New Zealand supports rich temperate forests believed to have occupied up to 80% of its land area below climatic tree line prior to human arrival in the 11th century, but deforestation, particularly motivated by conversion to agricultural systems in the last 150 years, has decreased today’s forest cover to less than 30% of the original estimate. There is currently interest in relatively large-scale afforestation of degraded lands, and this has initiated research and development to improve seeding of native forest species. We provide a synthesis of available literature, ongoing research, and practical experience to identify critical aspects of candidate afforestation sites, summarize practices and techniques used in current seeding research and operations, and recognize factors that affect success or failure of seeding native species. The main challenges are that pastoral farming has dramatically altered the soil microbiome, non-native mammalian herbivores and weeds reduce seedling establishment success, and many native trees are mast seeding or have recalcitrant seeds. Selection of sites with predictably adequate rainfall, deployment of fast germinating pioneer species, procurement of high-quality seed, availability of appropriate soil symbionts, and post-establishment weed and animal control are all important components of success when seeding native forest species in New Zealand.

Upon the alleviation of abiotic stress, seeds can resume development, a distinct physiological phenomenon termed recovery germination. While the inhibitory effects of salinity, extreme thermal regimes, heavy metals, and osmotic stress on initial germination are extensively documented, the reverse trajectory, the transition from stress-induced inhibition to successful germination post-relief, remains critically understudied. This study advances the hydrotime framework for post-stress kinetics, while evaluating the current state of knowledge across four major domains: salinity, heat, heavy metals, and osmotic recovery. We further examine the ecological significance of recovery germination as an adaptive strategy underpinning persistence in fluctuating abiotic environments. Evidence is synthesized from experimental studies, population-level models, and field ecology to establish a conceptual framework for recovery germination as a measurable, heritable, and ecologically meaningful seed trait. We identify key knowledge gaps: the absence of standardized recovery germination protocols, the scarcity of multi-stress interaction studies, and the underrepresentation of recovery germination in predictive vegetation models. We propose a research agenda to address these deficiencies. The recovery germination concept has significant implications for crop improvement under climate change, ecological restoration, and seed bank management.

Sweden is known for its coniferous forests, but two oak species occur in the south, Quercus robur and Q. petraea, in pure stands or mixed with other species. Oak forests have declined due to land use changes, industrial forestry favoring conifers, and browsing by wild ungulates. Oak grows best on deep, fertile soils but can survive on a range of sites, supporting high biodiversity, and have cultural, aesthetic, and recreational value. The temperate climate is expected to change, and the increased temperature and rainfall potentially will favor oak over other species. Historically, high sowing rates and low-cost labor contributed to successful oak establishment; planting has since become the main method. Interest in seeding is returning, but predation and germination risks make it less certain than planting. Site preparation and high seeding density can help mitigate losses where heavy acorn predation by rodents is expected. Competition from other vegetation requires intensive mechanical site preparation and periodic cleaning operations. Seeding is more successful on abandoned farmland with less rodent habitat and where agricultural practices can be used for site preparation and maintenance. Expensive fencing is required for protection from browsing, especially in the first 10 years. Restoration success requires regular assessment and management, with lower oak seedling densities acceptable if other species are present. Lack of experience among managers is a barrier; more information and communication about successful practices are needed.

Container characteristics can influence seedling morphology and quality by affecting root development and seedling growth during nursery production. This study evaluated the effects of two container types, Plantagrah and Hiko, on the morphology and quality of one-year-old seedlings of Quercus frainetto, Q. petraea, and Q. pubescens. Twenty seedlings per species and container type were randomly selected. Morphological traits, dry mass traits, rooting intensity (ROIN), and Dickson Quality Index (DQI) were assessed. The effects of species, container type, and their interaction were analyzed using two-way ANOVA, while multivariate variation was explored using principal component analysis (PCA). Significant differences among species were observed for most measured traits. Quercus petraea generally exhibited the greatest diameter, height, and seedling dry mass, whereas Q. frainetto showed the lowest values for most growth-related traits. Container type significantly affected diameter, fine root dry mass, total root dry mass, H/D index, and DQI. Seedlings grown in Hiko containers exhibited larger diameters, greater root biomass, lower H/D values, and higher DQI values than seedlings grown in Plantagrah containers. Significant interactions between species and container type were detected only for shoot:root ratio, indicating that container effects were generally consistent across species. PCA showed clearer separation among species than among container types. The results indicate that container type influences several important indicators of seedling quality and that Hiko containers provide favorable conditions for the production of high-quality seedlings of the studied oak species during the first nursery year.

Mexico is the country with the highest number of species of the genus Quercus, but there has been little research on their propagation in nurseries. Quercus crassifolia is distributed across more than 50% of the national territory; however, no studies have been conducted to document its morphological growth and plant quality in nurseries for reforestation and forest restoration. Some of the key factors in plant production, principally in a technified system, are the selection of containers, substrates, and fertilizer doses. This study therefore evaluated two container sizes, two mixtures of organic substrates, and two doses of controlled-release fertilizer. After nine months of growth in the nursery, morphometric parameters of the plants were recorded, and quality indices were determined based on these values. The results showed that container size, substrate choice, and fertilization dose all influenced the quality of the plant produced. With both fertilizer doses, the 25:25:50 substrate mixture of fresh pine sawdust, composted pine bark, and moss peat produced plants with the highest values of height, diameter, and shoot, root, and total dry biomass. Considering the factors evaluated, the use of 200 mL containers with the aforementioned substrate mixture and the addition of 7 g L^-1 of controlled-release fertilizer will produce plants of Quercus crassifolia suitable quality for use in reforestation.

We present a novel way of estimating embryo lethals using doubled haploid (dihaploid or DH) female gametophytes grown in tissue culture. This DH-based lethals estimate is hypothesized to be lower than the more common method where lethals are estimated from one generation of selfing. The chief reasoning is the early mortality spike observed for selfed embryos of larch and other genera in the Pinaceae. This early mortality spike occurs at the stage when diploid embryos embed into haploid female gametophyte tissue. However, this stage is missing for DH embryos which grow in a petri dish thus the DH lethals estimate is hypothesized to be lower compared to seed counts. This DH estimate is based on 20,000 haploid female gametophytes cultures from which two surviving diploidized embryos were recovered. Lethals based on diploidized haploids (DH) have not been reported for a conifer previously because, aside from larch, only a few conifer species continue female gametophyte development in absence of pollen. Our chief finding is that, contrary to our hypothesis, the DH-based lethals estimate was similar to lethals estimated obtained from selfed seeds in published studies. Thus doubling haploid female gametophytes can be used to estimate embryo lethals when diploidization is conducted on a massive scale.

This article is aimed as a basic introduction to conifer somatic embryogenesis for someone with a general interest in applications of this technique and/or who is interested in starting some practical work in the field. We also present data from an example study on individual trees’ ability to initiate somatic embryogenesis in Norway spruce (Picea abies). A total of 158 trees were each tested for ability and relative competence to initiate somatic embryogenesis from the zygotic embryos by observing the initiation frequency for ten zygotic embryos from each individual tree. Furthermore, we conducted a case study by following the process for SE plant formation for a selection of 48 cell lines that were monitored through the SE developmental pathway, with data collected on the success rates at different steps. We then evaluated the relative importance of different steps for the outcome of plant formation and yield.

An adult tree of Larix decidua Mill., European larch, was produced from doubling one haploid female gametophyte. Whether this tree can produce normal male meiocytes is the crucial question. This adult’s pollen mother cells (PMCs), or male meiocytes, were squashed and stained. Male meiosis was normal and no abortive pollen grains were observed. This female gametophytic apomict of a conifer, a dihaploid adult, is 100% homozygous yet also reproductively competent with normal male meiosis and functional male pollen. Here we show that doubled female gametophytes can produce embryos and reproductively competent adult trees. This shows a way to gain rapid homozygosity and produce completely inbred lines for larch. This is a novel breeding shortcut reported for the first time for a conifer species.

The production of high-quality planting material for the most commonly used woody species in urban greening is a complex challenge influenced by several factors. One of the key factors in seedling production, especially in pots, is the selection of an appropriate substrate. Testing various substrates for different species is an ongoing process. In Bosnia and Herzegovina, four of the most frequently used taxa for urban planting in the region were tested: two varieties of northern white-cedar (Thuja occidentalis L.), namely 'Smaragd' and 'Columna', as well as European boxwood (Buxus sempervirens L.) and Forsythia (Forsythia × intermedia). One-year-old rooted cuttings were transplanted into two-liter pots using five different substrates: plain soil, compost, lumbrico humus, peat, and a combination of all these substrates. At the end of the growing period, morphometric parameters of the seedlings were measured, and based on these measurements, quality indices were determined. The results showed that each species and variety responded differently to the various substrates. Generally, the best results for most of the taxa were obtained using locally produced lumbrico humus and compost. However, some seedlings, such as Thuja occidentalis 'Smaragd', exhibited similar growth characteristics across all substrates tested. Considering the varying costs of the substrates, it is possible to plan the production of these seedlings with significantly better quality while also reducing production costs.

Sonderegger pine (Pinus x sondereggeri H.H. Chapm.), the natural hybrid of longleaf (Pinus palustris Mill.) and loblolly pine (Pinus taeda L.), commonly occurs in longleaf pine seedlots grown in forest tree seedling nurseries in the southeastern United States. Because longleaf pine seedlings have a grass stage with minimal epicotyl development (< 1 cm), the initiation of stem growth (12 to 15 cm) in longleaf pine seedlots has been used to indicate that hybridization with loblolly pine (Pinus taeda L.) has occurred. Sonderegger pine seedlings are typically culled at the nursery due to observations of poor form and wood quality after outplanting. However, research documenting Sonderegger pine seedling morphology has not been published for more than 60 years, and to our knowledge, no seedling quality assessments have been made. To better understand how morphological traits of longleaf and loblolly pine are expressed in hybrid seedlings, stem length, hypocotyl length, and root collar diameter (RCD) were compared among one-year-old container-grown longleaf, loblolly, and seedlings visually classified as Sonderegger pine. Sonderegger pine seedlings had a range of stem development, with most (62%) seedlings measuring < 12 cm tall. Some pure longleaf pine seedlings had up to 10 cm of stem elongation, but the cause of early height growth in these seedlings is unknown. More than 90% of Sonderegger pine seedlings met or exceeded RCD recommendations for planting loblolly (≥ 3.2 mm) and longleaf pine (≥ 4.75 mm).