
Frangipani trees are tropical plants, and your area of Victoria is not an ideal climate for them, because minimum temperatures for most of the year are not high enough. Plants grown outside a suitable climate zone are more prone to diseases. There can be, within climate zones, microclimates in protected areas where temperature variations are not as extreme as those in the general area, and plants that need warmer conditions can be grown in these positions – if you prepared to give them extra care through autumn, winter and spring.





The only variety you could possibly grow is the hardier white Frangipani, and you would need to grow that in a position that is protected from wind, and against a north-facing brick wall where the thermal properties of the bricks keep the air around the plant slightly warmer at night. If you find someone in your area who is successfully growing a white frangipani, and is prepared to give you a cutting, now is the perfect time to take frangipani cuttings. See my post on how to prepare frangipani cuttings for planting.

Otherwise, I think it might be wiser to choose a different tree that is more suited to the local climate.

Wollemi pine update

wollemi pine 2The recently discovered Wollemi pine was a topic of discussion on the Don Burke gardening radio program recently. This fossil conifer has been a source of considerable disappointment to many gardeners since its release. One could reasonably think that a species of tree that has survived for 200 million years, according to the accompanying care guide, would be fairly hardy, but this is not the case. These trees cannot handle heavy rainfall, drought, or full sun. They are easily stressed, and prone to phytophthora root rot, as well several other soil diseases.

The tree I received last Christmas was soon re-potted into a slightly larger container with some coco peat, compost and worm castings as fertiliser, and a little coarse river sand. After re-potting, the tree was positioned on a verandah on the northern side of our house, but it quickly became apparent that it was not happy in a warm environment, and was transferred to the verandah on the south side where it has survived, but has made only a couple of centimetres growth. The care guide gives no real indication of the species’ fussy moisture requirements other than the vague advice to “check moisture levels regularly”. Neither did the care guide state that soil in the area where the trees were discovered could have a pH as low as 4, which is too acidic for most plants to survive, or that a coir supplier had developed a special potting mix for these trees.

Don said that little information on the species had been available, resulting in the death of a lot of purchased Wollemi pines, and asked a spokesman from Sydney’s Botanic Gardens why the tree had been released for sale prematurely. The spokesman’s response was that it was to prevent people from damaging the discovery site when attempting to obtain a specimen of these trees. This reasoning would be easier to accept if they didn’t charge such exorbitant prices for these pines.

My advice, if you would like to grow a Wollemi pine, is to visit the web site below and find out if you can provide suitable conditions for this plant before outlaying any money.

wollemipine.com

Rose planting time…

rdrose2Some nurseries are advertising bare-rooted roses for sale. This is just a reminder to, if possible, avoid purchasing bare-rooted roses before the end of June, as roses that have been lifted before they are fully dormant do not usually grow well.
Potted roses can be planted as soon as they are dormant, if your area is not prone to severe frosts.
For rose planting guide-lines see: here
And
Planting shrubs and vines

Wollemi Pine

wollumi.jpg‘Santa’ surprised me at Christmas with the gift of a potted Wollemi Pine (Wollemia nobilis). This particular species is an ancient and rare Australian native that was recently discovered. The location of the pines has been kept secret to prevent people taking seedlings and damaging the forest. Plants available from nurseries have been reproduced by tissue culture. Each tree comes with a Certificate of Authenticity and a monthly care guide.
Unlike most pines, this living fossil from the Jurassic age has flattened leaflets that grow more in the manner of fern fronds than pine branches. The Wollemi pine also tends to grow with multiple trunks. New growth is pinky-bronze, changing to apple green, then deep green. After the age of 7 years, it will produce both male and female cones at the tips of the branches. ‘Polar caps’ form to protect the growing tips from cold weather. And, sap oozing from the stem is not a sign of disease but an indication that a new growth bud is about to emerge from the bark.
I will put my pine into a larger pot for the time being; as I need to have a serious think about where it should be planted. It is said to require a “well-drained, fertile soil” but, as Wollemi Pines prefer a low phosphorus fertiliser, planting the tree amid exotics that have high fertiliser requirements would not be an option. They can grow, at the rate of half a metre per annum to 20 m x 5 m. As our house was built on a stony ridge, the best positions for this tree would be some distance from the house. They will grow in part shade to full sun, are quite water-efficient, and can be pruned, if necessary, during winter.
However, as these pines can also be grown as tub plants in a sheltered position, out of full sun, I may eventually decide to grow it in a tub, near the house, so that I can enjoy its unusual foliage and growth habit through the seasons.
The Wollemi pine, Maidenhair Tree (Ginkgo biloba), California Redwood (Sequoia sempervirens), Grass Trees (Xanthorrhoea) and the Asian and Australian cycads and their relatives (Cycas, Bowenia, Lepidozamia and Macrozamia) all provide a fascinating insight into our planet’s flora long before man walked the earth. These trees have proven their adaptability over thousands of years and some, including the Calfornia Redwood, grow to more modest proportions in our climate. Many of these lovely plants are suitable for cultivation in gardens or parks, especially if they are grown organically to maintain a good level of soil micro-organism activity.

Pruning hibiscus

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Hawaiian hibiscus are pruned in spring at the beginning of new growth. This is because these plants are very sensitive to ‘cold snaps’ after pruning, and it is also easier to see just where to prune. In temperate areas, leaving the pruning of Hawaiian hibiscus until the first weekend in October is a good rule of thumb.
Immediately before new growth begins, lower leaves turn bright yellow and fall from the plants, and growth buds swell. Pruning hibiscus during First Quarter phase will result in faster recovery from pruning. Remove all withered branches with sharp secateurs, and also remove any branches pointing towards the centre of the plant. Then reduce the size of each plant by a third, cutting above an outward-facing growth bud.
Finally, give the plants a deep watering, a generous feeding of poultry-based organic fertiliser and a drink of seaweed extract tea. Add some compost to the soil surface, if you have it, and cover it with a 7-8 cm thick layer of organic mulch. Hawaiiian hibiscus are heavy feeders, and will continue to supply large blooms if further light applications of organic fertiliser are given every 6 weeks, or so, until May.
All species of hibiscus other than Alyogynes can be pruned at the same time as Hawaiian hibiscus. Alyogynes are pruned lightly after summer flowering.

Frangipani

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Frangipani trees do not require regular pruning. If a branch is inconveniently placed, it can be removed during winter while the tree is dormant. Frangipani trees will bleed sap if pruned during a growth period. Do not shorten branches of frangipani trees, or dieback will occur. On all trees and shrubs, a thickening of the stem forms where the new branch begins to grow. This is called the ‘collar’, or ‘wrinkle’. On frangipani trees, remove the entire branch, cutting through the branch at the outer edge of the collar. If you remove the branch flush with the trunk, scar tissue that forms will damage the phloem layer that transports carbohydrates in plants.
If you want to take cuttings from your frangipani, the best time to do this is at the end of winter. Remove a lateral branch for each cutting, as described above. Keep these in a dry spot, out of direct sunlight, for a couple of weeks to allow the cut end to form scar tissue. If you take the cuttings during Last Quarter phase, they should be ready for potting during the following Full Moon phase.
For each cutting, half fill a 20 cm pot (with plenty of holes in the base) with well-washed coarse sand that has a little moistened coco peat or compost mixed through it to help keep the mixture damp. Avoid using a normal potting mix for frangipani cuttings because they will rot if the mixture stays too moist. Anchor the cutting in the sandy mix, and gradually fill the pot with the same mix. If the cutting is very large, you may need a short stake to keep it upright. Gently water the mix to settle it around the cutting. A drink of seaweed extract tea can help stimulate root growth. Place potted cuttings in a warm, well-lit area, out of direct sunlight, and keep the cutting mix just damp. During spring, when white roots appear at the holes near the base of the pot, your cutting is ready for transplanting.
Frangipani roots are very brittle, and may snap if you tip the plant out of the pot. Gently remove the mix from the top half of the pot, and then use a hose to gently wash the rest of the sand away. Transplant into well-drained soil in a sunny position. Mature frangipanis are quite drought-tolerant but young plants will require a weekly watering in dry weather until they are making good growth. Organic mulch is beneficial if it is kept well clear of the trunk. These trees only require a light application of complete organic fertiliser in spring (but not at planting time).